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Viral infections and trace elements: Complex interaction

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Several trace elements are essential micronutrients and are required for various body functions and well being of the immune system. The deficiencies of trace elements and infectious diseases often coexist and exhibit complex interactions. Several trace elements such as selenium, zinc, copper, manganese, etc. have immunomodulatory functions and thus influence the susceptibility to the course and the outcome of a variety of viral infections. Some trace elements inhibit virus replication in the host cells, thus showing antiviral activity. Many trace elements act as antioxidants or help such functions that not only regulate immune responses of the host, but also may alter the genome of the viruses. The grave consequences of this may be the emergence of new infections. The trace elements, viruses and immune system interactions have been briefly reviewed in this article to highlight the importance of trace element nutrition of host in not only optimizing immune response to infections, but also in preventing viral mutations which could increase viral pathogenicity.
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REVIEW ARTICLE
CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1536
*For correspondence. (e-mail: uchaturvedi@yahoo.com)
Viral infections and trace elements: A complex
interaction
U. C. Chaturvedi*, Richa Shrivastava and R. K. Upreti
Biomembrane Division, Industrial Toxicology Research Centre, Mahatma Gandhi Marg, Lucknow 226 001, India
Several trace elements are essential micronutrients and
are required for various body functions and well being
of the immune system. The deficiencies of trace elements
and infectious diseases often coexist and exhibit complex
interactions. Several trace elements such as selenium, zinc,
copper, manganese, etc. have immunomodulatory func-
tions and thus influence the susceptibility to the course
and the outcome of a variety of viral infections. Some
trace elements inhibit virus replication in the host cells,
thus showing antiviral activity. Many trace elements
act as antioxidants or help such functions that not only
regulate immune responses of the host, but also may alter
the genome of the viruses. The grave consequences of
this may be the emergence of new infections. The trace
elements, viruses and immune system interactions
have been briefly reviewed in this article to highlight
the importance of trace element nutrition of host in not
only optimizing immune response to infections, but also
in preventing viral mutations which could increase vi-
ral pathogenicity.
VIRUSES are the smallest infectious agents consisting of a
single nucleic acid (RNA or DNA) encased in a protein shell,
which may be covered with a lipid-containing membrane.
More than 300 viruses are known to be pathogenic in humans
and animals producing a variety of syndromes. Viruses are
still the most common agents of all human ailments. In a
large majority of the cases, viral infections are not apparent
or subclinical; only in some of them is a clinical disease
produced. Clinical illness following a virus infection depends
upon factors both in the virus and the host. The most impor-
tant factor in a virus is genomic alterations. The factors in
the host mostly depend upon the nutritional status and the
optimum functioning of the immune system. The life cycle
of a virus starts with its entry into a host; it reaches the susce-
ptible target cell, enters it, replicates and causes cell injury,
and may be cell death. At any of these steps the life cycle
of the virus can be aborted by various body mechanisms,
mainly by the immune response1.
Malnutrition has long been associated with increased
susceptibility to infectious diseases. The increase in seve-
rity of infectious diseases and susceptibility in malnouri-
shed hosts is thought to be the result of an impaired immune
response. For example, malnutrition could influence the
immune response by inducing a less effective ability to
manage the challenge of an infectious disease. It has been
demonstrated that not only is the host affected by the nutri-
tional deficiency, but also the invading pathogen2. Nutri-
tional deficiency could be of major food components or trace
elements. The minerals that are important for body func-
tions are divided into two groupsmacro elements and trace
elements. The trace elements comprise of metals in biologi-
cal fluids at concentrations less than 1 µg/g wet weight.
They combine with vitamins, form enzymes and are neces-
sary for almost every physiological process. Even if one
mineral is lacking, the body cannot function properly. Most
of the trace metals are essential nutrients for humans and
animals and include selenium, zinc, copper, cobalt, man-
ganese, molybdenum, chromium, nickel and iron. Trace
elements are found in a broad range of plant and animal
foods, as well as in drinking water. The functions of trace
elements are determined by their charges, mobilities and
binding constants to biological ligands. Some of them are
used as charge carriers to conduct electric impulses along
nerves, etc. while others form moderately stable complexes
with enzymes, nucleic acids and other ligands. They act as
triggers/activators controlling biological functions. Another
group of trace elements form strong static complexes and
become the integral part of proteins and enzymes. Several
biological systems depend upon dietary micronutrients
(e.g. copper, zinc and manganese superoxide dismutase).
Oxidative stress may be an important factor in infection if
micronutrients are deficient3. Some of the features of trace
elements discussed here have been summarized in Table 1.
Trace elements and some of their compounds show anti-
viral activity by combining with cellular proteins and inacti-
vating them. On the other hand, some trace elements enhance
severity of various viral infections. Thus, trace elements
may play an important role in diseases caused by viruses.
This article gives an overview of the role of trace elements
(micronutrients) on viral infections. Iron has not been inclu-
ded in the present discussion because a number of reviews
have appeared recently on this topic4–7.
Effect of trace elements on immune system
The immune system contributes to the maintenance of physio-
logical integrity of the body mainly by eliminating foreign
material and infectious microbes. This is mediated through
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1537
Table 1. Function of trace metals and effect of their deficiency in humans157
Enzyme and protein
Trace metal Biochemical function Class Example Effect of deficiency
Selenium Antioxidant Oxidoreductases, transferases Glutathione peroxidase Cardiomyopathy, striated
muscle degeneration
Zinc Nucleic acid and protein Transferases, hydrolases, RNA polymerases, alcohol Growth retardation, alopecia,
synthesis and degradation, lyases, isomerases, ligases, dehydrogenases, glucocorticoid dermatitis, immunologic
alcohol metabolism oxidoreductases, transcription receptor dysfunction, gonadal
factor atrophy, impaired
spermatogenesis, congenital
malformations
Copper Haemoglobin synthesis, Oxidoreductases Superoxide dismutase, Anaemia, growth retardation,
connective tissue metabolism, ferroxidase ceruloplasmin defective keratinization and
bone development pigmentation of hair,
hypothermia, scurvy-like
changes in skeleton
Cobalt Methionine metabolism Transferases Haemocysteine methyl- Anaemia (B12) deficiency
transferases
Manganese Oxidative phosphorylation, Oxidoreductases, hydrolases, Diamine oxidase, pyruvate Bleeding disorder (increased
fatty acid, mucopolysaccharide ligases carboxylase prothrombin time)
and cholesterol metabolism
Molybdenum Xanthine metabolism Oxidoreductases Xanthine oxidase ?Oesophageal cancer
Chromium Binding of insulin to cells, ? ? Impairment of glucose
glucose metabolism tolerance
Nickel ?Stabilizing RNA structure Oxidoreductases, hydrolases Urease ?
?, Not known.
nonspecific or specific acquired immunity, which is a com-
plicated process involving coordinated efforts of several
types of cells and their secretory products; for example,
various antigen presenting cells, including macrophages
and T- and B-lymphocytes. Macrophages are among the
cells of first line of defence due to their phagocytic, cyto-
toxic and secretory activities. Any foreign material that enters
the body is phagocytosed and digested by macrophages. In
this process the macrophage may also be damaged, thereby
affecting its functions.
Micronutrients such as zinc, selenium, iron, copper, etc.
can influence several components of innate immunity. Select
micronutrients play an important role in alteration of oxi-
dant-mediated tissue injury, and phagocytic cells produce
reactive oxidants as part of the defence against infectious
agents. Adequate micronutrients are required to prevent
damage of cells participating in innate immunity. Defici-
encies in zinc may reduce natural killer cell function, whereas
supplemental zinc may enhance their activity. The specific
effects of micronutrients on neutrophil functions are not clear8.
T- and B-lymphocytes are the effector cells of the im-
mune system. B-lymphocytes produce specific antibodies
in response to antigen, while T-lymphocytes help B-cells
in antibody production besides mediating the cellular
immune response. Cytokines are soluble glycoproteins relea-
sed by cells of the immune system, which act non-enzy-
matically through specific receptors to regulate immune
responses. They include a vast array of relatively low mole-
cular weight, pharmacologically active proteins that are
secreted by one cell for the purpose of altering either its
own functions (autocrine effect) or those of adjacent cells
(paracrine effect). Cytokines resemble hormones in that
they act at low concentrations, bound with high affinity to
a specific receptor. Cytokine secretion profiles correlate
well with the distinctive functions of helper T (Th)1 and
Th2 cells, which are the major subsets of fully differenti-
ated CD4+ Th cells. Th1 cells secrete interferon-gamma
(IFN-γ), interleukin (IL)-2 and tumour necrosis factor-
beta (TNF-β) and are responsible for cell-mediated infla-
mmatory reactions, delayed-type hypersensitivity and tissue
injury in infections and autoimmune diseases. Th2 cells
secrete IL-4, IL-5, IL-6, IL-10 and IL-13 and are associ-
ated with B-cell antibody production. Cross-regulation of
the two clones is mediated by IL-10 and IFN-γ. Further-
more, TNF-α and IL-10 form an autoregulatory loop, in
which TNF-α is an inducer of IL-10, and IL-10 is a down-
regulator of TNF-α. Infections9–13 eliciting a dominant humo-
ral immune response induce a higher expression of Th2-
related cytokines and are associated with low levels of
IFN-γ and IL-2, whereas those characterized by delayed-
type hypersensitivity response show a higher expression
of Th1 cytokines IFN-γ and IL-2 and low levels of IL-4.
In a number of viral infections such as human immunode-
ficiency virus (HIV), herpes simplex, dengue and influ-
enza viruses, a Th1-type response is linked to recovery from
infection, while a Th2-type response tends to lead to severe
pathology and exacerbation of the disease11,14–16. Animal
viruses have evolved strategies to survive in harmony with
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the host in which they replicate. Viruses have the ability to
subvert or impair the immune response to varying degrees.
Impairment of immune system often results in increased
susceptibility towards pathogenic virus.
There are a large numbers of biologically active com-
pounds which may have direct, primary or secondary effect
on the immune system. The effect of chemicals, including
drugs, pesticides, hydrocarbons, heavy and trace elements
and many other organic and inorganic substances on the
human immune system is of interest to pathologists, immuno-
logists and toxicologists.
Various trace elements are responsible for many bio-
chemical, immunological and physiological essential acti-
vities of the body as micronutrients. Nutrient status is an
important factor contributing to immune competence. Under-
nutrition impairs the immune system, suppressing immune
functions that are fundamental to host protection. Under-
nutrition can be due to insufficient intake of energy and
macronutrients and/or due to deficiencies in specific micro-
nutrients. Often these occur in combination. Trace elements
that have been demonstrated to be required for the immune
system to function efficiently include zinc, copper, iron and
selenium. Animal and human studies have demonstrated
that adding the deficient nutrient back to the diet can re-
store immune function and resistance to infection. Among
the trace elements studied the most in this regard are zinc and
selenium. Increasing intake of some nutrients above habi-
tual and recommended levels can enhance some aspects
of the immune function. However, excess amounts of some
nutrients also impair the immune function. A summary of
the effects of the deficiency of various trace elements on
the functions of different components of the immune system
is presented in Table 2.
Effect of trace elements as antioxidants on virus
infections
Free oxygen radicals may protect against virus attack and
can produce tissue damage during this protection by trig-
gering inflammation17. Free radicals interact with neigh-
bouring entities and can damage molecules, cells, tissues,
DNA and finally the entire organs. The body has evolved
mechanisms for neutralizing free radicals, including en-
zymes like superoxide dismutase, catalase and glutathione
peroxidase. Oxidative stress is implicated in the patho-
genesis of atherosclerosis, and of viral infections caused
by Sendai virus, influenza and HIV. Infection with
cytomegalovirus (CMV) causes generation of intracellular
reactive oxygen species, which activate NF-kappa B, a
cellular transcription factor. NF-kappa B mediates expres-
sion of the CMV promoter and of genes involved in the
immune and inflammatory responses. Antioxidants and
aspirin inhibit intracellular reactive oxygen species, NF-
kappa B and CMV18. Speir et al.19 reported that in the
case of CMV, free radicals induce a viral promoter gene as
well as turning on transcription of immediate-early and
late proteins, and a number of virions. Antioxidant viral
defence mechanisms become overwhelmed in chronic viral
diseases. Virtually every known antioxidant, including
glutathione and its precursor cysteine, is depleted by viral
infection. The effects of deficient antioxidant status are
Table 2. Effect of deficiency of trace metals on the immune system
Components immune system
Killing of NK cells
bacteria by non-specific Macrophage T- B- Humoral Cell-mediated
Trace metal neutrophils immunity phagocytosis lymphocyte lymphocyte Cytokine response response
Selenium46,47 Suppressed Suppressed Suppressed CD8- and CD2- Suppressed Reduced Suppressed Suppressed
T cell decreased leucocyte migra-
tion inhibitory
factor
Zinc66,74–78 Suppressed NK cell activity Suppressed No effect on mito- Suppressed IL-1, -6, -2R and Abnormal Suppressed
decreased gen stimulation INF-ã decreased proportion of
Ig, or no effect
Copper114–117 ? Suppressed Suppressed Suppressed TNF, IFN Suppressed No effect
decreased
Cobalt Suppressed Suppressed Suppressed ? ? ? ? ?
Manganese158,159 ? NK cell activity Suppressed
decreased.
Molybdenum* ? ? ? ? ? ? ? ?
Chromium13 Suppressed Suppressed Suppressed Suppressed Suppressed Suppressed Suppressed
or or or or or or or
stimulated stimulated stimulated stimulated stimulated stimulated stimulated
Nickel158 ? NK cell activity Suppressed No change No change ? ? ?
decreased
?, Not known; *Effects described are via creating deficiency of copper by molybdenum supplements.
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1539
visible at the cellular level. Products of lipid peroxidation
can be toxic. When membranes are degraded, these toxins
are released into the body. Glutathione affects at least
four fundamental processes: liver detoxification, lympho-
cyte activation, viral transactivation and mitochondrial func-
tion. Patients with chronic hepatitis C have significant
glutathione deficiency. Clinical and in vitro studies
strongly support the use of antioxidants in persistent viral
infection. Currently, the most important antioxidant that
needs to be restored and maintained in AIDS patients is
glutathione. It is possible that the basic mechanisms of
oxidant/antioxidant viral activation/deactivation apply to
other viruses also. The trace elements copper, manganese,
selenium and zinc act as cofactors of antioxidant enzymes
to protect the body from oxygen free radicals that are
produced during oxidative stress. It is necessary to main-
tain a balance between the harmful pro-oxidant compo-
nents produced and the antioxidant compounds that
counter these effects20–22. A delicate balance also exists
for the redox trace elements such as copper, which can
initiate free radical reactions but is also a cofactor of cop-
per/zinc-superoxide dismutase, a free radical scavenging
enzyme. Metal chelators, such as ceruloplasmin play an im-
portant role to contain the reactive copper ion. Selenium is
most severely deficient in traumatized patients who need
adequate supplementation during parenteral micronutrition to
assist the free radical scavenging activity of glutathione
peroxidase and the immune system. Mice deficient in se-
lenium are more susceptible to infection with coxsackievi-
rus, as well as with influenza virus. By linking HCV
replication and pathogenesis to the selenium status and
dietary oxidant/antioxidant balance of the host, the existence
of a viral glutathione peroxidase (GPx) gene could help ex-
plain why HCV disease progression is accelerated by
oxidant stresses such as alcoholism and iron overload23.
GPx is a prototypical eukaryotic selenoprotein, with the
rare amino acid selenocysteine (Sec) at the enzyme active site,
encoded by the UGA codon in RNA. Selenium-dependent
GPx modules are encoded in a number of RNA viruses,
including HIV-1, HIV-2, HCV, coxsackievirus B3 (B3V),
and measles virus. Analysis of the sequences of multiple viral
isolates reveals conservation of the putative GPx-related
features, at least within viral subtypes or genotypes, sup-
porting the hypothesis that these are functional GPx
modules24.
The immune system is altered in selenium-deficient
animals, as is the viral pathogen itself. Sequencing of viral
isolates recovered from selenium-deficient mice demonstrates
mutations in the viral genome of both coxsackievirus and
influenza virus. These changes in the viral genome are
associated with increased pathogenesis of the virus. The
antioxidant selenoenzyme, glutathione peroxidase-1, is found
to be critically important, as glutathione peroxidase knock-
out mice develop myocarditis, similar to the Se-deficient
mice, when infected with the benign strain of myocarditis25.
Abundant evidence demonstrates the antioxidant role of zinc.
Two antioxidant mechanisms have been proposed for zinc:
zinc ions may replace redox active molecules, such as iron
and copper at critical sites in cell membranes and proteins;
alternatively, zinc ions may induce the synthesis of meta-
llothionein, sulfhydryl-rich proteins that protect against
free radicals26. Selenium and copper concentrations in eryth-
rocytes can improve the trace element dependent antioxi-
dative status20. Some unknown interactions between the
essential micronutrients zinc and selenium on the one hand
and zinc and redox metabolism on the other are key fea-
tures of the cellular homeostatic zinc system22.
Interaction of trace elements with virion
Trace elements bind to the proteins that serve essential
functions in a virion. The NS3 region of the hepatitis C
virus encodes for a serine protease activity, which is nec-
essary for processing of the nonstructural region of the
viral polyprotein. The minimal domain with proteolytic
activity resides in the N-terminus, where a structural tet-
radentate zinc-binding site is located. The ligands have been
identified by X-ray crystallography as three cysteines
(Cys97, Cys99, and Cys145) and one histidine residue
(His149), which are postulated to coordinate the metal
through a water molecule. Evidence for rearrangements of
the metal coordination geometry induced by complex
formation with an NS4A peptide cofactor have been repor-
ted27. A unique structural feature of the HCV NS3 protein
N-terminal domain has been reported to be the presence
of a zinc-binding site exposed on the surface, subject to a
slow conformational exchange process28,29. A survey of iso-
steric replacements of the phosphonoalanine side chain
coupled with a process of conformational constraint of a
bisbenzimidazole-based, Zn (2+)-dependent inhibitor of HCV
NS3 serine protease results in the identification of novel
series of active compounds with extended side chains.
However, Zn (2+)-dependent HCV NS3 inhibition is relati-
vely insensitive to structural variations, but dependent on
the presence of negatively charged functionality. This result
is interpreted in the context of an initial electrostatic in-
teraction between protease and inhibitor that is subse-
quently consolidated by Zn (2+), with binding facilitated
by the featureless active site and proximal regions of the
HCV NS3 protein30. The matrix protein M1 of influenza
virus has a peptide linker (M1Lnk). The pH-dependent con-
formational transition of M1Lnk strongly suggests that the
inter domain linker region of M1 also undergoes a pH-
dependent unfoldingrefolding transition in the presence
of Zn(2+). A small but significant portion of the M1 protein
is bound to Zn(2+) in the virion, and the Zn(2+)-bound
M1 molecule may play a special role in virus uncoating
by changing the disposition of the N- and C-terminal do-
mains upon acidification of the virion interior31.
Zinc binds to several other viruses, for example, Ebola and
human papillomavirus type 16. VP30 is an essential acti-
vator of Ebola virus transcription. A conspicuous structural
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feature of VP30 is an unconventional zinc-binding Cys
(3)-His motif that stoichiometrically binds zinc ions in a
one-to-one relationship. Substitution of the conserved cys-
teines and histidine within the motif leads to a complete
loss of the capacity for zinc binding32. The E6 protein of
human papillomavirus 16 has two putative zinc ion binding
sites crucial for its function. Degenkolbe et al.33 reported
that a specific chelating agent, which functionally mimics
a metallochaperone, stabilized the soluble monomeric
form of E6 and inhibited multimerization in vitro. They
have proposed that chelating agents of appropriate strength
could assist zinc delivery to recombinant metalloproteins
in vitro and may even destabilize existing agglomerates.
Specific zinc-finger architecture is required for the nucleic
acid chaperone function of HIV-1 nucleocapsid protein34,
while Wu35 has reported that ZAS: C2H2 zinc finger pro-
teins are involved in growth and development. Studies by
Bergstrom et al.36 have shown that polysulfonates derived
from metal thiolate complexes are inhibitors of HIV-1 and
various other enveloped viruses in vitro. HIV-1 nucleo-
capsid Zn (2+) fingers are required for efficient reverse
transcription, initial integration processes and protection
of newly synthesized viral DNA37. HIV-1 Tat protein direc-
tly activates neuronal N-methyl-D-aspartate receptors at an
allosteric zinc-sensitive site38. McGrath et al.39 have repor-
ted that human cellular nucleic acid-binding protein Zn2+
fingers support replication of HIV-1 when they are substi-
tuted in the nucleocapsid protein. Lee et al.40 have descri-
bed zinc-finger-dependent HIV-1 nucleocapsid proteinTAR
RNA interactions.
GPx is the prototypical eukaryotic selenoprotein, with the
rare amino acid selenocysteine at the enzyme active site,
encoded by the UGA codon in RNA. Molluscum contagio-
sum, a DNA virus, has been shown to encode a functional
selenium-dependent GPx enzyme. Using modifications of
conventional sequence database searching techniques to
locate potential viral GPx modules, combined with structu-
rally guided comparative sequence analysis provides com-
pelling evidence that selenium-dependent GPx modules
are encoded in a number of RNA viruses, including poten-
tially serious human pathogens like HIV-1, HIV-2, HCV,
CB3V and measles virus. Analysis of the sequences of multi-
ple viral isolates reveals conservation of the putative
GPx-related features, at least within viral subtypes or geno-
types, indicating that these may be functional GPx modu-
les23. By linking HCV replication and pathogenesis to the
selenium status and dietary oxidant/antioxidant balance
of the host, the existence of a viral GPx gene could help
explain why HCV disease progression is accelerated by
oxidant stresses such as alcoholism and iron overload24.
Effect of trace elements on virus infections
During most viral infections the plasma levels of trace
elements change, but it is not clear if this reflects changes
in the infected tissues also. Influence of trace elements have
been studied in a large number of viruses belonging to dif-
ferent groups. Table 3 presents a list of viruses that have
been studied with each trace element. The trace elements
that have predominantly toxic effects on the body have
been excluded from the present discussion.
Effect of selenium
Selenium is a trace element which is also essential for nor-
mal functioning of the immune system. Plant foods are the
major dietary sources of selenium and also some meats
and seafood. The amount of selenium in the soil determines
its amount in the plant foods that are grown in that soil
and the animals that feed on those grains or plants. Soils in
some parts of the US have very high levels of selenium,
while very low amounts are seen in some parts of China
and Russia41–44. Selenium deficiency is linked to Keshan
disease, which is associated with an enlarged heart and
poor heart function45.
Selenium is an essential component of selenocysteine-
containing protein. It is involved in most aspects of cell
biochemistry and function and influences the immune sys-
tem. It is an important part of antioxidant enzymes that
protect cells against the effects of free radicals, which are
produced during normal oxygen metabolism. The antioxidant
GPx protects neutrophils from oxygen-derived radicals that
are produced to kill ingested foreign organisms46. As a
constituent of selenoproteins, selenium is required for the
functioning of neutrophils, macrophages, NK cells and T-
lymphocytes. Selenium has also been associated with re-
duced apoptosis in animal models46. In addition, adequate
selenium may enhance resistance to infections through
modulation of interleukin production and subsequently
the Th1/Th2 response. Selenium supplementation up-regu-
lates IL-2 and increases activation, proliferation, differen-
tiation, and apoptosis of T helper cells. Elevated selenium
intake may reduce cancer risk and may alleviate other
pathological conditions, including oxidative stress and in-
flammation. Selenium appears to be a key nutrient in
counteracting the development of virulence and inhibition
of HIV progression to AIDS. It is required for sperm mo-
tility and may reduce the risk of miscarriage. Selenium
deficiency has been linked to adverse mood states and
some findings suggest that selenium deficiency may be a
risk factor in cardiovascular diseases47.
Effect of selenium on coxsackie B virus infection: The
classical example of relationships between nutrition and
viral infection is juvenile cardiomyopathy known as Ke-
shan disease. It has been shown that selenium-deficient
mice develop myocarditis when infected with a normally
benign strain of coxsackievirus. Thus, a non-myocarditic
strain of Coxsackie B virus (CBV) is converted to viru-
lence when inoculated into selenium-deficient mice2,25.
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Table 3. Studies on the effect of trace metals on different virus infections
Trace metal*
Virus Selenium Zinc Copper Cobalt Manganese Molybdenum Chromium Nickel
Adeno 134, 135
AMV 113
CoxBV 2, 25, 4852 49, 106 106 154, 155
EBV 139
EMV 126, 127 138
ECHO 63
Ebola 32
HAV 88, 89 64
HBV 64 64, 73, 9093 64 128 138
HCV 64 23, 24, 2730, 64,
9497 117–119
HIV 5762 23, 3440, 120 144
76, 78, 98105
HPV 30
HSV 50, 63 122125 140 144, 145
HSV Bovine 114, 115 114 151
Influenza 2, 25, 5356 145
IBRV 116 118 152, 153
IPNV 107
JEV 132, 133
MCMV 156
Measles 129
Polio 63 108 118 108, 130, 131
Pox 50 136 145
Rhino V 8187
SFV 121 138
Sindbis 109111
Sandfly fever 150
VEE 138
WN 118
*Reference number; AMV; Avian myeloblastosis virus; IBRV, Infectious bovine rhinotrachietis virus; CoxBV, Coxsackie B virus; IPNV,
Infectious pancreatic necrosis virus; HPV, Human papilloma virus.
This conversion is accompanied by changes in the genetic
structure of the virus so that its genome closely resembles
that of other known virulent CBV strains. Similar altera-
tions in virulence and genomic composition of CBV could
be observed in mice fed with normal diet, but genetically
deprived (knockout mice) of the antioxidant selenoenzyme
GPx2,25,48. Ilback et al.49 have reported that concentrations
of a number of trace elements in the serum and pancreas
change preceding the development of pancreatitis during
the early phase of CBV infection in female Balb/c mice.
Cermelli et al.50 studied the antiviral effects of selenium
compounds on coxsackievirus B5 replication. The inhibi-
tory activity of selenite on viral replication is due to its toxi-
city following its interaction with thiols. Zinc is another
inhibitor of selenite toxicity, which also counteracts the
antiviral effect of selenite. A direct inhibitory effect of
selenite on coxsackievirus replication may explain the effi-
cacy demonstrated by this compound in the prophylaxis
of Keshan disease. Mercury, a selenium antagonist is known
to aggravate CBV virus infection51.
Beck and Matthews52 have reported that infection with
myocarditic strains of CBV induces an inflammatory res-
ponse in the cardiac tissue. Heart damage is induced by
immune response and not by the direct viral effects on the
heart tissue. Chemokines are secreted during an infection
in order to attract immune cells to the site of injury, and
have been found to be important for the development of
CBV-induced myocarditis. Further, a deficiency in sele-
nium influences the expression of mRNA for the chemokine,
monocyte chemo-attractant protein-1, which may have
implications for the development of myocarditis in the se-
lenium-deficient host. Expression of mRNA for IFN-γ is
also greatly decreased in selenium-deficient animals52.
Thus, a deficiency in selenium can have profound effects
on the host as well as on the virus itself. How the alteration
of immune response of selenium-deficient animals affects the
development of the virulent genotype remains to be ans-
wered.
Effect of selenium on influenza virus infection: Seleno-
cystamine inhibits influenza virus-associated RNA tran-
scriptase, thus inhibiting the virus replication in eggs even
when added up to 4 h after virus infection53,54. It was sugge-
sted to be due to chelation of zinc by selenocystamine. Se-
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1542
lenium-deficient mice develop severe pneumonitis when
infected with a mild strain of influenza virus A/Bangkok/
1/79. The increased virulence observed in the selenium-
deficient mice is due to mutations in the influenza virus
genome, resulting in a more virulent genotype. The muta-
tions occur mostly in the gene for the M1 matrix protein,
an internal protein that is thought to be relatively stable.
A total of 29 nucleotide changes are observed in this gene,
and all 29 changes are identical in three separate isolates
taken from three different selenium-deficient mice. In con-
trast, only one to three mutations are seen in the genes for the
haemagglutinin or neuraminidase proteins, surface anti-
gens that are known to be highly variable. Once the muta-
tions have occurred, even hosts with normal nutritional
status are susceptible to the newly virulent strain55. The
immune system is altered in selenium-deficient animals,
as is the viral pathogen itself. These changes in the viral
genome are associated with the increased pathogenesis of
the virus2,47,56.
Effect of selenium on HIV infection: HIV/AIDS-related
malabsorption can deplete levels of many nutrients. Sele-
nium deficiency is commonly associated with HIV/AIDS,
and has been associated with a high risk of death from
this disease and faster disease progression57–59. Selenium
also may be needed for the replication of the HIV virus,
which could deplete host levels of selenium58.
Selenium supplementation may down-regulate the ab-
normally high levels of IL-8 and TNF-α observed in HIV
disease, which has been associated with neurological dam-
age, Kaposi’s sarcoma, wasting syndrome, and increased
viral replication60. Taken together, these findings suggest a
new mechanism through which selenium may affect HIV-1
disease progression. If one considers all nutrient factors that
are associated with survival, only selenium deficiency is a
significant predictor of mortality. The profound effect of
selenium on disease progression may reflect its action in
antioxidant defence systems as well as gene regulation60,61.
In combination with known cellular mechanisms involving
selenium, viral selenoproteins may represent a unique mecha-
nism by which HIV-1 monitors and exploits an essential
micronutrient to optimize its replication relative to the host.
It is likely that several of the biological effects of sele-
nium are linked with selenoprotein activity. Effects of the
anti-oxidant selenoprotein GPx on the inhibition of HIV
activation have been well documented. Hence, increased
expression of this enzyme can stimulate viral replication
and subsequent appearance of cytopathic effects associ-
ated with an acutely spreading HIV infection. The effects
of GPx on both phases of the viral life cycle are likely to
be mediated via its influence on signalling molecules that
use reactive oxygen species. Similarly, selenium can alter
mutagenesis rates in both viral genomes62. A comparison
between the effects of selenium and selenoproteins on viral
infections may yield new insights into the mechanisms of
action of this element.
Effect of selenium on herpes simplex virus infection:
Heart damage caused by herpes simplex virus (HSV-1) is
significantly milder in selenium-deficient than in selenium-
adequate mice. Therefore, the selenium status of the murine
host selectively influences the degree of viral-induced
myocarditic lesions63. Selenium compounds show only
limited activity against HSV-1 and vaccinia virus50. This
shows that selenium deficiency does not affect all viral
infections to the same extent.
Effect of selenium on hepatitis virus infection: Kalkan
et al.64 have studied serum trace elements, including sele-
nium in sera of patients with viral hepatitis (A, B, C, D,
E) cases, and statistically compared with the controls. A
significant decrease in selenium levels has been suggested
in patients with HCV infection due to the defence strate-
gies of organisms probably induced by substances like retinol
or various carotenoids.
Effect of zinc
Zinc is found in a wide variety of foods including beans, nuts,
certain seafoods, whole grains and dairy products. Oysters
contain more zinc than any other food, but red meat and
poultry provide a major part. Zinc is an essential mineral
that is found in almost every cell. It stimulates the activity
of approximately 100 enzymes65,66. Zinc supports a healthy
immune system and is needed for wound healing, the sense
of taste and smell, and for DNA synthesis66–69.
Zinc deficiency most often occurs when zinc intake is
inadequate or poorly absorbed, due to increased losses of
zinc from the body, or when the body’s requirement for
zinc increases70–72. Signs of zinc deficiency include growth
retardation, hair loss, diarrhoea, delayed sexual maturation
and impotence, eye and skin lesions, and loss of appetite.
Zinc mostly remains intracellular and participates in
many physiological mechanisms. Liver functions like urea
formation require the presence of zinc73. Adequate zinc
status is essential for T-cell division, maturation and diffe-
rentiation, lymphocyte response to mitogens, programmed
cell death of lymphoid and myeloid origins, gene tran-
scription and biomembrane functions66,74. The immune sys-
tem is adversely affected by even moderate degrees of zinc
deficiency. Severe zinc deficiency depresses immune func-
tion75. Primary and secondary antibody responses are redu-
ced in zinc deficiency and generation of splenic cytotoxic
T-cells is reduced after immunization76.
When zinc supplements are given to individuals with low
zinc levels, the number of T-cell lymphocytes circulating
in the blood increases and the ability of lymphocytes to
fight infection improves. However, high dosages of zinc
evoke negative effects on immune cells and cause altera-
tions similar to those observed with zinc deficiency. Fur-
thermore, when peripheral blood mononuclear cells are
incubated with zinc in vitro, the release of cytokines such
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1543
as IL-1 and -6, TNF-α, soluble IL-2-receptor (IL-2R) and
IFN-γ is induced.77. Zinc deficiency can change immune
functions from predominantly Th1 responses to Th2 res-
ponse and adversely influence the course of several dis-
eases, including AIDS78. Zinc is the structural component
of a wide variety of proteins, neuropeptides, hormone rece-
ptors and polynucleotides. Among the best known zinc-
dependent enzymes and hormones are copperzinc-super-
oxide dismutase, an enzyme component of the antioxidant
defence system and thymulin, which is essential for the
formation of T-lymphocytes. Thymulin is a hormone which
is produced by the epithelial cells of thymus. Zinc also
inhibits the production of TNF, which is implicated in the
pathophysiology of cachexia and wasting in AIDS76.
Zinc in metalloproteins, particularly viral (v) and cellu-
lar (c) zinc finger proteins (ZFP) plays a crucial role in cell
proliferation, neovascularization, apoptosis and viral infec-
tion. Zinc acts as a key agent in controlling viral and proli-
ferative diseases. It is known that zinc deficiency, resulting
from exposure of culture cells to membrane-permeable Zn2+
chelators can induce apoptosis in virally transformed cells,
while normal cells remain unaffected under these condi-
tions. Apoptosis is possibly due to simultaneous inactiva-
tion of vZFP and cZFP, which are essential for maintenance
of cellular and viral structure and which are activated in
virally transformed cells. Zinc metalloproteins may be useful
to prevent transmission of viral diseases79. Natural resis-
tance-associated macrophage protein 1 (Nramp1) is a pro-
ton/divalent cation antiporter exclusively expressed in
monocyte/macrophage cells with a unique role in innate
resistance to intraphagosomal pathogens. In humans, it is
linked to several infectious diseases, including HIV. Al-
ter-Koltunoff et al.80 have demonstrated that the restricted
expression of Nramp1 is mediated by the macrophage
specific transcription factor and have identified Myc inter-
acting zinc finger protein 1 (Miz-1) as a new interacting
partner.
Effect of zinc on rhinovirus infection: In absence of effec-
tive treatment for common cold, zinc has been used in its
prevention or treatment. However, the effect of zinc treat-
ment on the severity or duration of cold symptoms is deba-
table. A study of over 100 human subjects indicated that
zinc lozenges decreased the duration of colds by one-half,
although no differences were seen in the duration of fevers
or the level of muscle aches81. In another study of 213 pa-
tients with recent onset of cold symptoms, 108 patients
received zinc therapy and 105 received placebos. It was
shown that zinc taken as nasal gel within 24 h of the onset
of cold is effective in shortening the duration of symptoms
of common cold82. The study by Novick et al.83 showed
that free ionic zinc (Zn+2) in saliva shortens the duration
and severity of common cold symptoms. It has been pro-
posed that Zn+2 complexes with proteins of critical nerve
endings and surface proteins of human rhinovirus (HRV)
and interrupts nerve impulse and blocks docking of HRV
on intracellular adhesion molecule-1 (ICAM-1) on the
somatic cells and thereby interrupts HRV infection. Since
leukocyte function associated antigen-1 (LFA-1) binds
leukocyte to cells through ICAM-1 initiating inflamma-
tion, Zn+2 is expected to block LFA-1/ICAM-1 binding
and thereby suppress inflammation83. Zinc ions may be
an important anti-inflammatory factor because they can
block the docking of both HRV and LFA-1 with ICAM-1.
On the other hand several studies have shows that zinc
has no effect on common cold. The study by Takkauche
et al.84 suggested that the intake of zinc is not related to
the occurrence of common cold in the population. Simi-
larly, Marshall85 also suggested that treatment with zinc
lozenges did not reduce the duration of cold symptoms.
Another study examined the effect of zinc supplements on
cold duration and severity in over 400 randomized sub-
jects. In their first group, a rhinovirus was used to induce
cold symptoms. The duration of illness was significantly
lower in the group receiving zinc gluconate lozenges, but
not in the group receiving zinc acetate lozenges. None of the
zinc preparations affected the severity of cold symptoms
during the first three days of treatment. In the second
study, which examined the effect of zinc supplements on
duration and severity of natural colds, no differences were
seen between individuals receiving zinc and those receiving
a placebo (sugar pill). It suggests that the effect of zinc
may be influenced by the ability of the specific supple-
ment formula to deliver zinc ions to the oral mucosa86.
Turner87 evaluated the effectiveness of intranasal zinc
gluconate for prevention of experimental rhinovirus infec-
tion and illness, and observed that zinc has no effect on
total symptoms score, rhinorrhoea, nasal obstruction, or the
proportion of infected volunteers, who developed clinical
colds. More detailed studies are needed to determine whether
zinc compounds have any effect on common cold.
Effects of zinc on hepatitis A virus infection: In an in vitro
study it has been shown that zinc inhibits the replication
of hepatitis A virus (HAV) in BSC-1 cells88. However, stu-
dies by Bishop and Anderson89 showed that zinc had no
effect on the binding of HAV to the cultured cells.
Effects of zinc on hepatitis B virus infection: It is known
that cytotoxic T-lymphocytes are responsible for viral clea-
rance in chronic hepatitis B virus (HBV) infection. Zinc
deficiency affects development of acquired immunity by
preventing certain functions of T-lymphocytes (Table 2).
The study by Gur et al.73 suggested that zinc supplemen-
tation might improve hepatic encephalopathy by increasing
the efficiency of the urea cycle. In this study they deter-
mined the hepatic zinc concentration in patients with chronic
liver disease due to HBV and to ascertain the relationship
between the severity of liver disease and hepatic zinc con-
tent. The results indicated that as the severity of liver damage
increases, the hepatic zinc concentration decreases.
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1544
Transgenic mice that express the viral coat proteins of
HBV in the liver display hepatocellular damage, inflam-
mation, regeneration, hyperplasia and eventually neoplasia
similar to those of people with chronic, active hepatitis caused
by HBV infection. Hepatocellular regeneration, in the con-
text of chronic injury and inflammation, is thought to expose
dividing cells to excessive oxygen radicals, which is beli-
eved to lead to DNA damage and ultimately neoplasia.
Metallothioneins are known to scavenge free radicals.
Studies on mice that expresses excess metallothionein I
(MT-I mice) and the HBV surface antigens (HBsAg) have
shown that MT-I produces a beneficial effect on HBV-
induced hepatitis90.
Fota-Markowska et al.91 studied the serum zinc level
dynamics in patients with acute hepatitis B and the early
recovery periods.. They observed significantly decreased
serum zinc levels during hospitalization and that the diffe-
rences in initial and early recovery periods compared to
control groups were markedly at random. Ozbal et al.92
have reported that the mean baseline serum zinc, alanine
aminotransferase and HBVDNA values, histologic acti-
vity index, periportal necrosis and fibrosis scores are pre-
dictive of response to IFN-α2b therapy. Their studies indicate
that serum zinc levels may be used as a factor predicting
response to IFN-α2b therapy, and may help in identifying
patients with a better chance of response. These findings
are further supported by those of Selimoglu et al.93, show-
ing the relationship of serum zinc status to liver histopatho-
logy at the end of IFN therapy response. Kalkan et al.64
have also shown the decrease in zinc levels in sera of patients
with viral hepatitis (A, B, C, D, E).
Effect of zinc on hepatitis C virus infection: Nutritional
status of zinc influences the effect of IFN on hepatitis C
patients. This fact is supported by the study of Nagamine
et al.94, who observed that basal zinc levels in the serum
are significantly lower in chronic hepatitis C patients.
Administration of IFN-α to hepatitis C patients augments
serum zinc reductions up to 40% in 8 h. Serum zinc level
and zinc/copper ratio are higher in complete responders
than in non-responders to IFN therapy at each time point.
T-lymphocytes and immunoregulatory cytokines play
an important role in the host response to HCV infection.
Takagi et al.95 evaluated the synergistic effect of zinc
supplementation on the response to IFN-α therapy in pati-
ents with intractable chronic hepatitis C. They showed that
zinc supplementation enhances the response to IFN ther-
apy, being most effective in infection with genotype 1b. In
another study, Nagamine et al.96 investigated the differ-
ence between two compounds of zinc, zinc sulphate and
polaprezinc, on the effectiveness of IFN-α therapy. The
data suggest that polaprezinc increases the therapeutic res-
ponse of IFN-α. Grungreiff et al.97 determined the clini-
cal significance of the cytokines sIL-2R, IL-6, transforming
growth factor (TGF)-β1, neopterin, and of zinc in chronic
HCV infection, in the serum of 16 patients before, during
and at the end of therapy with IFN-α, and after 6 months
follow-up. The mean serum zinc concentrations were found
to be slightly decreased in all three patient groups.
Effect of zinc on HIV infection: Zinc deficiency is the most
prevalent micronutrient abnormality seen in HIV infection.
Low levels of plasma zinc predict a three-fold increase in
HIV-related mortality, whereas normalization has been asso-
ciated with significantly slower disease progression and a
decrease in the rate of opportunistic infections. Zinc defi-
ciency characterized by low plasma zinc levels over time
enhances HIV-associated disease progression, and low
dietary zinc intake is an independent predictor of mortal-
ity in HIV-infected drug users. The amount of zinc supple-
mentation in HIV infection appears to be critical, because
deficiency, as well as excessive dietary intake of zinc,
have been linked with declining CD4 cell counts and redu-
ced survival98. Further studies are needed to determine the
optimal zinc supplementation level in HIV-infected patients.
HIV replicates preferentially in Th-0 and Th-2 cells but
not in Th-1 cells, which contain more zinc78. This may be
because the zinc ion is known to inhibit intracellular HIV
replication78. Zinc is involved in the replication of the
HIV virus at a number of sites99. In HIV infection, serum
level of zinc is frequently diminished. Wellinghausen et
al.100 studied the zinc level in 79 HIV-1 seropositive patients
and found zinc deficiency in 23% of the patients associated
with a low CD4 cell count, high viral load and increased
neopterin and IgA levels. Earlier, Reich and Church101
had reported zinc deficiency in HIV-infected adults and
suggested that zinc may act as an antiviral agent. Following
oral zinc treatment, six out of 13 patients showed normal
serum zinc level and only two had increased CD4+ cell
numbers. Studies by Koch et al.102 have shown severe
zinc deficiency in 29% and borderline levels in an addi-
tional 21% of AIDS patients. Zinc levels were not associ-
ated with the length of HIV seropositivity, CD4 count
and degree of malnutrition. The mitogenic effect of zinc
on lymphocyte proliferation response has been observed in
HIV-1-positive individuals. Zinc treatment of PHA stimula-
ted peripheral blood mononuclear cell cultures has been
shown to enhance 3H-thymidine incorporation significantly
in both asymptomatic and symptomatic groups. A decrea-
sed percentage of apoptotic cells could be identified in
cell cultures from HIV-1 positive individuals submitted
to zinc treatment compared to cells treated only with
PHA103. Extracellular matrix zinc plays an important role
against the HIV infection. The zinc-bound form of thy-
mulin (active thymulin, Zn FTS) is strongly reduced in
stage IV of the disease with decrease in CD4+ cell count and
zincemia values and increase in unbound form of thymulin
(inactive, FTS). In vitro addition of zinc to plasma sample
induces a recovery of the thymulin active form, suggesting
low zinc bioavailability as the cause of impaired thymic
functions with consequent CD4+ depletion104.
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1545
The HIV-1 transcriptional regulatory protein, Tat is a pleio-
tropic factor that represses expression of the human man-
ganese-superoxide dismutase. Tat increases oxidative stress,
as shown by decreased glutathione and NADPH levels.
These changes enhance proliferation and apoptosis and alter
the activity of zinc thiolate containing proteins such as Sp-1.
The zinc chelator TPEN sensitizes HeLa-tat cells to apoptosis.
In these cells binding of the zinc-containing factor Sp1 to its
DNA sequence is higher than in parental cells. It is obser-
ved that Sp-1 DNA interaction decreases more rapidly in the
Hela-tat cells after TPEN treatment. Tat protein, via direct
or indirect mechanism, increases proliferation, sensitizes
cell to apoptosis, and changes the conformation of Sp-1,
affecting its ability to bind to its cognate DNA sequence
and to retain its zinc105.
Effect of zinc on CBV infection: Infection with human
CBV in the murine model results in viral replication and
inflammation in the pancreas and myocardium. Infected
mice develop a pronounced decrease in zinc concentration
in the serum on day 1. On day 3, concentrations of several
trace elements, including copper, zinc, manganese, etc. show
pronounced changes in both the serum and the pancreas49.
Earlier, Funseth et al.106 observed increased levels of manga-
nese, cobalt and copper and decreased levels of zinc in the
myocardium. Determination of some of these trace elements
in the plasma may be useful to indicate target tissue involve-
ment in the early pre-inflammatory stage of an infectious
disease. Some of these elements are important nutrients for
the immune system, while others may be associated with
the development of disease complications, such as cardiac
arrhythmias. But the pathogenic significance of these
changes in trace metals, preceding the development of pan-
creatitis or myocarditis is not known and warrants further
studies.
Effect of zinc on infectious pancreatic necrosis virus in-
fection: Zinc acts as an environment stressor and increa-
ses susceptibility of grouper (a fish) to infectious pancreatic
necrosis virus (IPNV) infection. ZnCl2 has been used to treat
groupers before and after virus infection. Cumulative morta-
lities in the experimental group were 96100% within 42
days. Only 515% mortality was observed in most of the
groups that were exposed to zinc or virus infection alone.
The study indicates that an IPNV with only low patho-
genicity could cause high mortality in groupers when
combined with zinc107.
Effect of zinc on polio virus infection in vitro: Marchetti
et al.108 have investigated the inhibitory activity of differ-
ent milk proteins on poliovirus infection in Vero cells.
Viral cytopathic effect was prevented by the lactoferrins in
a dose-dependent manner. Further experiments were carried
out in which lactoferrins fully saturated with ferric, manga-
nese or zinc ions were added to the cells during different
phases of viral infection. All lactoferrins were able to pre-
vent viral replication, but the strongest inhibition was
with zinc-lactoferrin which is the sole compound capable
of inhibiting a phase of infection subsequent to virus inter-
nalization into the host cells.
Effect of zinc on other viral infections: Infection of many
cultured cell types with Sindbis virus triggers apoptosis
through a commonly utilized caspase activation pathway.
The results of Lin et al.109 suggest that Sindbis virus may
activate apoptosis by reducing intracellular zinc superoxide
dismutase levels, thus defining a novel redox signalling
pathway by which viruses can trigger cell death. In an ear-
lier study, zinc ions were reported to inhibit the replication
of Sindbis virus in chicken embryo fibroblast cultures110.
Bergstrom et al.111 have shown that sodium 2-mercapto-
ethanesulfonate-Zn(II) complex has modest antiviral acti-
vity against vesicular stomatitis virus respiratory syncytial
virus, Junin virus and Tacaribe virus, but is cytotoxic.
Effect of copper
Copper is essential for a variety of biochemical processes
and is needed for certain critical enzymes to function in
the body. Copper is also involved in the functioning of the
nervous system, in maintaining the balance of other useful
metals in the body such as zinc and molybdenum, and other
body functions. The main source of copper is through diet
and is present in mineral-rich foods like vegetables, legumes,
nuts, grains, fruits and chocolate. Copper is a natural ele-
ment found in the earth’s crust and the surface water.
Groundwater that is used for drinking purposes also con-
tains copper. Certain foods and water kept for an extended
period of time in copper ware may contain copper trans-
ferred from their surface. Copper is an integral part of many
important enzymes involved in a number of vital biological
processes (Table 1). Although normally bound to proteins,
copper may be released and become free to catalyse the
formation of highly reactive hydroxyl radicals that have
capacity to initiate oxidative damage and interfere with
important cellular events. Zinc removes copper from its
binding site, where it may cause free radical formation112.
Effect of copper on avian myeloblastosis virus infection:
Cupric complexes inhibit DNA synthesis catalysed by avian
myeloblastosis virus (AMV) reverse transtriptase. The inhi-
bitory effect is seen even after initiation of polynucleotide
synthesis. Infection of the one-day-old chicks with AMV
pretreated with cupric complexes prevents symptoms of
leukaemia due to virus inactivation113.
Effect of copper on HSV infection: Arthington et al.114
have demonstrated the effect of copper deficiency on acute-
phase protein concentrations, superoxide dismutase activity,
leukocyte numbers, and lymphocyte proliferation in heifers
(young cow) inoculated with live bovine HSV-1. Their data
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1546
indicate that copper deficiency alters the acute-phase protein
response to viral infection and may affect lymphocyte res-
ponsiveness to mitogen stimulation. Studies indicate that
copper has no significant role during some of the infec-
tions. It has been suggested that hypocuparaemia and hypo-
cuprosis are not consistent features of Border disease and
thus have no aetiological significance115.
Effect of copper on infectious bovine rhinotrachitis virus
infection: Data reported by Gengelbach et al.116 indicate that
dietary levels of copper can affect body temperature and
feed intake responses of calves to intranasal inoculation
with live infectious bovine rhinotrachitis virus disease by
affecting plasma TNF and other cytokines.
Effect of copper on hepatitis virus infection: Serum con-
centration of copper plays an important role in the inter-
relation among immunoglobulins IgA, IgM and IgG in
subjects with various forms of liver diseases117. Copper
accumulation in fibrotic livers caused by chronic HCV
infection may contribute to hepatic injury. Hatano et al.118
have shown that the hepatic copper contents increased
with the progression of hepatic fibrosis and concluded that
the presence of copper may enhance HCV infection. The
study by Pramoolsinsap et al.119 on serum levels of copper in
young adult patients in the early ecteric phase of acute
HBV infection has shown significantly elevated serum
copper levels indicating alteration of copper metabolism dur-
ing the acute icteric phase of uncomplicated hepatitis. Kal-
kan et al.64 have studied serum trace elements, including
copper in sera of patients with viral hepatitis (A, B, C, D, E)
cases and the controls. They have shown elevation in copper
levels and have suggested that this probably resulted from
defence strategies of organism and induced by hormone-
like substances. The role of copper during hepatitis virus
infection needs further investigations.
Effect of copper on retrovirus infection: Role of murine
acquired immunodeficiency syndrome (MAIDS) on the
mineral status of liver, heart and muscle has been investi-
gated in C57BL/6 mice. Retrovirus infection which has
not proceeded to murine AIDS results in a significant increase
in heart Cu and Zn concentration compared with uninfected
mice. Early retrovirus infection alters tissue micronutrient
levels, and may thus contribute to immunological changes120.
Effect of copper on Semliki Forest and other viral infec-
tion: Treatment of chicken embryo fibroblast tissue cultures
with copper, nickel and cobalt salts enhances the plating
efficiency of Semliki Forest virus. This augmented plaque
formation may be due to a higher adsorption rate of virions
to the cell surface under the influence of the transition metal
ions. The plating efficiency of West Nile virus in chicken-
embryo fibroblasts and, to a lesser degree, of poliovirus type 1
and 2 in KB-cells is also enhanced by copper sulphate121.
Effect of cobalt
Cobalt is an important constituent of vitamin B12, which is
needed to maintain normal bone marrow function for pro-
ducing erythrocytes. The food sources of cobalt are meat,
dairy products and green leafy vegetables. Cobalt chelates
act as antiviral agents.
Effect of cobalt on CBV infection: CBV infection may
result in viral replication, subsequent inflammation and
changed trace element levels in the myocardium. Funseth
et al.106 studied trace element levels in the plasma and
heart of adult male A/J mice during the pre-inflammatory
stage of CBV myocarditis for cobalt, copper, manganese,
selenium, zinc, etc. In the heart, the levels decrease for cobalt
and selenium and are increased for manganese and copper.
Decreased levels of zinc were noted in the plasma,
whereas increased levels of manganese, cobalt and copper
were seen. Determination of some of these trace elements
in the plasma may be an useful indicator of target tissue
involvement in the early pre-inflammatory stage of an in-
fectious disease. Some of these elements may be associ-
ated with the development of disease complications, such
as cardiac arrhythmias106.
Effect of cobalt on HSV infection: Vellema et al.122 inve-
stigated the effect of cobalt supplementation on the im-
mune reactivity in vitamin B12-deficient lambs by compar-
ing the humoral and cell-mediated immune responses
against bovine HSV-1 and Mycobacterium paratuber-
culosis. The results demonstrated a significantly lower lym-
phoblastic response in non-supplemented lambs compared
with supplemented ones. No differences were found in total
and differential white blood cell counts, in total protein,
albumin, alpha-, beta- and gamma-globulin and in anti-
body production against bovine HSV-1.
Cobalt(III) Schiff base complexes have been shown to
inhibit the replication of ocular herpes virus123. The study by
Asbell et al.124 shows that all CTC series of cobalt chelate
complexes inhibit HSV-1 replication in vitro, CTC-96 being
best. Topical CTC-96 application is effective in diminish-
ing the symptoms of disease and corneal surface virus.
Schwartz et al.125 reported that the CTC series of cobalt che-
lates display in vitro and in vivo activity against HSV-1
and HSV-2. Furthermore, CTC-96 inhibits plaque formation
by varicella-zoster virus and vesicular stomatitis virus as
efficiently as by HSV-1. Collectively, these experiments
suggest that CTC-96 is a broad-spectrum inhibitor of infe-
ction by enveloped viruses and that it inhibits HSV-1 in-
fection at the point of membrane fusion independent of the
type of virus and cellular receptors present.
Effect of cobalt on encephalomyocarditis and other virus
infection: Cobalt sulphate given orally does not inhibit
the protective activity of New Castle disease virus against
encephalomyocarditis virus induced mortality, but excess
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1547
cobalt inhibits the protective activity of poly I/poly C
against encephalomyocarditis virus-induced mortality126.
Another study has reported cobalt deficiency in young calves
suffering from tick-borne fever virus infection127.
Effect of cobalt on hepatitis virus infection: Activity of
cobalt-activated acylase in the serum was investigated in
120 children aged between 3 months and 15 years suffer-
ing from viral hepatitis. No differences were found in the
mean values of acylase activity128.
Effect of manganese
Manganese is an antioxidant nutrient and is important in
the breakdown of amino acids and the production of energy.
It is essentially required for the metabolism of vitamin B-
1, C and E and for activation of various enzymes which
are important for proper digestion and utilization of foods.
Manganese acts as a catalyst in the breakdown of fats and
cholesterol and also helps in the nourishment of the nerves
and the brain. It is necessary for normal skeletal develop-
ment and maintains sex hormone production. The best natu-
ral sources of manganese are whole grains, cereal products,
nuts and green leafy vegetables. Dairy products, meat,
fish and poultry are poor sources. A deficiency can cause
poor reproductive performance, growth retardation, abnor-
mal formation of bone and cartilage and an impaired glucose
tolerance.
Effect of manganese on measles virus infection: Measles
virus infection of B-cells results in marked alterations in
proliferation and immunoglobulin production. The mitocho-
ndrial protein, manganese superoxide dismutase (MnSOD)
is upregulated in B-cells during measles virus infection.
Intracellular MnSOD inhibits proliferation of B-cells and
decreases the titre of virus produced from infected cells.
MnSOD may play an important role in the alteration of im-
mune function during the infection of B-cells with measles
virus129.
Effect of manganese on polio virus infection: Marchetti
et al.108 have shown that lactoferrin saturated with man-
ganese inhibits the replication of poliovirus in Vero cells.
Viral RNA-dependent RNA polymerases exhibit great
sequence diversity. Only six core amino acids are con-
served across all polymerases of positive-strand RNA viru-
ses of eukaryotes. Arnold et al.130 have analysed the divalent
cation specificity of poliovirus RNA-dependent RNA poly-
merase, 3D(pol). In the presence of Mn(2+), 3D(pol) acti-
vity is increased by greater than ten-fold relative to that in
the presence of Mg(2+). The ability of 3D(pol) to catalyse
RNA synthesis de novo is also stimulated approximately
ten-fold using Mn(2+), and the enzyme is capable of utiliz-
ing a DNA template for primer-independent RNA synthesis.
While exploring the function of conserved residues, aspara-
gine 297 in the prototypic poliovirus polymerase 3D(pol),
Crotty et al.131 have identified three viable mutants with
noncanonical amino acids at this conserved position. The
viruses exhibited Mn(2+)-dependent RNA replication and
viral growth. The finding that strictly conserved residues
in the nucleotide-binding pocket of the polymerase can be
altered in a manner that supports virus production, sug-
gests that drugs targetting this region of the enzyme will
still be susceptible to the problem of drug-resistant escape
mutants.
Effect of manganese on Japanese encephalitis virus infec-
tion: Japanese encephalitis virus (JEV) infection is commonly
associated with inflammatory reaction and neurological dis-
ease that occurs in the infected animals and humans. Reactive
oxygen species have been implicated as a critical mediator
for inflammation and disease. Liao et al.132 have investi-
gated the change in redox potential in glial cells follow-
ing JEV infection. JEV infection induces the generation
of superoxide anion and nitric oxide in rat cortical glial
cells. Manganese superoxide dismutase, but not copper/zinc
superoxide dismutase is activated by JEV infection. In
addition, the increased superoxide dismutase activity is
also apparent in acutely or persistently JEV infected con-
tinuous cell lines. These results suggest that cellular fac-
tors regulating oxidative pathway may play roles in res-
ponding to JEV infection. Uchil and Satchidanandam133
have reported that in vitro the JEV replication complex
synthesizes viral RNA utilizing a semiconservative and
asymmetric mechanism. Among divalent cations, Mg(2+)
is essential and exhibits cooperative binding for its two
replicase-binding sites. Mn(2+), despite having sixfold
higher affinity for the replicase, elicited only 70% of the
maximum Mg(2+)-dependent activity, and deficit of either
cation lead to the synthesis of incomplete RNA products.
Effect of manganese on adenovirus infection: Adeno-
virus gene therapy is a promising tool in the clinical treat-
ment of many genetic and acquired diseases. However, it also
causes pathogenic effects in organs such as the liver. The
redox-sensitive transcription factors AP-1 and NF-kappa
B have been implicated in these effects. Zhang et al.134
have studied the mechanisms of adenovirus-mediated AP-
1 and NF-kappa B activation and the possible involvement
of oxidative stress in adenovirus transduction. For this, rats
were injected with either replication-defective recombinant
adenovirus with DNA containing the cytomegalovirus pro-
moter region only (AdCMV), adenovirus containing human
MnSOD cDNA (AdMnSOD), or the vehicle. Compared
to the vehicle and AdCMV transduction, MnSOD gene
transfer yielded a fivefold increase in liver MnSOD activity
7 days postinjection. MnSOD overexpression abolishes
this activation. Glutathione/glutathione disulphide ratios
are decreased by adenovirus transduction and restored by
MnSOD overexpression. These data indicate that cellular
transduction by recombinant adenovirus stimulates AP-1
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1548
DNA binding activity. The results suggest that MnSOD over-
expression decreases AP-1 DNA binding activity by regu-
lating intracellular redox status, with the possible involvement
of Ref-1 in this redox-sensitive pathway. Overexpression of
MnSOD has been postulated as one possible mechanism of
protection from oxidative damage and free radicals. Cullen
et al.135 have reported that enforced expression of MnSOD
by adenovirus transfection in the rapid growing cell line
MIA PaCa-2 increases MnSOD immunoreactivity and
MnSOD activity and decreases growth rate.
Effect of manganese on pox virus infection: Martins and
Shuman136 have suggested that the baculovirus and pox
virus triphosphatases are a distinct lineage within the metal-
dependent RNA triphosphatase family. Synergistic activation
of the lymphoid enhancer factor (LEF)-4 triphosphatase
by manganese and magnesium suggests a two-metal mecha-
nism of gamma phosphate hydrolysis.
Effect of manganese on encephalomyocarditis, semliki
forest and Venezuelan equine encephalitis virus infection:
Seth et al.137 have investigated the impact of exposure of toxic
doses of manganese on encephalomyocarditis and Semliki
Forest virus, and Venezuelan equine encephalitis virus in-
fection. Pretreatment with a single oral dose of manganese
increased the susceptibility of mice to a sub-lethal infec-
tion of these viruses as observed by increased severity of
symptoms and mortality. An early onset of virus infection
was found in brains of manganese-treated animals.
Effect of manganese on HBV infection: Urban et al.138
investigated the metal ion preferences of HBV poly-
merase for both the protein-priming and reverse transcrip-
tion activities of this enzyme and found that reverse
transcription of HBV is dependent on magnesium, however,
protein-priming is strongly favoured by manganese ions.
Effect of manganese on EpsteinBarr virus infection:
During the course of acute EpsteinBarr virus (EBV) in-
fection, there is a rise in oxygen radical production. As a
consequence, the production of oxygen radical scavenger
MnSOD is increased. Patients with acute EBV infections
regularly develop autoantibodies against MnSOD that are
able to inhibit the enzyme activity in vitro. Two main epi-
topes p(no15) and p(no30) of MnSOD show sequence
homologies with EBV-encoded proteins. Thus, a mole-
cular mimicry causes the occurrence of cross-reactive
anti-MnSOD antibodies that are able to block the protec-
tive effects of MnSOD in a model for oxidative damage
produced by xanthine/xanthine oxidase in EAhy926 endo-
thelial cells139. Thus, these autoantibodies may contribute
in vivo to clinical symptoms by accumulation of toxic
oxygen radicals.
Effect of manganese on HSV infection: In vitro bypass of
damaged DNA by replicative DNA polymerases is usually
blocked by helix-distorting or bulky DNA lesions. Villani
et al.140 have reported that substitution of the divalent
metal ion Mg2+ with Mn2+ promotes quantitative repli-
cation of model DNA substrates containing the major cis-
platin or N-2-acetylaminofluorene adducts by the catalytic
subunit (UL30) of the replicative DNA polymerase of HSV.
The ability of Mn2+ ions to confer bypass of bulky lesions
was not observed with other replicative DNA polymerases
of the B family, such as bacteriophage T4 or delta poly-
merases. Manganese induced a conformational change in
the structure of UL30 bound to the platinated substrate.
Taken together, the latter findings suggest a mechanism
by which manganese might allow UL30 to efficiently pro-
mote translesion DNA synthesis in vitro.
Effect of molybdenum
Molybdenum is an essential nutrient needed in trace
amounts by animals and humans. Tissue content of molyb-
denum is low, with the highest concentrations in the liver,
kidney, adrenal gland and bone. Molybdenum forms oxides
and is a component of a pterin coenzyme essential for the
activity of xanthine oxidase, sulfite oxidase, and aldehyde
oxidase. These enzymes share a common ‘molybdenum
cofactor’. Food sources of molybdenum are legumes, cereals,
organ meat and leafy vegetables. The concentration of moly-
bdenum in plants is directly related to its concentration in
the soil. Hard water is an important source for some peo-
ple141–143.
Effect of molybdenum on IBRV infection: The effects of
supplementing a diet deficient in molybdenum on phago-
cytic cell function and disease resistance of calves inocula-
ted intranasally with live IBRV have shown that dietary
levels of molybdenum and copper can affect body tempera-
ture and feed intake responses to disease by affecting
TNF and other cytokines116.
Effect of molybdenum on HSV infection: Molybdenum
induces copper deficiency. Ceruloplasmin, a copper-depen-
dent acute phase protein, increases after challenge in con-
trol but not in copper-deficient heifers (young cow).
Erythrocyte SOD activity is reduced in copper-deficient
heifers. The challenge with bovine HSV-1 has no effect
on SOD activity. The lymphocyte proliferative response
to PHA stimulation is decreased in copper-deficient heif-
ers following bovine HSV-1 challenge. No difference is
detected when lymphocytes are stimulated with Concana-
valin A or pokeweed mitogens114. Therefore, it is possible
that molybdenum-induced copper deficiency can alter the
acute phase protein response to viral infection, which may
affect lymphocyte responsiveness to mitogen stimulation.
Effect of molybdenum on retrovirus infection: Inouye et
al.144 have reported that a novel heteropolyoxomolybdate
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CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1549
(PM-104) is associated with potent anti-HIV activity by
interfering with virus adsorption and/or penetration into
the cells. It also blocks the replication of HSV-1 and
HSV-2. They have suggested that the antiviral properties
of PM-104 could be attributed to the combined effect of
europium atoms and its peculiar three-dimensional anion
structure. In an interesting study, a screening for inhibi-
tors of HIV-1 among various types of isopolyoxomolyb-
dates and heteropolyoxomolybdates was carried out using
an in vitro assay system measuring the cytopathogenicity
of HIV-1 in CD4+ human MT-4 cells. It was found that a
novel heteropolyoxomolybdate (PM-104) is associated
with potent anti-HIV-1 activity. PM-104 interferes with
virus infection during early stages of adsorption and/or
penetration into the cells. In addition to the cytopathic effect
of HIV-1 on MT-4 cells, syncytium formation between
mock-infected MOLT-4 cells and MOLT-4 cells chroni-
cally infected with either HIV-1 or HIV-2 is also suppressed
by PM-104. The antiviral properties of PM-104 could be
attributed to the combined effect of europium atoms and
its peculiar three-dimensional anion structure.
Effect of molybdenum on other viral infections: Tonew
et al.145 have reported significant antiviral activity of bis
cyclopentadienyl titanium dichloride in vitro against a
number of enveloped DNA and RNA viruses, for example,
inhibition of vaccinia, herpes virus, orthomyxoviruses,
paramyxovirus and rhabdovirus. The compound bis cyclo-
pentadienyl molybdenum dichloride has no antiviral action
on vaccinia and influenza viruses. Furthermore, PM-104
also blocks the replication144 of HSV-1 and HSV-2.
Effect of chromium
Chromium is a naturally occurring metal found commonly
in the environment in trivalent (Cr III) and hexavalent (Cr
(VI) forms. Cr(VI) compounds have been declared as a potent
occupational carcinogens among workers in chrome plating,
stainless steel, and pigment industries146. On the contrary,
Cr(III) salts such as chromium polynicotinate, chromium
chloride and chromium picolinate are used as micronutri-
ents and nutritional supplements and have been demon-
strated to exhibit a significant number of health benefits
in animals and humans. Various cells of animals have the
capacity to reduce toxic Cr(VI) to non-toxic Cr(III)147.
Food sources of chromium are fruits, vegetables, vegetable
oils, whole grains, seeds, brewer’s yeast, etc. Chromium plays
an important role in glucose and cholesterol metabolism
and is thus essential to man and animals. Chromium is an
essential nutrient required by the human body to promote
the action of insulin in body tissues, so that the body can
use sugars, proteins and fats. Chromium picolinate has
been used to control blood sugar in diabetes and may re-
duce cholesterol and blood pressure levels. Chromium in-
creases insulin binding to cells, insulin receptor number
and activates insulin receptor kinase leading to increased
insulin sensitivity. It also has beneficial effect on both muscle
strength and body composition13,148,149.
Effect of chromium on sandfly fever virus infection: Acute
infection with sandfly fever virus reduces availability of
circulating chromium, which may contribute to the altered
glucose metabolism characteristic of acute infection even
in the presence of elevated insulin levels and other hormonal
changes150.
Effect of chromium HSV infection: Arthington et al.151
have observed that chromium-supplementation does not alter
stress responses of calves experimentally inoculated with
bovine HSV-1. Rectal temperatures are elevated but are not
affected by chromium treatment. Secretion of ACTH,
cortisol or plasma TNF-α is not affected by chromium
treatment, although clear circadian variation in ACTH
and cortisol occurs. No difference is detected in the con-
centrations of trace minerals excreted daily in the urine,
lymphocyte proliferative response to mitogen stimulation
and neutrophil bactericidal function. The acute phase pro-
teins, ceruloplasmin and fibrinogen, also are not affected
by treatment or viral challenge. However, it will be inter-
esting to study the effects of chromium on human herpes vi-
rus infection.
Effect of chromium on IBRV infection: Kegley et al.152
have reported that when steers are inoculated with IBRV
intranasally, average daily gain from day 0 to day 80 is
increased by supplemental chromium. Transportation of
steers increased the ratio of neutrophils to lymphocytes.
Supplemental chromium did not affect rectal temperature
after the IBRV challenge or the antibody response to
IBRV or porcine red blood cells. Supplemental chromium
did not affect any immune response that was measured.
According to another report, supplemental chromium has
no effect on antibody response to IBRV, parainfluenza 3
and bovine respiratory syncytial virus. However, it en-
hanced the antibody titres of calves in response to the bovine
viral diarrhoea vaccine. On the other hand, chromium did
not show any significant effect on antibody responses as
well as on antibody titres of calves following vaccination
with Pasteurella haemolytica153. These findings suggest
that supplemental chromium can enhance humoral response
of market-transmit-stressed calves, but its enhancement on
vaccine efficacy is antigen-dependent and variable.
Effect of nickel
Nickel is an essential micronutrient. The best sources of nickel
include oatmeal, legumes, nuts, cocoa, whole wheat bread,
and some leafy vegetables such as kale and lettuce. Nickel
is found in blood and tissues at consistent levels, and is also
associated with DNA and RNA in amounts that suggest
REVIEW ARTICLE
CURRENT SCIENCE, VOL. 87, NO. 11, 10 DECEMBER 2004 1550
physiological significance. Nickel is required for normal
growth and reproduction in animals, and presumably in
human beings as well. It appears to have a role in the
modulation of the immune system and in development of
brain.
Effect of nickel on CBV infection: Ilback et al.154 inves-
tigated immunotoxic effect of a ten-week low dose admini-
stration of nickel chloride (NiCl2) prior to CBV infection.
This dose did not influence CBV-induced mortality. Seven
days after inoculation, impulse-counting showed that the
infection induced increase of 63Ni in pancreas and heart.
Nickel tends to increase spleen B- and T-cell activities,
but thymocyte activity remained unaffected. The activity
of spleen NK cells decreased, whereas there was an in-
creased blood cell activity. The number of cytotoxic T-
cells, helper T-cells and Mac 2+ cells in the lesions of heart
decreases with the nickel treatment154. These results suggest
that nickel may contribute to the progression of target organ
pathology in CBV infection-induced diseases of an auto
immune and/or inflammatory character, such as diabetes
and myocarditis.
A potentially toxic metal such as nickel can affect the
magnitude of inflammatory lesions in the heart of CBV-
infected mice. New target organs for nickel during this
infection were the heart, pancreas and lungs in which in-
flammatory lesions were present. This increased uptake was
correlated with the disturbed function of immune cells and an
increased inflammatory reaction. Nickel has a direct effect
on immune cells that resulted in changed natural killer
cell activity and decreased mobilization of macrophages,
CD4+ and CD8+ cells into the inflammatory lesions155.
Effect of nickel on murine cytomegalovirus infection:
When female C3H/HeJ or CD+ mice are infected with a
sublethal dose of murine cytomegalovirus and then exposed
to nickel chloride, enhanced mortality and a reduction in virus
augmented NK cell activity are observed at doses as low as
10 mg NiCl2/kg, i.m.156.
Conclusion
Although it is widely recognized that essential trace ele-
ments are required for the differentiation, activation and
performance of numerous functions of immune cells, the
specific roles of these micronutrients remain largely unde-
fined. New insights about the participation of zinc, sele-
nium, iron and copper in the selection, maturation and
early activation events of the immune cells have been ob-
tained by judicious use of available tools in cell biology,
molecular genetics and array technology. Randomly con-
trolled clinical and community trials demonstrate that zinc
supplementation can enhance immunocompetence and
decrease the incidence and severity of some infections in
individuals with diagnosed or suspected mild zinc defi-
ciency. These existing results inspire to evaluate the pote-
ntial benefits of supplementation programmes with trace
elements status as cost-effective means of reducing the risk
of infectious diseases. Several trace elements have immu-
nomodulatory functions and thus influence the susceptibi-
lity of a host to various viral infections. Some trace metals
have antiviral activity, while others may alter the genome
of the viruses enhancing their virulence. Further research,
both basic and applied, is needed to assess properly the
possible role of malnutrition in contributing to the emer-
gence of novel viral diseases.
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ACKNOWLEDGEMENTS. U.C.C. was an Emeritus Scientist of the Coun-
cil of Scientific and Industrial Research, New Delhi. R.S. is a Senior Res-
earch Fellow of the Indian Council of Medical Research, New Delhi.
Received 9 February 2004; revised accepted 31 July 2004
... The human body requires minute quantities of these nutrients to aid in enhancing the immune system, defending against pathogens, and promoting a quicker recovery from serious infections. Essential microelements are thus engaged in several enzymatic reactions and immunologic processes and in overall metabolism (Chaturvedi et al. 2004;Selvaraju et al. 2009;Rajan et al. 2014). In addition, micronutrients also play a pivotal role in the biosynthesis of plant secondary metabolites. ...
Chapter
Integrating greeneries into the indoor dwelling environment boosts work performance and relieves stress to add to the overall psychological well-being especially in deserted urban settings. In addition to mental soothing, thermal regulation, air purification, aesthetics, public health, and comfort, the addition of plants to indoor settings may also contribute to the conservation of dwindling floral biodiversity. Despite authorities’ pledge for sustainable urban management, the status of indoor gardening has hitherto remained unexplored in the emerging megapolis of Bangladesh—Chattogram—the second largest urban center of the country. In addressing that gap, this study aims to explore the composition, diversity, and management of indoor plants in urban dwellings at Halishahar of Chattogram based on interviews on 48 households selected through multistage random sampling. Data from all selected households were collected by using a semi-structured questionnaire through physically visiting the households. Almost half of the households (48%) living at Halishahar had indoor plants in their dwellings. The study recorded a handsome 120 indoor plant species belonging to 108 genera from 60 families. While the diversity was in no way comparable to the tropical ecosystem of the country, in consideration of the strict set of requirements for plants to be suitable for an indoor setting, the diversity seemed excellent as evident from four diversity indices. Soil mixed with compost, sand, and surki at different ratios is used as potting media. Pests were identified as the major challenge in managing the indoor plants. Application of domestic manure with the potting media was common as a means to maintain the nutrient flow. Bruised tea leaf is the most frequently added nutrient supplement. Apart from the aesthetic values, urban dwellers from Halishahar reported the immense potential of indoor gardening in supplementing daily nutrition and in mitigating the impacts of climate change. The lessons from this study can be used in informed policymaking for the promotion of biodiversity conservation and other benefits from indoor greening among urban dwellers in Bangladesh.
... The human body requires minute quantities of these nutrients to aid in enhancing the immune system, defending against pathogens, and promoting a quicker recovery from serious infections. Essential microelements are thus engaged in several enzymatic reactions and immunologic processes and in overall metabolism (Chaturvedi et al. 2004;Selvaraju et al. 2009;Rajan et al. 2014). In addition, micronutrients also play a pivotal role in the biosynthesis of plant secondary metabolites. ...