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ImmunoTargets and Therapy 2015:4 143–157
ImmunoTargets and erapy Dovepress
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REVIEW
open access to scientific and medical research
Open Access Full Text Article
http://dx.doi.org/10.2147/ITT.S61528
The hygiene hypothesis: current perspectives and
future therapies
Leah T Stiemsma1,2
Lisa A Reynolds3
Stuart E Turvey1,2,4
B Brett Finlay1,3,5
1Department of Microbiology &
Immunology, University of British
Columbia, 2The Child and Family
Research Institute, 3Michael Smith
Laboratories, University of British
Columbia, 4Department of Pediatrics,
University of British Columbia,
5Department of Biochemistry and
Molecular Biology, University of
British Columbia, Vancouver, BC,
Canada
Correspondence: B Brett Finlay
Michael Smith Laboratories, 2329 West
Mall, University of British Columbia,
Vancouver, BC, V6T 1Z4, Canada
Email bnlay@msl.ubc.ca
Abstract: Developed countries have experienced a steady increase in atopic disease and
disorders of immune dysregulation since the 1980s. This increase parallels a decrease in infec-
tious diseases within the same time period, while developing countries seem to exhibit the
opposite effect, with less immune dysregulation and a higher prevalence of infectious disease.
The “hygiene hypothesis”, proposed by Strachan in 1989, aimed to explain this peculiar genera-
tional rise in immune dysregulation. However, research over the past 10 years provides evidence
connecting the commensal and symbiotic microbes (intestinal microbiota) and parasitic helminths
with immune development, expanding the hygiene hypothesis into the “microflora” and “old
friends” hypotheses, respectively. There is evidence that parasitic helminths and commensal
microbial organisms co-evolved with the human immune system and that these organisms are
vital in promoting normal immune development. Current research supports the potential for
manipulation of the bacterial intestinal microbiota to treat and even prevent immune dysregula-
tion in the form of atopic disease and other immune-mediated disorders (namely inflammatory
bowel disease and type 1 diabetes). Both human and animal model research are crucial in
understanding the mechanistic links between these intestinal microbes and helminth parasites,
and the human immune system. Pro-, pre-, and synbiotic, as well as treatment with live helminth
and excretory/secretory helminth product therapies, are all potential therapeutic options for
the treatment and prevention of these diseases. In the future, therapeutics aimed at decreasing
the prevalence of inflammatory bowel disease, type 1 diabetes, and atopic disorders will likely
involve personalized microbiota and/or helminth treatments used early in life.
Keywords: inflammatory bowel disease, microbiota, helminths, atopic disease, type 1
diabetes
Introduction
The Millennial generation (born 1980–1999) displays a marked increase in prevalence of
atopic diseases (asthma, anaphylaxis, allergic rhinitis, food allergy, and atopic dermatitis
[AD]) and immune-mediated disorders (including type 1 diabetes [T1D], and inflamma-
tory bowel disease [IBD]), which have been steadily increasing in developed countries
since the 1980s.1–3 These disorders comprise a unique sector within immune dysregulation
characterized by an irrational immune cell response to a foreign (or in the case of autoim-
munity, a self) antigen which would, under normal circumstances, not occur. The short
developmental timeframe of these diseases (from the 1980s onward, roughly within one
generation) decreases the likelihood that a changing genetic component is significantly
involved. Hence, researchers are assessing the potential effects of environmental factors,
such as diet and antibiotic exposure.4 Furthermore, the increase in immune disorders and
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atopic diseases parallels a decrease in prevalence of infectious
diseases over the same time period, which can be attributed
to increased vaccine and antibiotic treatments, and improved
sanitation standards.4 An in-depth look at the effects of these
“hygienic” environmental factors suggests that lack of expo-
sure to infectious agents may be the culprit for the increase in
immune-mediated and atopic disease prevalence, a concept
most commonly referred to today as the “hygiene hypothesis”.
This review aims to provide readers with the historical and
current perspectives of the hygiene hypothesis and to elabo-
rate on the modern scientific and medical applications of this
theory. We also discuss the increasing evidence connecting the
hygiene hypothesis to the development of atopic disease and
immune-mediated disorders, in addition to discussing future
therapies capitalizing on this knowledge.
A history of “hygiene” in immune
modulation
One of the first observations relating infectious agents and
immune dysregulation occurred in Western Nigeria, where
Greenwood noted the low incidence of rheumatoid arthritis
and deduced that this low incidence may be attributed to
immunological disturbance resulting from frequent exposure
to malaria (Figure 1).5 Greenwood et al also observed sup-
pressed spontaneous autoimmune disease, characterized by
delayed Coombs test positivity and reticulocytosis in mice
infected with Plasmodium berghei (a causative agent of
rodent malaria).6 In the late 1970s, a discrepancy between
urbanized and rural environments emerged when Gerrard
et al observed a lower prevalence of allergy in indig-
enous populations in Northern Canada compared to urban
Caucasian populations.7
In 1989, Strachan proposed the hygiene hypothesis
of allergic disease after observing that hay fever was less
common among children with older siblings.8 He reasoned
that children growing up in larger families may experience
increased exposure to microbes in early childhood due to
inevitable unhygienic contact with older siblings or prenatal
exposure from the mother infected by similar unhygienic con-
tact.8 Strachan proposed that this increased microbial exposure
in early life could protect children from developing immune
hypersensitivities later in life.8 Strachan et al supported this
theory by assessing family history, medical records, and
allergy skin prick test results in a cohort of 1 1,765 children and
found that household size was inversely correlated with the
development of hay fever.9 Additional epidemiological studies
supporting the hygiene hypothesis associate a reduction in
allergen sensitization with pet exposure, daycare attendance,
and an increased number of siblings.10,11 Early childhood
infections have also been associated with decreased atopy in
children. A retrospective case-control study showed that atopic
patients exhibited a lower prevalence of Toxoplasma gondii,
Helicobacter pylori, and hepatitis A when compared to non-
atopic controls.12 More recently, single-strand polymorphism
analysis and culture techniques were used to identify microbial
exposures among two cohort studies of European children.13
2011
1976
Gerrard et al observe lower
prevalence of allergy in indigenous
populations in Northern Canada
compared to urban Caucasian
populations7
Ege et al show that children
growing up on farms are exposed
to a wider range of microbial
exposures and lower prevalence of
asthma and atopy13
"Old friends" hypothesis
proposed22
Strachan proposes
the "hygiene
hypothesis"8
Greenwood observes low incidence
of rheumatoid arthritis in Western
Nigeria where malaria exposure is
frequent5
Greenwood et al show
suppressed spontaneous
autoimmune disease in New
Zealand mice infected with
Plasmodium berghei
Mosmann et al expose Th1 and Th2
cell subsets14
"Microflora" hypothesis
proposed32
Strachan et al show inverse
correlation between household size
and the development of hay fever9
Matricardi et al correlate exposure to
childhood infections with reduced risk
of atopy later in life12
1969
1970
19701965 1975 1980 1985 1990 1995 2000 2005 2010 2015
1986 2005
1996
1989 2000
2004
6
Figure 1 Timeline displaying key ndings leading up to the proposal of the “hygiene hypothesis”, proposal of the “old friends” and “microora” hypotheses, and key
microbiological and immunological ndings in support of these theories.
Abbreviation: Th, T-helper.
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The hygiene hypothesis: a review
In both cohort studies, researchers found that children grow-
ing up on farms in Central Europe encountered a wider
range of microbial exposures and had a lower prevalence of
asthma and atopy than the reference group.13 A closer look
at the immunological mechanisms behind Strachan’s hygiene
hypothesis of allergic disease will enhance the connection
between early life infectious exposures and the development
of immune tolerance.
Immunological support for the
hygiene hypothesis
In 1986, just prior to Strachan’s proposal of the hygiene
hypothesis, Mosmann et al described the T-helper (Th)1
and Th2 cell subtypes, providing an immunological basis
for this otherwise observational theory.14 They discovered
that fully differentiated murine CD4+ T-cells secreted two
separate cytokine profiles (Th1: IFN-γ; Th2: IL-4) and that
the different cytokines produced two different inflammatory
responses.14 Th2 cells play a primary role in the allergen
sensitization process.15 Infection with viruses and intracel-
lular bacteria generally stimulates Th1 immune responses,
which suppress Th2 cytokine activity through the induction
of IFN-γ.16,17 Consequently, the concept of a Th1 versus Th2
balance arose whereby a Th1-dominated immune phenotype
(brought on by early life microbial exposures) was thought to
inhibit atopic immunopathology. Research related to helminth
parasites stimulated the need for further explanation beyond
this binary view, as these organisms paradoxically induce Th2
responses while suppressing allergic reactivity.18 T-cell plas-
ticity and additional T-cell phenotypes (eg, Th17, Th9, and T
regulatory [Treg] cells) have more recently been implicated
in the control of hypersensitivity disorders.19,20 Additionally,
many innate cytokines (eg, IL-25, IL-33, and thymic stromal
lymphopoietin) and cell types (eg, eosinophils, basophils,
mast cells, and epithelial cells) also play significant roles
in hypersensitivity disease.21 It is now understood that the
process of allergen presentation and consequent initiation of
the allergic response involves both the innate and adaptive
branches of the immune system. Thus, the immunological
foundation of the hygiene hypothesis has been modified
to consider the balance between many adaptive and innate
immune cell populations. Further, extending the hygiene
hypothesis to account for the role of various parasites (ie,
intestinal helminths) and microbiota compositional shifts
provides insight into how early life environmental exposures
shape the human immune system. These extensions are
known as the “old friends” and “microflora” hypotheses,
respectively.22,23
The old friends hypothesis: parasitic
helminths
The old friends hypothesis, proposed by Rook et al, notes the
co-evolution of microorganisms and macroorganisms, such
as parasitic helminths, with the development of the human
immune system.22 Similar to the hygiene hypothesis, it sug-
gests that these organisms are required for normal immune
system development.22,24 For example, a study in Gabon found
that school children diagnosed with schistosomiasis, caused
by infection with helminth parasites from the Schistosoma
genus, exhibited lower levels of allergen reactivity than their
uninfected classmates.25 Since then, additional studies have
highlighted this seemingly protective effect of helminths in
many mouse models of allergic diseases.26–28 A live Helig-
mosomoides polygyrus (H. polygyrus; a murine helminth
parasite) infection reduces lung cellular influx, eosinophilia,
allergen recall responses, bronchial hyperreactivity, and
histopathology in ovalbumin (OVA)- and house dust mite
(HDM)-driven mouse models of asthma.26,27 Additionally,
Schistosoma mansoni infection has been shown to be protec-
tive in an experimental mouse model of fatal anaphylaxis,
probably due to the induction of a regulatory IL-10-producing
B cell population.28 There is also experimental animal model
evidence suggesting the ability of helminths to ameliorate
symptoms of T1D and colitis (Table 1). Non-obese diabetic
(NOD) mice spontaneously develop T1D, which is signifi-
cantly inhibited when they are infected with H. polygyrus or
the filarial nematode Litomosoides sigmodontis.29–32 Helm-
inth infection has also been shown to reduce inflammation
in murine models of colitis.33 Studies such as these support
live helminth infection as a potential therapy to combat
hypersensitivity and other immune disorders; however,
referring back to Strachan’s original hygiene hypothesis, the
question of whether live helminth infection in early life is
an effective treatment to protect against the development of
these disorders is still unclear. Future therapeutics to treat
immune dysregulation may involve the excretory/secretory
(ES) products of these parasites and/or the intestinal micro-
biota (Tables 1 and 2).
The microora hypothesis
The microflora hypothesis is another modern extension
of the hygiene hypothesis, which suggests that early life
perturbations (driven by factors such as antibiotic use,
infection, or diet) to the bacteria residing in the human
intestine (the intestinal microbiota) disrupt the normal
microbiota-mediated mechanisms promoting immunological
tolerance and consequently bias the immune system toward
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Stiemsma et al
a state that promotes hypersensitivity disorders.23 Current
research focuses on the mechanisms by which the intestinal
microbiota influences immune system development and
homeostasis, and potentially confers protection against
immune dysregulation.35–50
A mutualistic bond
The human intestine is a densely populated zone in the body
harboring a diverse microbial community of 500–1,000
different bacterial species among other microbes such as
archaea, eukarya, and viruses.34 The most striking illustration
Table 1 Helminth-based therapeutic studies
Organism Disease Treatment Description of effects Reference
Mouse OVA-alum and Der p1-alum
(HDM allergen)-driven models
of allergic airway inammation
H. polygyrus larvae H. polygyrus-infected mice had reduced airway cellular
inltrates (including reduced
eosinophilia and neutrophilia), reduced lung type 2
cytokines, and reduced lung histopathology
26
Mouse OVA-alum-driven model of
allergic airway inammation
H. polygyrus larvae H. polygyrus-infected mice had reduced airway
eosinophilia, reduced bronchial hyperreactivity,
and reduced allergen-specic Th2 responses
27
Mouse OVA-alum-driven model of
allergic airway inammation
HES HES given at allergen sensitization or challenge reduced
airway cellular inltrates and lung eosinophilia
110
Mouse Alternaria alternata-driven model
of allergic airway inammation
HES HES blocked lung eosinophilia, IL-33 release, and innate
lymphoid cell type 2 cytokine production
111
Mouse TNBS-induced colitis Schistosoma mansoni- or
Ancylostoma caninum-soluble
proteins
Intraperitoneal helminth protein administration
reduced macroscopic inammation scores and reduced
proinammatory cytokine release (IL-17 and IFN-γ)
112
Mouse Systemic–fatal anaphylaxis S. mansoni cercariae S. mansoni-infected mice were protected from anaphylaxis 28
Mouse T1D (spontaneous
development in NOD mice)
H. polygyrus larvae H. polygyrus infection delayed disease onset 29,30
Mouse T1D (spontaneous
development in NOD mice)
Litomosoides sigmodontis
larvae
L. sigmodontis infection prevented disease onset 31,32
Mouse OVA-alum-driven model of
allergic airway inammation and
DSS-induced colitis
Recombinant cysteine
protease inhibitor (cystatin)
of Acanthocheilonema viteae
A. viteae cystatin treatment during OVA sensitization or
prior to OVA challenge reduced airway BALF cell counts,
airway eosinophilia, bronchial hyperreactivity, and lung
histopathology. In the DSS–colitis model, intrarectal
A. viteae cystatin resulted in signicant reductions in
colonic inammatory index compared to control animals
114
Mouse DSS-induced colitis Ancylostoma ceylanicum crude
extract or ES products
Helminth-product-treated mice had reduced clinical and
colonic microscopic inammation scores compared to
control mice
113
Mouse T1D (spontaneous
development in NOD mice)
S. mansoni infection, or
treatment with soluble
worm or egg extracts
Exposure to worm or egg extract prevented disease
onset if given before 4 weeks of age
116
Mouse DSS-induced colitis ES products from A. caninum Exposure to helminth products reduced intestinal
proinammatory cytokine expression
115
Humans CD and UC Live Trichuris suis eggs Three out of four CD patients entered remission; fourth
patient had a reduction in symptoms. UC patients had a
reduction in clinical colitis activity index
106
Humans CD Live T. suis ova 79.3% of patients had a reduction in CD activity index or
remitted
103
Humans CD Live T. suis ova All doses tested were well tolerated and did not result in
treatment-related side effects. Efcacy of a reduction in
disease severity not assessed
104
Humans UC Live T. suis ova A reduction in disease activity was seen in helminth-
infected patients compared to placebo group, although
this did not reach statistical signicance
108
Humans CD Necator americanus larvae IBD questionnaire results were improved, and cumulative
CD activity index scores were decreased
105
Humans Allergic rhinoconjunctivitis N. americanus larvae Infection well tolerated; no signicant differences in
allergic symptoms between groups given placebo or
N. americanus larvae
107
Abbreviations: OVA, ovalbumin; alum, potassium aluminum sulfate; ES, excretory/secretory; HES, H. polygyrus excretory/secretory product; HDM, house dust mite; BALF,
bronchoalveolar lavage uid; IL, interleukin; IFN, interferon; DSS, dextran sulfate sodium; TNBS, 2,4,6-trinitrobenzene sulfonic acid; T1D, type 1 diabetes; NOD, non-obese
diabetic; CD, Crohn’s disease; UC, ulcerative colitis; IBD, inammatory bowel disease; Th, T-helper.
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The hygiene hypothesis: a review
Table 2 Microbiota-based therapeutic studies
Organism Disease Treatment Description of effects Reference
Rat HLA-B27 transgenic rats
(colitis model)
Inulin and FOS Decreased severity of intestinal inammation (FOS treatment
resulted in less disease severity than inulin)
135
Rat T1D (BB-DP rat model) Lactobacillus johnsonii Administration of L. johnsonii isolated from BB-diabetes-
resistant rats resulted in decreased incidence of T1D and
reduced levels of IFNγ and inducible nitric oxide synthase in
BB-diabetes-prone rats
92
Mouse T1D (spontaneous
development in NOD mice)
VSL#3 (probiotic compound:
containing Bidobacteria,
Lactobacilli, and Streptococci
species).
Reduced insulitis and decreased beta cell destruction 124
Mouse HDM-driven model of
allergic airway inammation
Diet supplemented with 30%
pectin
Increased concentrations of SCFAs and decreased allergic
inammation in the lungs of murine HDM model of airway
inammation
46
Mouse OVA-alum-driven model of
airway inammation
scGOS/lcFOS, and scGOS/
lcFOS + pAOS
Suppressed airway inammation and hyperresponsiveness 134
Mouse CMA model scGOS/lcFOS + Bidobacterium
breve
Increased serum galectin-9 and galectin-9 expression by
intestinal epithelial cells. Also, reduced acute allergic skin
reaction and mast cell degranulation
137
Rat T1D (STZ model) Lactobacillus gasseri engineered
to secrete GLP-1(1-37)
GLP-1(1-37) secreted by L. gasseri stimulated rat intestinal
epithelial cells to become glucose-responsive insulin-secreting
cells. Resulted in increased insulin levels and glucose tolerance
in diabetic rats
125
Mouse IBD (IL-10-decient colitis
model)
Lactobacillus plantarum Prior to SPF ora exposure, treatment of GF IL-10 decient
mice with L. plantarum and continued L. plantarum therapy
attenuated colitis
122
Mouse IBD (DSS-induced colitis
model)
Lactobacillus rhamnosus,
L. plantarum, Lactobacillus casei,
Lactobacillus lactis, Bidobacterium
lactis, Bidobacterium bidum,
Bidobacterium adolescentis,
Bidobacterium infantis
Mice receiving the probiotic mixture for 7 days prior to DSS
induction of colitis showed reduced mucosal inammation
and damage compared to controls that did not receive the
therapy
123
Mouse IBD (IL-10-decient and
DSS-induced colitis models)
Lactobacillus salivarius Oral treatment with L. salivarius did not attenuate colitis
symptoms in IL-10-decient or DSS-treated mice
132
Mouse OVA-alum-driven model of
airway inammation
Bidobacterium longum Protected against airway inammation in OVA-sensitized mice
and blocked induction of OVA-specic IgE
66
Mouse OVA-alum-driven model of
airway inammation
Lactobacillus reuteri, L. salivarius L. reuteri decreased airway hyperresponsiveness. L. salivarius
had no effect
64
Human Eczema Lactobacillus rhamnosus and
L. reuteri
After 6 weeks of probiotic therapy, 56% of children (aged
1–13 years) experienced improved eczema, while only 15%
of placebo controls reported improved symptoms
127
Human UC Enema solution containing
L. reuteri
Improved mucosal inammation and decreased inammatory
cytokines in children with UC
128
Human AR L. johnsonii + levocetirizine Compared with patients receiving levocetirizine only,
L. johnsonii + levocetirizine improved AR symptoms including
increased IFNγ and IL-10 and decreased IL-4 concentrations,
and improved FVC and FEV1 spirometry measurements in a
24-week, two-phase crossover treatment program
141
Human Pollen allergy B. longum Reduced ocular symptom scores during exposure to Japanese
cedar pollen
142
Human Peanut allergy L. rhamnosus + peanut oral
immunotherapy
Subjects (82.1%) receiving combination peanut oral
immunotherapy + L. rhamnosus achieved possible sustained
unresponsiveness to peanut 2–5 weeks after discontinuation
of treatment compared to only 3.6% receiving placebo
126
Human AD, recurrent wheeze,
allergic urticaria
scGOS + lcFOS Prebiotic group had signicantly lower incidences of allergic
manifestations
56
Human AD scGOS/lcFOS + B. breve
(Immunofortis®)
Increased galectin-9 expression and reduced AD in infants
with IgE-mediated eczema 12 weeks posttreatment
137
Human Asthma scGOS/lcFOS + B. breve
(Immunofortis)
Decreased prevalence of frequent wheezing and usage of
asthma medications in children with AD after 1 year follow-
up evaluation
139
(Continued)
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Stiemsma et al
of the importance of the intestinal microbiota for mammalian
immune development comes from studies conducted in germ-
free (GF) mice, in which the lack of a microbiota results in
reduced Peyer’s patches, smaller germinal centers and fewer
plasma cells, and increased susceptibility to pathogen invasion
when compared to conventionally raised mice.35–38 Although
GF murine models are valuable in mechanistic studies, they
do have many caveats.39 To fully elucidate the underlying
mechanisms driving the relationship of the gut microbiota
with atopic disease development, many different murine
models, including GF, gnotobiotic, and antibiotic-treated
models, along with models supplemented with specific bac-
terial species, should be used. In addition, murine systems
with a reconstituted human immune system would be even
more valuable.
Specific bacterial species within the microbiota have
been shown to induce expression of antimicrobial peptides
(eg, Bacteroides thetaiotaomicron induction of regenerat-
ing islet-derived 3 γ expression by Paneth cells) and mucin
production, which ultimately confers protection against
pathogen invasion, and combined with regular stimulation
of pattern recognition receptors, contributes to intestinal
homeostasis.40–42 The presence of the microbiota can
stimulate CD4+ T-cell proliferation, Th17 cell differentia-
tion through the induction of IL-1β, and accumulation of
colonic Tregs.43–45 The intestinal microbiota also metabo-
lizes food components that are indigestible by mammalian
enzymes, such as human milk oligosaccharides (HMOs)
and dietary fiber.46,47 This produces short-chain fatty acids
(SCFAs), which are essential energy sources for many host
tissues and prominent immune modulators.48–50 There are
many factors that likely contribute to the development of
immune dysregulation: perturbations to the composition of
the intestinal microbiota, caused by environmental factors
such as antibiotic exposure, birth mode, or diet, are one
potential explanation linking early life hygiene with the
development of atopic and immune-mediated disorders
(Figure 2).
The intestinal microbiota in atopic
disease: human studies
A longitudinal study comparing the early life intestinal micro-
biota compositions of school-age asthmatic and non-asthmatic
children showed that significant decreases in overall gut micro-
bial diversity at 1 week and 1 month of age were correlated
with asthma development at school age.51 Additionally, a recent
characterization of the gut microbiota of 166 Canadian infants
revealed an increased Enterobacteriaceae/Bacteroidaceae ratio
in children sensitized to food allergens at 3 months and 1 year
of age compared to non-sensitized children.52 Also, lower gut
microbial richness was observed at 3 months of age only.52
Studies such as these suggest that therapeutic microbial inter-
vention early in human life may be favorable, and highlight the
need for animal studies in which experimentation to confirm
causality is possible.
Many human studies lend support for the hygiene and
microflora hypotheses by assessing the impact of early
life environmental factors known to disturb the intestinal
microbiota on atopic disease development later in life. For
example, antibiotic usage in the first 2 years of life has been
associated with the development of asthma at 7.5 years of
age in a dose-dependent manner.53 Additionally, antibiotic
usage was reported to precede the manifestation of wheeze
in the first 2 years of life in a questionnaire-based analysis
of the KOALA (acronym in Dutch for “Child, parents and
health: lifestyle and genetic constitution”) Birth Cohort
Table 2 (Continued)
Disease Treatment Description of effects Reference
Human Asthma, eczema, allergic
rhinoconjunctivitis
L. reuteri Oral supplementation with L. reuteri ATCC 55730 in the
last month of gestation through the rst year of life is not
associated with lower prevalence of allergic disease at
7 years of age
130
Human UC Escherichia coli Nissle
(Mutaor®)
Mutaor® is as effective at preventing relapses as the
established mesalazine therapy in patients with UC. Patients
(36.4%) receiving Mutaor for 12 months experienced
relapses compared to 33.9% in the mesalazine group
129
Human UC Inulin-oligofructose
(Synergy® 1) + B. longum
Reduced chronic inammatory markers of UC (TNFα and
IL-1α)
140
Abbreviations: HLA, human leukocyte antigen; FOS, fructooligosaccharide; T1D, type 1 diabetes; BB-DP, bio-breeding diabetes-prone; NOD, non-obese diabetic;
IFN, interferon; IL, interleukin; OVA, ovalbumin; alum, potassium aluminum sulfate; SCFA, short-chain fatty acid; DSS, dextran sulfate sodium; scGOS, short-chain
galactooligosaccharide; lcFOS, long-chain fructooligosaccharide; pAOS, pectin-derived acidic oligosaccharide; CMA, cow’s milk allergy; GLP, glucagon-like peptide; UC,
ulcerative colitis; STZ, streptozotocin; SPF, specic pathogen-free; GF, germ-free; AD, atopic dermatitis; AR, allergic rhinitis; HDM, house dust mite; IBD, inammatory bowel
disease; FVC, forced expiratory vital capacity; FEV1, forced expiratory volume in 1 second; ATCC, American Type Culture Collection; Ig, immunoglobulin.
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The hygiene hypothesis: a review
Study in the Netherlands.54 Birth by Caesarean sec-
tion was associated with lower total microbial diversity,
delayed colonization with Bacteroidetes, and decreased
Th1 responses in the first 2 years of life.55 Breastfeeding
promotes colonization with commensal microbes such as
Bifidobacteria spp. and provides the intestinal microbiota
with necessary nutrients in the form of HMOs.46,56 Specific
HMOs, short-chain galactooligosaccharides (GOSs) and
long-chain fructooligosaccharides (FOSs), administered
in the first 6 months of life have been shown to reduce
the cumulative incidences of AD, recurrent wheezing,
and allergic urticaria.57 In line with Strachan’s original
proposal, one study found that an increased number of
older siblings was associated with decreased colonization
with Clostridium difficile and Clostridium cluster 1, and
a decreased risk of developing AD.58 Correlative human
studies such as these shed light on the environmental fac-
tors that may be associated with atopic disease through
manipulation of the intestinal microbiota; however,
research regarding factors such as antibiotic exposure,
breastfeeding, and birth mode remains controversial, and
there are studies that suggest these factors have little or
no effect on atopic disease development.59–64 Additional
longitudinal human studies are necessary to determine
which early life factors are most influential in promoting
the intestinal dysbiosis associated with the development
of immune hypersensitivities, and animal model research
is a crucial complementary approach to elucidate the
mechanisms behind these associations.
The intestinal microbiota in atopic disease:
mouse models
Murine model studies mechanistically support a link between
the intestinal microbiota and atopic disorders through the
experimental manipulation of microbiota compositions. In
an OVA-driven model of asthma, Forsythe et al show that
oral supplementation with live Lactobacillus reuteri reduced
airway hyperresponsiveness as well as levels of TNFalpha,
monocyte chemotactic protein 1, IL-5, and IL-13 in the
bronchoalveolar lavage fluid (BALF), while treatment with
Lactobacillus salivarius had no effect.65 Intranasal supple-
mentation of mice, polysensitized to birch and grass pollen
allergens, with Bifidobacterium longum and Lactobacillus
paracasei at the time of sensitization resulted in reduced
IgE-dependent basophil degranulation in response to allergen
challenge.66 Only B. longum displayed protective effects when
mice were supplemented prior to allergen sensitization.66
Additionally, oral supplementation of mice with B. longum
protected against airway inflammation, increased Peyer’s
patch and splenic Tregs, and blocked serum IgE induction in
OVA-sensitized animals.67
More recent research focuses on the earliest time point at
which gut microbial intervention must occur to prevent the
onset of hypersensitivity disease. In an OVA-driven model of
allergic inflammation, neonatal (but not adult) exposure of
previously GF mice to a conventional microbiota reduced the
severity of allergic inflammation characterized by decreased
accumulation of invariant natural killer (NK) T-cells to the
lung and reduced serum IgE levels and eosinophil frequencies
Early life exposures
• Diet (breast milk vs
formula)
• Birth mode (vaginal
vs Caesarean section)
• Infection
• Antibiotic exposure
• Household size and
number of siblings
Dysbiotic
intestinal
microbiota
Normal
intestinal
microbiota
Intestinal homeostasis
and
Immune tolerance
Immune dysregulation
(atopic disease, T1D, and
IBD)
• Furred pet exposure
Figure 2 A depiction of the early life environmental exposures differentially associated with promoting a healthy intestinal microbiota, which results in intestinal homeostasis
and immune tolerance, and a dysbiotic (unhealthy) intestinal microbiota, which may induce the development of immune dysregulation.
Abbreviations: vs, versus; T1D, type 1 diabetes; IBD, inammatory bowel disease.
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in the BALF.68 Arnold et al show in OVA- and HDM-driven
mouse models of allergic inflammation that oral infection
of neonatal mice with H. pylori prior to OVA or HDM chal-
lenge resulted in the significant reduction of eosinophils in
the BALF, and a decrease in IL-5 and IL-13 cytokine levels
when compared to uninfected mice and infected adult mice.69
Russell et al found that perinatal vancomycin treatment of
OVA-challenged mice alters gut microbial composition
and exacerbates asthma-related immune responses, which
may be driven by increased serum IgE levels and reduced
Treg populations.70 Interestingly, perinatal treatment with
streptomycin did not result in exacerbated disease after OVA
challenge, but perinatally streptomycin-treated mice showed
exaggerated lung inflammation when compared to untreated
or vancomycin-treated mice in a Th1/Th17-driven model of
hypersensitivity pneumonitis.70,71 This highlights the ability
of altered microbiota compositions to differentially control
disease severity depending on the immunological basis of
the disease.71 Additional studies including human subjects
and supporting mechanistic animal models are necessary
to provide a holistic view of the role of the intestinal micro-
biota in atopic disease. Currently, there is also increasing
evidence supporting a role of the intestinal microbiota and
early life environmental exposures in other immune-mediated
disorders.72 For the purpose of this review, we focus on IBD
and T1D.
The hygiene and microora
hypotheses and immune-
mediated disorders
IBD
IBD is an inflammatory disorder of the gastrointestinal (GI)
tract encompassing Crohn’s disease (CD) and ulcerative
colitis (UC), both of which are highest in prevalence in North
America and Europe.73 The presence of intestinal bacteria
appears to be required for the development of experimental
colitis, while the composition influences the severity of IBD.
GF IL-10-deficient mice show no evidence of experimental
colitis, while IL-10-deficient mice housed under specific
pathogen-free (SPF) conditions spontaneously develop
the disease.74 Additionally, antibiotics have been shown to
attenuate the symptoms of experimental colitis.75–77 Exposure
of SPF IL-10-deficient mice to antibiotics displays differ-
ential and localized roles of specific bacteria in mediating
experimental colitis.77 For example, treatment of SPF IL-10-
deficient mice with vancomycin–imipenem and metronida-
zole eliminated anaerobic bacteria and reduced colonic injury,
while ciprofloxacin and vancomycin–imipenem decreased
cecal inflammation and reduced the prevalence of Escheri-
chia coli and Enterococcus faecalis.77
Some human studies suggest that early life antibiotic
exposure is associated with IBD.78–80 This discrepancy is
likely because antibiotics in murine IBD experiments are
typically given as treatment after disease onset, whereas
human studies are often retrospective and assess the effects
of antibiotic exposure prior to disease onset. In a nested case-
control study, children diagnosed with IBD at approximately
8 years of age were 2.9 times more likely to have received
antibiotics in the first year of life.80 Additionally, antibiotic
exposure in the first 3 months of life was associated with
childhood CD.79 Conversely, antibiotic combination therapy
has been shown to be effective in treating UC in humans.81
Thus, effects after antibiotic exposure in humans are likely
disease specific and/or dependent on when antibiotics are
administered (ie, before or after disease onset).
Diet may also play an important role in IBD. Maternal
secretory IgA (a component of breast milk) has been shown
to alter the intestinal microbiota composition and the expres-
sion of genes associated with intestinal inflammation.82
Additionally, a systematic review negatively correlated breast
milk exposure with the development of early onset IBD in
humans, suggesting a protective effect of breastfeeding on
IBD development.83
Altogether, these results suggest that IBD is driven by the
composition of the intestinal microbiota, which is strongly
influenced by early life environmental factors. Early life diet
(breastfeeding) is likely protective against IBD development,
while effects of antibiotic exposure are more complicated.
If antibiotics are given in early life, they may result in an
intestinal microbiota that promotes IBD development.79,80
However, after disease onset, antibiotics alleviate disease
severity by shifting the prevalence of specific microbes that
may be promoting the disease.75–77,79,81 Regardless, factors
related to early life hygiene are involved in IBD development,
and there is also evidence that the hygiene and microflora
hypotheses are applicable to immune-mediated disorders not
associated with the GI tract, such as T1D.84–96
T1D
The prevalence of childhood T1D, an autoimmune disorder
resulting from T-cell mediated destruction of beta cells in the
pancreas, is steadily increasing worldwide, and developed
countries such as Canada and the UK exhibit the highest
incidences of the disease.84,85 Epidemiological evidence sup-
ports a link between environmental factors associated with
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The hygiene hypothesis: a review
the hygiene hypothesis and the onset of T1D. Having older
siblings is negatively correlated with childhood onset T1D,
suggesting a protective effect.86 Furred pet exposure seems
to also play a role, as one study found in a birth cohort of
3,000 children: children exposed to an indoor dog were less
likely to develop T1D than unexposed children.87 Breast-
feeding has been associated with protection from T1D, and
children born by Caesarean section exhibit a higher risk of
T1D than children born vaginally.88–90
Lending support for the microflora hypothesis, a recent
study compared the gut microbial compositions of children
with T1D and healthy children and concluded that children
with T1D showed a significant increase in Bacteroides spp.,
which was later reduced to that of controls after insulin
treatment for 2 years.91 Oral administration of Lactobacillus
johnsonii isolated from bio-breeding (BB) diabetes-resistant
rats was shown to delay the onset of T1D in BB-diabetes
prone rats.92 Additionally, MyD88-deficient NOD mice
are protected from disease onset in SPF environments,
and segmented filamentous bacteria have been reported to
protect female NOD mice from disease development.93,94
Additionally, antibiotic therapy in mice has been shown to
protect against virus-induced T1D through the alteration of
intestinal microbiota composition.95 However, in humans the
contribution of antibiotics to T1D development is currently
unclear, as a population-based human cohort study found
no association between T1D and antibiotic exposure in the
first 8 years of life.96 Thus, similar to atopic disease and IBD,
early life factors common to industrialized countries such
as birth mode, diet, and antibiotic exposure seem to play a
role in T1D development. However, additional mechanistic
research is needed before significant conclusions regarding the
gut microbial composition and immunological consequences
can be made. The use of appropriate animal models will be
critical in continuing to determine whether the relationship
between microbiota composition and immune dysregulation
is causal, or an effect of a dysregulated immune environment.
Regardless, research related to the hygiene, old friends, and
microflora hypotheses supports early life intervention as
the primary therapeutic component for averting immune
dysregulation in the form of atopic and immune-mediated
disorders.
Future therapeutics
Future therapeutic options to prevent the development of
immune dysregulation will likely involve the millions of
micro- and macroorganisms living commensally or symbi-
otically (microbiota), or even parasitically (helminths) in the
human body. In this section, we discuss potential helminth-
based (Table 1) and microbiota-based therapies (Table 2) in
the prevention of these disorders.
Helminth-based therapies
Clinical trials to date have focused on the use of live helminth
infection as an ameliorative, rather than preventative, strategy
due to the potential for diminished vaccine responsiveness in
mice and humans infected with helminths early in life.97–101
The majority of early phase clinical trials to determine the
safety and efficacy of live helminth infection have been con-
ducted in CD and UC patients.102 Initial clinical trials using
ova from the porcine whipworm, Trichuris suis, or larvae
from the human hookworm, Necator americanus, have not yet
found any cause for major safety concerns in IBD or asthma
patients.103–107 T. suis ova administration seemed to reduce
intestinal inflammation in a small number of CD and UC
patients, and administration of N. americanus larvae to CD
patients resulted in a nonsignificant improvement in intestinal
inflammation scores.104–108 These initial clinical trials were
promising, although follow-up studies with the inclusion of
placebo control groups show mixed results.102,107,108
Live helminth parasites release a suite of ES immu-
nomodulatory products that likely mediate many of their
suppressive effects in models of allergic disease and experi-
mental colitis.109 In mice exposed to both OVA- and Alter-
naria alternata-driven asthma models, administration of ES
material from the murine intestinal nematode, H. polygyrus
(HES), was sufficient to suppress lung eosinophilia and
histopathology in response to antigen challenge.110,111 HES
appears to suppress lung inflammation when given at the
point of antigen sensitization and antigen challenge, making
it a promising therapeutic candidate.110 Soluble products from
several different helminth parasites have also been shown
to reduce measures of disease severity in murine models of
trinitrobenzene sulfonic acid-induced and dextran sulfate
sodium-induced colitis and T1D.112–116 Administration of
helminth ES products rather than live helminths has not yet
begun in human patients, but evidence from murine models
suggests that this is a promising approach for future clinical
trials.
Researchers are beginning to elucidate the mechanisms
that mediate the potent immunoregulatory effects of these hel-
minth products. ES products from N. americanus mediate the
rapid proteolysis of eotaxin, an eosinophil chemoattractant,
and HES can stimulate the induction of Tregs through a TGF-
β-dependent pathway.117,118 Whether the administration of
helminth products modifies the composition of the intestinal
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Stiemsma et al
microbiota is not yet reported. However, infection of mice
with live helminth parasites results in a marked disruption of
intestinal microbiota composition, suggesting that the immu-
nosuppressive effects following helminth infection could be
due to an indirect modulation of the microbiota.119–121 The
relative contribution of the microbiota or helminth-secreted
products in ameliorating immune dysregulation remains to
be determined. If microbiota compositional shifts following
helminth infection are shown to have a direct role in disease
modulation, future probiotic administration to drive the
microbiota composition toward that seen during helminth
infection may be a novel therapeutic approach.
Microbiota-based therapies
Probiotics are live bacteria which, when administered, are
beneficial to host health. Animal model research using
probiotics shows their ability to ameliorate symptoms in
atopic disease, IBD, and T1D.66,92,119,122–125 Additionally, pro-
biotic administration in humans has been shown to protect
against allergic rhinitis, peanut allergy, AD, and UC.124,126–129
However, research thus far reveals many gaps in probiotic
therapy, likely due to individualized disease phenotypes that
may or may not be linked to the specific microbial species
tested.130–132 Consequently, prebiotic and synbiotic therapeu-
tics are also being explored.
Prebiotics are chemicals or food components (eg, inu-
lin, pectin, GOSs, and FOSs), which are indigestible by
pancreatic and intestinal enzymes, but are important in the
growth and proliferation of intestinal microbiota.133 Prebiotic
substances can induce the production of SCFAs by intestinal
microbes, which have been shown to promote effector (Th1
and Th17) and anti-inflammatory IL-10-producing FoxP3+
and non-FoxP3+ T-cell differentiation.48,49 As such, they con-
tinue to be a promising microbe-based therapeutic option to
modulate intestinal immune responses. Supplementation of
mice with a mixture of short-chain GOS, long-chain GOS,
and pectin-derived acidic oligosaccharides prior to OVA
challenge suppressed airway inflammation and hyperrespon-
siveness compared to controls.134 Additionally, Trompette
et al show that a high-fiber diet (diet supplemented with
30% pectin) metabolized by the gut microbiota increases
the concentrations of circulating SCFAs and decreases aller-
gic inflammation in the lungs of an HDM-driven model of
allergic inflammation.47 In humans, prebiotic oligosaccharide
formula supplementation in the first 6 months of life has been
associated with decreased incidences of allergic manifesta-
tions until 2 years of age, supporting early life intervention
in humans.57 Additionally, prebiotics have been implicated
in protection from IBD development. Human leukocyte
antigen-B27 transgenic (HLA-B27, TG) rats supplemented
with FOS and inulin prior to disease onset showed decreased
intestinal inflammation compared to untreated rats; however,
FOS-treated rats compared to inulin-treated rats showed less
intestinal inflammation, suggesting FOS as a more effective
prebiotic treatment for spontaneous colitis.135 Conversely,
FOS was not an effective treatment for CD, as patients
receiving the treatment after 4 weeks exhibited higher GI
symptoms compared to the placebo group, despite the
reduced IL-6 and increased IL-10 production from lamina
propria dendritic cells.136
Synbiotic therapies involve supplementation with both
pre- and probiotics. In a murine model for cow’s milk allergy,
mice fed the synbiotic mixture (GOS, FOS, and Bifidobacte-
rium breve M-16V) showed increased galectin-9 expression
by intestinal epithelial cells, which correlated with reduced
acute skin reaction and mast cell degranulation.137 Similar
results were measured in humans fed the synbiotic mixture,
suggesting a mechanism by which this therapy may be
effective in protecting against AD in humans.137 Conversely,
a clinical trial using a similar synbiotic mixture, Immuno-
fortis®, found no difference in AD severity in the synbiotic
group versus the placebo group.138 However, this research
group did later find in infants with AD that supplementation
with this mixture for 12 weeks correlated with decreased
prevalence of wheezing and asthma medication usage after
1 year.139 Synbiotics are also potential therapeutics for IBD.
In a controlled pilot trial involving 18 patients with active
UC, short-term synbiotic therapy combining B. longum and
inulin-oligofructose significantly reduced chronic inflamma-
tory biomarkers of the disease, including decreased TNFα
and IL-1α levels.140
The effects of early life factors such as diet and antibiotic
exposure discussed throughout this review suggest that the
application of live helmiths/helminth ES products, and pro-,
pre-, and synbiotics prior to disease onset may be key in
averting disease development, because interventions occur-
ring later in life or after disease onset may be ineffective after
the neonatal immune developmental window has closed. The
timing of this developmental window could be driven by
epigenetic alterations to specific, microbially regulated fac-
tors, such as the CXCL16 gene described by Olszak et al.68
In previously GF mice colonized neonatally with a conven-
tional microbiota, the presence of a conventional microbiota
decreased hypermethylation of CXCL16, which consequently
decreased accumulation of invariant NK T-cells in the colon
(this did not occur in previously GF mice colonized until
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The hygiene hypothesis: a review
they reached adulthood). This suggests that microbe-based
therapeutics aimed at protecting against hyperinflammatory
diseases are age-sensitive.67 Additionally, the incongruity of
current research highlights the need for future microbiota-
based treatments that are constructed as individualized thera-
peutics specific to the disease phenotype and microbiota of
the affected patient.
Conclusion
The progression of research since Strachan’s 1989 proposal
of the hygiene hypothesis exemplifies the scientific method
in health research, progressing from observational theory
to experimental therapy. The hygiene hypothesis has been
expanded today to include commensal and symbiotic intes-
tinal microbes, which are profoundly involved in human
immune development, and parasitic helminths, which are
also strong therapeutic candidates to protect against immune
dysregulation. More research addressing the early life “critical
window” for microbiota intervention, currently being assessed
in mice for hypersensitivity diseases, is needed if researchers
hope to use these therapeutics to prevent immune dysregulation
in humans.68–71 Children undergo large shifts in their intestinal
microbiota compositions throughout the first few months of
life; thus, it may be possible in the near future to shift the gut
microbial composition using pro-, pre-, and synbiotics toward
a microbiota that promotes immune tolerance.72
Acknowledgments
LT Stiemsma is supported by the University of British
Columbia Four-Year Fellowship. SET holds the Aubrey
J Tingle Professorship in Pediatric Immunology and is a
clinical scholar of the Michael Smith Foundation for Health
Research. Work in the Finlay and Turvey labs is supported by
a Canadian Institutes of Health Research (CIHR) Emerging
Team Grant in partnership with Genome BC and AllerGen
NCE, the Allergy, Genes and Environment Network.
Disclosure
The authors report no conflicts of interest in this work.
References
1. [No authors listed]. Worldwide variation in prevalence of symptoms of
asthma, allergic rhinoconjunctivitis, and atopic eczema: ISAAC. The
International Study of Asthma and Allergies in Childhood (ISAAC)
Steering Committee. Lancet. 1998;351(9111):1225–1232.
2. Anandan C, Nurmatov U, van Schayck OC, Sheikh A. Is the prevalence
of asthma declining? Systematic review of epidemiological studies.
Allergy. 2010;65(2):152–167.
3. Okada H, Kuhn C, Feillet H, Bach JF. The ‘hygiene hypothesis’ for
autoimmune and allergic diseases: an update. Clin Exp Immunol. 2010;
160(1):1–9.
4. Brooks C, Pearce N, Douwes J. The hygiene hypothesis in allergy
and asthma: an update. Curr Opin Allergy Clin Immunol. 2013;13(1):
70–77.
5. Greenwood BM. Polyarthritis in Western Nigeria. I. Rheumatoid arthri-
tis. Ann Rheum Dis. 1969;28(5):488–496.
6. Greenwood BM, Herrick EM, Voller A. Suppression of autoimmune
disease in NZB and (NZB x NZW) F1 hybrid mice by infection with
malaria. Nature. 1970;226(5242):266–267.
7. Gerrard JW, Geddes CA, Reggin PL, Gerrard CD, Horne S. Serum IgE
levels in white and metis communities in Saskatchewan. Ann Allergy.
1976;37(2):91–100.
8. Strachan DP. Hay fever, hygiene, and household size. BMJ. 1989;
299(6710):1259–1260.
9. Strachan DP, Taylor EM, Carpenter RG. Family structure, neonatal
infection, and hay fever in adolescence. Arch Dis Child. 1996;74(5):
422–426.
10. Ownby DR, Johnson CC, Peterson EL. Exposure to dogs and cats in
the first year of life and risk of allergic sensitization at 6 to 7 years of
age. JAMA. 2002;288(8):963–972.
11. Benn CS, Melbye M, Wohlfahrt J, Björkstén B, Aaby P. Cohort study
of sibling effect, infectious diseases, and risk of atopic dermatitis during
first 18 months of life. BMJ. 2004;328(7450):1223.
12. Matricardi PM, Rosmini F, Riondino S, et al. Exposure to foodborne and
orofecal microbes versus airborne viruses in relation to atopy and aller-
gic asthma: epidemiological study. BMJ. 2000;320(7232):412–417.
13. Ege MJ, Mayer M, Normand AC, et al; GABRIELA Transregio 22
Study Group. Exposure to environmental microorganisms and childhood
asthma. N Engl J Med. 2011;364(8):701–709.
14. Mosmann TR, Cherwinski H, Bond MW, Giedlin MA, Coffman RL.
Two types of murine helper T cell clone. I. Definition according to
profiles of lymphokine activities and secreted proteins. J Immunol.
1986;136(7):2348–2357.
15. Bosnjak B, Stelzmueller B, Erb KJ, Epstein MM. Treatment of aller-
gic asthma: modulation of Th2 cells and their responses. Respir Res.
2011;12:114.
16. Huang L, Krieg AM, Eller N, Scott DE. Induction and regulation of
Th1-inducing cytokines by bacterial DNA, lipopolysaccharide, and
heat-inactivated bacteria. Infect Immun. 1999;67(12):6257–6263.
17. Oriss TB, McCarthy SA, Morel BF, Campana MA, Morel PA.
Crossregulation between T helper cell (Th)1 and Th2: inhibition of
Th2 proliferation by IFN-gamma involves interference with IL-1.
J Immunol. 1997;158(8):3666–3672.
18. Maizels RM, McSorley HJ, Smyth DJ. Helminths in the hygiene
hypothesis: sooner or later? Clin Exp Immunol. 2014;177(1):38–46.
19. O’Shea JJ, Paul WE. Mechanisms underlying lineage commitment
and plasticity of helper CD4+ T cells. Science. 2010;327(5969):
1098–1102.
20. Lloyd CM, Saglani S. T cells in asthma: influences of genetics, envi-
ronment, and T-cell plasticity. J Allergy Clin Immunol. 2013;131(5):
1267–1274; quiz 1275.
21. Holgate ST. Innate and adaptive immune responses in asthma. Nat Med.
2012;18(5):673–683.
22. Rook GA, Adams V, Hunt J, Palmer R, Martinelli R, Brunet LR.
Mycobacteria and other environmental organisms as immunomodula-
tors for immunoregulatory disorders. Springer Semin Immunopathol.
2004;25(3–4):237–255.
23. Noverr MC, Huffnagle GB. The ‘microflora hypothesis’ of allergic
diseases. Clin Exp Allergy. 2005;35(12):1511–1520.
24. Rook GA, Brunet LR. Microbes, immunoregulation, and the gut. Gut.
2005;54(3):317–320.
25. van den Biggelaar AH, van Ree R, Rodrigues LC, et al.
Decreased atopy in children infected with Schistosoma hae-
matobium: a role for parasite-induced interleukin-10. Lancet.
2000;356(9243):1723–1727.
26. Wilson MS, Taylor MD, Balic A, Finney CAM, Lamb JR, Maizels RM.
Suppression of allergic airway inflammation by helminth-induced
regulatory T cells. J Exp Med. 2005;202(9):1199–1212.
ImmunoTargets and Therapy 2015:4
submit your manuscript | www.dovepress.com
Dovepress
Dovepress
154
Stiemsma et al
27. Kitagaki K, Businga TR, Racila D, Elliott DE, Weinstock JV, Kline JN.
Intestinal helminths protect in a murine model of asthma. J Immunol.
2006;177(3):1628–1635.
28. Mangan NE, Fallon RE, Smith P, van Rooijen N, McKenzie AN, Fallon
PG. Helminth infection protects mice from anaphylaxis via IL-10-
producing B cells. J Immunol. 2004;173(10):6346–6356.
29. Liu Q, Sundar K, Mishra PK, et al. Helminth infection can reduce
insulitis and type 1 diabetes through CD25- and IL-10-independent
mechanisms. Infect Immun. 2009;77(12):5347–5358.
30. Mishra PK, Patel N, Wu W, Bleich D, Gause WC. Prevention of type 1
diabetes through infection with an intestinal nematode parasite requires
IL-10 in the absence of a Th2-type response. Mucosal Immunol.
2013;6(2):297–308.
31. Hübner MP, Stocker JT, Mitre E. Inhibition of type 1 diabetes in
filaria-infected non-obese diabetic mice is associated with a T helper
type 2 shift and induction of FoxP3+ regulatory T cells. Immunology.
2009;127(4):512–522.
32. Hübner MP, Shi Y, Torrero MN, et al. Helminth protection against
autoimmune diabetes in nonobese diabetic mice is independent of a
type 2 immune shift and requires TGF-beta. J Immunol. 2012;188(2):
559–568.
33. McSorley HJ, Maizels RM. Helminth infections and host immune
regulation. Clin Microbiol Rev. 2012;25(4):585–608.
34. O’hara AM, Shanahan F. The gut flora as a forgotten organ. Embo
Reports. 2006;7(7):688–693.
35. Pollard M, Sharon N. Responses of the Peyer’s patches in germ-free
mice to antigenic stimulation. Infect Immun. 1970;2(1):96–100.
36. Round JL, Mazmanian SK. The gut microbiota shapes intestinal immune
responses during health and disease. Nat Rev Immunol. 2009;9(5):
313–323.
37. Fagundes CT, Amaral FA, Vieira AT, et al. Transient TLR activation
restores inflammatory response and ability to control pulmonary bacte-
rial infection in germfree mice. J Immunol. 2012;188(3):1411–1420.
38. Inagaki H, Suzuki T, Nomoto K, Yoshikai Y. Increased susceptibility to
primary infection with Listeria monocytogenes in germfree mice may
be due to lack of accumulation of L-selectin+ CD44+ T cells in sites
of inflammation. Infect Immun. 1996;64(8):3280–3287.
39. Yi P, Li L. The germfree murine animal: an important animal model
for research on the relationship between gut microbiota and the host.
Vet Microbiol. 2012;157(1–2):1–7.
40. Cash HL, Whitham CV, Behrendt CL, Hooper LV. Symbiotic
bacteria direct expression of an intestinal bactericidal lectin. Science.
2006;313(5790):1126–1130.
41. Lindén SK, Florin TH, McGuckin MA. Mucin dynamics in intestinal
bacterial infection. PLoS One. 2008;3(12):e3952.
42. Rakoff-Nahoum S, Paglino J, Eslami-Varzaneh F, Edberg S, Medzhi-
tov R. Recognition of commensal microflora by toll-like receptors is
required for intestinal homeostasis. Cell. 2004;118(2):229–241.
43. Cording S, Fleissner D, Heimesaat MM, et al. Commensal microbiota
drive proliferation of conventional and Foxp3(+) regulatory CD4(+) T
cells in mesenteric lymph nodes and Peyer’s patches. Eur J Microbiol
Immunol (Bp). 2013;3(1):1–10.
44. Shaw MH, Kamada N, Kim YG, Núñez G. Microbiota-induced IL-1beta,
but not IL-6, is critical for the development of steady-state TH17 cells
in the intestine. J Exp Med. 2012;209(2):251–258.
45. Atarashi K, Tanoue T, Shima T, et al. Induction of colonic regulatory
T cells by indigenous Clostridium species. Science. 2011;331(6015):
337–341.
46. Marcobal A, Barboza M, Froehlich JW, et al. Consumption of human
milk oligosaccharides by gut-related microbes. J Agric Food Chem.
2010;58(9):5334–5340.
47. Trompette A, Gollwitzer ES, Yadava K, et al. Gut microbiota metabolism
of dietary fiber influences allergic airway disease and hematopoiesis.
Nat Med. 2014;20(2):159–166.
48. Wong JM, de Souza R, Kendall CW, Emam A, Jenkins DJ. Colonic
health: fermentation and short chain fatty acids. J Clin Gastroenterol.
2006;40(3):235–243.
49. Park J, Kim M, Kang SG, et al. Short-chain fatty acids induce both effec-
tor and regulatory T cells by suppression of histone deacetylases and
regulation of the mTOR-S6K pathway. Mucosal Immunol. 2015;8(1):
80–93.
50. Smith PM, Howitt MR, Panikov N, et al. The microbial metabolites,
short-chain fatty acids, regulate colonic Treg cell homeostasis. Science.
2013;341(6145):569–573.
51. Abrahamsson TR, Jakobsson HE, Andersson AF, Björkstén B,
Engstrand L, Jenmalm MC. Low gut microbiota diversity in
early infancy precedes asthma at school age. Clin Exp Allergy.
2014;44(6):842–850.
52. Azad MB, Konya T, Guttman DS, et al; CHILD Study Investigators.
Infant gut microbiota and food sensitization: associations in the first
year of life. Clin Exp Allergy. 2015;45(3):632–643.
53. Hoskin-Parr L, Teyhan A, Blocker A, Henderson AJ. Antibiotic exposure
in the first two years of life and development of asthma and other aller-
gic diseases by 7.5 yr: a dose-dependent relationship. Pediatr Allergy
Immunol. 2013;24(8):762–771.
54. Kummeling I, Stelma FF, Dagnelie PC, et al. Early life exposure to
antibiotics and the subsequent development of eczema, wheeze, and
allergic sensitization in the first 2 years of life: the KOALA Birth Cohort
Study. Pediatrics. 2007;119(1):e225–e231.
55. Jakobsson HE, Abrahamsson TR, Jenmalm MC, et al. Decreased
gut microbiota diversity, delayed Bacteroidetes colonisation and
reduced Th1 responses in infants delivered by caesarean section. Gut.
2014;63(4):559–566.
56. Penders J, Thijs C, Vink C, et al. Factors influencing the composition
of the intestinal microbiota in early infancy. Pediatrics. 2006;118(2):
511–521.
57. Arslanoglu S, Moro GE, Schmitt J, Tandoi L, Rizzardi S, Boehm G.
Early dietary intervention with a mixture of prebiotic oligosaccharides
reduces the incidence of allergic manifestations and infections during
the first two years of life. J Nutr. 2008;138(6):1091–1095.
58. Penders J, Gerhold K, Stobberingh EE, et al. Establishment of the intes-
tinal microbiota and its role for atopic dermatitis in early childhood. J
Allergy Clin Immunol. 2013;132(3):601–607. e8.
59. Mullooly JP, Schuler R, Barrett M, Maher JE. Vaccines, antibiotics, and
atopy. Pharmacoepidemiol Drug Saf. 2007;16(3):275–288.
60. Ortqvist AK, Lundholm C, Kieler H, et al. Antibiotics in fetal and early
life and subsequent childhood asthma: nationwide population based
study with sibling analysis. BMJ. 2014;349:g6979.
61. Sears MR, Greene JM, Willan AR, et al. Long-term relation between
breastfeeding and development of atopy and asthma in children
and young adults: a longitudinal study. Lancet. 2002;360(9337):
901–907.
62. Almqvist C, Cnattingius S, Lichtenstein P, Lundholm C. The impact
of birth mode of delivery on childhood asthma and allergic diseases –
a sibling study. Clin Exp Allergy. 2012;42(9):1369–1376.
63. Maitra A, Sherriff A, Strachan D, Henderson J, Team AS. Mode of
delivery is not associated with asthma or atopy in childhood. Clin Exp
Allergy. 2004;34(9):1349–1355.
64. Kramer MS, Matush L, Vanilovich I, et al; Promotion of Breastfeed-
ing Intervention Trial (PROBIT) Study Group. Effect of prolonged
and exclusive breast feeding on risk of allergy and asthma: cluster
randomised trial. BMJ. 2007;335(7624):815.
65. Forsythe P, Inman MD, Bienenstock J. Oral treatment with live
Lactobacillus reuteri inhibits the allergic airway response in mice.
Am J Respir Crit Care Med. 2007;175(6):561–569.
66. Schabussova I, Hufnagl K, Wild C, et al. Distinctive anti-allergy prop-
erties of two probiotic bacterial strains in a mouse model of allergic
poly-sensitization. Vaccine. 2011;29(10):1981–1990.
67. Lyons A, O’Mahony D, O’Brien F, et al. Bacterial strain-specific induc-
tion of Foxp3+ T regulatory cells is protective in murine allergy models.
Clin Exp Allergy. 2010;40(5):811–819.
68. Olszak T, An D, Zeissig S, et al. Microbial exposure during early life
has persistent effects on natural killer T cell function. Science. 2012;
336(6080):489–493.
ImmunoTargets and Therapy 2015:4 submit your manuscript | www.dovepress.com
Dovepress
Dovepress
155
The hygiene hypothesis: a review
69. Arnold IC, Dehzad N, Reuter S, et al. Helicobacter pylori infection
prevents allergic asthma in mouse models through the induction of
regulatory T cells. J Clin Invest. 2011;121(8):3088–3093.
70. Russell SL, Gold MJ, Willing BP, Thorson L, McNagny KM, Finlay BB.
Perinatal antibiotic treatment affects murine microbiota, immune
responses and allergic asthma. Gut Microbes. 2013;4(2):158–164.
71. Russell SL, Gold MJ, Reynolds LA, et al. Perinatal antibiotic-induced
shifts in gut microbiota have differential effects on inflammatory lung
diseases. J Allergy Clin Immunol. 2015;135(1):100–109.
72. Arrieta MC, Stiemsma LT, Amenyogbe N, Brown EM, Finlay B. The
intestinal microbiome in early life: health and disease. Front Immunol.
2014;5:427.
73. Molodecky NA, Soon IS, Rabi DM, et al. Increasing incidence and
prevalence of the inflammatory bowel diseases with time, based on
systematic review. Gastroenterol. 2012;142(1):46–54. e42; quiz e30.
74. Sellon RK, Tonkonogy S, Schultz M, et al. Resident enteric bacteria are
necessary for development of spontaneous colitis and immune system
activation in interleukin-10-deficient mice. Infect Immun. 1998;66(11):
5224–5231.
75. Madsen KL, Doyle JS, Tavernini MM, Jewell LD, Rennie RP,
Fedorak RN. Antibiotic therapy attenuates colitis in interleukin 10 gene-
deficient mice. Gastroenterol. 2000;118(6):1094–1105.
76. Bamias G, Marini M, Moskaluk CA, et al. Down-regulation of intes-
tinal lymphocyte activation and Th1 cytokine production by antibiotic
therapy in a murine model of Crohn’s disease. J Immunol. 2 002;169(9):
5308–5314.
77. Hoentjen F, Harmsen HJ, Braat H, et al. Antibiotics with a selective
aerobic or anaerobic spectrum have different therapeutic activities in
various regions of the colon in interleukin 10 gene deficient mice. Gut.
2003;52(12):1721–1727.
78. Shaw SY, Blanchard JF, Bernstein CN. Association between the use of
antibiotics and new diagnoses of Crohn’s disease and ulcerative colitis.
Am J Gastroenterol. 2011;106(12):2133–2142.
79. Hviid A, Svanström H, Frisch M. Antibiotic use and inflammatory
bowel diseases in childhood. Gut. 2011;60(1):49–54.
80. Shaw SY, Blanchard JF, Bernstein CN. Association between the use
of antibiotics in the first year of life and pediatric inflammatory bowel
disease. Am J Gastroenterol. 2010;105(12):2687–2692.
81. Koido S, Ohkusa T, Kajiura T, et al. Long-term alteration of intestinal
microbiota in patients with ulcerative colitis by antibiotic combination
therapy. PLoS One. 2014;9(1):e86702.
82. Rogier EW, Frantz AL, Bruno ME, et al. Secretory antibodies in
breast milk promote long-term intestinal homeostasis by regulating the
gut microbiota and host gene expression. Proc Natl Acad Sci U S A.
2014;111(8):3074–3079.
83. Barclay AR, Russell RK, Wilson ML, Gilmour WH, Satsangi J,
Wilson DC. Systematic review: the role of breastfeeding in the develop-
ment of pediatric inflammatory bowel disease. J Pediatr. 2009;155(3):
421–426.
84. Karvonen M, Viik-Kajander M, Moltchanova E, Libman I, LaPorte R,
Tuomilehto J. Incidence of childhood type 1 diabetes worldwide. Dia-
betes Mondiale (DiaMond) Project Group. Diabetes Care. 2000;23(10):
1516–1526.
85. DIAMOND Project Group. Incidence and trends of childhood
Type 1 diabetes worldwide 1990–1999. Diabet Med. 2006;23(8):
857–866.
86. D’Angeli MA, Merzon E, Valbuena LF, Tirschwell D, Paris CA, Mueller
BA. Environmental factors associated with childhood-onset type 1 dia-
betes mellitus: an exploration of the hygiene and overload hypotheses.
Arch Pediatr Adolesc Med. 2010;164(8):732–738.
87. Virtanen SM, Takkinen HM, Nwaru BI, et al. Microbial exposure in
infancy and subsequent appearance of type 1 diabetes mellitus-associated
autoantibodies: a cohort study. JAMA Pediatr. 2014;168(8): 755–763.
88. Brugman S, Visser JTJ, Hillebrands JL, Bos NA, Rozing J. Prolonged
exclusive breastfeeding reduces autoimmune diabetes incidence and
increases regulatory T-cell frequency in bio-breeding diabetes-prone
rats. Diabetes Metab Res Rev. 2009;25(4):380–387.
89. Cardwell CR, Stene LC, Joner G, et al. Caesarean section is associated
with an increased risk of childhood-onset type 1 diabetes mellitus:
a meta-analysis of observational studies. Diabetologia. 2008;51(5):
726–735.
90. Bonifacio E, Warncke K, Winkler C, Wallner M, Ziegler AG. Cesarean
section and interferon-induced helicase gene polymorphisms combine
to increase childhood type 1 diabetes risk. Diabetes. 2011;60(12):
3300–3306.
91. Mejía-León ME, Petrosino JF, Ajami NJ, Domínguez-Bello MG, de
la Barca AM. Fecal microbiota imbalance in Mexican children with
type 1 diabetes. Sci Rep. 2014;4:3814.
92. Valladares R, Sankar D, Li N, et al. Lactobacillus johnsonii N6.2
mitigates the development of type 1 diabetes in BB-DP rats. PLoS
One. 2010;5(5):e10507.
93. Wen L, Ley RE, Volchkov PY, et al. Innate immunity and intestinal
microbiota in the development of Type 1 diabetes. Nature. 2008;
455(7216):1109–1113.
94. Kriegel MA, Sefik E, Hill JA, Wu HJ, Benoist C, Mathis D. Naturally
transmitted segmented filamentous bacteria segregate with diabetes
protection in nonobese diabetic mice. Proc Natl Acad Sci U S A. 2011;
108(28):11548–11553.
95. Hara N, Alkanani AK, Ir D, et al. Prevention of virus-induced
type 1 diabetes with antibiotic therapy. J Immunol. 2012;189(8):
3805–3814.
96. Hviid A, Svanström H. Antibiotic use and type 1 diabetes in childhood.
Am J Epidemiol. 2009;169(9):1079–1084.
97. Apiwattanakul N, Thomas PG, Iverson AR, McCullers JA. Chronic
helminth infections impair pneumococcal vaccine responses. Vaccine.
2014;32(42):5405–5410.
98. Bobat S, Darby M, Mrdjen D, et al. Natural and vaccine-mediated
immunity to Salmonella typhimurium is impaired by the helm-
inth Nippostrongylus brasiliensis. PLoS Negl Trop Dis. 2014;
8(12):e3341.
99. Cooper PJ, Espinel I, Paredes W, Guderian RH, Nutman TB. Impaired
tetanus-specific cellular and humoral responses following tetanus vac-
cination in human onchocerciasis: a possible role for interleukin-10.
J Infect Dis. 1998;178(4):1133–1138.
100. Cooper PJ, Chico M, Sandoval C, et al. Human infection with Ascaris
lumbricoides is associated with suppression of the interleukin-2
response to recombinant cholera toxin B subunit following vaccina-
tion with the live oral cholera vaccine CVD 103-HgR. Infect Immun.
2001;69(3):1574–1580.
101. Sabin EA, Araujo MI, Carvalho EM, Pearce EJ. Impairment of tetanus
toxoid-specific Th1-like immune responses in humans infected with
Schistosoma mansoni. J Infect Dis. 1996;173(1):269–272.
102. Fleming JO, Weinstock JV. Clinical trials of helminth therapy in
autoimmune diseases: rationale and findings. Parasite Immunol.
2015;37(6):277–292.
103. Summers RW, Elliott DE, Urban JF Jr, Thompson R, Weinstock JV.
Trichuris suis therapy in Crohn’s disease. Gut. 2005;54(1):87–90.
104. Sandborn WJ, Elliott DE, Weinstock J, et al. Randomised clinical trial:
the safety and tolerability of Trichuris suis ova in patients with Crohn’s
disease. Aliment Pharmacol Ther. 2013;38(3):255–263.
105. Croese J, O’Neil J, Masson J, et al. A proof of concept study establish-
ing Necator americanus in Crohn’s patients and reservoir donors. Gut.
2006;55(1):136–137.
106. Summers RW, Elliott DE, Qadir K, Urban JF Jr, Thompson R,
Weinstock JV. Trichuris suis seems to be safe and possibly effective
in the treatment of inflammatory bowel disease. Am J Gastroenterol.
2003;98(9):2034–2041.
107. Feary J, Venn A, Brown A, et al. Safety of hookworm infection in
individuals with measurable airway responsiveness: a randomized
placebo-controlled feasibility study. Clin Exp Allergy. 2009;39(7):
1060–1068.
108. Summers RW, Elliott DE, Urban JF Jr, Thompson RA, Weinstock JV.
Trichuris suis therapy for active ulcerative colitis: a randomized
controlled trial. Gastroenterol. 2005;128(4):825–832.
ImmunoTargets and Therapy 2015:4
submit your manuscript | www.dovepress.com
Dovepress
Dovepress
156
Stiemsma et al
109. Hewitson JP, Grainger JR, Maizels RM. Helminth immunoregulation:
the role of parasite secreted proteins in modulating host immunity. Mol
Biochem Parasitol. 2009;167(1):1–11.
110. McSorley HJ, O’Gorman MT, Blair N, Sutherland TE, Filbey KJ,
Maizels RM. Suppression of type 2 immunity and allergic airway
inflammation by secreted products of the helminth Heligmosomoides
polygyrus. Eur J Immunol. 2012;42(10):2667–2682.
111. McSorley HJ, Blair NF, Smith KA, McKenzie AN, Maizels RM.
Blockade of IL-33 release and suppression of type 2 innate lymphoid
cell responses by helminth secreted products in airway allergy.
Mucosal Immunol. 2014;7(5):1068–1078.
112. Ruyssers NE, De Winter BY, De Man JG, et al. Therapeutic potential
of helminth soluble proteins in TNBS-induced colitis in mice. Inflamm
Bowel Dis. 2009;15(4):491–500.
113. Cançado GG, Fiuza JA, de Paiva NC, et al. Hookworm products
ameliorate dextran sodium sulfate-induced colitis in BALB/c mice.
Inflamm Bowel Dis. 2011;17(11):2275–2286.
114. Schnoeller C, Rausch S, Pillai S, et al. A helminth immunomodulator
reduces allergic and inflammatory responses by induction of IL-10-
producing macrophages. J Immunol. 2008;180(6):4265–4272.
115. Ferreira I, Smyth D, Gaze S, et al. Hookworm excretory/secretory
products induce interleukin-4 (IL-4)+ IL-10+ CD4+ T cell responses
and suppress pathology in a mouse model of colitis. Infect Immun.
2013;81(6):2104–2111.
116. Zaccone P, Fehérvári Z, Jones FM, et al. Schistosoma mansoni antigens
modulate the activity of the innate immune response and prevent onset
of type 1 diabetes. Eur J Immunol. 2003;33(5):1439–1449.
117. Culley FJ, Brown A, Conroy DM, Sabroe I, Pritchard DI, Williams TJ.
Eotaxin is specifically cleaved by hookworm metalloproteases pre-
venting its action in vitro and in vivo. J Immunol. 2000;165(11):
6447–6453.
118. Grainger JR, Smith KA, Hewitson JP, et al. Helminth secretions induce
de novo T cell Foxp3 expression and regulatory function through the
TGF- β pathway. J Exp Med. 2010;207(11):2331–2341.
119. Rausch S, Held J, Fischer A, et al. Small intestinal nematode infection
of mice is associated with increased enterobacterial loads alongside
the intestinal tract. PLoS One. 2013;8(9):e74026.
120. Reynolds LA, Smith KA, Filbey KJ, et al. Commensal-pathogen
interactions in the intestinal tract: lactobacilli promote infection with,
and are promoted by, helminth parasites. Gut Microbes. 2014;5(4):
522–532.
121. Walk ST, Blum AM, Ewing SA, Weinstock JV, Young VB. Alteration
of the murine gut microbiota during infection with the parasitic helm-
inth Heligmosomoides polygyrus. Inflamm Bowel Dis. 2010;16(11):
1841–1849.
122. Schultz M, Veltkamp C, Dieleman LA, et al. Lactobacillus plan-
tarum 299V in the treatment and prevention of spontaneous colitis
in interleukin-10-deficient mice. Inflamm Bowel Dis. 2002;8(2):
71–80.
123. Nanda Kumar NS, Balamurugan R, Jayakanthan K, Pulimood A,
Pugazhendhi S, Ramakrishna BS. Probiotic administration alters the
gut flora and attenuates colitis in mice administered dextran sodium
sulfate. J Gastroenterol Hepatol. 2008;23(12):1834–1839.
124. Calcinaro F, Dionisi S, Marinaro M, et al. Oral probiotic administra-
tion induces interleukin-10 production and prevents spontaneous
autoimmune diabetes in the non-obese diabetic mouse. Diabetologia.
2005;48(8):1565–1575.
125. Duan FF, Liu JH, March JC. Engineered commensal bacteria repro-
gram intestinal cells into glucose-responsive insulin-secreting cells
for the treatment of diabetes. Diabetes. 2015;64(5):1794–1803.
126. Tang ML, Ponsonby AL, Orsini F, et al. Administration of a probiotic
with peanut oral immunotherapy: a randomized trial. J Allergy Clin
Immunol. 2015;135(3):737–744. e8.
127. Rosenfeldt V, Benfeldt E, Nielsen SD, et al. Effect of probiotic
Lactobacillus strains in children with atopic dermatitis. J Allergy Clin
Immunol. 2003;111(2):389–395.
128. Oliva S, Di Nardo G, Ferrari F, et al. Randomised clinical trial: the
effectiveness of Lactobacillus reuteri ATCC 55730 rectal enema in
children with active distal ulcerative colitis. Aliment Pharmacol Ther.
2012;35(3):327–334.
129. Kruis W, Fric P, Pokrotnieks J, et al. Maintaining remission of ulcerative
colitis with the probiotic Escherichia coli Nissle 1917 is as effective
as with standard mesalazine. Gut. 2004;53(11):1617–1623.
130. Abrahamsson TR, Jakobsson T, Björkstén B, Oldaeus G, Jenmalm MC.
No effect of probiotics on respiratory allergies: a seven-year follow-up
of a randomized controlled trial in infancy. Pediatr Allergy Immunol.
2013;24(6):556–561.
131. Boyle RJ, Bath-Hextall FJ, Leonardi-Bee J, Murrell DF, Tang ML.
Probiotics for the treatment of eczema: a systematic review. Clin Exp
Allergy. 2009;39(8):1117–1127.
132. Feighery LM, Smith P, O’Mahony L, Fallon PG, Brayden DJ.
Effects of Lactobacillus salivarius 433118 on intestinal inflam-
mation, immunity status and in vitro colon function in two mouse
models of inflammatory bowel disease. Dig Dis Sci. 2008;53(9):
2495–2506.
133. Cummings JH, Macfarlane GT, Englyst HN. Prebiotic digestion and
fermentation. Am J Clin Nutr. 2001;73(2 Suppl):415S–420S.
134. Vos AP, van Esch BC, Stahl B, et al. Dietary supplementation with
specific oligosaccharide mixtures decreases parameters of allergic
asthma in mice. Int Immunopharmacol. 2007;7(12):1582–1587.
135. Koleva PT, Valcheva RS, Sun X, Gänzle MG, Dieleman LA. Inulin and
fructo-oligosaccharides have divergent effects on colitis and commen-
sal microbiota in HLA-B27 transgenic rats. Br J Nutr. 2012;108(9):
1633–1643.
136. Benjamin JL, Hedin CR, Koutsoumpas A, et al. Randomised, double-
blind, placebo-controlled trial of fructo-oligosaccharides in active
Crohn’s disease. Gut. 2011;60(7):923–929.
137. de Kivit S, Saeland E, Kraneveld AD, et al. Galectin-9 induced by
dietary synbiotics is involved in suppression of allergic symptoms in
mice and humans. Allergy. 2012;67(3):343–352.
138. van der Aa LB, Heymans HS, van Aalderen WM, et al; Synbad Study
Group. Effect of a new synbiotic mixture on atopic dermatitis in
infants: a randomized-controlled trial. Clin Exp Allergy. 2010;40(5):
795–804.
139. van der Aa LB, van Aalderen WM, Heymans HS, et al; Synbad Study
Group. Synbiotics prevent asthma-like symptoms in infants with atopic
dermatitis. Allergy. 2011;66(2):170–177.
140. Furrie E, Macfarlane S, Kennedy A, et al. Synbiotic therapy
(Bifidobacterium longum/Synergy 1) initiates resolution of inflamma-
tion in patients with active ulcerative colitis: a randomised controlled
pilot trial. Gut. 2005;54(2):242–249.
141. Lue KH, Sun HL, Lu KH, et al. A trial of adding Lactobacillus
johnsonii EM1 to levocetirizine for treatment of perennial allergic
rhinitis in children aged 7–12 years. Int J Pediatr Otorhinolaryngol.
2012;76(7):994–1001.
142. Xiao JZ, Kondo S, Yanagisawa N, et al. Clinical efficacy of probiotic
Bifidobacterium longum for the treatment of symptoms of Japanese
cedar pollen allergy in subjects evaluated in an environmental exposure
unit. Allergol Int. 2007;56(1):67–75.
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