Content uploaded by Gulzar Ahmad Nayik
Author content
All content in this area was uploaded by Gulzar Ahmad Nayik on Jun 14, 2016
Content may be subject to copyright.
Citation: Jan N, Sha F, bin Hameed O, Muzaffar K, Dar SM, Majid I, et al. An Overview on Edible Vaccines and
Immunization. Austin J Nutri Food Sci. 2016; 4(2): 1078.
Austin J Nutri Food Sci - Volume 4 Issue 2 - 2016
ISSN : 2381-8980 | www.austinpublishinggroup.com
Nayik et al. © All rights are reserved
Austin Journal of Nutrition and Food
Sciences
Open Access
Abstract
Edible vaccines offer cost-effective, easily administrable, storable and
widely acceptable as bio friendly particularly in developing countries. Oral
administration of edible vaccines proves to be promising agents for reducing
the incidence of various diseases like hepatitis and diarrhea especially in the
developing world, which face the problem of storing and administering vaccines.
Edible vaccines are obtained by incorporating a particular gene of interest into
the plant, which produces the desirable encoded protein. Edible vaccines are
specic to provide mucosal activity along with systemic immunity. Various foods
that are used as alternative agents for injectable vaccines include cereals (wheat,
rice, corn) fruits (bananas) and vegetables (lettuce, potatoes, tomatoes). Thus,
edible vaccines overcome all the problems associated with traditional vaccines
and prove to be best substitutes to traditional vaccines.
Keywords: Edible vaccines; Transgenic plant; Traditional vaccines
and do not need cold-chain maintenance. Edible vaccines can be
stored at the site of use thus avoiding long-distance transportation.
Syringes and needles are also not required, thus reduces the incidence
of various infections [3]. Important advantage of edible vaccines
is elimination of contamination with animal viruses-like the mad
cow disease, which is a hazard in vaccines developed from cultured
mammalian cells, as plant viruses cannot infect humans. Edible
vaccines act by stimulating the mucosal as well as systemic immunity,
as soon they meet the digestive tract lining. is dual mechanism of
action of edible vaccines provide rst-line defense against pathogens
attacking via mucosa, like Mycobacterium tuberculosis and carriers
causing diarrhea, pneumonia, STDs, HIV etc. [1]. Oral administration
of edible vaccines to mothers might prove to be useful in immunizing
the fetus-in-utero by transplacental movement of maternal antibodies
or the infant through breast-feeding. Edible vaccines enable the
process of seroconversion in the presence of maternal antibodies,
thus playing a possible role in protecting children against diseases
like group-B Streptococcus, respiratory syncytial virus (RSV), etc. At
present edible vaccines are produced for various human and animal
diseases (measles, cholera, foot and mouth disease and hepatitis B,
C and E). ey can also be used to prevent exceptional diseases like
dengue, hookworm, rabies, etc. by combining with other vaccination
programmes enabling multiple antigen delivery. Various foods
under investigation for use in edible vaccines include banana, potato,
tomato, lettuce, rice, etc. [4].
Developing an Edible Vaccine
e selected gene obtained from the microbes encoding specic
antigen can be handled in two dierent ways:
1. Suitable plant virus is genetically engineered to produce the
desired peptides/proteins. e recombinant virus is then
incorporated into the plant, which enables it to produce a
huge number of new plants from which chimeric virions are
isolated and puried. e consequential edible plant vaccine
can then be used for immunological applications.
2. In another method, the desirable gene is incorporated with
Introduction
Vaccines have proved to be boon for the prevention of infectious
diseases. In spite of the global immunization programme for children
against the six devastating diseases, 20% of infants still remain un-
immunized which lead to approximately two million unnecessary
deaths per annum, particularly in the far ung and poor parts of the
world [1]. is is because of the limitations on vaccine production,
distribution and delivery. is problem needs to resolve in order to
prevent the spread of infections and epidemics by un-immunized
populations in the immunized, safe areas [2]. Immunization for
certain infectious diseases, either do not exist or they are unreliable
or very expensive like; immunization via DNA vaccines is substitute
but is an expensive method, along with some undesirable immune
responses. Besides being expensive, these vaccines pose the problem
of storage and transportation, as many of them require refrigeration.
Hence, there is search for easily administrable, storable, fail-safe and
widely acceptable bio friendly vaccines and their delivery systems
especially in developing countries. erefore, as substitutes have to be
produced for traditional vaccines, it was envisaged that plants could
be promising agents for ecient production system for vaccines,
which in turn gave rise to the novel concept of edible vaccines.
Concept of Edible Vaccines
Development of edible vaccines involves the process of
incorporating the selected desired genes into plants and then
enabling these altered plants to produce the encoded proteins. is
process is known as transformation, and the altered plants are known
as transgenic plants. Edible vaccines like traditional subunit vaccines
consist of antigenic proteins and are devoid of pathogenic genes.
Despite this advantage, traditional subunit vaccines are unaordable
and technology-intensive, require purication, refrigeration and
produce poor mucosal response. Unlikely, edible vaccines would
eliminate the need for trained medical personnel required for oral
administration particularly in children. Production of edible vaccines
is eective process and can be easily scaled up. Edible vaccines oer
numerous advantages like they posses good genetic and heat stability
Review Article
An Overview on Edible Vaccines and Immunization
Naeema Jan1, Fouzia Sha1, Omar bin Hameed1,
Khalid Muzaffar2, Shuaib Mohammad Dar2,
Ishrat Majid2 and Nayik GA2*
1Division of Post Harvest Technology, SKUAST-Kashmir,
India
2Department of Food Engineering & Technology, SLIET,
Punjab, India
*Corresponding author: Nayik GA, Department of
Food Engineering & Technology, SLIET, Punjab, India
Received: March 03, 2016; Accepted: June 01, 2016;
Published: June 07, 2016
Austin J Nutri Food Sci 4(2): id1078 (2016) - Page - 02
Nayik GA Austin Publishing Group
Submit your Manuscript | www.austinpublishinggroup.com
plant vector by transformation. Many other approaches have
been utilized which can be categorized into following groups:
Agrobacterium mediated gene transfer
In this method, the suitable gene (recombinant DNA) is
incorporated into the T‐region of a disarmed Ti plasmid of
Agrobacterium; a plant pathogen, which is co-cultured with the plant
cells, or tissues that needs to be transformed (Figure 1). is approach
is slow with lower yield however; it showed satisfactory results in
dicotelydenous plants like potato, tomato and tobacco. Researches
in some elds have proven this approach good in expressing the
desirable traits by selected genes in several experimental animals and
plants [5,6].
Biolistic method
is sophisticated method involves the use of gene gun that
res the gene containing DNA coated metal (e.g. gold, tungsten)
particles at the plant cells [7]. Plant cells are then permitted to grow
in new plants, which are later on cloned to produce ample number
of crop with similar genetic composition. is approach is highly
attractive due to its undependability on regeneration ability of the
species as DNA is directly incorporated into cells of plant. However,
requirement of expensive device particle gun adds to the major
drawback to this method.
Electroporation
In this method DNA is inserted into the cells aer which they are
exposed to high voltage electrical pulse which is believed to produce
transient pores within the plasma lemma. is approach requires the
additional eort of weakening the cell wall as it acts as an eective
barrier against entry of DNA into cell cytoplasm hence, it requires
mild enzymatic treatment.
Mechanism of Action
Since almost all human pathogens invade at mucosal surfaces
via urogenital, respiratory and gastrointestinal tracts as their leading
path of entry into the body. us, foremost and prime line of the
defense mechanism is mucosal immunity [8]. e most ecient
path of mucosal immunization is oral route because oral vaccines
are able to produce mucosal immunity, antibody mediated immune
response and cell mediated immune response. As an advantage
orally administered antigen containing plant vaccine do not get
hydrolysed by gastric enzymes due to tough outer wall of the plant
cell. Transgenic plants containing antigens act by the process of bio-
encapsulation, i.e., outer rigid cell wall and are nally hydrolysed and
released in the intestines. e released antigens are taken up by M
cells in the intestinal lining that are placed on Payer’s patches and
gut-associated lymphoid tissue (GALT). ese are further passed on
to macrophages and locallymphocyte populations, producing serum
IgG, IgE responses, local IgA response and memory cells, that rapidly
counterbalance the attack by the real infectious agent [1] (Figure 2).
Advantages of Edible Vaccines
1. Edible vaccines have ecient mode of action for immunization,
as they do not require subsidiary elements to stimulate immune
response.
2. Edible vaccine unlike traditional vaccines brings forth mucosal
immunity.
3. Edible vaccines are comparatively cost eective, as they do not
require cold chain storage like traditional vaccines [9].
4. Edible vaccines oer greater storage opportunities as they seeds
of transgenic plants contain lesser moisture content and can be easily
dried. In addition, plants with oil or their aqueous extracts possess
more storage opportunities [10].
5. Edible vaccines do not need sophisticated equipments and
machines as they could be easily grown on rich soils and the method
is economical compared to cell culture grown in fermenters.
6. Edible vaccines are widely accepted as they are orally
administered unlike traditional vaccines that are injectable. us,
they eliminate the requirement of trained medical personnel and the
risk of contamination is reduced as they do not need premises and
manufacturing area to be sterilized [11].
7. Edible vaccines oer greater opportunity for second-generation
vaccines by integrating numerous antigens, which approach M cells
simultaneously
8. Edible vaccines are safe as they do not contain heat-killed
pathogens and hence do not present any risk of proteins to reform
into infectious organism.
9. Edible vaccine production process can be scaled up rapidly by
breeding.
Limitations of Edible Vaccines
Following are some major drawbacks of edible vaccines,
Figure 1: Development of edible vaccines from potato.
Austin J Nutri Food Sci 4(2): id1078 (2016) - Page - 03
Nayik GA Austin Publishing Group
Submit your Manuscript | www.austinpublishinggroup.com
• Individual may develop immune tolerance to the particular
vaccine protein or peptide.
• Dosage required varies from generation to generation and,
plant to plant, protein content, patient is age, weight, ripeness
of the fruit and quantity of the food eaten.
• Edible vaccine administration requires methods for
standardization of plant material/product as low doses may
produce lesser number of antibodies and high doses are
responsible immune tolerance.
• Edible vaccines are dependent on plant stability as certain
foods cannot be eaten raw (e.g. potato) and needs cooking
that cause denaturation or weaken the protein present in it
[12].
• Edible vaccines are prone to get microbial infestation e.g.
potatoes containing vaccine can last long if stored at 4oC
while a tomato cannot last long.
• Proper demarcation line is necessary y between ‘vaccine fruit’
and ‘normal fruit’ to avoid misadministration of vaccine,
which can lead to vaccine tolerance.
• Edible vaccine function can be hampered due to vast
dierences in the glycosylation pattern of plants and humans.
Challenges
General challenges
Many dierent challenges are confronted before developing a
plant-based vaccine. However, it has been proved in three successful
human clinical trials that sucient doses of antigen can be achieved
with plant-based vaccines [11]. But, to determine dose, following
considerations need to be born in mind viz. person’s weight, age;
fruit/plants size, ripeness and protein content. e quantity to be
eaten is important, particularly in infants, who might spit it, eat
only a part or eat it whole and throw it up aerwards. Lesser dosage
fails to produce sucient antibodies, and higher dosage may lead to
tolerance. Practically it would be more appropriate to concentrate the
vaccine into a teaspoonful of baby food rather than incorporating it
in a whole fruit. e transgenic plants can further be made available
in various shapes like; pills, puddings, chips, etc. Trials to enhance
the quantity of antigens produced present a challenge in the form of
under developed growth of plants and reduced tuber/fruit formation,
because many m-RNA from the transgene lead to gene-silencing in
plant genome.
One of the approaches to overcome above mentioned challenges
is listed as follows:
Expressing the plant nuclear genetic material in; plastids [13]
foreign genes [14] fused protein coats [15] and by standardizing and
optimizing the coding sequence of bacterial/viral genes.
Non scientic challenges
Albeit, edible vaccine production is focused in the developing
countries, which is basic, reason of poor research in this eld because
smaller organizations invest in it as larger companies are engaged
in livestock market than human application. Also very, few number
of international and local government organizations support which
mostly remains underfunded. Many of the organizations have lost
interest in edible vaccines research due to unavailability of investors,
assurance in returns on investments, grants, research aid and nancial
support. Also the already available inject able vaccines for diseases
like tetanus, diphtheria etc. provide lesser opportunity to develop
edible vaccines for them as recombinant vaccines are so cheap now.
Examples of Edible Vaccines
Transgenic potatoes for diarrhea
e rst successful human trial for an edible vaccine was conducted
in year 1997 in which volunteers were fed transgenic potatoes, which
possessed the b-subunit of the E. coli heat-labile toxin, responsible for
diarrhea. A 4-fold increase in serum antibodies 1999 was manifested
in ten out of the 11 volunteers [1]. Next clinical trial took place at the
Boyce ompson Institute at Cornell University, USA, in which 20
volunteers ate the potatoes containing the Norwalk virus (responsible
for vomiting and diarrhea), out of which19 showed an immune
response [1]. Potato-based edible vaccine has a major drawback that
it needs to be eaten as raw because cooking causes denaturation of
protein and makes it uneective.
Transgenic tomatoes against diarrhea
Transgenic tomatoes were produced at the Cornell University,
in the US, against the Norwalk virus, responsible agent for severe
diarrhea. e transgenic tomatoes are capable to produce surface
protein specic to the virus and it has been shown that mice fed with
transgenic tomatoes showed an immune response towards the virus.
Figure 2: Mechanism action of edible vaccines produced from potato.
Austin J Nutri Food Sci 4(2): id1078 (2016) - Page - 04
Nayik GA Austin Publishing Group
Submit your Manuscript | www.austinpublishinggroup.com
Other transgenic plants
Presently, banana is being exploited as a good source for edible
vaccine production because of it’s two major advantages it does not
require cooking and is locally grown plant. However, the protein
expression in transgenic banana is tissue specic promoter dependent.
Several other examples involve rabies glycoprotein expressed by viral
vectors in spinach [16] and hepatitis B surface antigen in case of
lettuce and potato [17].
Applications
Cancer therapy
Several plants have been successfully engineered to generate
monoclonal antibodies that have been veried as eective cancer
therapy agents. One example is that of monoclonal body in case
of soyabean (BR-96) is an ecient agent that attacks doxorubicin
responsible for breast cancer, ovarian cancer, colon cancer and lung
tumors [18].
Birth control
Administration of TMV produces protein that is found in
Mousezona pellucida (ZB3 protein) and is capable of preventing
fertilization of eggs in mice due to resulting antibodies [18].
Chloroplast transformation
As the chloroplast genome cannot be transmitted with in crops
via usual cross pollination due to its nature of maternal inheritance
[19]. It may contribute to its transmission as well as accumulation in
ample quantities in the form of transgenic protein.
Role in autoimmune diseases
In concern with autoimmune diseases, scaling up of self- antigen
production in plants is underway in it’s developmental stage. Few
of the diseases that are under study include; multiple sclerosis,
rheumatoid arthritis, lupus and transplant rejection. In one clinical
study strain of mouse susceptible to diabetes were fed with potatoes
capable of expressing insulin and a protein called GAD (glutamic acid
decarboxylase), linked to CT-B subunit. It has been found out that the
protein proved successful in suppressing immune attack and delayed
the onset of high blood sugar level [8].
Recombinant drugs/proteins
Besides, being major producers of vaccines and antibodies,
plant compositions are altered by engineered viral inoculations to
produce enzymes; drugs (albumin, serum protease and interferon)
e.g. glucocerebrosidase (hGC) production in tobacco plants for
treating Gaucher’s disease, Interleukin-10 to treat Crohn’s disease
is method of production is quite cheaper and reduces the cost by
thousand-fold [20]. e process of recombinant therapeutic protein
production from plants has been commercialized as hirudin which
is an antithrombin-anti-viral protein that inhibits the HIV virus
in vitro, trichosanthin(ribosome in activator) and angiotensin-I
(antihypersensitive drug) [20].
The Future of Edible Vaccines
Resistance towards GM foods presents a threat to the rising
future of edible vaccines. Transgenic contamination is also a major
concern which need to be addressed properly as it led United States
to pay o approximately $12 billion. Edible vaccines before launching
in market for human applications require certication by WHO in
terms of it’s quality, eciency and environmental eect. Despite
above concerns the future of edible vaccines is reected by enormous
increase in land area used for cultivation of transgenic crops from
1.7 to 44.2 million hectares from 1996 to 2000. Also the number
of countries growing them increased from 6 to 13 which predicted
that transgenic crops gained wide acceptance industrially as well as
in developing countries. Edible vaccines present good economical
and technological benets as more than 350 genetically engineered
products are presently in progress in the United States and Canada.
In the near future edible vaccine against smallpox, anthrax, plague,
etc can be produced on a large scale (upto millions of doses) within a
short span of time.
Conclusion
Edible plant-derived vaccines present a better possibility of safer
and more ecient immunization in the future. Limitations linked
with traditional vaccines, like production, distribution and delivery
can be eliminated by the use of edible vaccines through various
immunization programmes. Edible vaccines successfully embraced
the obstacles encountered in rising vaccine technology. Despite
restricted global access to health care and much attention still being
paid towards complex diseases like HIV, malaria, etc. e time is
not so far when there is need for an economical, safer and ecient
delivery system to be developed at a larger scale in the form of edible
vaccines e ray of hope is based on assumption that edible vaccines
may be grown mostly in the developing countries which is basically a
fact as in reality they would be used in these countries. Hence, edible
vaccines provide a greater opportunity in the near future when no
longer injectable needles be used but a fruitful path may be available
where an individual get protected from diseases by simply eating a
fruit.
Acknowledgement
e rst author is very much thankful to Ishrat Majid doctoral
fellow at Department of Food Engineering & Technology, SLIET
Longowal, Punjab, India for helping in writing this article.
References
1. Langridge WH. Edible vaccines. Sci Am. 2000; 283: 66-71.
2. Ramsay AJ, Kent SJ, Strugnell RA, Suhrbier A, Thomson SA, Ramshaw IA.
Genetic vaccination strategies for enhanced cellular, humoral and mucosal
immunity. Immunol Rev. 1999; 17: 27-44.
3. Webster DE, Thomas MC, Strugnell RA, Dry IB, Wesselingh SL. Appetising
solutions: an edible vaccine for measles. Med J Aust. 2002; 176: 434-437.
4. Giddings G, Allison G, Brooks D, Carter A. Transgenic plants as factories for
biopharmaceuticals. Nat Biotechnol. 2000; 18: 1151-1155.
5. Mercenier A, Wiedermann U, Breiteneder H. Edible genetically modied
microorganisms and plants for improved health. Curr Opin Biotechnol. 2001;
12: 510-515.
6. Chikwamba R, Cunnic J, Hathway D, McMurary J, Mason H. A functional
antigen in a practical crop: LT-B producing maize protects mice against E.coli
heat liable enterotoxin (LT) andchorea toxin (CT). Transl Res. 2002; 11: 479-
493.
7. Taylor NJ, Fauquet CM. Microparticle bombardment as a tool in plant science
and agricultural biotechnology. DNA Cell Biol. 2002; 21: 963-977.
8. Arakawa T, Yu J, Chong DK, Hough J, Engen PC, Langridge WH. A plant
based cholera toxin B subunit-insulin fusion protein protects against the
development of autoimmune diabetes. Nat Biotechnol. 1998: 16; 934-938.
Austin J Nutri Food Sci 4(2): id1078 (2016) - Page - 05
Nayik GA Austin Publishing Group
Submit your Manuscript | www.austinpublishinggroup.com
9. Nochi T, Takagi H, Yuki Y, Yang L, Masumura T, Mejima M, et al. Rice-
based mucosal vaccine as a global strategy for cold-chain- and needle-free
vaccination. Proc Natl Acad Sci U S A. 2007; 104: 10986-10991.
10. Pascual DW. Vaccines are for dinner. Proc Natl Acad Sci U S A. 2007; 104:
10757-10758.
11. Streateld SJ, Jilka JM, Hood EE, Turner DD, Bailey MR, Mayor JM, et al.
Plant-based vaccines: unique advantages. Vaccine. 2001; 19: 2742–2748.
12. Moss WJ, Cutts F, Grifn DE. Implications of the human immunodeciency
virus epidemic for control and eradication of measles. Clin Infect Dis. 1999;
29: 106-112.
13. Ruf S, Hermann M, Berger IJ, Carrer H, Bock R. Stable genetic transformation
of tomato plastids & expression of a foreign protein in fruit. Nat Biotechnol.
2001; 19: 870-875.
14. Nemchinov LG, Liang TJ, Rifaat MM, Mazyad HM, Hadidi A, Keith JM.
Development of a plant-derived subunit vaccine candidate against hepatitis C
virus. Arch Virol. 2000; 145: 2557-2573.
15. Modelska A, Dietzschold B, Sleysh N, Fu ZF, Steplewski K, Hooper DC, et al.
Immunization against rabies with plant-derived antigen. Proc Natl Acad Sci U
S A. 1998; 95: 2481-2485.
16. Yusibov V, Hopper DC, Spitsin SV, Fleysh N, Kean RB. Expression in plant
and immunogenicity of plant virus based experimental rabies vaccines.
Vaccine. 2002; 20: 3155-3164.
17. Richter LJ, Thanavala Y, Arntzen CJ, Mason HS. Production of hepatitis B
surface antigen in transgenic plants for oral immunization. Nat Biotechnol.
2000; 18: 1167-1171.
18. Moffat AS. Exploring transgenic plants as a new vaccine source. Science.
1995; 268: 658, 660.
19. Daniell H, Khan MS, Allison L. Milestones in chloroplast genetic engineering:
an environmentally friendly era in biotechnology. Trends Plant Sci. 2002; 7:
84-91.
20. Prakash CS. Edible vaccines and antibody producing plants. Biotechnol
Develop Mon. 1996; 27: 10-13.
Citation: Jan N, Sha F, bin Hameed O, Muzaffar K, Dar SM, Majid I, et al. An Overview on Edible Vaccines and
Immunization. Austin J Nutri Food Sci. 2016; 4(2): 1078.
Austin J Nutri Food Sci - Volume 4 Issue 2 - 2016
ISSN : 2381-8980 | www.austinpublishinggroup.com
Nayik et al. © All rights are reserved
