It is genetic engineering based plant product.

1. Edible
vaccines-

2. INTRODUCTION
• Edible vaccines are nothing but transgenic plant and animal
based production that trigger an animal’s immune response.
• Creating edible vaccines involves introduction of selected
desired genes into plants and then inducing these altered
plants to manufacture the encoded proteins. This process is
known as "transformation," and the altered plants are called
"transgenic plants.
• Like conventional subunit vaccines, edible vaccines are
composed of antigenic proteins and are devoid of
pathogenic genes. Thus, they have no way of establishing
infection, assuring its safety.

3. HOW EDIBLE VACCINES WORK
• Edible vaccines contain DNA fragments from the original
pathogen. These fragments code for a protein that is usually
a surface protein of the pathogen.
• Edible vaccines activate both mucosal and systemic
immunity, as they come in contact with the digestive tract
lining.
• This dual effect would provide first-line defense against
pathogens invading through mucosa, like Mycobacterium
tuberculosis and agents causing diarrhea, pneumonia, STDs,
HIV etc.

4. MECHANISM OF ACTION
• The antigens in transgenic plants are delivered through bio-
encapsulation, i.e the tough outer wall of plant cells, which
protects them from gastric secretions and finally break up in
the intestines.
• The antigens are released, taken up by M cells in the
intestinal lining. It overlie on gut-associated lymphoid tissue
(GALT), passed on to macrophage. Other antigen-
presenting cells and local lymphocyte generate serum IgG,
IgE responses, local IgA response and memory cells, which
would promptly neutralize the attack by the real infectious
agent.

5. Preparation of edible vaccines
• Introduction of foreign DNA into plant's genome can either
be done by bombarding embryonic suspension cell cultures
using gene-gun.
• It is commonly through Agrobacterium tumefaciens , a
naturally occurring soil bacterium, which has the ability to
get into plants through some kind of wound (scratch, etc.). It
possesses a circular "Ti plasmid" (tumor inducing), which
enables it to infect plant cell.
•

6. •The DNA integrates randomly into plant genome,
resulting Production of transgenic plants.
• Some antigens, like viral capsid proteins, have to
self-assemble into VLPs (virus-like particles).
VLPs mimic the virus without carrying DNA or
RNA and therefore are not infectious.
Continues…

7. VARIOUS STRATIGIES
Approaches to mucosal vaccine formulation include:-
(i) gene fusion technology, creating non-toxic derivatives.
(ii) genetically inactivating antigens by deleting an essential
gene
(iii) co-expression of antigen and a cytokine, which modulates
and controls mucosal immune response.
(iv) genetic material itself, which allows DNA/RNA uptake
and its endogenous expression in the host cell.

8. CLINICAL TRIALS
Antigen expression in plants has been successfully shown
in the past:-
• Like LT-B (ETEC) in tobacco and potato.
• Rabies virus-G protein in tomato.
• HBsAg in tobacco and potato.
• Norwalk virus in tobacco and potato.
• CT-B ( Vibrio cholerae ) in potato.

9. ADVANTAGES :-
• They are cheap; therefore they can be mass-produced.
• They can be ingested by eating the plant/part of the
plant. So, the need to process and purify does not arise.
• Extensive storage facilities like cold storage are not
required.
• If the local/native crop of a particular area is engineered
to produce the vaccine, then the need for transportation
and distribution can be eliminated.
• Most importantly, they trigger the immunity at the mucosal
surfaces such as those that line the mouth (mucosal
immunity) which is body first line defence.

10. DISADVANTAGES:-
• Initial trials have shown promising results in human
subjects ,it is not clear what will happen when the person
comes in contact with the actual virus.
• How can the vaccine dose be controlled? This remains
the most difficult task. There seems to be a danger that too
high a dose could provoke oral tolerance of an invading
bacteria or virus, instead of an immune response.
• Plants are living organisms that change, so the continuity of
the vaccine production might not be guaranteed.
• Glycosylation patterns in plant develop an allergy to the
fruit or vegetable expressing the foreign gene.

11. CONCLUSION
• The first trial on humans in 1997 (using the heat labile B-
toxin from E. coli) is a milestone on the road to creating in
expensive vaccines that might be particularly useful in
immunizing people in developing countries, where high
cost and logistical issues, such as transportation and the
need for certain vaccines to be refrigerated, can thwart
effective vaccination programs.
• The hope is that edible vaccines could be grown in many
of the developing countries where they would actually be
used . Whatever may be the current situation, a day is not
far off when we will be able to pluck a fruit from the
garden , eat it and be protected from diseases…making
needles needless…