Transcript Edible Vaccines

Edible Vaccines
HOW IS IT DONE
Approach 1
DNA sequences encoding antibodies
(molecule which is able to recognise a
disease-causing agent) are inserted
into the genomes of plants.
Plants produce the antibodies in their
cells.
These plants are then harvested and
purified for therapeutic use/consumed
with the rest of the plant, releasing the
antibodies in the process.
How it is done
Approach 2
Identification, selection and isolation of desirable genes from
the pathogen that encodes the surface antigen proteins. The
isolated gene can be then cloned in a suitable vector for gene
transfer
Introduction of selected desired genes into plants and
then inducing these altered plants to manufacture the
encoded proteins
Edible vaccines are composed of antigenic proteins and are
devoid of pathogenic genes. Thus, they have no way of
establishing infection, assuring its safety
When eaten, edible vaccines provoke antibody response.
Benefits
Needles provide only weak immunity at mouth, eyes, intestines
and urogential tract. Oral vaccines provide “mucosal immunity” at
these sites by secreting antibodies
• Don’t need to worry about re-use, misuse and lack of sterilisation.
Thus, low risk of infection.
•
Needle-free
Cheap
• Mass production: Can always plant more if diminishing
• Estimated cost of $0.005 to grow antigen for one dose of
hepatitis B vaccine in an unprocessed form. Vaccine programmes
for rarer diseases or diseases which are not so financially
rewarding for pharmaceutical companies (i.e. diseases which do
not affect developed countries) will benefit.
Cheap
• Heat-stable; do not require cold-chain maintenance; can be
stored near the site of use, eliminating long-distance
transportation.
• Administering oral vaccines would require little or no training at
all, which reduces the significant cost of vaccination programmes
which require trained professionals.
• The contamination of food crops through cross pollination
and of the vaccine itself in plant debris spreading as dust
Safety concern and as pollutants in surface and groundwater. The
• vaccine antigen may affect browsing animals and humans
1
living in the area drinking vaccine-polluted water or
breathing vaccine-polluted dust. Hence such crops should
be cultivated and produced in greenhouses or in plant
tissue culture to prevent their environmental release.
Safety concern 2
• May trigger immune tolerance: Thereby making
the individual susceptible to, for example, the
hepatitis B virus. (Daniell, Streatfield and Wycoff
2001/5/1)
Cholera Banana Vaccine
Source
http://www.genomenewsnetwork.org/articles/07_00/VACCINE_BASE2_5_8.
pdf
Other examples
Transgenic tobacco is successfully engineered for the production of edible
vaccines against Hepatitis B antigen using‘s gene of HBV (Hepatitis B
Virus). The optimum level of recombinant protein was obtained in leaves
and seeds.
Potato is one of the best sources for vaccine production but the raw
potatoes are not palatable and cooking destroys protein antigens. Vaccine
for cholera is successfully developed in potato.
Banana is the ideal plant for oral vaccine production due to its excellent
digestibility, palatability and availability throughout the year. Vaccine for
hepatitis B is successfully made in banana.
Tomato plants expressing rabies antigens