www.checkbiotech.org ; www.raupp.info ; www.czu.cz

?How to create a better vaccine? - that is the question that occupies many
researchers in the world. Although there is a multitude of vaccines produced
in the 21st Century, it is impossible to use them on a world-wide scale due
to their high cost and methods of application, January 2006 by Ana Hrus,
Checkbiotech.

A research team from the Biotechnology Foundation Laboratories at the
Thomas Jefferson University in Philadelphia, has been working on developing
an entirely new class of vaccines.

Under the direction of Hilary Koprowski, M.D., they have focused their
efforts on edible plants as a vehicle to produce antigens, which induce
immune responses that can protect against a variety of pathogens. Such
vaccines are less expensive to produce compared to the current vaccines,
they are safe, effective and suitable for widespread distribution even
through the developing countries.

In the publication in PNAS by Kisung et al., ?Inhibition of tumor growth by
plant-derived mAb,? Dr. Koprowski?s research group reported the production
of functional anti-tumor antibodies in tobacco. They demonstrate successful
production of plant-derived antibody CO17-1A, which recognizes a specific
type of cancer called Adenocarcinoma.

Tumor cells display a variety of specific molecules on their surfaces that
distinguish them from normal cells. These molecules are called tumor
antigens. Adenocarcinoma, a form of cancer, contains a large amount of the
antigen called GA733 on its cell surface, which the antibody CO17-1A
recognizes.

The displayed antigens can then be recognized by antibodies that are
specific to the given antigen. That way the organism recognizes foreign
molecules and initiates an immune response. Due to the antibody-antigen
recognition property, antibodies are often used in research for the
detection of antigens. Even more importantly, they can also be used for the
therapeutic purposes.

Dr. Koprowski?s research team first step was to generate transgenic tobacco
plants (Nicotiana tabacum) that were able to produce the desired antibodies.
Once the tobacco plants reached a certain growth stage, the researchers
harvested the leaves. The antibodies were prepared from 1 kg of fresh
tobacco leaves.

Once the antibodies were extracted from the tobacco leaves, it was important
to show that they still retained the ability to bind the antigen GA733-2.
Dr. Koprowski?s team tested this by using a method commonly used for protein
analysis called, Western Blot.

The Western Blot showed that the plant-derived antibodies had similar
specific binding activity on colorectal cancer cells compared to
conventional monoclonal antibodies produced in mice. Dr. Koprowski?s group
reported similar efficiency in inhibiting colorectal tumor growth in mice in
vivo.

Monoclonal antibodies, which have high specificity to a particular antigen,
are commonly produced by immunizing mice and fusion of their spleen cells to
immortalized cells. The procedure is more time consuming and expensive
compared to plant-made monoclonal antibodies. Dr. Koprowski told
Checkbiotech, ?The technology will allow the development of new, desperately
needed vaccines and will prevent many of the diseases currently ravaging the
developing world.?

Although antibodies produced in plants have different sugar modifications,
Dr. Koprowski?s team reports that their antibody still retained the same
activity that a mouse derived antibody had. That finding is truly
significant and opens the door to new possibilities of functional antibody
production.

The scientists of the Biotechnology Foundation Laboratories have so far
developed plant-based vaccines against rabies, respiratory syntial virus,
HIV, anthrax, and colorectal cancer. At present, they are focusing on
developing vaccines against, anthrax, smallpox, SARS, the common flu, and
pediatric vaccines that use plants as a delivery vehicle.

Dr. Koprowski believes that the technology they are developing can and will
change the face of human health worldwide. Inexpensive vaccines administered
by oral consumption, and not requiring the services of health professionals,
will make universal vaccination possible.

Ana Hrus is a Science Journalist for Checkbiotech and is currently finishing
her PhD degree in Cell Biology at the University of Basel, Switzerland.

www.checkbiotech.org

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