By Ana Hrus, Checkbiotech

“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.

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. Contact her at ana.hrus@fmi.ch. 

Original article:
Kisung et al. Inhibition of tumor growth by plant-derived mAb.
PNAS, 102 (2005), p. 7026-7030

Corresponding author:

Dr Hilary Koprowski, MD
Thomas Jefferson University
Biotechnology Foundation Laboratories
Room M-81 Alumni Hall
1020 Locust Street
Philadelphia, PA 19107
Telephone: 1-215-503 1420
Fax: 1-215-923 6786
Email: hilary.koprowski@jefferson.edu