B.L. Marrs and V. Yusibov
Fraunhofer Center for Molecular Biotechnology
9 Innovation Way
Newark, Delaware 19711

It is widely assumed that we cannot realistically hope to vaccinate the US civilian population against all possible bioterrorism agents. This assumption is based on cost and safety issues surrounding existing vaccine technology. Those assumptions are out of date. There is now a way to quickly and safely vaccinate populations at moderate cost. If we implement this newer technology, the bioterrorism threat would be neutralized, and obvious public health benefits would accrue as well. The new technology that makes this possible is a particular type of plant science known as Transient Gene Expression (TGE). We can use this technology to make vaccines in plants. People can become immunized by eating these vaccine-producing plants.

TGE makes use of years of fundamental research on how plant viruses reprogram plants to make more viruses. We can now easily create vehicles (Transient Gene Vehicles) in the laboratory that can reprogram plants to make proteins of our choice, including very effective vaccines. These vaccines can then be either purified and administered by injection or, in fact, the plant tissues can be eaten and immunity acquired without the need for injections. Although this is a relatively new technology, the first FDA-approved human trials have been successfully conducted.

Vaccines developed through TGE technology are so-called epitope or subunit vaccines. They are inherently safer than vaccines based on attenuated pathogens, because the recipient is only exposed to non-infectious, non-toxic bits of protein. There is zero risk of unkilled pathogens being administered. An additional safety factor results from the plant-based manufacturing of vaccine inherent in this plan. Plants do not harbor any known human pathogens, such as viruses or prions, which can be present in vaccines manufactured using animal cells, tissues or extracts.

TGE is well suited for responding to bioterrorism, because it has a very short cycle time. A new candidate vaccine can be ready for testing in a matter of weeks to months, rather than the years that competing technologies require. If the oral route is chosen, the possibility of harmful effects is vanishingly small, although there is still much to be learned about insuring the effectiveness of this route of immunization.

TGE technology makes it reasonable to contemplate multiple immunizations of large populations, because it is inexpensive to develop each vaccine, multivalent vaccines have been demonstrated, and administration can be as easy as eating a bowl of salad.

This technology requires active governmental support for its rapid and full development. To date, it has fallen into the cracks between the USDA, which supports development of plant-related research but proscribes human health work, and the NIH, which stays away from plant science. The public policy issue here is clear. The value of developing this highly credible counter-strategy against bioterrorism mandates immediate and significant US government support.