http://id.medscape.com/reuters/prof/2001/05/05.29/20010528drgd003.html

HIV-1 Tat Gene Expressed in Plants Has

Potential For Vaccine

ORLANDO, FL (Reuters Health) May 28 - Immunologically reactive HIV-1 tat protein is expressible by plants and may become an important component of vaccines, investigators reported at the 101^st general meeting of the American Society for Microbiology.

In a poster session here, Dr. Alexander V. Karasev presented results of research he and his colleagues conducted at Thomas Jefferson University, in Doylestown, Pennsylvania. Using synthetic primers, the researchers assembled the tat gene of a strain of HIV-1 and cloned it into a tobacco mosaic virus-based vector.

Inoculation of the vector into leaves of Nicotiana benthamiana and spinach resulted in the expression of approximately 330 µg of extractable protein per gram of leaf tissue, which the researchers note is at least as high a yield as that produced in animal tissue cultures. Further study showed the tat protein was reactive with tat-specific monoclonal antibodies.

“Only recently has the technology become available to produce biomedical products and vaccine components in plants,” Dr. Karasev told Reuters Health in an interview. He noted that other researchers have used transgenic plants in which target proteins are expressed constitutively.

“When we use virus vectors, we have transient expression and can control the time span when we want the protein produced,” he said. “One advantage of our process is the public concern about transgenic plants in general. It’s still an obstacle. In our case we use normal plants, the only thing we manipulate are the virus vectors.”

The other advantage of using plants, Dr. Karasev added, is that “nothing can be more safe.” That is because microbes harbored by plants are not pathogenic to humans.

“When vaccine components are produced in animal or human cells, there is always the underlying fear of contamination...because even if we use screening procedures, we can only test against something of which we’re aware. If there’s something present for which we have no testing systems, we can miss something potentially pathogenic.”

Vaccine component production in plants is also less expensive, and it is possible that resulting vaccines could be administered orally, the investigators note.

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