Vaccinations in our plants?

June 9, 2001

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 101st general meeting of the American

Society for Microbiology.

In a poster session here, Dr. V. Karasev presented results

of research

he and his colleagues conducted at 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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