Scientists at Johns Hopkins and in India report they have sequenced the complete genome of a form of HIV, the AIDS virus, from that country for the first time. The work has revealed unexpected variation in genes for one key part of the virus, prompting the researchers to suggest that currently favored approaches to vaccine development may not work.
The achievement, reported in this month's Journal of Virology, also suggests that different forms of HIV in India, unlike the single U.S. virus type, may be combining in a way that will further complicate vaccine development.
Researchers know that the genetic makeup of the virus varies with geography; they've catalogued 10 possible different HIV subtypes, lettered A to J. The United States subtype, for example, is largely subtype B. "India's strains are primarily subtype C, a variety also dominant in Africa and Southeast Asia," says Hopkins virologist Stuart C. Ray, M.D., who directed the U.S. arm of the study. "But we were curious to see if India's subtype C differed in important ways from the others." Knowing a subtype's makeup is an important step on the road to a vaccine, he says.
The research team drew blood samples from six newly infected Indian volunteers: two had received contaminated transfusions and four were clients of a sexually transmitted disease clinic in western India. The samples reflect HIV variation in that country, the researchers say. The PCR technique to amplify the viral genes and their resulting analysis took place at Hopkins.
The scientists found that, while the virus has much in common with
subtype C samples worldwide, the genes coding for proteins in the outer
"envelope" of the virus -- the target of most of the trial anti-viral vaccines
to date -- vary significantly from the subtype B strains that form the backbone
of vaccines currently in international trials. "It means we could expect
problems with any vaccine based
Contact: Marjorie Centofanti
Johns Hopkins Medical Institutions