[procaare] UAB study traces transmission of HIV to single invasive AIDS virus

["ProCAARE" <procaare@healthnet.org>]

UAB study traces transmission of HIV to single invasive AIDS virus
Birmingham News: Tuesday, May 20, 2008
Dave Parks: News staff writer
****************

Most HIV infections can be traced to the transmission of a single 
virus that has somehow penetrated the body's natural defenses, 
according to a UAB study published Monday.

The finding that only one virus is usually responsible for an HIV 
infection is surprising, and is expected to have a significant 
impact vaccine development, said Dr. George M. Shaw, a professor at 
the University of Alabama at Birmingham and the study's lead 
author.

"It's shining a light on the HIV transmission process," Shaw said. 
"It's yielding a surprising finding that very few viruses are 
actually responsible for transmission. And it's providing some 
benchmarks and genetic clarity to people who do vaccine studies in 
both primates and humans. It will help them understand if their 
vaccine is working, and if it's not working, why it's not working."

The study, which was published online Monday by the Proceedings of 
the National Academies of Science, analyzed blood from 102 people 
who had been recently infected with HIV. Led by UAB's Brandon 
Keele, researchers used the latest techniques for genetically 
analyzing viruses.

They were able to count generations, and learned that 76 percent of 
the cases could be tracked back to a single virus. The remaining 24 
percent could be tracked back to two to five viruses, Shaw said.

"The reason that's important is it says if we're trying to develop 
a vaccine or microbicide or whatever to prevent infection, the only 
thing it has to do is prevent the transmission of a single virus," 
Shaw said. "That should be possible. All you have to do is provide 
some additional block to what already is an efficient process."

By contrast, other sexually transmitted diseases, like gonorrhea or 
syphilis, invade the body en masse. "They just all come across, 10, 
20, 100, 200 bacteria or spirochetes," Shaw said.

But now scientists know that it only takes one AIDS virus to 
trigger a terrible onslaught.

"In the vast majority of cases a single virus has gone across the 
sexual mucosa, and that virus has infected a cell," Shaw explained. 
"That cell then makes a lot of virus. Now you just have a firestorm 
of HIV replication in the next couple weeks. Very quickly the 
person is populated by millions of viruses."

In retrospect, the finding makes sense, Shaw said. Scientists have 
long known that it usually takes several exposures for a person to 
become infected with HIV, and this explains why the virus's 
transmission is so inefficient.

It also helps explain why condoms help prevent the transmission of 
HIV - it's a method that has the potential to stop all viruses. By 
comparison, microbicides have been less effective, and that 
probably is because they don't stop all viruses.

Shaw noted that the UAB team, which worked in conjunction with a 
host of other major medical research centers, has solved a 
long-standing medical mystery. He said at least 20 research centers 
have been working on the problem, and many have been stunned by 
this latest finding.

`Crystal clear' findings:

Shaw is confident that the study will stand up to scientific 
scrutiny.

"It's crystal clear," he said. "What our discovery does is provide 
light on what was previously a very cloudy area of HIV infection. 
It puts acute and early transmission of HIV-1 in very sharp focus."

The study was funded by the National Institute of Allergy and 
Infectious Disease and the Bill and Melinda Gates Foundation.

In addition to UAB, medical centers involved in the project 
included Duke University, Los Alamos National Laboratory and Santa 
Fe Institute in New Mexico, University of Massachusetts in Amherst, 
University of North Carolina at Chapel Hill, University of Maryland 
in College Park, University of California at San Francisco, 
University of Rochester in New York and University of Cape Town in 
South Africa.

E-mail: dparks@bhamnews.com

Online: http://www.al.com/news/birminghamnews/index.ssf?/base/news/1211271337323440.xml&coll=2&thispage=2