Sexual transmission of HIV by a handful of virus variants

A team from The University of Alabama (UAB) have found that among billions of HIV variants only a few lead to sexual transmission.

George M. Shaw Professor in the UAB departments of Medicine and Microbiology and senior author on the report, said the research sheds new light on potential vulnerabilities in the virus at a time when science, medicine and society are still reeling from the failure of a major HIV vaccine clinical trial.

“We can now identify unambiguously those viruses that are responsible for sexual transmission of HIV-1. For the first time we can see clearly the face of the enemy. …Our findings allow us to identify not only the transmitted virus, but also viruses that evolve from it.”

The study was performed by sequencing many copies of the HIV envelope gene present in the viruses taken from 102 recently infected patients. The envelope gene encodes for a protein called Env that forms part of the outer covering of the virus, and is responsible for its infectiousness.

The researchers then used sophisticated mathematical models of HIV replication and genetic change to identify the virus or viruses responsible for transmission. In 80 percent of the newly infected patients, a single virus caused transmission, though each virus was different in each patient. In the other 20 percent of patients, two to five unique viruses caused transmission.

According to WHO, in 2007, 33.2 million people were estimated to be living with HIV, 2.5 million people became newly infected and 2.1 million people died from AIDS.

Elaine Warburton  www.geneticsandhealth.com