In the study, viral populations from blood and semen samples collected from 16 men with chronic HIV infection were compared. Using single genome sequencing, they analyzed the gene coding for the major surface protein of the virus in the samples. The results?
"The sequence differences between the blood and the semen were like a flashing red light, it was a big hint about the biology of virus in the seminal tract" said Swanstrom. "When we looked at sequences in the blood, we hardly found any that were the same, it was a very complex and diverse population. But when we looked in the semen, suddenly we were getting the same sequence over and over again."
They found two mechanisms that significantly altered the viral population in the semen, called clonal amplification and compartmentalization. In the former, one to several viruses are rapidly expanded over a short period of time such that the viral population is relatively homogeneous (compared to complex population in the blood). In the latter, the virus replicates in T cells in the seminal tract over a long period of time, creating a separate population of virus that is both complex and distinct from the virus in the blood.
Full article: http://www.sciencedaily.com/releases/2010/08/100819173842.htm