HIV-1 Subtype Linked to Transmission in Argentina

There appear to be two HIV-1 epidemics in Argentina: one in heterosexuals and IV drug users and another in gay men, scientists announced in Havana on April 9 at the Second Forum on HIV/AIDS/STD in Latin America and the Caribbean.

Biologist María de los Angeles Pando and colleagues at the National Reference Center of AIDS of the University of Buenos Aires recently studied 35 gay HIV-positive men and 175 heterosexual HIV-positive men and women. They found that 91 percent of gay men had HIV-1 subtype B, while 75 percent of heterosexuals had subtype F, with many of those patients appearing to have a mixture of both subtypes (B/F recombinant forms).

HIV-1 subtype B is the most prevalent form of HIV in North America and Western Europe, while subtypes A and C are the most common types in Africa and Asia. Together the three types -- or clades -- of HIV account for about 90 percent of infections worldwide.

The researchers analyzed samples from 77 HIV-positive injection drug users. Of the 21 samples tested in detail, they found that 100 percent were B/F recombinants, similar to the molecular patterns found in heterosexuals. "From a molecular point of view, AIDS epidemics seems to run along two parallel lines: MSM patients on one side, and heterosexual and IDUs on the other," said Pando.

The subtype differences may reflect the ability of different types of the virus to infect people according to transmission route, or it may be because of the index cases -- the first HIV-infected individuals who introduce the virus into the population -- had different virus strains. The findings suggest that HIV-positive MSM may eventually have a slightly different response to certain AIDS vaccines or antiretroviral drugs than heterosexuals or IDUs -- but this still has to be proven, researchers warned.

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