HIV highly homogeneous in early infection

Current findings suggest that the mucosal barrier is the major site of viral selection in sexual transmission of human immunodeficiency virus type 1 (HIV-1), transforming the complex inoculum to a small, homogeneous founder virus population. In a recent study from Zurich the authors analyzed HIV-1 viral seqiuences in the C2-V3-C3 region in 145 patients with characteristics  primary HIV-1 infection. They found that  the meedian viral diversity within env was 0.39% (range 0.04%–3.23%). Viral diversity did not correlate with viral load, but it was slightly correlated with the duration of infection.

They also found that  neither transmission mode, gender, nor STI predicted transmission of more heterogeneous founder virus populations. Only 2 patients (1.4%) were infected with CXCR4-tropic HIV-1 with a duakl-tropic R5/X4-tropic–mixed population. The other patients were infecetd by the CCR5-trophic virus which targets the macrophage series.

The authors concluded that transmission of multiple HIV-1 variants might be a complex process that is not dependent on mucosal factors alone. CXCR4-tropic viruses can be sexually transmitted in rare instances, but their clinical relevance remains to be determined. These results have imprtant implications for vaccine development.

An alternative explanation for these results, not discussed by the authors, is that the individuals were infected by a small number or even a single CCR5-trophic virus which subseqeuntly mutates to the complex virus soup that is seen in long-term infected subjects.

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