Molecular Epidemiology of HIV-1 Variants in the Global Aids Pandemic: an Update

The picture of HIV-1 genetic diversity in the global pandemic continues to evolve. Identification ofnew variants, including circulating and unique recombinant forms, recognition of new outbreaks andof changes in established epidemics, and characterization of growing numbers of full-length genomesprovide a view of high dynamism and increasing complexity. The pervasive role of recombination asa major driving force in the generation of diversity in the HIV-1 pandemic is becoming evident, andis particularly visible in areas in which different genetic forms meet, referred to as “geographic recombinationhotspotsâ€?. The importance of superinfection and its impact on HIV-1 diversification andpropagation is surfacing, although restrictions to superinfection are also apparent. Genetic diversitywithin subtypes is increasing over time and new geographically localized lineages derivingfrom point introductions are being recognized. Characterization of such variants may be of relevanceto vaccine development and may allow the detection of intrasubtype recombination andsuperinfection. Recent studies supporting the correlation of HIV-1 clades to immune responses andto drug resistance-associated mutations lend increasing relevance to the role of molecular epidemiologyas an essential tool in combating the AIDS pandemic. However, knowledge on the globalHIV-1 genetic diversity and its implications is still far from adequate and a major scaling up of effortsis needed.