HealthDay News – Although AIDS may be getting smarter about evading the immune system, it may also be evolving into a less contagious and less lethal infection overall, research published in the Proceedings of the National Academy of Sciences suggests.

“It is widely believed that epidemics in new hosts diminish in virulence over time, with natural selection favoring pathogens that cause minimal disease,” wrote Rebecca Payne, MD, of the University of Oxford in the United Kingdom, and colleagues.

To investigate the impact of HIV virulence of HIV adaption to HLA molecules that protect against disease progression, such as HLA-B*57 and HLA-B*58:01, the investigators studied cohorts in Botswana and South Africa.

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Both countries in Africa have been severely affected by the HIV epidemic. In Botswana, where the epidemic started earlier and adult seroprevalence has been higher, HIV adaption to HLA-B*57/58:01 is greater compared with South Africa (P=7×10-82), the protective effect of HLA-B*57/58:01 is absent (P=0.0002), and population viral replicative capacity is lower (P=0.03).

The viral evolution is occurring relatively rapidly, and that adaption of HIV to the most protective HLA alleles may contribute to a lowering of viral replication capacity at the population level, suggested the researchers.

The reduction of HIV transmission and decline of HIV virulence over the course of the epidemic could be a distinct benefit of the increase in antiretroviral therapy (ART) among the African population, suggested models developed by the team of scientists. The influx of ART treatment may also be responsible for the accelerated effects of HLA-mediated viral adaption.

“Modelling studies indicate that increasing antiretroviral therapy access may also contribute to accelerated declines in HIV virulence over the coming decades,” concluded the researchers.


  1. Payne R et al. PNAS. 2014; doi:    10.1073/pnas.1413339111