HIV spreads much more rapidly through the body after initial infection than previously believed, apparently causing immediate immune reactions that enable its replication. Publishing their findings in the journal Cell, researchers vaginally exposed 44 rhesus monkeys to SIV, HIV’s simian cousin, and analyzed the animals during the first few days post-infection.

The investigators found that, in most of the animals, viral RNA was present in at least one tissue outside the reproductive tract just one day after infection. As early as this same point, SIV had also apparently prompted an inflammatory immune response in tissues infected with the virus. There was a connection between increasing amounts of viral RNA and greater amounts of a protein that suppresses the immune response to viruses. The researchers also saw that the early workings of a mechanism by which certain cells are instructed correlated with a lower level of antiviral T-cell responses, as well as with higher levels of replication of SIV. These research findings suggest a much shorter time than previously believed when HIV only remains in the mucosal tissues where it was first deposited. Such knowledge may contribute to the research into vaccines, microbicides and pre-exposure prophylaxis (PrEP) methods.