Researchers have found that the HIV virus can evolve and independently replicate in patients’ brains early in the process, according to a study funded by the National Institutes of Health (NIH).

Not much was previously known about how quickly the virus could take over and thrive in the brain and there was limited information on how the virus could re-infect the body by hiding in the brain, even when it was eliminated from peripheral blood and lymph node tissue. Researchers from the National Institute of Mental Health (NIMH) compared HIV activity in cerebral spinal fluid (CSF) from untreated HIV-infected patients over the first two years of infection (n=72). The analysis showed about 10–22% of patients had evidence of HIV replication or inflammation in the brain at different time points within the first two years; these signs persisted in about 16% of patients over time.

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Specifically, a subset of patients’ HIV had started replication in the brain within the first four months of infection. About 30% of HIV-infected patients tracked showed transient signs of inflammation or viral replication in their CSF within the first two years of infection, which suggested an active infectious process. Further, researchers found evidence that the mutating virus could evolve a genome in the central nervous system (CNS) distinct from that in the periphery.

The team concluded that most patients’ peripheral forms of the virus infect the immune cells that spread to the brain via blood, whereas in some patients, genetic versions of the virus not found in blood evolve in the brain. Further research is needed to assess whether antiviral therapy can reverse potential brain damage caused by early HIV replication and inflammation.

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