"HIV can spread early, evolve in patients' brains"

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The AIDS virus can genetically evolve and independently replicate in patients' brains early in the illness process, researchers funded by the National Institutes of Health have discovered. An analysis of cerebral spinal fluid (CSF), a window into brain chemical activity, revealed that for a subset of patients HIV had started replicating within the brain within the first four months of infection. CSF in 30 percent of HIV-infected patients tracked showed at least transient signs of inflammation - suggesting an active infectious process - or viral replication within the first two years of infection. There was also evidence that the mutating virus can evolve a genome in the central nervous system that is distinct from that in the periphery.

"These results underscore the importance of early diagnosis and treatment with antiretroviral therapy," said Dianne Rausch, Ph.D., director of the Division of AIDS Research of the NIH's National Institute of Mental Health (NIMH). "Any delay runs the risk that the virus could find refuge and cause damage in the brain, where some medications are less effective - potentially enabling it to re-emerge, even after it is suppressed in the periphery."

NIMH grantees Serena Spudich, M.D., of Yale University, New Haven, Connecticut; Ronald Swanstrom, Ph.D., of the University of North Carolina, Chapel Hill; Richard Price, M.D., University of California, San Francisco; and Christa Buckheit Sturdevant, Ph.D., UNC (now at Duke), and colleagues, report on their findings March 26, 2015, in the journal PLoS Pathogens.

Prior to the study, it was known that HIV readily penetrates the brain and can trigger neurological problems and eventually cause dementia over the course of the infection. Yet there was little evidence about how quickly it can take hold and thrive there. Nor was it clear to what extent the brain serves as a hard-to-reach hideout from which the virus might re-infect the body - even if it is eliminated from peripheral blood and lymph node tissue by treatment.

To learn more, the researchers compared evidence of HIV activity in CSF versus blood from 72 untreated HIV-infected patients over the first two years of their infection. Overall, 10-22 percent of the patients showed evidence of HIV replication or inflammation in the brain at the different time points analyzed within the first two years - and the signs persisted over time in about 16 percent of the participants.

The evidence suggests that in most patients peripheral forms of the virus infect immune cells that spread to the brain via blood. Yet in some patients, genetic versions of the virus not found in blood evolve in the brain environment. So it could become an independent, compartmentalized viral reservoir, capable of generating treatment-resistant mutant forms that could break out and re-infect the rest of the body after seemingly successful treatment, explained Rausch.

Whether the potential brain damage caused by early HIV replication and inflammation might be reversible with antiviral therapy awaits further research, said Swanstrom.

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A team of researchers has discovered HIV can begin replicating in the brain as early as four months after initial infection. The study followed 72 treatment naïve participants during the first two years of HIV infection. Through analysis of cerebral spinal fluid (CSF) and blood samples, 20 percent of subjects showed replication in the central nervous system (CNS) at four months. Additionally, 30 percent of participants showed evidence of a marked CSF inflammatory response in at least one time point and 16 percent of study volunteers showed a marked CSF inflammatory response at multiple time points, suggesting an ongoing infection in the CNS. The findings will be published in the scientific journal PLoS Pathogens.
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"This shows that viral replication and inflammation can occur early in infection with the concern being that the damage caused could be irreversible," says study virologist Ronald Swanstrom, PhD, Director of the University of North Carolina's Center for AIDS Research (CFAR) and Professor of Biochemistry and Biophysics at UNC's School of Medicine. "HIV and inflammation have the potential to accelerate the aging process and cause neurocognitive impairment, in the extreme case resulting in HIV-associated dementia."

One-third of people not taking antiretroviral therapy (ART) to control their HIV will eventually develop HIV-associated dementia, Swanstrom says. For him, the study's results in these newly infected people stress the importance of routine HIV testing to catch the infection as early as possible to allow the prompt initiation antiretroviral therapy.

"This is yet another reason we want people on ART right away to limit the possibility of replication and inflammation in the brain," Swanstrom says.

Future studies could focus on whether or not damage to the brain caused by this early replication and inflammation is reversible. Swanstrom collaborated on the study with senior author and neurologist Serena Spudich, MD, Division Chief of Neurological Infections & Global Neurology and Associate Professor of Neurology at Yale School of Medicine, and neurologist Richard Price, MD, Professor of Neurology at the University of California San Francisco School of Medicine. The first author on the study was a UNC graduate student in the Department of Microbiology and Immunology, Christa Sturdevant, who is now a postdoctoral fellow at Duke University. The study was funded by the National Institute of Mental Health.