Scientists are finding that the Human Immunodeficiency Virus (HIV) can evolve and replicate itself inside patients' brains -- establishing a treatment-resistant viral outpost -- even early in the infection process. The new information, researchers say, highlights the importance of early diagnosis and treatment of infected individuals.
A new report from the National Institutes of Health (NIH) says that tests conducted of cerebral spinal fluid (CSF) of some newly infected patients showed that the virus was replicating within their brains within the first four months of infection.
Some 30 percent of patients showed signs of brain inflammation within the first year of infection, the NIH team found.
“These results underscore the importance of early diagnosis and treatment with antiretroviral therapy,” said Dianne Rausch 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," she explained, "potentially enabling it to re-emerge, even after it is suppressed in the periphery.”
A persistent problem with treating HIV is the virus' ability to "hide" in the body, penetrating the blood-brain barrier and other organs, enabling it to ride out assaults by antiretroviral medicines. Some patients have appeared to be completely clear of the virus, only to have it reappear years later.
Treatments designed to eliminate the virus either fall short of reaching the places where the virus hides or injure the patient's organs to such an extent that treatment is no longer therapeutic.
Studying patients' CSF is a window into what's happening in their brain and central nervous system. It has long been known that HIV can wreak havoc on patients' brain and nerve function, ultimately leading to dementia, neuropathy and other serious complications. Rausch's team found that the virus establishes its beachhead in the brain much earlier in the infection process than previously thought.
To learn more, scientists analyzed the CSF and blood of 72 untreated HIV patients taken over the course of two years. At different points in the testing cycle, 10 to 22 percent of patients were showing evidence of HIV activity and replication in the brain and central nervous system. Those signs were persistent over time in about 16 percent of patients.
Furthermore, doctors found that HIV samples taken from the brain appeared to be evolving separately from the HIV circulating in some patients' blood.
The brain is a somewhat rarefied environment in the body, having the brain-blood barrier in place as a shield against many invading pathogens and other blood-borne substances. HIV not only penetrates that barrier, but once inside some patients' brains, establishes 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."
Fellow researcher Ronald Swanson said that scientists are still trying to determine whether the neural damage done by HIV in early infection can be undone through antiviral therapy.
Recent estimates say that the vast majority of people carrying HIV in the U.S. do not realize that they have the virus. Grady Memorial Hospital in metro Atlanta began offering routine HIV testing to all patients as a matter of course and has since been averaging two to three new positive diagnoses per day. Up to half of those individuals have crossed over into full-blown AIDS, which makes them harder to treat and offers significantly poorer outcomes than patients who begin treatment soon after infection.