Study: HIV drug resistance different in blood and spinal fluid

In another blow to hopes that HIV antiretroviral therapy can keep the virus at bay indefinitely, researchers at Boston University Medical Center and Tufts University have discovered that HIV can mutate into two entirely different forms in the same person. Their research included an examination of mutations in the HIV genetic code of virus found in the blood and the cerebrospinal fluid of six patients, which uncovered virus with different mutations that make it resistant to different drugs in each of the two bodily compartments. "It's a very troubling finding," said researcher Paul Skolnik.

In one of the six patients studied, virus in the spinal fluid had developed a genetic mutation that made it resist nearly every drug in the nonnucleoside reverse transcriptase inhibitor class of medications, despite the fact that the HIV in the patient's blood was not resistant to any of these drugs. "This is the first time we've discovered a mutation for resistance to this class of drugs in the CSF at a time when it wasn't present in the blood," Skolnik says. "It indicates that the CSF may allow for the development of a resistant virus prior to the development of resistance in the blood. Thus, the CSF may provide a 'breeding ground' of sorts for HIV."

The researchers say their findings also may indicate that HIV's effects on the brain may be harder to control than previously realized. Because genetic tests on blood samples to scan for drug resistance cannot detect drug-resistant virus in CSF, HIV in the spinal fluid may respond poorly to medications being taken by the patient, which can allow it to more quickly replicate and lead to the development of neurological disorders.

The full study appears in the journal Clinical Infectious Diseases.