HIV evolves independently in blood and CSF

HIV evolves independently in different body compartments, enabling resistant mutants in the CSF to escape detection in blood, German researchers suggest.

Dr. Brigitte Wildemann and colleagues, from the University of Heidelberg, analysed viral loads and viral resistance mutations of HIV from paired blood and cerebrospinal fluid (CSF) samples of 30 patients. The results are published in the February 13th issue of Neurology.

CSF viral loads were significantly lower than were plasma viral loads, the authors report, and there was no correlation between viral loads in plasma and CSF. The viral loads in CSF were highest in three patients with neuropsychiatric symptoms.

In most patients (15 of 23), HIV mutation patterns differed in blood and CSF, the report indicates. Seven cases showed mutations in blood isolates that were not present in CSF and 10 cases showed mutations in CSF isolates that were not present in blood.

Fifteen of 18 patients showing signs of therapeutic failure carried viral isolates with resistance mutations to at least one of their current drugs. In four such patients the resistance mutations appeared only in CSF isolates.

“The results suggest divergent evolution of HIV-1 in different biologic compartments,” the authors conclude. “The presence of resistant mutants in the CSF may escape regular diagnosis in blood.”

This does not mean that CSF should be routinely examined for HIV-resistant mutants, Dr. Wildemann commented.

“A spinal tap is an invasive procedure. Therefore, we do not perform it in HIV patients on a routine basis. On the other hand, we…would analyse the CSF compartment before adapting the antiretroviral therapy if other causes of therapeutic failure (incomplete adherence, insufficient bioavailability, mutations in blood with specificity to the current regimen) are not apparent.”