To see whether or when blips mean possible mutation, the Hopkins team conducted a detailed genetic analysis of multiple blood samples from 10 HIV-positive patients, taking samples every two to three days for a period of three months between June 2003 and February 2004. All patients had their infection under long-term control, on HAART, and with viral loads of less than 50 copies per milliliter for at least six months. In total, 36 blood samples were taken from each patient.
Statistical analysis of the results showed that blips occurred in nine of the 10 patients with a median viral load of 79 copies per milliliter. The duration of the blips was typically less than three days, and blips were not related to any demographic factors, such as gender or age, nor to any clinical factors, such as illness, vaccination, or differences in antiretroviral drug regimens.
For every blip, the researchers conducted genetic tests on the samples before, during and shortly after the blip, to uncover any mutations in the virus. Measures of viral load were confirmed by using two independent laboratories to test each sample.
No new mutations were found in an analysis of nearly 1,000 viral clones for mutations in HIV's two key enzymes which are blocked by drug therapy, protease and reverse transcriptase. The authors also found that blips were not, again, detected when blood samples were assayed twice in independent laboratories.
"The lack of any consistency among the tests performed on blood samples confirms that there is no danger from these blips in viral load," says study lead author and infectious disease specialist Richard Nettles, M.D., an assistant professor at Hopkins. "These blips can be attributed to random statistical artifact inherent in measurements of
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Contact: David March
dmarch1@jhmi.edu
410-955-1534
Johns Hopkins Medical Institutions
15-Feb-2005