HIV becoming more virulent?

A study in the May issue of Clinical Infectious Diseases found a decline in the initial CD4+ T cell counts reported at diagnosis among some HIV-positive people in the U.S. from 1985 to 2007 -- a finding that suggests HIV may be adapting and becoming more virulent -- Reuters reports. The report analyzed data for 2,174 HIV-positive people who were enrolled in the TriService AIDS Clinical Consortium HIV Natural History Study. None of the participants previously had taken antiretroviral therapy, and all had their CD4+ cell counts measured within six months of HIV diagnosis.

The average initial CD4+ cell counts during the periods from 1985 to 1990, 1991 to 1995, 1996 to 2001, and 2002 to 2007 were 632, 553, 493 and 514, respectively. According to the report, the percentage of subjects with initial CD4+ cell counts less than 350 were 12%, 21%, 26% and 25%, respectively, during the same periods. Similar CD4+ cell count reductions were seen in black and white participants, and the report also noted that similar trends were seen in the CD4+ cell count percentage and the total lymphocyte count. Lead author Nancy Crum-Cianflone of the Naval Medical Center-San Diego said the study's findings "agree with those of other investigators" who report that "patients starting HIV care more recently may be presenting with lower initial CD4+ cell counts and requiring antiretroviral therapy initiation earlier in the disease course."

In an accompanying editorial, Maria Dorrucci of Rome's Istituto Superiore di Sanita and Andrew Phillips of London's University College Medical School write that although some current studies suggest that HIV virulence is rising, there have been other studies that report either stable or declining HIV virulence. Dorrucci and Phillips write that the differences may relate to how virulence is determined and that "it is unclear whether simple immunological or virological proxies for virulence can be expected to adequately capture the whole complexity of HIV virulence and host susceptibility" (Reuters, 4/15).

An abstract of the report is available online. A citation of the accompanying editorial is also available online.