April 16, 2009

Study Finds HIV May Be Growing More Virulent

A new report from the Naval Medical Center in San Diego said that CD4+ cell counts among newly-diagnosed HIV patients in the U.S. fell from 1985 to 2007, suggesting the virus may be growing more virulent.

CD4+ cells are immune-system cells that are indicate the severity of HIV infection.  As the infection advances, CD4+ cell counts decline.

The findings support previous research indicating that patients beginning HIV treatment in recent years may have lower CD4+ cell counts at diagnosis, and may need antiretroviral therapy earlier in the course of their disease, wrote Dr. Nancy Crum-Cianflone of the Naval Medical Center and her colleagues in the report.

The study's results are based on an analysis of data from 2,174 patients who tested positive for HIV antibodies and were involved in the TriService AIDS Clinical Consortium HIV Natural History Study.

None of the participants had received antiretroviral HIV treatment, and each had their CD4+ counts assessed within 6 months of diagnosis.

The average initial CD4+ cell counts during in1985-1990, 1991-1995, 1996-2001, and 2002-2007 were 632, 553, 493, and 514 cells per microliter, respectively.  At the same time, the percentage of participants with initial CD4+ cell counts below 350 cells per microliter was 12 percent, 21 percent, 26 percent, and 25 percent, respectively.

The decline in initial CD4+ cell counts was similar in white and African American patients, according to the report.  Comparable trends were also seen for the CD4+ cell count percentage and absolute lymphocyte counts.  Lymphocytes are a type of white blood cell involved in the immune response.

Dr. Andrew Phillips from University College Medical School, London, and Dr. Maria Dorrucci, from Istituto Superiore di Sanita, Rome, said that although some studies suggest that HIV virulence is on the rise, others have found that it is either stable or perhaps even decreasing.

This may be related to how the HIV virulence is assessed, they wrote in an accompanying editorial to the published study.

"It is unclear whether simple immunological or virological proxies for virulence can be expected to adequately capture the whole complexity of HIV virulence" they wrote.

The study was published in the May 2009 journal Clinical Infectious Disease.


Image Caption: Scanning electron micrograph of HIV-1 budding from cultured lymphocyte. This image has been colored to highlight important features. CDC


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