HIV selectively suppresses anti-HIV def...( A new study confirms what HIV researche...)

A new study confirms what HIV researchers until now only suspected: HIV selectively disables the immune systems response against the virus by disproportionately infecting the very cells designed to fight it. In fact, CD4+ T cells programmed to fight HIV are two to five times more likely to be infected with HIV than CD4+T cells programmed to take on other pathogens. This finding not only helps us better understand how the virus causes disease, it should also aid in developing effective HIV vaccines, comments Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID). The study, conducted by scientists at NIAIDs Vaccine Research Center (VRC) and their colleagues, will appear in the May 2 issue of Nature.

CD4+ T cells, also called helper T cells, are HIVs primary target. These cells help direct the immune systems response to various pathogens. HIV undermines the bodys ability to protect against disease by depleting these cells.

From 12 HIV-positive individuals, the researchers isolated three subgroups of helper T cells: HIV-fighting cells, cytomegalovirus-fighting cells, and a mixed group. The scientists then examined these cells for evidence of HIV infection. In each case, HIV infected a much greater percentage of HIV-specific cells than cells in the other two groups. The cytomegalovirus-specific and mixed group showed no significant differences in HIV infection rates.

For years we have known that the immune system does not produce a good CD4+ T cell response against HIV, and we have postulated that this might be because HIV preferentially infects HIV-specific CD4+ cells, says Richard Koup, M.D., senior study author and a senior investigator at the VRC. This study is the first to show that this phenomenon actually happens in the body. Dr. Koup and his team tested two possible mechanisms underlying this phenomenon and found evidence for both.

The first occurs when the immune system initia
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Contact: Jeff Minerd
jminerd@niaid.nih.org
301-402-1663
NIH/National Institute of Allergy and Infectious Diseases
1-May-2002

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