Meek immune response helps AIDS survival

ATLANTA, Sept. 22 (UPI) -- U.S. scientists say a paradoxical discovery might help explain why some species can live with immunodeficiency viruses that never progress to AIDS.

A team of scientists from Yerkes National Primate Research Center and the Emory Vaccine Center report the simian immunodeficiency virus -- the AIDS virus found in apes and monkeys -- does not lead to a strong immune response in sooty mangabeys, one of numerous African primate species that harbor SIVs, but remain healthy despite their infection. In contrast, humans and rhesus macaques mount a strong and sustained response to infection by an immunodeficiency virus, but eventually succumb to the infection.

In the new study, researchers report the paradoxical discovery that the vigorous immune response of humans and macaques actually harms the production and health of an essential class of immune system cells called effector cells, leading eventually to failure of the immune system and death.

The researchers, led by Dr. Mark Feinberg, found sooty mangabeys infected by SIV produce much less interferon alpha -- a chemical that alerts other immune system cells to the infection -- than do infected humans or macaques.

The study is reported in the online edition of the journal Nature Medicine.