WEDNESDAY, Aug. 11 (HealthDay News) -- A natural mechanism that may help prevent the development of AIDS in sooty mangabey monkeys has been discovered by scientists.

Sooty mangabey monkeys are a natural host for the simian immunodeficiency virus (SIV), but they don't develop AIDS even if they have a very high viral load. SIV -- a virus that infects monkeys -- is related to the human immunodeficiency virus (HIV) in people.

These monkeys may be able to avoid developing AIDS because they are better at regenerating T cells -- a type of white blood cell that allows the immune system to fight off microbial invaders.

Specifically, SIV-infected sooty mangabeys maintain effective levels of CD4+ T cells through rapid regeneration of their pool of naive CD4+ T cells (mature cells not yet exposed to toxins or other substances that stimulate the production of antibodies).

The finding may help explain why SIV and HIV lead to AIDS in other types of monkeys and nonhuman primates and in humans, according to the researchers at the Yerkes National Primate Research Center at Emory University in Atlanta.

For this study, the researchers compared sooty mangabeys and rhesus macaques infected with SIV.

"The results showed that while both species showed a similar extent of CD4+ T cell replenishment, the rhesus macaques regenerated their naive CD4+ T cells more slowly," team leader Mirko Paiardini said in an Emory news release. He also noted that in another primate species, macaques, giving the monkeys new CD4+ T cells heightens the animal's vulnerability to SIV. However, in the sooty mangabey this doesn't happen - in fact, the replenished cells appear to make the monkey "more resistant to SIV infection," Paiardini said.

Paiardini believes the new findings "have increased our understanding of the immune system and are critical to our continuing research to determine why some species are more susceptible than others to infectious diseases."http://www.healthscout.com/template.asp?page=newsDetail&ap=1&id=641984