Researchers at the Emory University in Atlanta have found that there could be a natural mechanism involved that prevents HIV/AIDS infection in certain type of monkeys.

The findings 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.

SIV or simian immunodeficiency virus (SIV) is a virus that caused AIDS in monkeys. SIV is related to the human immunodeficiency virus (HIV). The researchers compared sooty mangabeys and rhesus macaques infected with SIV, for the study.

On studying the development of AIDS in sooty mangabey monkeys, they found that the primates don't develop AIDS even if they have a very high viral load of SIV. Sooty 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.

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

"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.

In another primate species, macaques, giving the monkeys new CD4+ T cells heighten the animal's vulnerability to SIV, he noted. The replenished cells appear to make the monkey "more resistant to SIV infection," Paiardini said.

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," said Paiardini.