Tuberculosis (TB) is the leading cause of death in AIDS patients. Unfortunately, no one knows exactly why the disease is such a significant threat in people with immune systems compromised by the HIV virus.

But researchers at the University of Pittsburgh and the University of Wisconsin–Madison recently reported in Infection and Immunity that a new nonhuman primate model using Mauritian cynomolgus macaques may help bring scientists closer to understanding the AIDS-TB link. The immune systems of these animals are similar to humans, and they are susceptible to both SIV (the nonhuman primate version of HIV) and Mycobacterium tuberculosis (which causes TB).

The paper’s authors included Shelby O’Connor, associate professor of pathology and laboratory medicine at UW–Madison and the Wisconsin National Primate Research Center (WiNPRC), and researchers from the University of Pittsburgh and WiNPRC.

The researchers used 15 macaques in the study. Of the eight monkeys infected with only M. tuberculosis, four animals survived more than 19 weeks following infection. In stark contrast, the researchers found that that all seven animals previously infected with SIV exhibited rapidly progressive TB following co-infection with M. tuberculosis and all had to be humanely euthanized after 13 weeks.  

“Our study demonstrated that pre-existing SIV dramatically diminishes the ability to control M. tuberculosis co-infection from the start,” said Mark Rodgers, senior research specialist at the University of Pittsburgh and the study’s lead author.

Senior author Charles Scanga, research associate professor of microbiology and molecular genetics at the University of Pittsburgh, added that this finding has much larger implications for research into the AIDS-TB link.

“For the first time, we have a well-characterized nonhuman primate model that will facilitate research into vaccines or therapeutics to battle TB in people living with HIV,” he said.