Why does it matter that a team of researchers led by Dr. Beatrice Hahn, M.D., a Professor of Medicine and Microbiology at the University of Alabama at Birmingham, was able to trace the origin of the Human Immunodeficiency Virus (HIV), which causes AIDS, to specific communities of African chimpanzees?
“With a pandemic that is affecting over 60 million people, that seemed to come out of the blue, people wanted to know, where did it start?” Hahn says. “While it may not have direct practical application for treating people today, there was a fundamental urge to find out how this worked.”
There was a mystery to be solved, and Hahn and her fellow researchers, including her husband, Dr. George Shaw, M.D., solved it. In 1999, they announced that they had found a close association between HIV in humans and Simian Immunodeficiency Virus chimpanzee (SIVcpz) in the Pan troglodytes troglodytes, or P.t.t., of West-Central Africa, a chimpanzee sub-species that appeared to be the reservoir of the epidemic.
The announcement received worldwide attention but also generated some skepticism in the scientific community. “People said, ‘Well, it’s all fine and good, but these are captive chimps. Lots of stuff happens in captivity. Show me what’s in the wild,’“ Hahn says.
The critics also wanted more examples. Hahn believed that she was correct, but she would have to prove it.
“If I was going to be proven wrong, it better be me,” Hahn says, laughing. “I guess my personality is such that I don’t easily give up.”
Finding her proof would take seven years and the development of new, non-invasive methods for sampling wild chimpanzees. These methods were necessary because Hahn wanted enough data to support her findings.
“You don’t go into one area of the forest and observe five apes and draw a conclusion,” she says. “We wanted to cover the waterfront, and the only way you can do that is non-invasive. There is no other way unless you shoot them, which we didn’t want to do.”
Hahn and her colleagues looked for SIVcpz antibodies and nucleic acids in thousands of primate fecal samples collected by native trackers in remote regions. They determined that the prevalence of SIVcpz in some communities of P.t.t. chimps in Southern Cameroon reached 35 percent.
UAB’s Viral Sequencing Core, a world-class genetic sequencing and analysis facility of which Hahn is the co-director, was crucial to the research. By sequence analysis of SIVcpz strains, the researchers could trace the origins of HIV-1 to these distinct, geographically isolated chimpanzee communities, establishing these communities as the natural reservoir of HIV-1.
“We found viruses in the wild chimps that were even more closely related to the human strains than we had originally found in the captive chimps,” Hahn says. “And we now have 50 strains that we genetically fingerprinted, whereas before we had five.”
Hahn believes that HIV-1 was introduced into humans through exposure to blood during the hunting and field dressing of chimpanzees and other primates that have long served as a subsistence food source. “Understanding this gives you a sense of how these zoonotic infections, which are transmitted from animals to humans, how they work,” Hahn says. This is important because, as Hahn points out, AIDS is not necessarily the last such infection that could break out. “It may happen again and we would have no clue,” she says.
Hahn and Shaw have also wondered why the chimpanzee, almost identical to humans genetically, could be resistant to the ravages of the AIDS virus on the immune system. “That is a puzzle on my list to figure out,” Hahn says.
“These simian relatives of HIV are not pathogenic, and we don’t know why,” Hahn admits. “There is something about the way the host attracts the virus that is different in these primate species that have been infected for a long time and in us, who just got it 100 years ago, and somehow humans tend to overreact in their immune systems and in doing so don’t really solve the problem, but merely waste all of their immunological ammunition.”
Hahn, also a co-director of the Center for AIDS Research at UAB, continues to work closely with her husband, a professor of hematology and oncology at UAB. “I don’t know what the secret is,” Hahn says. “We just got lucky. Some couples can’t stand working together. In our case I think we need each other scientifically and that translates into a partnership at home.”
Hahn studies where the viruses come from and how they evolve, and Shaw looks at how the viruses attach and replicate, but they share a goal of helping to develop an effective treatment or vaccine for HIV-1.
“Working together has really helped both of our careers, except when we were young, and this is one of those gender things, we couldn’t officially work together,” Hahn says. Hahn and her husband were concerned that people would say, as she puts it, “‘She came along because she’s the wife, right?”
Has she often faced gender bias as a woman in the traditionally male domain of science? “It’s hard for me to answer this question,” Hahn says. “I was always a package deal, with my husband. When you’re a package deal within the academic system, it’s harder to take you on than if you’re just a single person. So it’s not fair to compare me in this setting with a woman who has to do it all on her own.
“On the other hand, every 10 years I have to go to my chairman and say, ‘You know, I’m really pissed I’m not making as much as my husband, and I do the same work,’“ Hahn says. “So there is clearly still a gender bias, but more on the pay line and moving through the ranks than it is someone saying, ‘You can’t do that because you’re a woman.’”
You can learn more about Beatrice Hahn and the Center for AIDS research online at www.uab.edu/avrc