In a recent study, researchers at the University of Michigan shared new developments on a chemical compound with potential to cure HIV. Published in the Journal of Medicinal Chemistry on March 7, the research outlines a joint effort by the Collins and Sherman labs to manipulate concanamycin A, a chemical compound produced by microorganisms, that could eventually lead to a cure for HIV.
HIV weakens the immune system by attacking white blood cells that fight infections in the body. As the number of white blood cells decreases, the body becomes more susceptible to cancers such as lymphoma, Kaposi sarcoma and human papillomavirus-related cancers or infections such as tuberculosis and pneumocystis pneumonia. If the white blood cell count falls below 200 cells per microliter of blood, HIV develops into AIDS.
The immune system fails to detect the presence of HIV because of the Nef protein, which allows the virus to hide from killer cells that normally eliminate viruses. Kathleen Collins, one of the co-authors of the study and a U-M professor of microbiology and immunology, has been studying the Nef protein for over 20 years. Collins said her lab developed a molecule screening technique called high-throughput screening to measure the levels of MHC class I molecules and find molecules that reverse the effects of Nef.
“We screened a lot of small molecule libraries that were available at the Chemical Genomics core facility at the Life Sciences Institute here at the University of Michigan,” Collins said. “We screened hundreds of thousands of molecules but didn’t find anything that would reverse this particular activity of Nef that we were looking at. Then, the director of the facility suggested we look at some new molecules that David Sherman’s lab collects from the ocean.”
David Sherman, a research professor at the U-M Life Sciences Institute, has developed a sample library of more than 50,000 microbial natural product extracts from marine microorganisms over the past 20 years. Collins looked through the library to find a match that could undo the effects of Nef, originally deciding on a compound called bafilomycin, which is produced by an organism from Papua New Guinea.
“When we discovered it was bafilomycin, we already knew that there was a larger family of this class of natural products called pleco macrolide,” Sherman said. “Some of them are commercially available, and we started to screen (them). We would purchase a small amount, just enough to test them, and it turns out that the one that was most potent was called concanamycin A.”
According to Sherman, CMA could cost almost $1,000 per milligram. A colleague gifted him a wild-type strain of bacteria that produced one milligram of CMA per liter, but the reactions conducted in the research required at least 30 milligrams of the compound. Filipa Pereira, a research investigator at the Life Sciences Institute and a senior member of the Sherman Lab, was able to increase concanamycin A production 2,000-fold by manipulating the environmental conditions of the bacteria and using genetic engineering to promote CMA production.
“(What are) the best conditions … to bring up the pathways required for the concanamycin production?” Pereira said. “It was just a little bit of growth condition optimization, culture optimization and also genetic engineering. This is the best I could do just by changing the environment, but what happens if I change the genome? And so combining both, we reached a very high-(producing) strain.”
An obstacle to using CMA in anti-HIV drug development is its inhibition of a cellular protein called Vacuolar ATPase, which plays an important role in protein turnover. As proteins grow old or become damaged, they must be degraded by the lysosome, which relies on V-ATPase. Collins said her lab worked to create versions of CMA that would increase the strength of inhibition against Nef but decrease the effect on V-ATPase.
“We wanted to make sure that if we were thinking about using it in people as a treatment that we reduced any possible toxicity … because it also has activity against a cellular protein called Vacuolar ATPase,” Collins said. “The main activity against (V-ATPase) is at higher concentrations, but we wanted to make sure that our safety window was as large as possible. And so we worked with David to make modifications to the CMA molecule that can be isolated from bacteria.”
Despite the new developments, Collins and Sherman stressed that a cure for HIV is still far away. Collins said that their in vitro studies, studies performed outside of a living organism, would need to be expanded to an animal model.
“It’s hard to predict from these in vitro studies how a drug will behave inside an animal,” Collins said. “And so we need to take our best molecules into an animal model system. We’ve done a little bit of that work so far, and it does look promising, but we need to do more.”
Sherman said that moving to an in vitro model would be difficult due to high costs and differences between viruses in humans and animals.
“The closest model is probably a monkey model … but that’s called a simian immunodeficiency virus, SIV,” Sherman said. “SIV is different enough from HIV that it’s not even clear that would be a good model. Plus, it would be enormously expensive to run these monkey models.”
There is no permanent cure for HIV, and existing treatments are only capable of preventing the virus from multiplying to keep HIV to low levels in the body. Treatment is estimated to cost between $1,800 and $4,500 a month, and patients must either take an HIV treatment pill every day or receive an HIV treatment shot every one to two months for the rest of their lives. Lauren Cupchak, College of Pharmacy student and social events coordinator for the Pre-Pharmacy Student Organization said a cure would have a significant impact on those currently undergoing lifelong treatment for HIV.
“HIV has been something that people have been studying for decades,” Cupchak said. “It would be really cool if we were finally able to develop a cure for it because the treatments that are in place now are only to prolong the infection before it develops to AIDS, not so much (to) completely eradicate the virus from the body. So I think it would be a huge step in the right direction if we were able to cure HIV.”
Collins said she was motivated to find a cure for HIV after seeing the early stages of the HIV/AIDS epidemic unfold as a student at Johns Hopkins University.
“When I was a Ph.D. student and a medical student down in Baltimore, the HIV pandemic was just emerging,” Collins said. “I experienced what it was like to try to take care of people, some of whom were quite young. I took care of a 5-year-old who had HIV, for which there was absolutely no treatment. Infection was essentially a death sentence. I knew that I needed to work on this virus because of all the harm that it was doing to people.”
Daily Staff Reporter Marissa Corsi can be reached at macorsi@umich.edu.