Mutation breaks HIV's resistance to drugs

"The 172K polymorphism makes certain forms of HIV less resistant to drugs," said Stefan Sarafianos, corresponding author of the study and researcher at MU's Bond Life Sciences Center. "172K doesn't affect the virus' normal activities. In some varieties of HIV that have developed resistance to drugs, when the 172K mutation is present, resistance to two classes of anti-HIV drugs is suppressed. We estimate up to 3 percent of HIV strains carry the 172K polymorphism."

HIV is a retrovirus, meaning it uses an enzyme called reverse transcriptase to create copies of its own genetic code. These copies are inserted into the victim's own genes where the virus highjacks the host's cellular machinery in order to reproduce itself. Two classes of drugs, nucleoside (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs), can stop this process in its tracks.

However, some HIV strains have developed resistance to NRTIs and NNRTIs. The 172K polymorphism suppresses this resistance and allows both classes of drugs to fight HIV more efficiently. The mutation is believed to be the first of its kind that blocks resistance to two families of drugs.

"Clinical doctors use a database of HIV mutations and the drugs they are susceptible to when they prescribe treatments to an HIV-infected patient," Sarafianos said. "Our finding will be integrated into this database. Once that happens, when doctors learn that their patients have HIV strains that carry the 172K polymorphism, they will know that the infections can be fought better with NRTIs and NNRTIs."

One of Sarafianos' colleagues at the AIDS Clinical Center in Japan found the 172K polymorphism by accident. The mutation was first discovered in a patient, and the researchers were able to recreate it in the laboratory.

The study "HIV-1 Reverse Transcriptase Polymorphism 172K Suppresses the Effect of Clinically Relevant Drug Resistance Mutations to Both Nucleoside and Nonnucleoside RT Inhibitors," was published in the Journal of Biological Chemistry. The lead author was Atsuko Hachiya of the AIDS Clinical Center at Japan's National Center for Global Health and Medicine in Tokyo. Stefan Sarafianos is associate professor of molecular microbiology & immunology in the MU School of Medicine and associate professor of biochemistry in the College of Arts and Science. Sarafianos also is associated with the Bond Life Science Center.