Blocking HIV Before It Can Infect Any Normal Cells

A fast, sensitive laboratory test that measures the molecular components involved during the critical moment when HIV infects a normal cell has been developed.

The advance was made by researchers in the University of California, San Diego (UCSD) School of Medicine and VA San Diego Healthcare System.

Described in the December 2001 issue of the Journal of Biological Chemistry (JBC), the test makes it possible to study and design new compounds to block the action of these molecular components before HIV can permanently infect a normal cell, causing it to manufacture more virus.

In recognition of the test as “groundbreaking work toward new pharmaceutical strategies to combat the virus that causes AIDS,” the GlaxoSmithKline pharmaceutical company awarded UCSD’s Richard Kornbluth, M.D., Ph.D., with a Drug Discovery and Development Award during a professional meeting last week in Chicago.

Kornbluth, who was senior author of the JBC article, is a UCSD associate professor of medicine and a researcher with the VA San Diego Healthcare System.

Kornbluth explains that once HIV enters a host cell’s DNA, the cell becomes permanently infected after the virus splices its genes into the DNA of the host cell, a process known as “integration.”

Drugs now available to treat HIV-infected individuals work by inhibiting enzymes that contribute to the spread of HIV, but no drugs have yet been approved that prevent the virus from integrating its DNA into the host cell.

“If we can find a way to intercept HIV during the integration process, when HIV DNA is spliced into normal cells, we can stop it before the cell is permanently infected,” Kornbluth says.

HIV drugs now used to treat patients inhibit reverse transcriptase and protease, two of the three enzymes that play a role in infection. Reverse transcriptase works after HIV has entered a host cell by copying the viruses RNA genome into a DNA form. Protease affects the structure of the virus by cutting viral proteins into short pieces that can be incorporated into new viruses.

The third enzyme, integrase, is part of a group of molecules called a preintegration complex (PIC) that promotes HIV integration into the host cell DNA. The entire PIC moves through a pore in the nucleus of the invaded cell, where integrase inserts genes from the viral DNA into the cell’s chromosomes, which is required for the production of more HIV viruses by the infected cell.

The test developed in the Kornbluth lab will allow scientists and drug developers to search millions of chemical compounds for potential drugs that can inhibit any of the components required for the PIC to integrate, not just drugs that inhibit the enzyme integrase.

“The major way that pharmaceutical companies develop drugs is to screen collections of chemicals, anywhere from 100,000 to three million,” Kornbluth says. “Our test will allow them to target the entire PIC which is the actual target a successful drug must attack. We believe that molecular components in the PIC, besides integrase, are critical to whether or not HIV is able to integrate into the host cell DNA.”

In addition to its ability to look at the entire PIC, Kornbluth’s test is considerably faster than a test developed in 1987, with results taking 2-3 hours rather than 2-3 days. There’s also increased volume: 100 tests can be done in 2-3 hours, compared to about 30 tests that were run over 2-3 days.

With Kornbluth, authors of the article in JBC were Alexei Brooun, Ph.D., a postdoctoral fellow in Kornbluth’s lab, and Douglas R. Richman, M.D., director of the UCSD AIDS Research Institute and professor of medicine and pathology, UCSD and VA San Diego Healthcare System.

The work was funded by the American Foundation for AIDS Research (amfAR), the National Institutes of Health, the State of California’s Universitywide AIDS Research Program, the UCSD Center for AIDS Research, the Department of Veteran Affairs and the Research Center on AIDS and HIV Infection of the VA San Diego Healthcare System.