June 19, 2009

Studies investigate potential HIV vaccines

Studies investigate potential HIV vaccines

Volunteers are needed for studies of two potential HIV vaccines at Vanderbilt Medical Center.

One of the studies is enrolling people who are at low risk of HIV infection, while the other seeks HIV-negative men who are at high risk for infection because they have sex with men.
Both are phase 2 studies conducted through the national HIV Vaccine Trials Network (HVTN).

The vaccine candidates have passed initial phase 1 safety studies in humans and are undergoing further safety testing in larger numbers of people. Phase 2 studies also gather information about the immune response and what may be the most effective dose and vaccination schedule.

The Vanderbilt HIV Vaccine Program began more than 20 years and 940 volunteers ago. The difficulty in developing a vaccine against the virus that causes AIDS testifies to its wiliness. The human immunodeficiency virus mutates rapidly to evade detection by the body’s immune system.

Each study, however, adds more information, said Kyle Rybczyk, M.S.N., the program’s clinic coordinator. “Without the volunteers … the science doesn’t happen. We wouldn’t be even where we are today,” he said.

Volunteers are paid for their time, but Rybczyk said most participate for altruistic reasons.

One of the vaccine candidates, HVTN 205, is being tested in low-risk individuals between 18 and 50 who have not been vaccinated against smallpox. That’s because it includes a booster of a modified vaccinia virus, which is also used in the smallpox shot.

Previous exposure to the smallpox vaccine may blunt the immune response against HVTN 205, he said.

The other vaccine candidate, HVTN 505, is being tested in HIV-negative men between 18 and 45 who have sex with men, who have been circumcised, and who test negative to an adenovirus antibody.

Adenovirus causes the common cold. A live but inactivated adenovirus, one not capable of causing an infection, is given with bits of non-infectious genetic material from HIV as a booster in this trial. Previous exposure to adenovirus may blunt the immune response to HVTN 505.

Researchers want to know whether HVTN 505 will reduce the “viral load,” or amount of HIV circulating in the bloodstream if a person later is infected with HIV, and whether it can alter the course of HIV disease. This information may help scientists design a vaccine that ultimately prevents HIV infection, Rybczyk said.

For more information, visit www.vanderbilthealth.com/HIV-vaccine-program or contact Rybczyk at 322-5641 or kyle.rybczyk@vanderbilt.edu.