A new AIDS vaccine is being tested in Boston, according to senior investigator Clyde Crumpacker, infectious disease specialist in the Virology Research Clinic at Beth Israel Deaconess Medical Center (BIDMC) and professor of medicine at Harvard Medical School’s Division of AIDS. The study, which will include a total of 160 participants at 10 sites throughout the U.S, will test a new “Ad5-HIV gag” recombinant vaccine being developed by Merck Research Laboratories. The study of HIV-infected patients will include 86 participants at 20 sites across the country, including BIDMC and Massachusetts General Hospital. Two trials will test the safety of the investigational vaccine, as well as its capacity to create an immune response. Because the vaccines are produced through genetic engineering techniques, they do not contain live HIV virus and, therefore, cannot cause an infection. “This new recombinant vaccine is composed of an adenovirus — a virus responsible for the common cold — to which a small portion of DNA from the HIV virus has been added,” says Crumpacker. Unlike a majority of vaccines — including, for example, the measles vaccine — which work by preventing the possibility of infection, the Ad5-HIV gag vaccine is designed to be both prophylactic and therapeutic.