The National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH, has opened enrollment in HVTN 505, an exploratory HIV vaccine clinical study examining whether a two-part vaccine regimen can decrease viral load (the amount of HIV in the blood) in study participants who later become infected with HIV. Viral load is an important health indicator in people who are infected with HIV because typically those with less virus remain healthier longer. Further, HIV-infected individuals with reduced levels of virus may be less likely to transmit the virus to other people.
Led by Scott M. Hammer, M.D., chief of the Division of Infectious Diseases at Columbia University in New York, HVTN 505 is being conducted by the NIAID-supported HIV Vaccine Trials Network (HVTN). The Phase II study employs a prime-boost strategy of two investigational vaccines developed by scientists at NIAID’s Vaccine Research Center (VRC): a series of three immunizations with recombinant DNA-based vaccine (the primer vaccine) over the course of eight weeks followed by a single immunization with a recombinant vaccine (the boosting vaccine) based on a weakened adenovirus type 5 (Ad5) that carries the vaccine contents and helps stimulate the immune system. Ad5 is a common virus that normally causes colds, but the Ad5 virus used in the VRC vaccine regimen has been disabled so that it cannot cause a cold or other respiratory illness. The Ad5 vaccine in this study encodes for HIV proteins found both inside the virus and on its outer envelope.
Neither of the two vaccines contains HIV and neither vaccine can infect study participants with the virus. Both vaccines have been found safe when tested in animals and when used in hundreds of people in earlier clinical trials.
HVTN 505 is planned to take place in 12 U.S. cities and is designed to enroll 1,350 HIV-negative men ages 18 to 45 years who have sex with men. Participants must be circumcised and at the time they are enrolling, without Ad5 antibodies resulting from previous exposure to the Ad5 virus. These enrollment requirements are in place as an added safety precaution because in the HIV vaccine study known as Step (see Statement: Immunizations Are Discontinued in Two HIV Vaccine Trials), which involved a slightly different Ad5 vaccine, more cases of infection were found among those gay and bisexual male participants who were not circumcised and who had Ad5 antibodies at the time of enrollment compared to participants with the same characteristics who were given a placebo vaccine.
The HVTN 505 study is intended to answer important scientific questions that could lead to the discovery and development of new and improved candidate HIV vaccines in the future. An exploratory study such as this is not part of a typical product development path of studies that would lead to vaccine licensure. Rather, this type of study serves as the basis for subsequent research that will build upon its findings.
For more information about the HVTN 505 study, see Questions and Answers: The HVTN 505 HIV Vaccine Regimen Study and www.hopetakesaction.org.