A large-scale study to evaluate a potential HIV vaccine is about to commence in South Africa. It will involve up to 3,000 participants and is being conducted by researchers from the United States and South Africa. Known as a Phase IIb trial, or test of concept trial, it will enable researchers to determine whether the test vaccine prevents HIV infection, results in lower HIV levels in those who become infected after vaccination, or both. Additionally, the trial will determine if the vaccine, which is based on clade B HIV, has the potential to protect against the clade C virus, the subtype prevalent in South Africa.
While the trial will not lead immediately to a wider rollout of the vaccine, it will show whether this type of vaccine approach offers promise to interrupt the continued spread of HIV.
"This trial will answer several major scientific issues that face all of us in the field of HIV-vaccine development," said researcher Lawrence Corey, from the Fred Hutchinson Cancer Research Center. "It will determine the usefulness of vaccines that induce high immune response to the parts of the virus that are similar between different strains of HIV-1."
The vaccine, known as the MRKAd5 HIV-1 trivalent vaccine, is manufactured by Merck and in earlier studies was found to stimulate cellular immune responses against HIV in more than half of volunteers. It is based on an adenovirus - a common cold virus that has been modified so that it cannot cause a cold in humans or be passed from person to person. The adenovirus is the carrier which transports copies of three HIV genes called gag, pol and nef. The researchers hope that these HIV genes will produce a cellular immune response to HIV and cause the body to make killer cells that are programmed to recognize and destroy cells that are infected with HIV.
The trial will also provide preventive care for all participants, who will receive extensive risk-reduction counseling on a regular basis as well as condoms. Participants will also be provided access to treatment for any sexually transmitted infection acquired during the study. Recent research has shown that men who are circumcised are less likely to become HIV infected, so access to medical circumcision also will be provided to male participants who choose to undergo the procedure.
"South Africa is an excellent location for this trial due to the high levels of infection coupled with the good clinical infrastructure, including internationally recognized immunology laboratories, a well-established national vaccine initiative and experience in running clinical trials," said James Kublin, one of the study's lead investigators. "Community involvement and education initiatives in South Africa are robust and mature, and they are essential for running trials involving thousands of volunteers," he concluded.
Based on material from the Fred Hutchinson Cancer Research Center
