New HIV Vaccine Shows Promise

Human clinical trials are starting this month in the United States for SAV001-H, a vaccine developed by a team of researchers at the University of Western Ontario’s Schulich School of Medicine and Dentistry led by Dr. Chil-Yong Kang. The vaccine recently passed the first phase of trials, which were conducted on 40 HIV-positive individuals.

Instead of using only certain genes or proteins of the virus, as previous HIV vaccines have attempted, SAV001-H uses the whole of HIV-1, which is the most common and pathogenic strain of the virus, representing some 90 percent of HIV and AIDS cases. This approach, which was used to create vaccines for polio, rabies and hepatitis A, is called “killed whole virus vaccine.”

“We infect the cells with a genetically modified HIV-1,” Kang explained to the Ontario Business Report. “The infected cells produce lots of virus, which we collect, purify and inactivate so that the vaccine won’t cause AIDS in recipients, but will trigger immune responses.”

What has made the testing of efficacy in the HIV vaccine so difficult is that there is no animal model (though that may be changing) — the vaccine must be tested on humans. The difficulty is evident. Just five months ago, the United States’ National Institute of Allergy and Infectious Diseases (NIAID) shut down their trial of HVTN 505, another hopeful HIV vaccine, after it was determined that the vaccine didn’t seem to reduce the risk of infection for those who were negative, or reduce the viral load in test subjects who were already infected. At the time of the shutdown, it appeared possible that the vaccine might actually have made vaccinated subjects slightly more likely to contract HIV.

AIDSVAX, developed by Genentech in San Francisco, California, was denied further trials by the U.S. Food and Drug Administration in 2003 because previous trials suggested some subjectes had become infected with HIV following vaccination and it was impossible to determine whether the vaccine had caused their change in status.

Four years later, another test — this time with V520, an experimental HIV vaccine developed by the pharmaceutical giant Merck & Co. — came to a stop when 24 of the 741 subjects who had received the vaccine developed HIV. The subjects were members of high-risk groups for HIV infection, but the U.S. National Institute of Health, which had partly funded the trial, determined the vaccine did not prevent HIV nor reduce viral load in those who became infected following vaccination.

Though it’s too early to tell whether Canada’s SAV001-H will deliver the best weapon we could hope for in fighting HIV and AIDS, it’s very promising to see that vaccinated HIV-positive subjects began producing greater quantities of antibodies to attack the virus without apparent adverse effects. It’s these results that encouraged the Food and Drug Administration to green-light the upcoming medical trials for SAV001-H.

“SAV001 will undergo three phases of human clinical trials,” says the Ontario Business Report. “Phase I will involve 40 HIV-positive people and will test the vaccine’s safety. Phase II will test immune responses in 600 HIV-negative people, and Phase III will test effectiveness, using 6,000 HIV-negative people at high risk of contracting the virus.”

To better understand the trial phases involved in testing the vaccine, check out GeekMash’s infographic on the topic.

Header image shows scanning electron micrograph of HIV-1 budding from cultured lymphocyte and comes from the Centers for Disease Control and Prevention’s Public Health Image Library.