CANFAR unveils a new HIV vaccine candidate

Toronto - Researchers funded by the Canadian Foundation for AIDS Research (CANFAR) unveil a new HIV vaccine candidate which can reduce - and in some cases, prevent - HIV progression by triggering the body's natural immune defenses.

This study is the work of Dr. Kelly MacDonald, Senior Author of the paper and Microbiologist at Mount Sinai Hospital in Toronto, and is being published in the Journal of Virology. The findings extend Dr. MacDonald's earlier studies of cellular immune function and its role in resisting HIV infection and disease in highly-exposed populations.

The study investigated two vaccine candidates: Delta 5 and Delta 6 simian immunodeficiency virus (SIV). Both were super-attenuated vaccines (a weakened form of the HIV virus used in primates.) Delta 5, the stronger vaccine, provides more protection from HIV.

The study showed that control of and protection from HIV depended on initial exposure to the Delta 5 vaccine, which primed immune responses to the virus. This is similar to the Canadian and Kenyan human subjects in Dr. MacDonald's previous study, who remained uninfected with high HIV exposure because their immune systems were primed by a weaker HIV virus.

"Using these super-attenuated viruses as vaccines in a primate model gives us an ideal opportunity to see how natural immunity to HIV can develop," said Dr. MacDonald.

The HIV virus enters the genital tract, then the genital lymph nodes, and finally invades the gut lymph nodes. The study highlighted the importance of controlling the virus before it enters the gut lymph nodes, because 70 per cent of the body's immune system is found in the digestive tract, and the memory of the immune system resides there. If the HIV virus reaches this area, eliminates immune memory, leaving the person vulnerable to the virus.

"Now, we need to test a practical vaccine delivery system that will intermittingly tickle the immune system to ensure the natural immunity is properly primed," said MacDonald. "This way, if HIV exposure does occur, the system can respond quickly when it enters the body and before it reaches the lymph nodes in the gut."

The vaccines were developed in conjunction with another CANFAR-funded researcher, Dr. Mark Wainberg at McGill University.

"This study indicates the importance of collaborative basic science research among virologists and immunologists, and will hopefully move us closer to our goal of successful HIV vaccine development," said Wainberg.

The research team has now adapted the Varicella virus (chicken pox) vaccine into a delivery system for an HIV vaccine. Live-attenuated Varicella is a licensed vaccine with a 20-year safety record. It provides the body long-term protection through silent reactivation of the chicken pox virus intermittingly, which triggers the immune system.

The researchers have inserted HIV genes into the live-attenuated Varicella virus to create a vaccine that is non-toxic and incapable of causing disease.

A trial for the new vaccine candidate will begin this spring. A successful vaccine will generate immunity to both chicken pox and HIV.

CANFAR remains committed to ending the HIV/AIDS pandemic through funding research initiatives such as Dr. MacDonald's vaccine candidate.

"The solution that will one day end AIDS can only be found through research. Canada is playing a key role in the search for that solution," said Kerry Whiteside, CANFAR's Executive Director. "The incredible work of Dr. MacDonald, supported by Dr. Wainberg, proves that this country has the great minds needed find to find a vaccine. At CANFAR, we will continue to raise the funds needed to further the work of these researchers, and bring the world closer to ending AIDS."

ABOUT CANFAR: Founded in 1987, the Canadian Foundation for AIDS Research raises awareness to generate funds for research into all aspects of HIV and AIDS. The only organization in Canada that operates for the sole purpose of privately funding HIV/AIDS research, CANFAR finances AIDS researchers across Canada. To date, CANFAR has provided approximately $16 million to HIV/AIDS research projects. Visit www.CANFAR.com for more
information.