Successful AIDS Vaccine Sidesteps the Host Immune System

Molecular virologists working with monkeys have developed a novel vaccine against simian immunodeficiency virus (SIV) that is a model for a similar vaccine against human HIV.

The novel approach taken by investigators at The Children's Hospital of Philadelphia (PA, USA) was to bypass the immune system of the host animal. Instead, they developed a series of artificial antibodies (immunoadhesins) and the genes required to synthesize them. These genes were then delivered to a test group of the monkeys by way of an adeno-associated virus (AAV) carrier virus.

Results published in the May 17, 2009, online edition of the journal Nature Medicine revealed that monkeys vaccinated with SIV-specific immunoadhesin genes developed immunity to SIV and were protected against challenge with virulent SIV. High titers of SIV-specific immunoadhesins remained in the blood of these animals for over a year. All the animals in the control group of un-immunized monkeys became infected by SIV, and two-thirds died of AIDS complications.

"We used a leapfrog strategy, bypassing the natural immune system response that was the target of all previous HIV and SIV vaccine candidates," said first author Dr. Philip R. Johnson, chief scientific officer at The Children's Hospital of Philadelphia. "However, to ultimately succeed, more and better molecules that work against HIV, including human monoclonal antibodies, will be needed."

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