To be really effective in people at a high risk of infection, an HIV vaccine needs to protect against not just one exposure but many, and recent research from GeoVax ($GOVX) presented at the 2012 Conference on Retroviruses and Opportunistic Infections (CROI) might bring this ideal type of protection a step closer, opening the door to clinical trials.
GeoVax's vaccine approach is two-pronged: It starts with a DNA vaccine that includes its own adjuvant. The DNA vaccine expresses granulocyte-macrophage colony-stimulating factor (GM-CSF) to stimulate the immune system as well as the HIV antigens that trigger production of antibodies against the virus. The antibodies can stop the virus infecting the cells. After getting two doses of this to prime the immune system, the second step is two booster shots of MVA, a recombinant poxvirus expressing HIV proteins.
In a study carried out at the Yerkes National Primate Research Center, non-human primates were vaccinated with a prototype version of GeoVax's two-step vaccine and then exposed to two different strains of simian immunodeficiency virus (SIV), the primate equivalent of HIV. When exposed to SIV after six months, 5 out of 7 vaccinated animals were protected. Of these, three animals receiving booster shots were still protected two years later.
"Repeated virus challenges in animals are used to mimic sexual transmission," explained Harriet L. Robinson, Ph.D., Chief Scientific Officer at GeoVax."The hope is that the results in the non-human primate models will translate into vaccine-induced prevention of infection in humans."
A version of the vaccine that does not co-express GM-CSF has successfully gone through Phase IIa clinical trials. GeoVax has received an "allowed to proceed" notice from the U.S. FDA to begin a Phase I trial of the DNA/MVA vaccine, sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH) and conducted by the NIAID-funded HIV Vaccine Trials Network (HVTN). Because the company already has safety data on the DNA and MVA vaccines (without the GM-CSF), it may be possible to move straight to a Phase IIb trial after this Phase I study.
- read the press release on trial results
- see the press release on the "allowed to proceed" notice