AIDSVAX (VaxGen, Inc., South San Francisco, CA), a possible
vaccine to protect against human immunodeficiency virus type 1 (HIV-1)
infection, is being tested for efficacy in phase 3 studies. It has been tested for potential efficacy in chimpanzees, and tested for safety and immunogenicity in human clinical studies. Four candidate
vaccines, each with a different envelope
protein antigen or combination of
antigens, have been produced in
alum formulations. In both design and clinical testing,
AIDSVAX has an excellent safety profile. Because these highly purified
proteins were prepared using
recombinant DNA technology, there is no possibility of these
vaccines causing
HIV infection. Having been administered to over 1200 people, the only side effects attributable to
AIDSVAX have been local
pain and
inflammation at the injection site. After immunization, essentially all recipients developed a robust antibody response, including binding and
neutralizing antibodies. The
neutralizing antibodies peaked after a 12-month boost. Excellent memory is induced. Two phase 3 trials of two bivalent formulations will evaluate their efficacy. One trial will use a bivalent subtype B formulation. This trial in North America will involve 5000 men who have sex with men and heterosexual women at high risk. The other study will use a bivalent subtype B/subtype E formulation. This trial in Thailand and will involve 2500 intravenous drug users. Both studies will be randomized, double-blinded and placebo controlled. The volunteers will be followed for 3 years. The end points of the studies are
infection, as defined by seroconversion to standard diagnostic tests, and viral load, as defined by commercial polymerase chain reaction (PCR) tests.