The first vaccine targeting the strains of HIV prevalent in sub-Saharan Africa and Asia, where millions of people are infected with the virus, has started Phase I volunteer studies in the USA.
Until recently, very few vaccine candidates have been developed against this strain, known as HIV-1 subtype C. And all clinical trials to date have been carried out in developed countries on vaccines for the B strain of the virus, which is prevalent in North America, Europe, South America, Australia and New Zealand.
The vaccine against the subtype C strain of the virus is based on a technology developed at the University of North Carolina at Chapel Hill School of Medicine and the US Army Medical Research Institute of Infectious Diseases. It is built around a disabled version of Venezuelan equine encephalitis (VEE) virus, which serves as a vector to deliver sequences coding for Gag, a major protein in the HIV particle.
The vaccine causes expression of Gag in the lymph nodes, which in turn stimulates an immunological response, both cellular and humoral, to the protein. US company AlphaVax has rights to the VEE technology used in the vaccine and supplied the clinical trial materials.
The vaccine is not expected to offer true protection against infection with HIV, at least in its first incarnation, but could still provide significant benefits by controlling virus replication so that people stay disease-free for longer, and by reducing virus shedding which could curb transmission.
Second- and third-generation versions of the vaccine will include other HIV proteins, such as envelope (Env) and polymerase (Pol) and Nef, and may offer greater protection, according to the researchers.