HIV-1 envelope evolution and vaccine efficacy

Transmission of human immunodeficiency virus type 1 (HIV-1) selects for envelope variants with a number of defined properties, including use of CCR5 as the preferred coreceptor, binding to CCR5 in a distinct manner compared to HIV-1 isolated later in infection, shorter variable (V) regions, and fewer N-linked glycosylation sites. These features define the ideal target for an envelope-containing vaccine designed to elicit neutralizing antibody. If a candidate vaccine were sufficiently potent to elicit sterilizing immunity, virus evolution would not be an issue. However, all results to date suggest that an envelope-containing vaccine will have a lesser impact, and that virus evolution will contribute to escape from the vaccine-induced antibody response. The key question is whether or not the early selection pressure imposed by neutralizing antibody will have a long term impact on HIV disease progression. Several recent reports suggest that HIV-1 will evolve to rapidly escape antibody selection, and that the cost to the virus in terms of entry fitness will be small. Durable effects of vaccination are predicted to be associated with a reduction in peak viremia and viral set point at the time of primary infection.