Single-cycle SIV: a novel AIDS vaccine approach

The search continues for an AIDS vaccine approach with a suitable safety and efficacy profile for use in individuals at risk of HIV-1 infection. A number of vaccine regimens based on recombinant DNA and/or viral vectors are now in clinical trials. However, these approaches may not provide adequate protection against the natural transmission of genetically diverse HIV-1 field isolates. Live attenuated strains of simian immunodeficiency virus (SIV) still afford the most reliable protection in animals. Unfortunately, justifiable safety concerns will likely preclude the use of live attenuated HIV-1 in humans for the foreseeable future. Genetically engineered strains of SIV, which are limited to a single cycle of infection have been recently developed and may provide a more promising safety and efficacy profile. These strains preserve many of the advantageous properties of live attenuated viruses but cannot regain a pathogenic phenotype through continuous cycles of virus replication.