Among the most pressing global public health problems at present is the AIDS epidemic.  While it is clear that chemotherapy and behavioral interventions have much to offer in limiting the spread of infections by the causative virus, HIV-1, interest in developing a vaccine remains strong.  Immunization would potentially provide a relatively cost-effective and scalable approach to minimizing the incidence of new infections on a global scale.

However, HIV-1 presents numerous challenges to would-be vaccine developers.  There are many different lineages of HIV-1 viruses with different clades dominating in different geographic regions of the world.  Even in a single infected patient, HIV-1 continues to generate many variants.  Astonishingly, according to Korber et al. (2001), “The diversity of influenza sequences world-wide in any given year appears to be roughly comparable to the diversity of HIV sequences found within a single infected individual at one time point ….”  The virion surface protein, gp120, which is critically involved in infecting host cells and is a major target for protective antibodies, contains regions that are especially variable in amino acid sequence.

In addition to the serious challenge of eliciting an immune response, of whatever sort, that can effectively provide immunity to the many viral variants in circulation, it remains unclear what types of immune responses are essential for providing a high level of protection against infection or disease.  Some investigators are focsed on eliciting strong cell-mediated immune response.  Others are devoting their efforts to generating humoral responses including potent and broadly-neutralizing antibodies.  There are several recent and interesting reports pertaining to this latter effort. (more…)