Mucosal Vaccination for Prevention of HIV Infection and AIDS

Most of HIV infections occur via the genital tract or the rectum and HIV replicates at high levels in lymphoid organs and intestinal mucosa, likely requiring a more diversified immunity than pathogens restricted to a single mucosal site, such as the gastrointestinal tract for Vibrio cholera, or the respiratory airways for the influenza virus.

Numerous AIDS vaccine candidates are under development and a general observation obtained from preclinical trials in non-human primates that failed to provide sterilizing immunity is that some infection protection or delayed onset of disease is observed in the presence of anti-SIV immunity. Recent clinical trials support difficulties to reproduce in humans the results observed in simian models, but at least one of them indicated that some protection of infection can be achieved. However, given the limited efficacy observed in the RV144 trial and concerns voiced in its statistical interpretation, preclinical trials should explore more effective immunogens, whether new or as combinations of existing ones, and mucosal routes of vaccinations in addition to the systemic routes, with the goal to maximize vaccination-mediated protection.

The rationale for generating both strong mucosal and systemic immunity comes from animal experiments, recent clinical trials, and other successful vaccines currently in use. Mucosal responses against SIV have been induced with a variety of SIV antigens and via different mucosal routes with a spectrum of effects on protection. This review covers the rational and the experimental data that support the validity to explore mucosal immunization for HIV infection and AIDS prevention.