An oral vaccine that protects both rectal and genital mucosas in mice from viral infections by specifically targeting the large intestine is published online this week in Nature Medicine.

Mucosal immunization induces adequate immune responses that protect against pathogens at mucosal sites. However, intracolorectal administration of a potential vaccine is not practical at the clinic and an oral route would likely destroy the vaccine because of the high pH in the stomach.

Jay Berzofsky and colleagues designed a nanoparticle releasing system to solve this problem. The nanoparticles contain peptide vaccine and immune adjuvants coated with a polymer that precludes premature uptake in the small intestine and release of contents before reaching the large intestine. In mice, the oral vaccine system induced immunity and protected against rectal and vaginal viral challenge similar to colorectal vaccination, and this was specific to targeting of the large intestine mucosa. Clinical studies in humans will be needed to optimize the formulation of the oral vaccine to the physical characteristics of the human gut.