Gastro-intestinal delivery of influenza subunit vaccine formulation adjuvanted with Gram-positive enhancer matrix (GEM) particles.

In this study, a liquid formulation of influenza subunit vaccine admixed with Gram-positive enhancer matrix (GEM) particles as adjuvant was delivered to upper and lower parts of intestinal tract. The aim was to determine the most effective immunization site in the intestines. Mice were vaccinated with a liquid formulation of GEM and influenza subunit vaccine orally and rectally. The oral administration of the vaccine with GEM particles induced a better systemic and mucosal immune response than oral (vaccine only) and rectal (with and without adjuvant) immunizations. Rectal administration elicited high IgG1 responses but little IgG2a, indicating a Th2 dominated immune response. In contrast, the oral immunization with GEM particles elicited a balanced IgG1 and IgG2a response. In conclusion, our results demonstrate that GEM-adjuvanted influenza vaccine should be targeted to the upper part of the intestinal tract.