Self-encapsulating Poly(lactic-co-glycolic acid) (PLGA) Microspheres for Intranasal Vaccine Delivery

Herein we describe a formulation of self encapsulating poly(lactic-co-glycolic acid) (PLGA) micro spheres for vaccine delivery. Self-healing encapsulation is a novel encapsulation method developed by our group that enables the aqueous loading of large molecules into premade PLGA microspheres. Calcium phosphate (CaHPO4) adjuvant gel was incorporated into the microspheres as a protein trapping agent for improved encapsulation of antigen. Microspheres were found to have a median size of 7.05 +/- 0.31 mu m, with a w/w loading of 0.60 +/- 0.05% of ovalbumin (OVA) model antigen. The formulation demonstrated continuous release of OVA over a 49-day period. Released OVA maintained its antigenicity over the measured period of >21 days of release. C57BL/6 mice were immunized via the intranasal route with prime and booster doses of OVA (10 mu g) loaded into microspheres or coadministered with cholera toxin B (CTB), the gold standard of mucosal adjuvants. Microspheres generated a Th2-type response in both serum and local mucosa, with IgG antibody responses approaching those generated by CTB. The results suggest that this formulation of self-encapsulating microspheres shows promise for further study as a vaccine delivery system.