Pharmaceutical and immunological evaluation of a single-dose hepatitis B vaccine using PLGA microspheres

The objective of the study was to investigate the feasibility of a single-dose hepatitis B vaccine based on three kinds of poly (D, L)-lactide-co-glicolide acid (PLGA) microspheres. PLGA microspheres loaded with recombinant hepatitis B surface antigen (HBsAg) were formulated using a double emulsion microencapsulation technique. The pharmaceutical characteristics of size, surface morphology, protein loading efficiency, antigen integrity, release of HBsAg-loaded PLGA microspheres and degradation of the polymer in vitro were evaluated. The degradation of the polymer corresponded with the composition of the polymer (lactide/glycolide ratio), molecular weight of the polymer (viscosity) and morphology of the microspheres. These PLGA microspheres were able to continuously release antigen under conditions that mimic the environment in vivo. The single subcutaneous injection of HBsAg-loaded PLGA50/50 microspheres, PLGA75/25 microspheres and a mixture of PLGA50/50, PLGA75/25, and PLGA50/50-COOH microspheres in mice resulted in comparable serum antibody titers to those of three injections of the conventional aluminum adjuvant formulated HBsAg vaccine. Based on these findings in vitro and in vivo, it was concluded that HBsAg was successfully loaded into the PLGA microspheres, which can auto-boost an immune response, and the HBsAg-loaded PLGA microsphere is a promising candidate for the controlled delivery of a vaccine.