Microencapsulated human parainfluenza virus induces a protective immune response

Human parainfluenza type 3 (PI3) virus was incorporated into microspheres composed of a biocompatible and biodegradable DL-lactide and glycolide copolymer. Sera from mice immunized with these microspheres showed an antibody response to the viral glycoproteins and neutralized virus infectivity. The microspheres were also evaluated by intraperitoneal, oral, or intranasal administration to determine their protective efficacy in the hamster. After challenge infection of the intraperitoneally immunized hamsters with live PI3 virus, a significant reduction of virus titers in the respiratory tract was observed, demonstrating the protective efficacy of the microencapsulated viral antigens.