Long-term studies of microencapsulated and adsorbed influenza vaccine nanoparticles.

Incorporation of antigens into nanometer-sized polymer particles was recently shown to lead to a good adjuvant effect. An optimal antibody response with killed influenza virus antigens was achieved with 0.5% poly(methyl methacrylate). Long-term experiments showed prolonged antibody response of polymer adjuvants with incorporated or adsorbed influenza virus. Adsorption also yielded an optimal adjuvant effect with 0.5% poly(methyl methacrylate). The antibody response was accompanied by protection of the mice against infection with mice-adapted influenza virus. In addition, the polymer vaccines were more stable against temperature inactivation than were vaccines with aluminum hydroxide or without adjuvants.