Virus-Like Particle (VLP) Vaccine Conferred Complete Protection against a Lethal Influenza Virus Challenge

We have previously demonstrated the formation and release of influenza virus-like particles (VLPs) from the surface of Sf9 cells infected with either a quadruple baculovirus recombinant that simultaneously expresses the influenza structural proteins hemagglutinin (HA), neuraminidase (NA), matrix 1 (M1) and M2, or a combination of single recombinants that include the M1 protein. In this work, we present data on the immunogenicity and protective efficacy afforded by VLPs (formed by M1 and HA) following immunization of mice. VLP vaccine (∼1 µg HA) were formulated with or without IL-12 as adjuvant and administered twice, at two weeks intervals, by either intranasal instillation or intramuscular injection. All VLP-vaccinated and influenza-immunized control mice demonstrated high antibody titers to the HA protein; however, intranasal instillation of VLPs elicited antibody titers that were higher than those induced by either intramuscular inoculation of VLPs or intranasal inoculation with two sub-lethal doses of...