DNA vaccination with HA or NP encoding plasmids results in rapid viral clearance after viral challenge

Abstract

Background: A relevant model for studying the efficacy of DNA vaccines is to examine viral replication in the nasal cavity after non-lethal viral challenge. In this study, we have investigated the humoral cell response after viral challenge of mice vaccinated with plasmids encoding the HA or NP genes. Methods: Seven-week-old BALB/c mice were immunised intramuscularly with three doses (100 μg) of HA, NP or backbone plasmid at 3-week intervals and challenged intranasally with homologous virus 13 weeks later. Mice were sacrificed and the antibody secreting cell response was examined systemically and in the respiratory tract. Serum antibody was analysed by haemagglutination inhibition and virus neutralisation assays. Results: DNA vaccination with HA and NP encoding plasmids significantly reduced viral replication in the nasal cavity. Antibody secreting cells were maintained in the systemic compartment after vaccination but upon viral challenge were located in the nasal associated lymphoid tissue. Conclusion: Intramuscular DNA vaccination resulted in immunological memory in the systemic compartment, which was rapidly reactivated upon viral challenge.