Vaccine Strategies for Protecting Mammals and Chickens from Influenza Infection using Liposomal M2e and NP Plasmid Vaccines
Introduction: Influenza mutates frequently with the potential to cause pandemics. Our study examined the immune responses of mice and chickens to the conserved portion of influenza M2 protein in a liposomal vaccine (L-M2e) and to the plasmid vector with the gene for the conserved influenza Nucleoprotein (NP) (NP-P).. Methods: L-M2e (100μgM2e/dose), liposome control (LC), and NP-P (250μg/dose) were given alone or as alternating vaccinations to B2 chickens or Swiss Webster mice. Sera collected post-vaccination were analyzed for Ab concentrations to M2e or NP. Vaccinated mice were intranasally. challenged with Influenza virus and monitored daily for morbidity to d28. Results: In chickens given L-M2e, anti-M2e Abs were 48pg/mL, but chickens given both L-M2e and NP-P, had lower Ab levels (34 pg/mL) suggesting that NP-P interfered with Ab responses to L-M2e. However, anti-NP Abs in chickens given NP-P or both vaccines had similar anti-NP Ab levels. In mice, there were also higher anti-M2e IgG1 Abs with L-M2e vaccination (~9 x 10^7 pg/mL) versus mice given the vaccine combination (~1x 10^7 pg/mL); mice had similar levels of anti-NP IgG1 whether given NP-P or the vaccine combination. With respect to survival, mice given L-M2e or both vaccines showed increased survival versus buffer (71% and 57% vs 14%). Conclusions: Although anti-M2e Ab levels were decreased following vaccination with both vaccines, this Ab reduction did not alter the protection in mice generated by the vaccine combination, suggesting that immune factors other than Ab concentration contributed to the protection.
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