Immunogenicity and protective efficacy of a DNA vaccine encoding a chimeric protein of avian influenza hemagglutinin subtype H5 fused to CD154 (CD40L) in Pekin ducks.

The potential of CD154 (CD40L) as a powerful immunological adjuvant has been shown in various strategies. In this study we examine the immunogenicity and protective efficacy of a CD40-targeting avian influenza hemagglutinin (HA) subunit DNA vaccine in ducks. DNA constructs encoded the ectodomain of the HA protein of LPAI A/mallard/BC/373/2005 (H5N2) with or without fusion to the ectodomain of duck CD154. CD40-targeting significantly accelerated and enhanced humoral responses to the vector-encoded HA protein. In viral challenge experiments with A/chicken/Vietnam/14/2005 (H5N1), DNA immunization conferred partial protection against the genetically distant HPAI. The observed improved kinetics and magnitude of immune induction suggest that CD40-targeting holds promise for influenza A vaccine development.