A recombinant fusion protein consisting of West Nile virus envelope domain III fused in-frame with equine CD40 ligand induces antiviral immune responses in horses.

•A subunit vaccine consisting of the E glycoprotein domain III fused in-frame to CD40L generates robust immune responses against West Nile virus (WNV).•The CD40L-WNV-DIII protein generated high anti-DII specific antibody and strong neutralization titers against WNV.•The CD40L-WNV-DII subunit vaccine stimulated CD4+T amd CD8+T cellular proliferation.•CD40L could be utilized as a non-toxic, alternative adjuvant to boost the immunogenicity of subunit vaccines in horses.