Enhanced efficacy of DNA vaccination against botulinum neurotoxin serotype A by co-administration of plasmids encoding DC-stimulating Flt3L and MIP-3α cytokines.

Targeting antigens encoded by DNA vaccines to the key antigen-presenting cells by chemotactic or growth factors, is an effective strategy for enhancing the potency of DNA vaccinations. Here, we report the effects of chemotactic or growth factors on a DNA vaccine against botulinum neurotoxin serotype A (BoNT/A) in a mouse model. We demonstrated that mice immunized with DNA constructs encoding the Hc domain of BoNT/A (AHc) fused with DC-stimulating Flt3L or MIP-3α cytokines failed to elicit an enhanced or efficacious AHc-specific humoral or protective response in mice. However, the potency of DNA vaccination was significantly modulated and enhanced by co-administration of AHc-expressing DNA with pFlt3L or pMIP-3α, which generated strong immune and protective responses against BoNT/A. Moreover, the enhanced potency was further boosted by co-administration of AHc-expressing DNA with the combination of pFlt3L and pMIP-3α in mice, but not with the Flt3L-MIP-3α fusion molecule, which indicated that co-immunization with both pFlt3L and pMIP-3α could synergistically enhance AHc-specific immune and protective responses against BoNT/A. In summary, our findings indicate that co-administration of plasmids encoding antigen and cytokine rather than administration of plasmids encoding cytokine-antigen fusion is effective to enhance the potency of AHc-expressing DNA vaccine.