Foot-and-Mouth Disease Virus neutralizing antibodies production induced by pcDNA3 and Sindbis virus based plasmid encoding FMDV P1-2A3C3D in swine

DNA vaccination against Foot-and-Mouth Disease Virus (FMDV) is an attractive and alternative strategy to the use of classical inactivated viral vaccines. The injection of a pcDNA3.1-based DNA vaccine encoding for FMDV P1-2A3C3D and GM-CSF proteins had previously been shown to induce the production of neutralizing antibodies against FMDV and partially protect swine against an experimental challenge. Based on the induction of FMDV humoral immune responses, the aim of the present study was to see if the Sindbis virus derived plasmid (pSINCP) backbone could advantageously replace pcDNA3.1 in DNA immunization against FMDV in swine. For this purpose, groups of 3 or 4 pigs received three injections by intramuscular route, intradermal route or an association of both routes, at 2–3 week intervals. The pcDNA3.1-based DNA vaccine was shown to induce the production of higher amounts of FMDV-neutralizing antibodies after intradermal injection. Intramuscular injection of the same vaccine, or intramuscular (IM) and/or intradermal (ID) injection of the pSINCP-based DNA vaccine resulted in a significantly lower induction of FMDV-neutralizing antibodies. In conclusion, the humoral immune response of a DNA vaccine encoding for FMDV P1-2A3C3D was not improved by the pSINCP backbone and was higher when the plasmids were injected by the intradermal route.