Search

A plasmid rendered replicative in mammalian cells by inserting the Porcine circovirus 2 (PCV2) origin of replication and replicase gene (Ori-rep) has been previously constructed. The aim of the present study was to evaluate if the replication capacity of this plasmid could be advantageously used to improve the protective immunity induced by DNA vaccination. In this case we used the porcine Pseudorabies virus (PrV) DNA vaccination model. The replicative capacity of the DNA vaccine did not improve the protective immunity against PrV in pigs, but on the contrary the presence of the PCV2 Ori-rep sequence was harmful in the induction of this immunity compared to an equivalent but non-replicative DNA vaccine. In addition, the distribution and the persistence of the replicative and non-replicative plasmids inside the body were the same. This is the first study showing an in vivo deleterious effect of the replicative active PCV2 Ori-rep on the natural and specific protection against PrV infection., (Copyright © 2012 Elsevier B.V. All rights reserved.)

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.

To evaluate the feasibility of using pseudorabies virus (PrV) glycoprotein B (gB) as a carrier of foot and mouth disease virus (FMDV) antigens in DNA immunization, FMDV B- and T-cell epitopes were inserted either between the two B-cell epitopes of the N-term subunit of PrV-gB (BT-PrV-gB-N-term construct) or within the B-cell epitope of the C-term subunit of PrV-gB (BT-PrV-gB-C-term construct). Two animal experiments were performed, each with three injections of plasmids 2 weeks apart, followed by a booster inoculation of peptides corresponding to the FMDV epitopes. Control groups of pigs were injected with plasmids encoding either PrV-gB or FMDV-BT, or with empty-pcDNA3. The results of both assays were combined. Significant titers of FMDV neutralizing antibodies were detected after the peptides boost in groups injected with the BT-PrV-gB-C-term construct. Insignificant amounts were detected in groups injected with the BT-PrV-gB-N-term and FMDV-BT constructs. PBMCs from the BT-PrV-gB-N-term groups, isolated after the peptide boost injection, produced IFN-gamma and IL-4 mRNAs in vitro when stimulated with FMDV peptides. This was not observed with the other groups. These results imply that PrV-gB can be used to carry FMDV antigens in a DNA vaccine.