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Abstract: 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 &y& Elsevier]

Abstract: This study was performed to determine whether electroporation can be used to enhance the efficacy of a DNA vaccine against pseudorabies virus (PrV) in pigs. Immune responses to PrV were measured in pigs following a single intramuscular injection of plasmids encoding PrV glycoprotein B, with or without electroporation. Plasmid injection coupled with electroporation increased production of specific antibodies against PrV and peripheral blood mononuclear cells proliferated in response to stimulation with PrV glycoproteins. These results show that electroporation can improve the performance of a DNA vaccine against PrV in pigs. However, additional work is required to maximise the effectiveness of the vaccination protocol. [Copyright &y& Elsevier]

Abstract: DNA vaccination has been widely studied to develop new, alternative, efficient and safe vaccines for humans and animals. Many efforts have been made to increase the immunising potential of these vaccines and three veterinary vaccines are now available on the market. Much work is also being dedicated to develop effective DNA vaccines for humans. However, this new vaccination technique raises issues concerning biosafety due to the nature of the vector, i.e. a DNA molecule that contains sequences of prokaryotic origin (e.g. genes for antibiotic resistance). This review describes the development of the new generation of DNA vectors that are partially or completely devoid of elements of prokaryotic origin and outlines the results of studies on the fate of plasmids after their injection in vivo. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Previous biodistribution studies of plasmids following intramuscular or intradermal injections of DNA vaccines have been performed in mice, rats or rabbits, but not in large mammals. The aim of the present study was to determine the biodistribution of plasmids in swine using the PRV-specific DNA vaccination model consisting of a single intramuscular (i.m.) injection of three plasmids individually encoding glycoproteins gB, gC and gD. The weak bioavailability of the plasmids (less than 10%) after i.m. injection was consistent with the tissue distribution study. Plasmids remained in the injected muscle for at least 4 weeks and were also detected in liver, spleen, kidney, lung, remote muscle, lymph nodes and ovaries for shorter periods. Differences in persistence, apparent elimination half-lives and clearance in blood were observed between the three plasmids. In conclusion, the three plasmids behaved differently and were transiently detected in most of the organs tested. The exact persistence in the injected muscle was not determined but exceeded 4 weeks. To date this is the first published DNA vaccine tissue distribution study in large animals. [Copyright &y& Elsevier]

Abstract: The present study demonstrates the protective potential of a novel prime-boost vaccination strategy of pigs against lethal Pseudorabies virus (PRV; Herpes suid 1) infection. Animals were primed with Sindbis virus-derived plasmids that express viral glycoproteins gC and gD (gC- and gD-pSIN) and subsequently booster immunized with Orf virus (ORFV; Parapoxvirus) recombinants expressing gC and gD (D1701-VrVgC and -VrVgD). The prime-boost vaccination induced strong humoral and cellular-like PRV-specific immune responses. All prime-boost vaccinated pigs survived the lethal challenge infection without PRV-specific clinical symptoms and presented excellent body weight loss attenuation. Most notably, nasal shedding of challenge virus was reduced by more than about 3log10, clearly reducing the risk of infection of non-immunized pigs. [Copyright &y& Elsevier]