The synthetic peptides bovine enteric ß-defensin (EBD), bovine neutrophil ß-defensin (BNBD) 9 and BNBD 3 are chemotactic for immature bovine dendritic cells.

Human and murine immature DCs (iDCs) are highly efficient in antigen capture and processing, while as mature cells they present antigen and are potent initiators of cell-mediated immune responses. Consequently, iDCs are logical targets for vaccine antigens. Originally discovered for their antimicrobial activity, and thought of as strictly part of the innate immune system, studies with defensins such as human ß (beta)-defensin 2 (hBD2) and murine ß-defensin 2 (mBD2) have shown that they can function as chemo-attractant for iDCs and, in vaccination strategies, can enhance antigen-specific adaptive immune responses. Most studies to date have been conducted in mice. In contrast, little is known about defensins in cattle. To expand our understanding of the role of defensins in modulating immune responses in cattle, DCs were generated from bovine monocytes and the immature state of these bovine DCs was characterized phenotypically and through functional assays. By day 3 (DC3), bovine monocyte-derived DCs stained positively for DC-specific receptors CD1, CD80/86, CD205, DC-Lamp and MMR. When compared to conventional 6-day DC cultures or DCs cultured for 10 days with and without maturation factors, these DC3 were functionally at their most immature stage. Fourteen of the 16 known bovine ß-defensins were synthesized and the synthetic peptides were screened for their ability to attract bovine iDCs. Bovine DC3 were consistently attracted to BNBD3, an analog of BNBD3 (aBNBD3), BNBD9 and bovine EBD in vitro and to aBNBD3 in vivo. These results are the first to describe chemotactic ability of synthetic bovine ß-defensins for immature bovine monocyte-derived DCs.

Development and registration of recombinant veterinary vaccines. The example of the canarypox vector platform.

The canarypox vaccine vector (ALVAC) technology has been used to develop and license several vaccines for companion animals and horses in the European Union and USA. ALVAC is a ubiquitous vector with high biosafety since it is non-replicative in mammalians, is genetically and physically stable, and able to induce both humoral and cell-mediated immune responses against the expressed transgene product. Specific rules apply for the development and registration of recombinant vector vaccines. The biology of the vector as well as the recombinant virus must be thoroughly documented to allow the risk assessment of its use in the target species. In particular, its safety for the host and the environment must be extensively demonstrated before field trials can be authorized.

Impact of plasmid supercoiling on the efficacy of a rabies DNA vaccine to protect cats.

As of today, most DNA vaccination trials have been performed with plasmid preparations highly enriched in supercoiled molecules (sc) and the importance of supercoiled versus open circular (oc) plasmid isoforms for vaccine immunogenicity has only received limited attention. This study demonstrated that a single rabies DNA vaccination fully protected cats against a lethal rabies challenge as early as 3 weeks post vaccination provided that the proportion of supercoiled isoform in the vaccinal solution is at least 48%. In contrast, vaccination with a plasmid containing only 20% of supercoiled molecules induced significant but only partial protection. Further, a single rabies DNA vaccination with plasmids containing at least 70% of supercoiled molecules triggered statistically significant specific antibody titers and specific Th-1 oriented cell-based immunity as early as 2 and 3 weeks post vaccination, respectively. It is concluded that the oc isoforms are less efficient than supercoiled isoforms at inducing a complete profile of immune responses. Therefore, it is proposed that the target threshold of supercoiling that must be met by a rabies DNA vaccine to guarantee optimal immune responses and protection, be set at 70% of supercoiled molecules in the vaccine solution.