ß-Glucan as Trained Immunity-Based Adjuvants for Rabies Vaccines in Dogs.

The mechanisms of trained immunity have been extensively described in vitro and the beneficial effects are starting to be deciphered in in vivo settings. Prototypical compounds inducing trained immunity, such as ß-glucans, act through epigenetic reprogramming and metabolic changes of innate immune cells. The recent advances in this field have opened new areas for the development of Trained immunity-based adjuvants (TIbAs). In this study, we assessed in dogs the potential immune training effects of ß-glucans as well as their capacity to enhance the adaptive immune response of an inactivated rabies vaccine (Rabisin®). Injection of ß-glucan from Euglena gracilis was performed 1 month before vaccination with Rabisin® supplemented or not with the same ß-glucan used as adjuvant. Trained innate immunity parameters were assessed during the first month of the trial. The second phase of the study was focused on the ability of ß-glucan to enhance adaptive immune responses measured by multiple immunological parameters. B and T-cell specific responses were monitored to evaluate the immunogenicity of the rabies vaccine adjuvanted with ß-glucan or not. Our preliminary results support that adjuvantation of Rabisin® vaccine with ß-glucan elicit a higher B-lymphocyte immune response, the prevailing factor of protection against rabies. ß-glucan also tend to stimulate the T cell response as shown by the cytokine secretion profile of PBMCs re-stimulated ex vivo. Our data are providing new insights on the impact of trained immunity on the adaptive immune response to vaccines in dogs. The administration of ß-glucan, 1 month before or simultaneously to Rabisin® vaccination give promising results for the generation of new TIbA candidates and their potential to provide increased immunogenicity of specific vaccines.

Development of antibody ELISA specific of Leptospira interrogans serovar Grippotyphosa, Canicola, and Icterohaemorrhagiae to monitor vaccine immunogenicity.

The antibody response after primary vaccination and annual revaccination with a multivalent DAPPi-L vaccine was assessed respectively in SPF dogs and in client owned dogs against the Grippotyphosa (Lg), Canicola (Lc) and Icterohaemorrhagiae (Li) Leptospira serovars. To overcome limitations of the microscopic agglutination test (MAT), we developed serovar-specific and sensitive blocking ELISA assays. Serovar-specific antibodies against Lg, Lc and Li were detected in 100%, 45% and 91% of dogs, respectively, after the first dose of vaccine, and in 100% of dogs for all serovars after the second dose. In addition, mean ELISA antibody titers increased 14 days after annual revaccination with most dogs remaining ELISA antibody positive against Lg (85.3%), Lc (90%) and Li (100%). Parallel testing of sera from the annual revaccination study in the MAT and ELISA assays resulted in an overall agreement of 72%, 67%, 77% of samples for Lg, Lc and Li serovars, respectively. More sera tested positive by ELISA than by MAT, suggesting that the ELISA assay is more sensitive than the MAT. These three new antibody-based assays are the first suitable and reliable ELISA assays for the assessment of the canine antibody response following vaccination and an attractive alternative to the MAT.