Blood cellular immune response in pigs immunized and challenged with Haemophilus parasuis

Abstract The cellular immune response to an experimental infection by Haemophilus parasuis , the etiological agent of Glasser’s disease in pigs, was characterized studying changes in peripheral blood mononuclear cells (PBMC) in colostrum-deprived pigs. Five groups were studied, four of those were previously immunized with different formulations and the fifth was maintained as non-immunized control. All groups were challenged with 5 × 10 9 CFU of H. parasuis serotype 5. The non-commercial bacterin conferred a complete protection, while the OMP-vaccine and the exposure to a subletal dose of 10 5 CFU of H. parasuis protected only partially, and the recombinant Tbp B-vaccine induced no protection. PBMC were analyzed using monoclonal antibodies against porcine CD45 + , CD3 + , CD4 + , CD8 α + , CD25 + , CD4 + naive, α IgM + and SWC3 + cells in single-colour fluorescence, and CD4 + /CD8 α + and CD8 α + /CD8 β + combinations in two-colour fluorescence. The different groups showed no significant changes in PBMC subsets following vaccination, and only minor changes were encountered after challenge, consisting mainly of significant increases ( P + ) and B cells ( α IgM + ), as well as a significant reduction in CD3 + cells ( P + cells, which was only observed for the bacterin-vaccinated group. These results suggest an increase of trafficking of inflammatory cells and the onset of the adaptive antibody response against H. parasuis infection; in addition, the blood cellular response developed by the different groups was not relevant to protection.