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

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 x 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 alpha(+), CD25(+), CD4(+) naive, alpha IgM(+) and SWC3(+) cells in single-colour fluorescence, and CD+/CD8 alpha(+) and CD8 alpha(+)/CD8 beta(+) 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 < 0.05) in the relative proportions of monocytes and granulocytes (SWC3(+)) and B cells (alpha IgM(+)), as well as a significant reduction in CD3+ cells (P < 0.05). These changes were similar for the five groups compared, except for the significant increase of CD25(+) 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. (c) 2008 Elsevier Ltd. All rights reserved.