Immunological alterations during the clinical and recovery phases of experimental swine dysentery

The aim of this study was to examine changes in the systemic immune response during the incubation period and following the onset of clinical swine dysentery, including the recovery period. Ten healthy conventional pigs were inoculated with Brachyspira hyodysenteriae. Blood was sampled at pre-inoculation, at days 4 and 14 post-inoculation, during the first 4 days with clinical signs of dysentery and at days 1, 3, 7, 11 and 15 of the recovery period. Eight pigs developed haemorrhagic diarrhoea. Flow-cytometric analyses of lymphocyte subpopulations showed that all animals, including the two that remained healthy, had an increase in CD8 alpha(+) CD4(-) cells and 6 T cells at days 4 and 14 post-inoculation. In addition, an increase in CD4(+) CD8 alpha(+) cells and CDB alpha(+) CD8 beta(+) cells was observed at days 4 and 14 post-inoculation in animals that developed dysentery. During clinical signs of dysentery, the acute-phase protein serum amyloid A was increased. There was a two- to threefold increase in both neutrophils and monocytes during signs of dysentery and at the beginning of the recovery period. The numbers of CD8 alpha(+) CD8 beta(-) CD4(-), CD45RA(-) lymphocytes also increased during the dysentery period. Circulating CD21(+) cells and CD21(+) CD45RA- cells decreased at the end of the incubation period, during signs of dysentery and at the beginning of the recovery period. The dysentery-affected animals developed antibodies to B. hyodysenteriae-specific antigens (similar to 16 kDa and similar to 30 kDa) from the first day of recovery, and gamma delta T cells showed an increase during the recovery period. In comparison with pre-inoculation, increased numbers of monocytes, neutrophils, CD8 alpha(+) CD8 beta(-) CD4(-) lymphocytes and CD45RA- lymphocytes were observed during clinical dysentery. Increased numbers of neutrophils, gamma delta T cells and specific antibodies were seen during the recovery period.