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Jonasson, Robert; Andersson, Märit; Johannisson, Anders; Jensen, Waern Marianne


Antibiotic resistant strains of pathogenic bacteria are a growing problem. A better understanding of the immune responses elicited against these pathogens is necessary in order to obtain better prophylactics such as effective vaccines. Experimental infections have benefits over field experiments since the environment, monitoring of the animals and sampling occasions can be controlled. Swine dysentery is a common and economically important diarrhoeal disease in pigs. This disease, caused by the spirochete Brachyspira hyodysenteriae, is characterised by severe muco-haemorrhagic diarrhoea that may cause death by dehydration and acidosis. There is evidence of a humoral immune response. However, this antibody response has not been related to recovery from disease or protection against reinfection, but has rather been an indication of prolonged or recent exposure to B. hyodysenteriae. Therefore other defence mechanisms seem to be of importance, but unfortunately the knowledge about the hosts immune response is limited. The aim of our studies was to investigate the cellular immune response, acute phase protein production and metabolic alterations during experimentally induced swine dysentery and the recovery period. Also, since some animals are susceptible to infection and some are not, we aimed to study differences in leukocyte and lymphocyte subpopulation levels between these animals prior to infection. Clinically healthy pigs were orally challenged with B. hyodysenteriae. Blood samples were sampled from all animals before challenge, during haemorrhagic diarrhoea and the recovery period. Total and differential white blood cell counts were performed and leukocytes were further analysed with flow cytometry by staining for T helper cells, cytotoxic T cells, B cells,  T cells, double positive T cells and activated lymphocytes. The plasma levels of 19 different amino acids were analysed with HPLC. Approximately 70% of the inoculated animals developed swine dysentery. High numbers of  T cells and low numbers of CD8+ cells (cytotoxic T cells or natural killer cells) before challenge was found in animals highly susceptible to swine dysentery compared to animals that remained healthy. The acute phase of this disease is manifested by a decreased general appearance, weight loss and substantial increases in neutrophils, monocytes, activated lymphocytes and CD8+ cells.  T cells increased during recovery while B cells and double positive T cells remained unaltered during disease and recovery. The dysentery-affected animals also show decreased plasma levels of important free amino acids such as glutamine and alanine during haemorrhagic diarrhoea

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Scandinavian Society for Laboratory Animal Science