Immune depression in bovine trypanosomiasis: effects of acute and chronic Trypanosoma congolense and chronic Trypanosoma vivax infections on antibody response to Brucella abortus vaccine

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Abstract
Cattle were vaccinated with B. abortus (S19) vaccine during acute (25 days) and chronic (25 wk) T. congolense and chronic T. vivax (25 wk) infections to determine the effect of such infections on the antibody response to the vaccine. The specific antibody responses of IgG1 and IgG2 sub-classes were profoundly depressed (80%) in both the acute and chronic infections with T. congolense. Whereas IgM antibody response was also profoundly depressed (90%) in cattle with the acute infection, it was only 50% depressed in those with chronic infection. There was no depression of IgG1, IgG2 or IgM in cattle infected with T. vivax. These animals had no detectable parasitemia at the time of vaccination and thereafter. Apparently, during acute infection with T. congolense depressive mechanisms could be acting on the afferent arm of the immune response, i.e., antigen recognition and/or processing.