CYTOKINE AND IMMUNOGLOBULIN SUBCLASS RESPONSES OF RATS TO INFECTION WITH EIMERIA-NIESCHULZI

SIV rats infected with a high dose (50000 oocysts) of Eimeria nieschul zi displayed clinical symptoms of coccidiosis such as diarrhoea (days 6 and 7 post-primary infection) and weight loss (days 6-8 post-primary infection) and were completely immune to challenge with a similar dos e. The ability of rats to produce tumour necrosis factor (TNF) in vivo was enhanced during the period of oocyst excretion in the primary inf ection but significant production of TNF did not occur after challenge infection. Thus, TNF does not appear to be an important factor in res istance to infection with E. nieschulzi but may play some role in resi stance to primary infection and in the pathology associated with E. ni eschulzi infection. Parasite-specific serum IgM levels (measured by en zyme-linked immunosorbent assay) were also increased during primary in fection but returned to background levels at the end of the patent per iod and were not affected by challenge infection. In contrast to TNF a nd IgM, serum concentrations of E. nieschulzi-specific IgG1, IgG2a, Ig G2b, IgG2c and intestinal tissue levels of IgA did not begin to increa se until after day 12 post-primary infection, reached peak levels betw een days 20 and 30 post-primary infection and were slightly increased by challenge infection.