Interactions between infections with Eimeria spp. and Trichinella spiralis in inbred mice

Parasitological and immunological interactions between Eimeria vermiformis or E. pragensis and Trichinella spiralis were investigated during concurrent infections in NIH, BALB/c and B10.G inbred mice. The establishment of T. spiralis was unaffected by the presence of either coccidium, but expulsion of adult worms was delayed significantly in mice infected with E. vermiformis; E. pragensis did not have this effect. Replication of E. vermiformis was enhanced in concurrent infections with T. spiralis, but that of E. pragensis was reduced. Specific immune responses to each parasite were unaffected in mice infected with T. spiralis and E. pragensis, but levels of some responses were reduced when T. spiralis and E. vermiformis were combined. Thus both in vitro antigen-induced proliferation of mesenteric lymph node cells (MLNC) and intestinal mastocytosis were lower than in singly infected mice. Mitogen (Con A) responsiveness of MLNC was not affected in mice infected with T. spiralis and E. vermiformis, and cells from these mice were capable of transferring protective immunity to the nematode in naive recipients. Injection of monoclonal antibody to interferon gamma, a major component of the cytokine response to E. vermiformis, did not prevent delay of worm expulsion in concurrent infections. The results are discussed in terms of possible interactions between the T helper cell subsets or the inflammatory components of the responses induced by each parasite.