T cell reactions of Eimeria bovis primary- and challenge-infected calves

Abstract

Eimeria bovis infections commonly have clinical impact only on young animals, as homologous reinfections generally are under immunological control. So far, the nature of the immune responses delivering protection to calves has not been investigated. In this study we therefore analysed local and peripheral proliferative T cell activities of primary and challenge-infected calves and investigated the occurrence of T cell phenotypes in the peripheral blood and in mucosal gut segments isolated either by bioptic means or by necropsies.We show that lymphocytes of E. bovis-infected calves exhibit effective, transient antigen-specific proliferative responses in the course of prepatency of primary infection but fail to react after homologous reinfection suggesting early abrogation of parasite development. Whilst in primary infection an expansion of peripheral CD4+ T cells was observed, reinfection had no effect on the proportions of CD4+, CD8+ subsets or gammadeltaTCR+ T cells. In contrast, both E. bovis primary and challenge infections had an impact on local tissue T cell distribution. Primary infection was characterised by a CD4+ T cell infiltration early in prepatency in ileum and later in colon mucosa, whereas CD8+ T cells were only found accumulating in the latter gut segment. Challenge infection led to infiltration of both CD4+ and CD8+ T cells in small intestine and large intestine segments indicating protective functions of both cell types. In contrast, infiltration of ileum and colon mucosa with gammadeltaTCR+ T cells was restricted to primary infection.

Efficacy of Toltrazuril 5 % Suspension against Eimeria bovis and Eimeria zuernii in Calves and Observations on the Associated Immunopathology

“…However, the numbers of animals used were similar to previous studies (e.g. Hermosilla et al 1999;Sühwold et al 2010) and the combinations of high p values and lack of any hint of biologically meaningful trends suggests that the results are likely a legitimate reflection of similar status in the two groups as far as cellular infiltration is concerned. Eosinophils were more common in the ileum and colon of animals classified as resistant, and tended to be associated with higher concentrations of TNF-a.…”

“…In their study, there was no evidence of any memory-associated Th1 reactions to challenge infections. The same group (Sühwold et al 2010) has also shown that after an initial expansion of CD4+ T cells and gd+ T cells in the gut of animals after primary infection there was no increased infiltration of either cell type after challenge infection. The phagocytosis of Eimeria by macrophages has also been clearly demonstrated in cattle, independent of the presence of immune serum (Behrendt et al 2008) and augmented by immune serum (Taubert et al 2009).…”

“…For all cell subpopulations except MHC class II-expressing cells, the labelled cells were manually counted in 12 randomly chosen S118 microscopic fields (40x objective). The vision field was placed so that half of the fields covered the tip and the other half the base of the villi as described previously (Sühwold et al 2010). The pattern of staining by MHC class II antigen-specific antibody did not allow us to count individual cells as reliably as other cell types because not all cells were well defined and there was some overlapping of cells.…”

“…The bovine immune response to infection with Eimeria seems to follow a sequential Th1 then Th2 pattern, although the effector mechanism that confers resistance in previously exposed calves remains elusive (Sühwold 2010). In 1999, Hermosilla et al demonstrated elevations of CD4+ lymphocytes in the circulation and lymph nodes of primarily infected calves.…”

Control strategies using diclazuril against coccidiosis in goat kids

“…The frequencies of the two other most prevalent species (E. arloingi and E. ninakohlyakimovae) increased thereafter but remained longer in time in contrast to E. christenseni, which might indicate a correlation with the farm history of sustained clinical coccidiosis observed in the farm in goat kids during the weaning period. The particularities of the life cycle, the virulence and the innate/acquired cellular immune response developed by the host against the different parasitic stages of each Eimeria species could explain those differences as reported for bovine coccidiosis (Hermosilla et al 2002;Daugschies and Najdrowski 2005;Taubert et al 2009;Sühwold et al 2010).…”