Vaccination against coccidiosis: host strain‐dependent evocation of protective and suppressive subsets of murine lymphocytes

Abstract

BALB/c mice are normally more resistant than C57BL/6 (B6) mice to infection with Eimeria vermiformis, but these phenotypes can be reversed by oral or parenteral vaccination with a crude antigen prepared from the parasite. Treatment of mice with antibodies specific for CD4+ or CD8+ T cells showed that the increased susceptibility of vaccinated BALB/c mice was associated with the presence of CD4+ T cells. This finding was confirmed when the recipients of CD4+ T cells selected from the mesenteric lymph nodes (MLN) of vaccinated BALB/c mice produced more oocysts after challenge than the recipients of a similar population of cells from sham-vaccinated mice. The residual population of cells (presumably enriched for CD8+ T cells, 'CD8+'), on the other hand, conferred some protection and, in B6 mice, the findings were reversed. Thus, vaccination induced suppressive or protective CD4+ cells and protective or suppressive 'CD8+' cells, depending upon the normal resistance/susceptibility phenotype of the host. Examinations of the isotypes (IgG1, IgG2a) of specific serum antibodies, and of the levels of IFN-gamma and IL-5 cytokines released by MLN cells stimulated ex vivo, did not allow any further characterization of the mechanisms involved.

Comparison of Protective Immune Responses to Apicomplexan Parasites

“…Thus, early work by Rose and colleagues has shown that humoral antibodies, induced by live Eimeria infection, can provide excellent passive protection against challenge infections with the same parasite [93, 94]. Likewise, studies on mice infected with T. gondii have shown that intestinal IgA antibodies to major surface protein SAG-1 (P30) were produced after peroral infection and found to inhibit infection of murine enterocytes by directly blocking the parasite entry [91].…”

Development and validation of real-time polymerase chain reaction assays specific to four species of Eimeria

“…The environmental phase of the lifecycle, the oocyst, is characteristically tough and provides straightforward access for enumeration and isolation. Indeed, oocyst enumeration has been widely employed to assess degree of infection (Shirley and Hoyle 1981;Bumstead et al 1995;Rose et al 2000;Smith et al 2002).…”