Humoral and cell-mediated immune (CMI) responses [i.e. proliferative responses and gamma interferon (IFN-γ) production], were elicited in five cows infected between 159 and 169 days of gestation by a combined intravenous-intramuscular inoculation of Neospora caninum tachyzoites. Analysis of antigen-specific immunoglobulin (IgG) subclasses revealed a predominant IgG2 response in two cows, a mixed IgG1-IgG2 response in two other cows and a predominant IgG1 response in one cow. No correlation was round between IgG2 titers and IFN-γ levels. CD4+ T cells were responsible for the CMI responses in peripheral blood mononuclear cells from three infected cows. All five fetuses removed from infected dams at week 9 post-infection (219-231 days of gestation) mounted strong Neospora-specific humoral responses and had a predominant IgG1 response, regardless of their ability to produce IFN-γ. However, CMI responses were highly variable between fetuses. These data indicate the complexity of the immune mechanisms associated with Neospora infection in both the dams and their fetuses.
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