Maternal transfer of antibodies induced by infection withEimeria maximapartially protects chickens against challenge withEimeria tenella

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Abstract
Infection of breeding hens withEimeria maximainduces production ofEimeria-specific IgG antibodies which are transferred to hatchlings via the egg yolk and confer a high degree of maternal immunity against homologous challenge and partial immunity to infection with another important species,Eimeria tenella. As an example, in an experiment using hatchlings from eggs collected between days 28 and 39 after infection of the hens with 20 000 sporulatedE. maximaoocysts, control chicks (challenged with 100 sporulated oocysts) excreted 6·8±1·2 million (mean±s.e., n = 10) or 5·8±1·2 million (n = 8) oocysts ofE. maximaorE. tenella, respectively, compared to 0·9±0·4 million (n = 5)E. maximaoocysts or 2·2±0·4 million (n = 9)E. tenellaoocysts excreted by hatchlings of infected hens. This represents an 87% reduction in oocyst excretion with regard toE. maximaand a 62% reduction in oocyst excretion with regard toE. tenellain the progeny of the infected hens. In another experiment, eggs were collected from days 28 to 37 and again from days 114 to 123 after infection of the hens withE. maximaand hatchling oocyst excretion rates were 82% and 62%, respectively, reduced forE. maximaand 43% and 41%, respectively, reduced forE. tenellain the progeny of hens infected withE. maximacompared to the progeny of uninfected hens. ELISA and Western blot analyses of maternally-derived IgG revealed a high degree of cross-reactivity to antigens ofE. maximaandE. tenella. Thus, maternally-derived, IgG-mediated cross- resistance to different species ofEimeriaoccurs in the chicken, most likely as a result of cross-recognition of conserved epitopes or proteins.