Eimeria tenella: quantitative in vitro and in vivo studies on the effects of mouse polyclonal and monoclonal antibodies on sporozoites

Summary Murine, polyclonal and monoclonal antibodies, raised against sporozoites of Eimeria tenella, were tested for their ability to neutralize sporozoite infectivity in vitro and in vivo. Neutralization was effected via three mechanisms. Firstly, sporozoites fixed complement, at low titres, and lysis occurred by the alternative pathway of complement activation. Secondly, in the absence of complement activity, the murine heat‐inactivated, hyperimmune antiserum neutralized sporozoites at relatively low titres. At high titres, even though sporozoites were agglutinated, neither the heat‐inactivated hyperimmune antiserum nor the monoclonal antibody neutralized sporozoites. Finally, in the presence of complement and specific antibodies, at titres which by themselves would not neutralize sporozoites, neutralization was effected due to lysis via the classical pathway of complement activation.