Systemic antibody responses of calves to low molecular weight Cooperia oncophora antigens

The systemic antibody responses to adult Cooperia oncophora antigen were studied using sera obtained from calves during a 6-week period following a single oral infection with either 20,000 or 100,000 third-stage C. oncophora larvae. Dose dependent increasing titres of IgG binding complete adult Cooperia antigen were found in the sera of Cooperia-infected calves. SDS-gel electrophoresis under reducing conditions, followed by Western blotting, revealed that the increase of IgG binding Cooperia antigens could be attributed mainly to specific binding of IgG to a complex of 12-15 kDa protein fragments of Cooperia adult antigen. This protein may represent a Cooperia oncophora-specific component that can be used for serodiagnosis.