Recognition of low molecular weight Cooperia oncophora antigens after primary and trickle infection of calves with third-stage infective larvae.

Recognition of low molecular protein fragments of adult Cooperia oncophora of calves was studied using sera obtained after a single oral (primary) infection with 100,000 infective 3rd-stage C. oncophora larvae, and after a 10-week period of trickle infection with moderate doses of these larvae. SDS-gel electrophoresis under reducing conditions, followed by western blotting, revealed that a complex of 14-16 kDa protein fragments, a 27 kDa and a 31.6 kDa band of Cooperia oncophora adult antigen were recognized by sera from calves both after primary and trickle infection. A 19 kDa and 30 kDa protein fragment were additionally bound by sera from calves after trickle infection. The data suggest that the systemic humoral immune response of calves to Cooperia oncophora after trickle infection is more pronounced (14-16, 27, 31.6 kDa) and extended (19, 30 kDa) than after primary infection with Cooperia.