LOW-MOLECULAR-WEIGHT COOPERIA-ONCOPHORA ANTIGENS - POTENTIAL TO DISCRIMINATE BETWEEN SUSCEPTIBLE AND RESISTANT CALVES AFTER INFECTION

The recognition of low molecular weight proteins by sera obtained duri ng a single oral (primary) infection with 100 000 3rd-stage Cooperia o ncophora larvae was studied in calves. Three groups of 6 or 7 calves w ere selected based on different egg excretion patterns. SDS-gel electr ophoresis of adult Cooper ia antigen under reducing conditions, follow ed by Western blotting, revealed that resistance of individual calves to C. oncophora might be related with antibody responses (42 days post infection) against at least 2 protein fragments (14-16kDa and 27kDa), The 14-16-kDa protein complex was bound, to some extent, by individua l sera from all calves. The intensity of staining was negatively corre lated with egg excretion on Day 42 p.i. Calves with high egg counts on Day 21 p.i. either did not or only weakly recognized the 27-kDa band. It has to be established whether the 14-16kDa (or recombinant 14.2kDa ) provides a tool for immunodiagnostics and whether the 27-kDa fragmen t can help further unravel immune-mediated resistance to Cooperia. (C) 1997 Australian Society for Parasitology.