LOW-MOLECULAR-WEIGHT COOPERIA-ONCOPHORA ANTIGENS - CHARACTERIZATION AND HUMORAL IMMUNE-RESPONSES IN CALVES MONO-INFECTED WITH 100000 INFECTIVE LARVAE

Characteristics of the humoral immune response of Cooperia oncophora-i nfected calves to low molecular weight antigens of C. oncophora were s tudied. Immunoblotting with sera obtained from calves 6 weeks after a single oral infection with 100 000 third-stage (L(3)) C. oncophora lar vae revealed several corresponding antigenic fragments between adult w orms and the fourth-stage (L(4)) larvae. No reactivity in the immune s era was found against the L(3) stage. A previously defined complex of low molecular weight proteins (12-15 kDa) was found on both L, and adu lt Cooperia stages, but not on the L(3) stage. C. oncophora adults dif fered from the L(4) larvae at the 31/32 and 37 kDa level. Several adul t and L(4) proteins were bound by biotinylated Concanavalin A, as was also true for L(3) proteins. A 31/32 kDa glycoprotein of adult worms w as recognised by a monoclonal antibody with specificity for phosphoryl choline. Using monoclonal antibodies in ELISA and Western blotting, th e serum antibody response of C. oncophora-infected calves to adult wor m antigen was almost entirely IgG1. Binding of the IgG1 antibodies was restricted to a complex of reduced 12-15 kDa protein(s) and a 27 kDa fragment of adult worms. The data suggest that the systemic humoral im mune response of calves during a primary infection with C. oncophora c onsists mainly of an IgG1 response, and is directed to a non-glycosyla ted Cooperia protein (molecular weight estimated at 12-15 kDa under re ducing conditions and 18 kDa under nonreducing conditions). This prote in is probably present in both L(4) larvae and adults. Since it was no t bound by immune sera from calves mono-infected with several other ne matodes, the 12-15 kDa protein complex may represent a Cooperia-specif ic component that can be used for serodiagnosis.