Surface antigens of Obeliscoides cuniculi inducing local and systemic humoral responses in infected rabbits

125I-radiolabelled surface proteins of various developmental stages of Obeliscoides cuniculi were used to analyze serum and gastrointestinal immunoglobulin responses of the host to primary infection with 10,000 larvae of the nematode, using a radioimmunoprecipitation method. Serum IgM, IgA, and IgG antibodies reacted mostly with infective larval and adult nematodal surface proteins. The highest binding activity was shown by IgG against the surface of infective larvae on days 56 and 86 after infection. Local (gastric mucosal) antibodies were also predominantly directed against surface antigens of infective larvae and adults, although considerable binding of the fourth-stage larval surface proteins by gastric mucosal IgG occurred 35 days after infection. Physicochemical analysis of the radiolabelled surface antigens revealed that the strongest antigenicity was found in proteins with molecular weights of 40,000 and 145,000. Nonspecific binding demonstrated in our tests by infective larval surface proteins was associated with particles with a molecular weight of 550,000.