IMMUNOGLOBULIN-G SUBCLASS ANTIBODIES AGAINST EXCRETORY SECRETORY ANTIGENS OF ANCYLOSTOMA-CANINUM IN HUMAN ENTERIC INFECTIONS/

Most patients with proven or suspected enteric infection with the comm on hookworm of dogs, Ancylostoma caninum, produce immunoglobulin G (Ig G) and IgE antibodies to an immunodaminant excretory/secretory antigen (Ac68) of the parasite. These antibodies were detected in both enzyme -linked immunosorbent assay (ELISA) and Western blots; the Western blo t to detect IgG antibodies to Ac68 was the most specific and sensitive . The subclasses of IgG of the antibody response to the parasite were analyzed using Western blots with anti-IgG subclass-specific monoclona l antibodies as marker systems in an attempt to further improve the sp ecificity of the assay. Eight patients with confirmed enteric infectio ns with A. caninum (positive controls) were tested six had antibodies in all IgG subclasses against Ac68. Twenty sera from patients with sus pected enteric infection with A. caninum (manifested as eosinophilic e nteritis or unexplained abdominal pain with peripheral eosinophilia) w ere tested; 16 had total IgG antibodies to Ac68, while IgG1, IgG2, IgG 3, and IgG4 responses were found in 11, 10, 9, and 12 of these sera, r espectively. Small numbers of sera from groups of patients infected wi th other helminths and from healthy blood donors had various combinati ons of IgG, IgG1, IgG2, and IgG3 antibodies to Ac68, but none of these sera had IgG4 antibodies to Ac68. Sera from all nine patients with hu man hookworm infection had IgG, IgG1, IgG2, and IgG3 antibodies to Ac6 8 and eight of the nine were also positive for IgG4 antibodies. These results indicate the Western blot to detect IgG4 antibodies to Ac68 is the most reliable immunodiagnostic test yet described for enteric inf ection with A. caninum, although this test does not discriminate betwe en infections with human and canine hookworms.