ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR COPRO-DIAGNOSIS OF GIARDIASIS AND CHARACTERIZATION OF A SPECIFIC GIARDIA-LAMBLIA ANTIGEN IN STOOLS

An enzyme-linked immunosorbent assay (ELISA) has been evaluated for coprodiagnosis of giardiasis with anti-trophozoite antibody to capture specific Giardia lamblia stool antigen (GLSA), which was then detected by specific antibody conjugated with horseradish peroxidase. GLSA was demonstrated in stool eluates from all the 24 confirmed cases of giardiasis. None of the stool eluates from apparently healthy subjects or from patients carrying intestinal parasites other than G. lamblia had GLSA. Of the 25 microscopy-negative clinically suspected cases of giardiasis, 17 (68%) patients had GLSA in their stool eluates; these patients responded to anti-giardial therapy. The specific antigen was isolated and affinity-purified by the use of specific antibody; it had a M(r) of 66 Kda, and its immunoreactivity was lost after treatment with heat or trypsin but unaltered by metaperiodate. ELISA seems to be a sensitive and specific method for copro-diagnosis of giardiasis, especially in highly suspected cases.