ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR DETECTION OF SERUM ANTIBODY TO BLASTOCYSTIS-HOMINIS IN SYMPTOMATIC INFECTIONS

An enzyme-linked immunosorbent assay was devised in order to search fo r antibodies against Blastocystis hominis in infected humans. Reaction proteins were obtained from washed, axenic B. hominis cells, as sonic ate. Sonicate was diluted to provide 17 and 34 mu g of protein per wel l. Dilutions of patients' sera were applied, followed by phosphatase-c onjugated goat anti-human serum and phosphatase substrate. Color was m easured at 405 mu m wavelength. Immunoglobulin G antibodies to high ti ters were found. Of 30 sera tested from 28 patients, 3 were negative a t the 1/50 threshold dilution, 8 were positive at 1/50, 3 at 1/100, 2 at 1/200, 3 at 1/400, 6 at 1/800, and 5 at 1/1,600. Normal sera (42 bl ood bank sera) were all negative at 1/50. Each serum was subjected to multiple testing. Duplicate tests were included for each run, and runs were made from 4 to 6 for each serum. Blastocystis hominis is increas ingly recognized to be a cause of human enteric disease, with symptoms often like those in giardiasis. Demonstration of strong antibody resp onse is consistent with this view.