Detection of sarcocystis antigens in the sera of experimentally-infected pigs and mice by an immunoenzymatic assay

Immunoglobulins raised against Sarcocystis miescheriana and Sarcocystis muris cystozoite antigens were isolated from rabbit immune sera by affinity chromatography (using CNBr-actibated Sepharose 4B for antigen immobilization). The specific immunoglobulin were incorporated into double-antibody sandwich immuno-enzymatic assays which were firstly quantitated and then used to detect soluble Sarcocystis antigens in the sera of experimentally-infected pigs and mice. Assays employing immunoglobulins attacthed to the solid-phase at concentration of 80 μg/ml were capable of detecting homologous soluble cystozoite and sporozoite reference antigens at concentrations as low as 8 μg/ml. Circulating antigens were detected both in the presence and absence of acute clinical disease in pigs experimentally-infected with high and low doses of S. miescheriana sporocysts. The antigenemia detected was transitory (occuring from 3–20 days post-inoculation: dpi) and coincided well with the sporozite and merozoite phases of parasite development. Circulating antigens were also detected during subclinical infections in mice (from 4–9 dpi)_following their experimental infection with low doses of S. muris sporocysts. Specific immuno-enzymatic assays for circulating Sarcocystis antigens may therefore prove useful in the clinical diagnosis of acute sarocytosis.