Immunoglobulins raised against Sarcocystis miescheriana and Sarcocystis muris cystozoite
antigens were isolated from rabbit
immune sera by affinity chromatography (using CNBr-activated
Sepharose 4B for
antigen immobilization). The specific
immunoglobulins 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 attached to the solid-phase at concentrations of 80 micrograms/ml were capable of detecting homologous soluble cystozoite and sporozoite reference
antigens at concentrations as low
as 8 micrograms/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 (occurring from 3-20 days post-inoculation: dpi) and coincided well with the sporozoite and merozoite phases of parasite development. Circulating
antigens were also detected during
subclinical infections in mice (from 4-49 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
sarcocystosis.