Identification of immunodominant surface antigens of Eimeria acervulina sporozoites and merozoites.

Immunodominant surface antigens of Eimeria acervulina sporozoites and merozoites were identified by 125I-labeling and immunoblotting studies. Using these methodologies 60% of the immunodominant sporozoite antigens and 90% of the immunodominant merozoite antigens were observed to be 125I-surface labeled. However, several major 125I-labeled sporozoite and merozoite proteins did not represent prominent antigens as measured by immunoblotting. Immunodominant surface antigens were found over a wide size range for sporozoites (21-110 kDa) and for merozoites (20-250 kDa). In order to relate these findings to a 'natural' infection, two groups of 3-week old chickens were inoculated 5 times over a 2.5 week period with either a low or high dose of E. acervulina oocysts. The serum response to sporozoites and merozoites, indicated by enzyme-linked immunosorbent assay titers, was rapid; less than or equal to 7 days post-infection with 10(4) oocysts and less than or equal to 3 days with 10(5) oocysts. Many of the antigens identified by immunoblotting of sera from sporozoite- and merozoite-immunized animals were recognized by sera from both high dose and low dose E. acervulina-infected chickens. Furthermore, the sporozoite and merozoite antigens could be grouped into those constituents which induced a serum response early or late in the infection.