cDNA encoding an immunogenic region of a 22 kilodalton surface protein of Eimeria acervulina sporozoites.

cDNA encoding an immunogenic region of a 22 kDa surface protein of Eimeria acervulina sporozoites was cloned and expressed in the bacteriophage lambda gt11 vector. The recombinant beta-galactosidase fusion protein, designated MA1, has an apparent molecular size of 125 kDa. Immunofluorescence staining of intact E. acervulina sporozoites and merozoites and immunoblotting of 125I-surface labeled protein from both stages revealed exclusive expression of the cloned cDNA in the sporozoite stage. The gene encoding the 22 kDa surface protein appears to exist as a single copy sequence as revealed by Southern blot hybridization utilizing the cDNA insert as a probe. Although not recognized by immune serum, purified recombinant MA1 antigen induced significant in vitro activation of T lymphocytes obtained from chickens immune to E. acervulina. DNA sequencing and hydropathic analysis of the predicted amino acid sequence revealed a central hydrophilic region surrounded by two hydrophobic areas which may represent exposed and transmembrane regions of the protein.