Analysis of Pneumocystis carinii antigens by CIEP, SDS-PAGE and immunoblotting

Pneumocystis carinii (Pc) from rabbit and rat lungs were analyzed by counterimmunoelectro-phoresis (CIEP), Polyacrylamide gel electrophoresis and immunoblotting. In CIEP, considerable cross-reactivity was demonstrated using rabbit polyclonal antisera raised against the rabbit and the rat-derived Pc components. In immunoblotting, both the rat and the rabbit Pc antigens also showed reactivity with the two antisera. Rabbit-derived Pc antigens of about 24-27,39,42-45, 55, 110 and 116 kDa were revealed with infection-derived rabbit sera. The 39, 42-45 and 116 kDa antigens were further recognized by both human and rat immune sera. In addition, many human sera detected the rabbit Pc antigen of 42-45 kDa. Using rat infection-derived sera, rat Pc antigens of 39, 55 to 60, 110 and 116 kDa were identified. The sera from Pc infected rabbits and humans recognized the bands in the regions of 39, 55 and 116 kDa. Carbohydrate residues were further analyzed by Concanavalin A (Con A)-binding experiments, periodate Schiff (PAS) and Alcian Blue (AB) stainings. The 55 and 116 kDa bands of both rabbit and rat Pc strongly reacted with Con A and were stained by PAS indicating the presence of hydroxyl and mannosyl/glycosyl residues. The AB staining-bands were 39, 42-45 and 55 kDa for rabbit Pc isolates and 39, 45, 55-60 and 70 kDa for rat Pc isolates, indicating the presence of carbohydrate residues with acidic function. The rabbit Pc immunodominant 39, 55 and 116 kDa antigens then appeared to be glycoproteins with characteristics similar to those of their counterparts in rats. The implications of these findings are discussed.