Expression and characterization of a cDNA clone encoding an immunodominant surface glycoprotein of Pneumocystis carinii

Abstract

Most studies of antigens of Pneumocystis carinii have focused on an abundant, immunogenic 95- to 140-kDa surface glycoprotein referred to as gpA. Expression cloning of gpA from P. carinii obtained from ferrets resulted in isolation of colinear fragments of gpA cDNA encoding--87 kDa of the core protein. Northern hybridization detected an abundant, single species of gpA-specific mRNA of 3600 nucleotides. Southern hybridization revealed gpA-specific bands only in P. carinii-infected lung genomic DNA, suggesting that the gpA cDNA did not result from induction of a host lung gene. Antiserum raised against a fragment of recombinant gpA detected P. carinii cysts and isolated native P. carinii gpA, indicating retention of epitopes be-tween the nonglycosylated recombinant gpA and glycosylated native gpA. The deduced amino acid sequence is hydrophilic and contains 12 potential N-linked glycosylation sites and 47 cys-teine residues, consistent with the surface orientation of gpA on the organism and other known characteristics of the native molecule. As the magnitude of the AIDS epidemic increases, Pneu-mocystis carinii is unquestionably recognized as one of the most important opportunistic pathogens among patients who have a symptomatic infection with the human immuno