EXPRESSION, STRUCTURE, AND LOCATION OF EPITOPES OF THE MAJOR SURFACE GLYCOPROTEIN OF PNEUMOCYSTIS-CARINII F SP. CARINII

The major surface glycoprotein (MSG) of Pneumocystis carinii f. sp. ca rinii consists of a heterogeneous family of proteins that are encoded by approximately 100 unique genes, A genomic expression library was sc reened with a panel of MSG-specific monoclonal antibodies (MAbs) to id entify conserved and rare epitopes. All of the antibodies reacted with epitopes that are encoded within the 5' end of MSG, The results from the expression screening identified antibodies that recognize highly c onserved, moderately conserved, and rare epitopes, Four MAbs (MAbs RA- F1, RA-E7, RA-G10, and RB-E3) reacted with a maltose binding protein-M SG-B fusion protein ((MBP)MSG-B41-1065) by immunoblotting and enzyme-l inked immunosorbent assay, Three of the MAbs (MAbs RA-F1, RA-G10, and RA-E7) reacted with the same continuous epitope that was localized to amino acids 278 to 290 of MSG-B, Comparison of the sequence of the RA- F1-, RA-G10-, and RA-E7-reactive epitope to the deduced amino acid seq uences of multiple MSGs demonstrated that it is highly conserved, The reactivity of RB-E3 with MSG-B was shown to be dependent on amino acid s 184 to 192, which may comprise a portion of a discontinuous epitope.