CHARACTERIZATION OF MAJOR SURFACE GLYCOPROTEIN GENES OF HUMAN PNEUMOCYSTIS-CARINII AND HIGH-LEVEL EXPRESSION OF A CONSERVED REGION

To facilitate studies of Pneumocystis carinii infection in humans, me undertook to better characterize and to express the major surface glyc oprotein (MSG) of human P. carinii, are important protein in host-path ogen interactions. Seven MSG genes mere cloned from a single isolate b y PCR or genomic library screening and were sequenced. The predicted p roteins, like rat MSGs, were closely related but unique variants, with a high level of conservation among cysteine residues. A conserved imm unodominant region (of approximately 100 amino acids) near the carboxy terminus was expressed at high levels in Escherichia coli and used in Western blot studies. All 49 of the serum samples, which were taken f rom healthy controls as well as from patients with and without P, cari nii pneumonia, mere reactive with this peptide by Western blotting, su pporting the hypothesis that most adult humans have been infected with P. carinii at some point, This recombinant MSG fragment, which is the first human P. carinii antigen available in large quantities, may be a useful reagent for investigating the epidemiology of P. carinii infe ction in humans.