Serologic Responses to Epitopes of the Major Surface Glycoprotein of Pneumocystis jiroveci Differ in Human Immunodeficiency Virus–Infected and Uninfected Persons

The major surface glycoprotein (Msg) of Pneumocystis jiroveci (P. jiroveci) is important in the immunopathogenesis of Pneumocystis pneumonia (PcP), but is difficult to study in humans. We generated 3 overlapping recombinant Msg fragments (MsgA, MsgB and MsgC), and analyzed their reactivity with serum samples from 95 healthy blood donors and 94 human immunodeficiency virus (HIV)–infected persons. Reactivity to the Msg fragments varied with HIV infection and prior episodes of PcP but not with geographic origin. Recognition of MsgA was lower—and recognition of MsgB was significantly lower—in HIV+ serum compared with donor serum. Serum samples from HIV-positive patients with prior PcP recognized MsgC more frequently than did serum samples from those without PcP. None of the serum samples drawn from 9 patients before they had developed PcP recognized MsgC. These data suggest that these novel recombinant proteins are useful for the analysis of antibody responses to Msg