Geographical variation in serological responses to recombinant Pneumocystis jirovecii major surface glycoprotein antigens

The use of recombinant fragments of the major surface glycoprotein (Msg) of Pneumocystis jirovecii has proven useful for studying serological immune responses of blood donors and human immunodeficiency virus (HIV)-positive (HIV+) patients. Here, we have used ELISA to measure antibody titres to Msg fragments (MsgA, MsgB, MsgC1, MsgC3, MsgC8 and MsgC9 in sera isolated in the USA (n=200 and Spain (n=326), to determine whether geographical location affects serological responses to these antigens. Blood donors from Seville exhibited a significantly greater antibody titre to MsgC8, and significantly lower responses to MsgC3 and MsgC9, than did Cincinnati (USA) donors. Spanish blood donors (n=162 also exhibited elevated responses to MsgC1, MsgC8 and MsgC9 as compared with Spanish HIV+ (n=patients. HIV+ patients who had Pneumocystis pneumonia (PcP+) exhibited a higher response to MsgC8 than did HIV+ PcP- patients. These data show that geographical location plays a role in responsiveness to Msg fragments. Additionally, these fragments have utility in differentiating HIV+ PcP and HIV+ PcP+ among patient populations.