Long-term serologic responses to the pneumocystis jirovecii major surface glycoprotein in HIV-positive individuals with and without p. jirovecii infection

Background. The immune responses to Pneumocystis jirovecii major surface glycoprotein (Msg) in individuals with human immunodeficiency virus (HIV) infection are poorly understood. Methods. We examined the sequential serologic responses to recombinant Msg carboxyl terminus fragments (MsgC1, MsgC3, MsgC8, and MsgC9) by enzyme-linked immunosorbent assay in a cohort of individuals with HIV infection for the 5.5 years before death and autopsy. Analyses included mean antibody levels by status at death (Pneumocystis pneumonia, P. jirovecii colonization, or neither), factors associated with high antibody levels, and antibody responses before and after active Pneumocystis pneumonia. Results. Patients who died from Pneumocystis pneumonia had higher levels of antibody to MsgC8 than did patients who died from other causes. Previous episode of Pneumocystis pneumonia, geographic location, and age were independent predictors of high levels of anitbodies to most or all Msgs. Failure to take Pneumocystis pneumonia prophylaxis was associated with high levels of antibody to MsgC1. Patients who developed and recovered from active Pneumocystis pneumonia during the study exhibited an increase in serum antibody levels that persisted for months after the infection, whereas patients who developed another acquired immunodeficiency syndrome-defining illness did not. Conclusions. Serum antibodies to Msgs are important markers of P. jirovecii infection in patients with HIV infection and are influenced by host and environmental factors in complex ways.