Monoclonal Antibodies to Pneumocystis carinii: Identification of Specific Antigens and Characterization of Antigenic Differences Between Rat and Human Isolates

Abstract

To increase understanding of the antigenic structure of Pneumocystis carinii, we developed monoclonal antibodies to rat and human P. carinii. The specificity of the antibodies was demonstrated by immunofluorescence and immunoblot studies. Only one of five monoclonal antibodies to rat P. carinii reacted with human P. carinii, and none of four monoclonal antibodies to human P. carinii reacted with rat P. carinii. Two antibodies to human P. carinii reacted by immunofluorescence with only one human P. carinii isolate. Immunoblot studies identified major antigens of rat P. carinii with molecular masses of 40,000-100,000 daltons and of human P. carinii with molecular masses of 22,000-95,000 daltons. These studies document the existence of antigenic differences between rat and human P. carinii and are consistent with the suggestion that individual isolates of human P. carinii are also antigenically different. Further studies with these antibodies should increase understanding of the antigenic nature of P. carinii and of the interaction of P. carinii with its host.

Pneumocystis carinii-induced activation of the respiratory burst in human monocytes and macrophages

“…Rat lung tissue prepared and opsonized in the same way as pneumocysts and adjusted to the same protein content as 15 X 10'' pneumocysts could not stimulate the cells, suggesting that the effect was specific and not caused by lung tissue inevitably trapped in the pneumocyst suspension. Pneumocysts used in this study came from a rat source, and although species differences between pneumocysts from different hosts can be demonstrated using MoAbs [17], cross-reactivity between rat and human pneumocysts has been found [18,19]. Only pneumocysts opsonized with serum could activate the respiratory burst in monoeyles.…”

Pneumocystis

“…These glycoproteins are proposed to participate in attachment of Pneumocystis to host lung cells, as well as in evading host defenses (Gigliotti et al 1986(Gigliotti et al , 1988Linke et al 1989;Lundgren et al 1993;O'Riordan et al 1995;Vuk-Pavlovic et al 2001). The gpA/ MSG isoform expressed is immunogenic and antigenically distinct in the different species of Pneumocystis that infect different mammalian hosts (Kovacs et al 1989;Gigliotti 1992;Kovacs et al 1993;Stringer and Keely 2001). Of the .80 gpA/MSG found in the P. carinii genome, only a single isoform of gpA/MSG is expressed at any given time.…”

Evidence for high prevalence of Pneumocystis jirovecii exposure among Cameroonians

“…The major surface glycoprotein (Msg) is commonly used as antigen for serologic analyses because it is the most antigenic and there is some cross-reactivity between Msg from different Pneumocystis species (Bauer et al, 1993; Kovacs et al1988; Kovacs et al, 1989; Kutty et al, 2008; Meuwissen et al, 1977; Tanabe et al, 1989; Walzer and Linke, 1987; Walzer and Cushion, 2004; Walzer et al, 2008; Walzer et al, 2009). However, Pneumocystis organisms are host species-specific and Msg molecules in any given Pneumocystis species are diverse (∼80 distinct genes in P. carinii ) (Stringer 2007; Stringer and Keely, 2001).…”

“…The reactivity of anti- P. jirovecii Msg antibodies with P. carinii or P. murina Msg would not be expected to be as high or specific compared to P. jirovecii Msg. The development of a serological test specifically for P. jirovecii antibody titers has clinical and human epidemiological applications and protocols specific for immunoserological assays of P. jirovecii recombinant Msg have been developed (Daly et al, 2002; Daly et al, 2004; Daly et al, 2006; Daly et al, in press; Kovacs et al, 1989; Walzer et al, 2009). An ELISA protocol has been developed employing three overlapping recombinant Msg fragments (MsgA1, MsgB, MsgC1) that span the entire length of a P. jirovecii Msg.…”