IDENTIFICATION AND INITIAL CHARACTERIZATION OF PNEUMOCYSTIS-CARINII SOLUBLE-ANTIGENS IN RABBIT SERUM AND LUNG LAVAGE

Lung lavage and serum samples from Azathioprin-treated (acute-phase in fection) and untreated (non acute-phase infection) rabbits were used i n the immunoblotting technique to look for Pneumocystis carinii (Pc) s oluble antigens, using rabbit polyclonal antibodies raised against rab bit-derived Pc antigens and labeled with peroxidase. Analysis of the s upernatant of lavage fluid after centrifugation to sediment intact org anisms revealed components of approximately 80, 60-65, 55, 39 and 27 k Da in acute-phase samples. The components in the regions of 80, 60-65, 55 kDa and to a lesser extent 39 kDa were also present in non acute-p hase lung lavage samples. In acute-phase serum samples, a major compon ent of 80 kDa and minor components of about 65 and 39 kDa are detectab le. The 80 and 65 kDa components are also detectable in some of the se rum samples from the untreated rabbits. Immunofluorescent staining wit h FITC-conjugated affinity-purified antibodies to the 80, 60-65, 55, 3 9 or 27 kDa-components showed that they shared epitopes with both Pc c ysts and trophozoites. The affinity-purified antibodies also cross-rea cted in immunoblotting with several antigens in the Pc whole preparati ons. The putative Pc soluble antigens in serum and lung lavage were th en isolated by affinity chromatography with polyclonal antibodies to P c. Preliminary characterization of the column-extracted antigens revea led complete inactivation by trypsin whereas only the 55 and 80 kDa an tigens bind to Concanavalin A. In conclusion, the results of this stud y suggest that Pc soluble antigens are present even in non acute-phase samples and only the low-molecular weight antigens (39 and 27 kDa) se em specific for the acute-phase. These findings are consistent with pr evious investigations reported by others that development of Pc could occur in nonimmunosuppressed rabbits.