Development and evaluation of a direct fluorescent antibody method for the diagnosis of Pneumocystis carinii infections in experimental animals.

Because no fully satisfactory diagnostic method has been available for use in pneumocystis infection, an attempt was made to apply the fluorescent antibody technique in the identification of Pneumocystis carinii. Hyperimmune sera were prepared in rabbits against P. carinii from human and rat sources. After proper adsorption, these antisera were conjugated with fluorescein isothiocyanate and used as reagents in a direct fluorescent antibody procedure. Each of the two reagents was found to stain trypsin-treated P. carinii organisms from either human or rat sources, indicating the presence of common antigens. Stained organisms were demonstrated in the hypopharyngeal material from rats in which pneumocystis infection had been activated by the administration of corticosteroid. From the results reported here, the procedure outlined is considered sufficiently sensitive and specific to justify tests on pneumocystis infections in man. The findings in a series of specimens from human subjects will be reported separately. The method also provides an extended approach to related research problems. The need for controls of the procedure at all points is emphasized.