SEVERE PULMONARY PNEUMOCYSTOSIS IN SIMIAN ACQUIRED-IMMUNODEFICIENCY-SYNDROME INDUCED BY SIMIAN IMMUNODEFICIENCY VIRUS - ITS CHARACTERIZATION BY THE POLYMERASE-CHAIN-REACTION METHOD AND FAILURE OF EXPERIMENTAL TRANSMISSION TO IMMUNODEFICIENT ANIMALS

Pneumocystis carinii (Pc) infection was observed in three of five rhes us monkeys infected with simian immunodeficiency virus (SIVmac251). Th ey showed severe symptoms similar to those associated with human acqui red immunodeficiency syndrome (AIDS). Histopathology revealed severe p ulmonary pneumocystosis in one of three Pc-positive monkeys, and anti- Pc antibodies were detected in sera from two of the three monkeys. Loc alization of Pc organisms in various organs of the monkeys was examine d by the polymerase-chain-reaction (PCR) method, and Pc-specific bands of DNA amplification were detected in the liver, kidney, spleen, adre nal gland, testis, brain, and other organs examined, but no Pc organis m was found in these organs by histopathologic examination. These resu lts suggest that the activation of a latent infection of Pc occurs in SIV-infected rhesus monkeys as well as in human AIDS. Experimental tra nsmission of Pc derived from a simian was attempted in severe combined immunodeficiency (SCID) mice and athymic nude (rnu/rnu, F344) rats. T hese animals were inoculated intranasally with 10(4) Pc cysts, but nei ther histopathologic changes nor Pc organisms were detected in SCID mi ce at 4 months after inoculation or in nude rats at 2 months postinocu lation, suggesting that simian Pc is species-specific.