NATURAL-HISTORY OF ASYMPTOMATIC AND SYMPTOMATIC PNEUMOCYSTIS-CARINII INFECTION IN HIV-INFECTED PATIENTS

The natural appearance of Pneumocystis carinii in induced sputum sampl es was studied in 60 HIV-infected patients with severe immunodeficienc y and without a history of P. carinii pneumonia (PCP). The patients we re prospectively evaluated for occurrence of P. carinii in induced spu tum samples, PCP diagnosis and CD4+ cell counts during observation per iods of 2 to 31 months. P. carinii was detected in 16 patients ah of w hom developed clinical PCP. In 5 patients P. carinii was detected 3 we eks to 8 months prior to clinical symptoms. Immunofluorescence using m onoclonal antibody 3F6 was more sensitive than toluidine in detecting P. carinii in sputum samples (p < 0.05). In the patients who developed PCP a drop of the mean CD4 count to 40-50 x 10(6)/l was observed 200 days before diagnosis. However, out of 13 patients with CD4 counts of 0-20 x 10(6)/l only 7 developed PCP during 200 days of observation. Th e results do not support the suggested reactivation of a latent infect ion present in the vast majority of adults. PCP may instead result fro m exposure to the organism or presence of an unknown cofactor. We conc lude that P. carinii is present in some asymptomatic HIV patients and that the detection of the organism in sputum should be regarded as pat hological and prophylaxis or treatment inserted. The risk of transmiss ion of P. carinii to patients with severe immunodeficiency should be s eriously considered.