Alterations in T lymphocyte profiles of Bronchoalveolar lavage fluid from SIV- and Pneumocystis carinii-coinfected rhesus Macaques

The goal of this study was to examine SIV- and Pneumocystis carinii-coinfected rhesus macaques as a model of P. carinii infection in HIV-seropositive humans. The influence of P. carinii infection on the cellular composition of bronchoalveolar lavage (BAL) fluid from SIV-infected and normal rhesus macaques was examined by flow cytometric analysis and polymerase chain reaction (PCR). BAL fluid from SIV- and P. carinii-coinfected macaques showed a substantial T lymphocyte influx composed of more than 90% CD8(+) T cells. These results are in contrast to BAL fluid from SIV-infected macaques with no detectable P. carinii-specific PCR product, where CD4(+) T cells were present in significant numbers and the CD8(+) T cell population was less than 70% of total CD3(+) lymphocytes. We observed no significant differences in peripheral blood CD4(+) or CD8(+) T cell levels in the SIV- infected animals, regardless of P. carinii status, indicating that the CD8(+) T cell infiltration in the lungs of the P. carinii-positive animals was likely the result of P. carinii infection. These results demonstrate that although peripheral blood CD4(+) T cell levels are predictive of susceptibility to P. carinii infection in this model, the levels are not reflective of the T cell profile in the lung during SIV and P. carinii coinfection. The SIV- and P. carinii-coinfected macaques showed a spectrum of lung disease severity that was histologically similar to human P. carinii pneumonia (PCP). Interestingly, even mild P. carinii infection was sufficient to alter the normal CD4(+)/CD8(+) T cell profiles in the lungs of SIV- infected rhesus macaques. These results are similar to immunologic findings in human AIDS-associated PCP and support the usefulness of this model in the study of immune responses to P. carinii.