NEW YORK (Reuters Health) – Antiretroviral drugs effective against HIV-1 have little or no activity against Pneumocystis carinii in in vitro or in vivo tests, according to a report in the November 15th issue of The Journal of Infectious Diseases.
Recent reports had suggested that HIV protease inhibitors (PIs) were active against Pneumocystis carinii in cell culture, the authors explain, but studies in animal models should be conducted before reaching definitive conclusions regarding their effectiveness.
Dr. Peter D. Walzer and colleagues from the Veterans Affairs Medical Center and University of Cincinnati College of Medicine in Cincinnati, Ohio tested the anti-P. carinii activity of PIs and other antiretroviral classes in an ATP cytotoxicity assay and then in immunosuppressed mice.
Slight anti-P. carinii activity was seen with indinavir in vitro, the authors report, but only at levels that cannot be achieved clinically in serum.
None of the other PI drugs were active against P. carinii, the report indicates, and no anti-P. carinii activity was shown by any of the nucleoside reverse transcriptase inhibitors or the nonnucleoside reverse transcriptase inhibitors.
None of the antiretroviral drugs, alone or in combination, significantly reduced the P. carinii cyst count below that in the control mice, the researchers note.
In contrast, the positive control drugs (pentamidine in vitro and trimethoprim-sulfamethoxazole in vivo) showed excellent activity against P. carinii, whereas the negative control (ampicillin in vitro) did not.
"The present report has shown that PIs and other anti-HIV drugs have little or no anti-P. carinii activity," the authors conclude. "Only time and additional investigation will determine whether anti-HIV drugs have activity against P. carinii. Until these studies are done, caution in interpreting in vitro data is advised."