Therapeutic efficacies of chitosan against Pneumocystis pneumonia of immunosuppressed rat.

This study was designed to investigate the therapeutic efficacy of chitosan on Pneumocystis pneumonia (PCP) in immunosuppressed rats. The PCP rat model was established using intramuscular injections of dexamethasone sodium phosphate. To estimate treatment effects of chitosan on rat PCP, weight gain, lung weight, lung weight/body weight (LW/BW) ratio and per cent survival were measured and the HSP70 mRNA expression of Pneumocystis carinii was detected using real-time PCR analysis. Rat lung tissues were stained with HE, and their pathological changes, inflammatory cells and alveolar macrophages were observed by light microscopy. Rat lymphocyte numbers and the concentrations of IL-10, IFN-γ and TNF-α were measured by flow cytometry and ELISA analysis. Additionally, the ultrastructure of P. carinii was examined by electron microscopy to evaluate the effects of chitosan on the protist. Our results demonstrated that chitosan has some apparent treatment effects on rat PCP by reducing HSP70 mRNA expression and lung inflammation, increasing the concentrations of IL-10 and IFN-γ as well as CD4(+) T-lymphocyte numbers, reducing the CD8(+) T-lymphocyte numbers and the concentration of TNF-α and inducing significant ultrastructural damage to P. carinii. Although its precise therapeutic mechanism has yet to be determined, these results lay a theoretical foundation for PCP chitosan therapy.