Animal pneumocystosis: a model for man.

Pneumocystis carinii is an important pulmonary pathogen responsible for morbidity and mortality in patients with AIDS. Apart from AIDS, cases of pneumocystosis have been reported in patients receiving immunosuppressive therapy associated with organ transplantation without chemoprophylaxis and in malignant blood diseases. In vitro models are only of limited interest because there is no continuous in vitro culture. The in vivo models have contributed a great deal to the understanding of human Pneumocystis carinii pneumonia. Indeed, animal models remain of prime interest for many purposes, principally comparative medicine, pathogenesis, epidemiology and immunology. Among animal models, the rabbit is a very susceptible host to P. carinii infection, and does not need glucocorticoid treatment. Moreover, antigenic and genomic data suggest that rabbit-derived Pneumocystis strains are more closely related to human Pneumocystis than those of mice or rats. We have therefore shown that the rabbit model permits the study of the pulmonary surfactant modification due to P. carinii infection. This model should be a very interesting model for pathogenesis or immune response studies in immunocompetent animals. The rabbit model could also be used for epidemiological studies. P. carinii transmission appears to be very rapid via contact of Pneumocystis-free rabbits with infected rabbits. These Pneumocystis-free animals could be helpful for characterizing the source and the reservoir and studying parasite transmission.