EXPERIMENTAL PARACOCCIDIOIDOMYCOSIS OF HAMSTER INOCULATED IN THE CHEEK POUCH

We compared the granuloma morphology and immune response of hamsters i noculated with Paracoccidioides brasiliensis (Pb) into the cheek pouch , which lacks lymphatic drainage, and into the footpad, which is rich in lymphatics. Our objective was to better understand the modulation o f Pb granuloma in an immunocompetent animal inoculated in an immunolog ically privileged site. The humoral immune response (ELISA) and cell m ediated immunity (footpad test) became positive on days 7 and 14, resp ectively in animals inoculated into footpad and on days 35 and 60 in a nimals inoculated into the pouch. Typical epithelioid granulomas were observed at both sites on day 14. The number of fungi gradually decrea sed from the beginning of the experiment in footpad lesions, but only after day 35 in pouch granulomas, when cell mediated immunity was dete ctable. The results indicate that typical epithelioid paracoccidioidom ycotic granulomas may develop in the absence of a detectable immune re sponse; however, they are incapable of controlling fungal reproduction . Lack of lymphatic drainage delays the appearance of a detectable imm une response, but with time fungi escape from the pouch, elicit an imm une response and reach other organs. Our results further indicate the importance of the lymphatics in the pathogenesis of paracoccidioidomyc osis.