CELL-MEDIATED-IMMUNITY IN HOST-RESISTANCE AGAINST INFECTION CAUSED BYPENICILLIUM-MARNEFFEI

Penicillium marneffei is one of the most important opportunistic infec tious pathogens in AIDS patients in Thailand and Southeast Asia. Howev er, very little is known about the host defence mechanisms against P. marneffei infection. In the present study, we established the first ex perimental murine model of chronic pulmonary and disseminated infectio n using P. marneffei, and examined the immunological response to such infection in euthymic and athymic mice. In this model, micro-organisms inoculated intratracheally multiplied progressively in the lungs and disseminated to the liver and spleen. However, the number of organisms decreased gradually in these organs. In contrast, congenitally athymi c mice developed severe pulmonary and disseminated systemic mycosis. P ulmonary penicilliosis marneffei was associated with a marked cellular inflammatory response as evident by histological abnormalities and in creased intraparenchymal leucocyte count. To confirm the importance of cell-mediated immunity in host resistance to P. marneffei infection, we transferred nylon wool non-adherent spleen cells into the athymic m ice. Such treatment significantly reduced the number of yeasts in the organs of athymic mice. Taken together, our results demonstrate that t he cell-mediated immunity play a central role in a host defence mechan ism against infection with P. marneffei, and suggest that our new mode l may be a useful approach for studying the pathogenesis of this funga l disease.