Histopathological study of murine pulmonary cryptococcosis induced by Cryptococcus gattii and Cryptococcus neoformans.

Although Cryptococcus gattii can cause life-threatening complications, putative virulence factors of C. gattii remain controversial. Therefore, we conducted the present study to elucidate the virulence factors of the yeast and found that the mortality rate of mice infected with C. gattii R265 was significantly higher than that of those infected with C. gattii 5815; however, no difference was found in the mortality rates between mice infected with C. gattii R265 and Cryptococcus neoformans H99. In contrast, we found a significant difference in histopathological findings of the lungs between mice infected with C. gattii R265 and C. neoformans H99. The former showed alveolar expansion due to yeast proliferation with much lesser macrophage response, whereas the latter showed numerous nodules in the alveolar space consisting of macrophages and multinucleated giant cells. Furthermore, alveolar expansion was more enhanced in mice infected with C. gattii R265 than in those infected with C. gattii 5815. Our study confirmed that there is a different pathophysiology leading to death during C. gattii and C. neoformans infections. The result can provide two characteristics of C. gattii: one includes some mechanisms to escape from host recognition via macrophage and another includes a high performance of pulmonary structural alteration. These characteristics may be associated with the high virulence of C. gattii.