The catalase gene CAT2 and its role in the virulence of one sub-cluster of Cryptococcus gattii VGI clinical isolates.

Cryptococcus gattii causes cryptococcosis and life-threatening cryptococcal meningitis. Currently, the pathogenic virulence mechanisms of C. gattii remain a significant area of ongoing research with considerable unexplored aspects. On the basis of our established research, a sub-cluster of strains with independent evolutionary relationships from WM276 in the phylogenetic analysis of VGI-type strains is identified. In vivo infection experiments on this sub-branch of strains reveal that there are hypervirulent strains and hypovirulent strains among these strains, and the virulence differences are significant ( P < 0.001). Bioinformatic interrogation of differentially expressed genes reveals that the catalase-encoding gene CGB_J0620W, CAT2, is a pivotal virulence-associated gene. The hypervirulent clinical isolate G4 (G4-WT) is selected as the parental strain, from which an isogenic CAT2-knockout mutant ( cat2Δ) is constructed via homologous recombination, which shows increased sensitivity to oxidative stress, as well as growth defects in response to hyperosmosis, 5-fluorocytosine, fluconazole and amphotericin B. The cat2Δ::CAT 2 strain exhibits phenotypic restoration to wild type (WT). In the mouse experiments, significant differences in survival ( P < 0.001), pulmonary fungal burden ( P < 0.01), and alveolar structural damage are observed between the WT and cat2Δ strains, which are completely different from C. neoformans. Moreover, comparative transcriptome analysis is performed on the WT and cat2Δ strains, which reveals that enzymes encoded by CAT2 may be involved in oxidative stress, metabolism and sugar transport. In conclusion, this study may explain the differences in virulence among different genetic evolutionary processes of a sub-cluster of the VGI geneotype of C. gattii and provide a theoretical basis for targeted therapy in a specific genotype population in the future.