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

<i>Cryptococcus gattii</i> causes cryptococcosis and life-threatening cryptococcal meningitis. Currently, the pathogenic virulence mechanisms of <i>C</i>. <i>gattii</i> 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. <i>In vivo</i> 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 ( <i>P</i> < 0.001). Bioinformatic interrogation of differentially expressed genes reveals that the catalase-encoding gene CGB_J0620W, <i>CAT2</i>, is a pivotal virulence-associated gene. The hypervirulent clinical isolate G4 (G4-WT) is selected as the parental strain, from which an isogenic <i>CAT2</i>-knockout mutant ( <i>cat2Δ</i>) 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 <i>cat2Δ::CAT</i>2 strain exhibits phenotypic restoration to wild type (WT). In the mouse experiments, significant differences in survival ( <i>P</i> < 0.001), pulmonary fungal burden ( <i>P</i> < 0.01), and alveolar structural damage are observed between the WT and <i>cat2Δ</i> strains, which are completely different from <i>C</i>. <i>neoformans</i>. Moreover, comparative transcriptome analysis is performed on the WT and <i>cat2Δ</i> strains, which reveals that enzymes encoded by <i>CAT</i>2 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 <i>C</i>. <i>gattii</i> and provide a theoretical basis for targeted therapy in a specific genotype population in the future.