De novo lysine synthesis is required for the virulence of Cryptococcus neoformans

Lysine is an essential amino acid for cellular functions, and its de novo biosynthesis pathway, conserved in fungi but absent in vertebrates, is a promising antifungal target. We systematically evaluated the essentiality of this pathway in Cryptococcus neoformans, a fatal fungal meningitis pathogen. We identified five key enzymes in the lysine synthesis pathway of C. neoformans. The resulting knockout strains failed to grow in lysine-deficient medium, and phenotypic defects were fully rescued by genetic complementation. Virulence factor assays showed impaired capsule and melanin production across all mutants. These strains also displayed increased susceptibility to temperature stress, oxidative stress, and antifungal drugs. In a murine systemic infection model, lung and brain fungal burdens were markedly reduced for lys1Δ and lys9Δ mutants, and survival times for all knockout-infected mice were significantly extended. Notably, mice infected with lys9Δ remained asymptomatic for 60 days post-infection, with no detectable fungal cells in brain or lung tissues. These findings suggest that disrupting the lysine biosynthesis pathway represents a promising avenue for drug development against C. neoformans.