Population structure and pathogenicity of C. neoformans in Vietnam.

Most cryptococcal meningitis occurs in patients with underlying immune deficit. Occasionally, disease occurs in immunocompetent patients. Using AFLP and MLST, we have made the novel finding of a genotype of C. neoformans var. grubii, VNIgamma, that causes 92% of disease in the immunocompetent but only 35% in HIV patients. Genotypes do not segregate by HIV risk group, gender, or temporally, suggesting the novel type has increased pathogenicity. This hypothesis drives the fellowship. Pathogenicity is likely a function of adaptation of this saprophytic organism to the environment. Genomic and epigenomic factors are implicated. I will sample the environment to define the diversity of the Vietnamese C. neoformans population and create a multilayered map in order to determine whether there is spatial clustering, and to identify the niche that VNIgamma occupies. I will use a macrophage model to determine the variability of pathogenicity within and between genotypes. I will use comparativ e genomics and RNAseq to test the validity of previously defined virulence factors and to define novel genetic and transcriptional differences that determine pathogenesis in the rabbit model of meningitis. These findings will be prospectively tested using RT-PCR in cerebrospinal fluid samples from human HIV infected and uninfected patients with cryptococcal meningitis.