Project description:The basidiomycetous yeast Cryptococcus neoformans is an important human fungal pathogen. Two varieties, C. neoformans var. neoformans and C. neoformans var. gattii, have been identified. Both are heterothallic with two mating types, MATa and MATalpha. Some rare isolates are self-fertile and are considered occasional diploid or aneuploid strains. In the present study, 133 isolates, mostly from Italian patients, were investigated to detect the presence of diploid strains in the Igiene Università Milano culture collection. All of the diploid isolates were further investigated by different methods to elucidate their origins. Forty-nine diploid strains were identified by flow cytometry. PCR fingerprinting using the (GACA)(4) primer showed that the diploid state was associated with two specific genotypes identified as VN3 and VN4. Determination of mating type on V8 juice medium confirmed that the majority of the strains were sterile. PCR and dot blotting using the two pheromone genes (MFa and MFalpha) as probes identified 36 of the 49 diploid isolates as MATa/alpha. The results of pheromone gene sequencing showed that two allelic MFalpha genes exist and are distinct for serotypes A and D. In contrast, the MFa gene sequence was conserved in both serotype alleles. Amplification of serotype-specific STE20 alleles demonstrated that the diploid strains contained one mating locus inherited from a serotype A parent and one inherited from a serotype D parent. The present results suggest that diploid isolates may be common among the C. neoformans population and that in Italy and other European countries serotype A and D populations are not genetically isolated but are able to recombine by sexual reproduction.
Project description:A singleplex PCR assay using a single primer pair targeting the putative sugar transporter gene was developed here to distinguish Cryptococcus neoformans var. grubii, Cryptococcus neoformans var. neoformans, and Cryptococcus gattii according to the distinct size of the amplicon. The interspecies and intravarietal hybrids were also characterized on the basis of distinct combined profiles of amplicons. This PCR assay is a rapid, simple, and reliable approach suitable for laboratory diagnoses and large-scale epidemiologic studies.
Project description:Cryptococcus neoformans is the most common cause of fungal meningitis, with high mortality and morbidity. The reason for the frequent occurrence of Cryptococcus infection in the central nervous system (CNS) is poorly understood. In this study, we find that inositol plays an important role in the transversal of Cryptococcus across the blood-brain barrier (BBB) both in an in vitro human BBB model and in vivo animal models. The inositol stimulation of BBB crossing is dependent upon fungal inositol transporters. The upregulation of genes involved in the inositol catabolism pathway is evident in a microarray analysis. The expression of CPS1, a gene encoding the hyaluronic acid synthase in Cryptococcus, is also upregulated by the inositol treatment. The production of hyaluronic acid increased in cells treated with inositol, which leads to the enhanced binding ability of Cryptococcus cells to the human brain microvascular endothelial cells (HBMECs) constituting the BBB. Overall, our studies provide a mechanism for inositol-dependent Cryptococcus transversal of the BBB, supporting our hypothesis that host inositol utilization by the fungus contributes to Cryptococcus CNS infection.