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Cryptococcus gattii isolates from the British Columbia cryptococcosis outbreak induce less protective inflammation in a murine model of infection than Cryptococcus neoformans.

ABSTRACT: The fungal pathogen Cryptococcus neoformans causes approximately one million cases of cryptococcosis per year in people with AIDS. In contrast, the related species C. gattii is responsible for a much smaller number of cases, but these often occur in immunocompetent people. In fact, C. gattii has emerged in the last decade as the frequent cause of cryptococcosis in otherwise healthy people in British Columbia. We analyzed the immune responses elicited by three C. gattii strains and one C. neoformans strain in mice as a first step toward understanding why C. gattii is able to cause disease in immunocompetent hosts. The C. gattii strains all induced a less protective inflammatory response in C57BL/6 mice by inhibiting or failing to provoke the migration of neutrophils to sites of infection. The C. gattii strains also failed to elicit the production of protective cytokines, such as tumor necrosis factor alpha, compared to the ability of the C. neoformans strain. Despite these differences, the strain representing the major outbreak genotype from British Columbia showed a virulence equivalent to that of the C. neoformans strain, while two other C. gattii strains had reduced virulence. Taken together, our results indicate that C. gattii strains thrive in immunocompetent hosts by evading or suppressing the protective immune responses that normally limit the progression of disease caused by C. neoformans.

SUBMITTER: Cheng PY

PROVIDER: S-EPMC2747943 | biostudies-literature |

REPOSITORIES: biostudies-literature

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A rare genotype of Cryptococcus gattii caused the cryptococcosis outbreak on Vancouver Island (British Columbia, Canada).

Project description:Cryptococcus gattii causes life-threatening infection of the pulmonary and central nervous systems in hosts with normal immunity and traditionally has been considered to be restricted geographically to tropical and subtropical climates. The recent outbreak of C. gattii in the temperate climate of Vancouver Island, BC, Canada, led to a collaborative investigation. The objectives of the current study were to ascertain the environmental source of the outbreak infections, survey the molecular types of the outbreak and environmental cryptococcal isolates, and determine the extent of genetic diversity among the isolates. PCR-fingerprinting and amplified fragment length polymorphism (AFLP) were used to examine the genotypes, and mating assays were performed to determine the mating type of the isolates. All outbreak and environmental isolates belonged to C. gattii. Concordant results were obtained by using PCR-fingerprinting and AFLP analysis. The vast majority of clinical and veterinary infections were caused by isolates of the molecular type VGII/AFLP6, but two were caused by molecular type VGI/AFLP4. All environmental isolates belonged to molecular type VGII/AFLP6. Two or three subtypes were observed within VGII/AFLP6 among outbreak and environmental isolates. All mating-competent isolates were of the alpha-mating type. The emergence of this usually tropical pathogen on Vancouver Island highlights the changing distribution of this genotype and emphasizes the importance of an ongoing collaborative effort to monitor the global epidemiology of this yeast.

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Expression data analysis of murine pulmonary cryptococcosis induced by Cryptococcus gattii and Cryptococcus neoformans

2016-06-22 | GSE83594 | GEO

Expression data analysis of murine pulmonary cryptococcosis induced by Cryptococcus gattii and Cryptococcus neoformans

Project description:Our previous investigation indicated that high-virulence C. gattii (C. gattii R265) tend to reside in the alveoli, whereas low-virulence C. gattii (C. gattii 5815) tend to be washed out from the alveoli and move into the central side of the respiratory system of the mice. Furthermore, C. gattii R265 and 5815 infected mice showed much lesser macrophage response than C. neoformans H99 infected mice. To elucidate the mechanism of this phenomenon from the viewpoint of genetic analysis, we performed this microarray assay. C. gattii R265, C. gattii 5815, and C. neoformans H99 were prepared for the study. The mice were anesthetized and the spore suspension was intratracheally injected into each mouse. Mice were sacrificed 15 days after the infection and then examined. Lungs of the mice infected with C. gattii R265 (n=4), C. gattii 5815 (n=4), and C. neoformans H99 (n=3) and of a normal control (n=1) were obtained. RNA targets preparation was performed according to the manufacturer's protocol using GeneChip(R) 3' IVT Express Kit (Affymetrix). One hundred nanograms of total RNA were converted into double-stranded cDNA template for transcription. In vitro transcription synthesized amplified RNA (aRNA) and incorporated a biotin-conjugated nucleotide. After purification and fragmentation of aRNA, 12.5 ug of them was hybridized to GeneChip(R) Mouse Genome 430 2.0 Array (Affymetrix).The Probe Array was scanned using a GeneChip(R) Scanner 3000 7G.

2016-06-22 | E-GEOD-83594 | biostudies-arrayexpress

Differences in nitrogen metabolism between Cryptococcus neoformans and C. gattii, the two etiologic agents of cryptococcosis.

Project description:Two members of the Cryptococcus neoformans-gattii species complex, the etiologic agents of cryptococcosis, can be differentiated by biological, biochemical, serological and molecular typing techniques. Based on their differences in carbon and nitrogen utilization patterns, cost effective and very specific diagnostic tests using D-proline and canvanine-glycine-bromthymol blue (CGB) media have been formulated and are widely used for identification of the two species. However, these methods have yet to be tested for strains with confirmed molecular types to assess the degree of specificity for each molecular type in the two species. We collected global isolates of every major molecular type available and tested their patterns of nitrogen utilization. We confirmed specificity of the CGB test to be 100% regardless of molecular type while the D-proline test yielded 8-38% false negative results in three of the four C. gattii molecular types, VGI-VGIII. The utilization pattern of a new set of amino acids: D-alanine, L-tryptophan and L-phenylalanine, showed species specificity comparable to that of D-proline. We discovered that the transcription factor Gat1 (Are1) regulates the utilization of nitrogen differently between C. neoformans and C. gattii strains. Unlike in C. neoformans, expression of the genes encoding glycine decarboxylase complex in C. gatti was only partially suppressed by nitrogen catabolite repression in the presence of ammonium. GAT1 in C. neoformans controlled the induction of three of the four genes encoding the glycine decarboxylase complex when glycine was used as the sole nitrogen source while in C. gattii its regulation of these genes was less stringent. Moreover, while virulence of C. neoformans strains in mice was not affected by Gat1, the transcription factor positively influenced the virulence of C. gattii strain.

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Dectin-3 Recognizes Glucuronoxylomannan of Cryptococcus neoformans Serotype AD and Cryptococcus gattii Serotype B to Initiate Host Defense Against Cryptococcosis.

Project description:Cryptococcus neoformans and Cryptococcus gattii cause life-threatening meningoencephalitis or lung diseases in immunocompetent individuals or immunocompromised ones. C. neoformans and C. gattii are subdivided into five serotypes based on their capsular glucuronoxylomannan (GXM). C. neoformans consists of serotypes A, D, and AD hybrid, and C. gattii consists of serotypes B and C. Given structural differences of GXM between C. neoformans and C. gattii, it remains unclear that how innate immune system recognizes GXM. Here, we report that C-type lectin receptor Dectin-3 (MCL encoded by Clec4d) is a direct receptor for GXMs from C. neoformans serotype AD (C.n-AD) and C. gattii serotype B (C.g-B). GXMs from C.n-AD and C.g-B activated NF-?B and ERK pathways to induce pro-inflammatory cytokine production, whereas it was completely abolished due to deficiency of Dectin-3 or caspase recruitment domain family member 9 (CARD9). Upon pulmonary C.n-AD and C.g-B infection, Dectin-3- and CARD9-deficient mice were highly susceptible and showed augmented lung injury due to impairment of alveolar macrophage accumulation and killing activities. Our study provides the first biological and genetic evidence demonstrating that Dectin-3 recognizes GXM of C.n-AD and C.g-B to initiate host defense against cryptococcosis.

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Spread of Cryptococcus gattii in British Columbia, Canada, and detection in the Pacific Northwest, USA.

Project description:Cryptococcus gattii, emergent on Vancouver Island, British Columbia (BC), Canada, in 1999, was detected during 2003-2005 in 3 persons and 8 animals that did not travel to Vancouver Island during the incubation period; positive environmental samples were detected in areas outside Vancouver Island. All clinical and environmental isolates found in BC were genotypically consistent with Vancouver Island strains. In addition, local acquisition was detected in 3 cats in Washington and 2 persons in Oregon. The molecular profiles of Oregon isolates differed from those found in BC and Washington. Although some microclimates of the Pacific Northwest are similar to those on Vancouver Island, C. gattii concentrations in off-island environments were typically lower, and human cases without Vancouver Island contact have not continued to occur. This suggests that C. gattii may not be permanently colonized in off-island locations.

| S-EPMC2725832 | biostudies-literature

TNF-α-Producing <i>Cryptococcus neoformans</i> Exerts Protective Effects on Host Defenses in Murine Pulmonary Cryptococcosis.

Project description:Tumor necrosis factor alpha (TNF-α) plays a critical role in the control of cryptococcal infection, and its insufficiency promotes cryptococcal persistence. To explore the therapeutic potential of TNF-α supplementation as a booster of host anti-cryptococcal responses, we engineered a C. neoformans strain expressing murine TNF-α. Using a murine model of pulmonary cryptococcosis, we demonstrated that TNF-α-producing C. neoformans strain enhances protective elements of host response including preferential T-cell accumulation and improved Th1/Th2 cytokine balance, diminished pulmonary eosinophilia and alternative activation of lung macrophages at the adaptive phase of infection compared to wild type strain-infected mice. Furthermore, TNF-α expression by C. neoformans enhanced the fungicidal activity of macrophages in vitro. Finally, mice infected with the TNF-α-producing C. neoformans strain showed improved fungal control and considerably prolonged survival compared to wild type strain-infected mice, but could not induce sterilizing immunity. Taken together, our results support that TNF-α expression by an engineered C. neoformans strain while insufficient to drive complete immune protection, strongly enhanced protective responses during primary cryptococcal infection.

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Comparative gene genealogies indicate that two clonal lineages of Cryptococcus gattii in British Columbia resemble strains from other geographical areas.

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