Cryptococcus neoformans var. gattii in Australia.

An examination of 45 clinical isolates of Cryptococcus neoformans revealed an unusually high incidence of C. neoformans var. gattii in South Australia (65%) and in the Northern Territory (95%). In assessing all the available data from Australian isolates of C. neoformans, there appeared to be an endemic focus for the incidence of C. neoformans var. gattii in the rural aboriginal population of the Northern Territory.     

Karyotype instability in Cryptococcus neoformans infection.

The electrophoretic karyotypes of 32 clinical and 3 environmental Cryptococcus neoformans isolates from New York City were studied by contour clamped homogeneous electrophoresis. There was extensive variation among the electrophoretic karyotypes of isolates from different patients. Sequential C. neoformans isolates from patients with chronic or relapsing infection had very similar karyotypes. However, minor differences in electrophoretic karyotypes were detected among sequential isolates from 50% of the patients studied, suggesting the occurrence of chromosomal rearrangements or deletions in vivo. This hypothesis was tested by infecting mice, recovering isolates from mouse organs, and comparing the electrophoretic karyotypes before and after passage. Three clinical and three environmental strains were studied before and after passage in mice. Karyotype differences were detected after mouse passage for one clinical and two environmental strains. Our results indicate (i) extensive karyotype variation among isolates from a small geographic regions, (ii) a high frequency of electrophoretic karyotype differences among sequential isolates from individual patients, and (iii) the occurrence of electrophoretic karyotype changes during experimental infection of mice. The implications of these observations are discussed.     

Laccase expression in murine pulmonary Cryptococcus neoformans infection

Cryptococcus neoformans laccase expression during murine infection was investigated in lung tissue by immunohistochemistry and immunogold electron microscopy. Laccase was detected in the fungal cell cytoplasm, cell wall, and capsule in vivo. The amount of laccase found in different sites varied as a function of the time of infection.     

Surfactant protein D facilitates Cryptococcus neoformans infection

Concurrent with the global escalation of the AIDS pandemic, cryptococcal infections are increasing and are of significant medical importance. Furthermore, Cryptococcus neoformans has become a primary human pathogen, causing infection in seemingly healthy individuals. Although numerous studies have elucidated the virulence properties of C. neoformans, less is understood regarding lung host immune factors during early stages of fungal infection. Based on our previous studies documenting that pulmonary surfactant protein D (SP-D) protects C. neoformans cells against macrophage-mediated defense mechanisms in vitro (S. Geunes-Boyer et al., Infect. Immun. 77:2783–2794, 2009), we postulated that SP-D would facilitate fungal infection in vivo. To test this hypothesis, we examined the role of SP-D in response to C. neoformans using SP-D^−/− mice. Here, we demonstrate that mice lacking SP-D were partially protected during C. neoformans infection; they displayed a longer mean time to death and decreased fungal burden at several time points postinfection than wild-type mice. This effect was reversed by the administration of exogenous SP-D. Furthermore, we show that SP-D bound to the surface of the yeast cells and protected the pathogenic microbes against macrophage-mediated defense mechanisms and hydrogen peroxide (H₂O₂)-induced oxidative stress in vitro and in vivo. These findings indicate that C. neoformans is capable of coopting host SP-D to increase host susceptibility to the yeast. This study establishes a new paradigm for the role played by SP-D during host responses to C. neoformans and consequently imparts insight into potential future preventive and/or treatment strategies for cryptococcosis.     

Disseminated infection caused by urease-negative Cryptococcus neoformans.

We report a case of fungemia and disseminated disease caused by a urease-negative strain of Cryptococcus neoformans in a patient with the acquired immune deficiency syndrome. Except for failure to hydrolyze urea, the microbiological characteristics of the isolate were typical of C. neoformans. Laboratory specialists should be aware of the occurrence of atypical strains of C. neoformans, particularly those recovered from patients with the acquired immune deficiency syndrome.     

Role of interleukin-4 in resistance to Cryptococcus neoformans infection

The role of interleukin (IL)-4 in cryptococcal disease was studied in IL-4 knockout (IL-4KO) and wild-type (WT) mice infected with Cryptococcus neoformans isolates that vary widely in their virulence. Delayed-type hypersensitivity responses were reduced in IL-4KO mice following primary infection with either isolate. Splenic T helper 1 (Th1) cytokine responses were increased in the IL-4KO mice infected with the weakly virulent isolate (184A) but did not change during infection with the highly virulent isolate (NU-2). Th2 cytokine responses (IL-5, IL-10) were downregulated in the IL-4KO mice infected with either isolate. Survival after primary infection with either isolate was not influenced by the absence of IL-4. Fewer colony-forming units were found in the lungs of 184A-infected, IL-4KO mice as compared to WT mice, suggesting that some immunity had developed. IL-4KO mice, primed with small doses of cryptococcal antigen (CneF), had significantly enhanced delayed-type hypersensitivity responses after intravenous infection with 184A and were more resistant to infection compared with WT mice. Increased expression of IL-5 with decreased interferon-gamma contributed to the inability of primed WT mice to resist infection with 184A. Enhanced immunity in the primed IL-4KO mice was reflected in a more moderate increase in IL-5 and IL-10 with maintenance of interferon-gamma levels.     

Pathogenesis of pulmonary Cryptococcus neoformans infection in the rat.

The pathogenesis of Cryptococcus neoformans pulmonary infection in the rat was studied after intratracheal inoculation. Lungs were examined at various times following infection for histopathology in conjunction with macrophage markers, proliferating cell nuclear antigen (PCNA), and capsular glucuronoxylomannan (GXM) antigen. Serum GXM, immunoglobulin M (IgM) and IgG titers and organ fungal burden were compared with pathological findings. C. neoformans organisms were in the lung parenchyma 2 h postinoculation, and GXM antigen was present in surrounding tissues shortly thereafter. Extrapulmonary dissemination occurred early in infection. Two phases of host cellular inflammatory response were discernible: early local macrophage recruitment at 2 to 4 days followed by granulomatous inflammation, which reached maximum intensity 14 days after infection. The granulomatous phase was preceded by lymphocyte influx with macrophage proliferation and maturation into epithelioid histiocytes; this was paralleled by a shift of yeasts from extracellular to intracellular spaces. Tissue IgG deposits, serum IgG to GXM, and localization of tissue GXM immunoreactivity to epithelioid cells were noted at 2 to 4 weeks. A 10-fold decrease in lung fungal burden occurred 25 days postinfection and was associated with resolving granulomas, fewer proliferating cells, and decreased tissue GXM. The present study demonstrates that (i) C. neoformans penetrates the lung parenchyma shortly after infection; (ii) immunocompetent rats control pulmonary cryptococcosis efficiently, with minimal extrapulmonary dissemination and low levels of serum GXM; and (iii) macrophage activation is likely to play a crucial role in limiting C. neoformans infection in the rat lung.     

Experimental systemic infection with Cryptococcus neoformans var. grubii and Cryptococcus gattii in normal and immunodeficient mice.

Cryptococcus neoformans (Cn) var. grubii or Cryptococcus neoformans var. neoformans infection is usually associated with immunocompromised hosts, whereas Cryptococcusgattii more frequently causes disease in immunocompetent hosts. We examined the effects of immunodeficiency and glucocorticoid-induced immunosuppression on systemic murine infection induced by i.v. inoculation with these pathogens. SCID and immunocompetent BALB/c and C57BL/6 mice were infected with 相似文献   

First case of feline systemic Cryptococcus albidus infection.

This paper, as best as the authors can determine, is the first to describe a documented case of systemic infection caused by Cryptococcus albidus in a cat. The patient had a history of paralysis of the hind legs and had been treated with prednisone for 1 month. Microscopic examination of a fine needle biopsy specimen from a right popliteal lymph node showed granulomatous inflammation with many encapsulated yeast cells. Moreover, microscopic examination of Indian ink preparations of the cerebrospinal fluid revealed encapsulated ovoid yeast cells. Thus this case was diagnosed to be cryptococcosis. However, the cat died after treatment for three days with voriconazole. Isolates recovered from samples of the cerebrospinal fluid, liver and spleen were identified as C. albidus by molecular analysis, as well as through morphologic and biochemical studies. Therefore, this case indicates that C. albidus should be considered as a potential feline pathogen.     

Cryptococcus neoformans capsule structure evolution in vitro and during murine infection

Cryptococcus neoformans capsule structure modifications after prolonged in vitro growth or in vivo passaging have been reported previously. However, nothing is known about the dynamics of these modifications or about their environmental specificities. In this study, capsule structure modifications after mouse passaging and prolonged in vitro culturing were analyzed by flow cytometry using the glucuronoxylomannan-specific monoclonal antibody E1. The capsule structures of strains recovered after 0, 1, 8, and 35 days were compared by using the level of E1-specific epitope expression and its cell-to-cell heterogeneity within a given cell population. In vitro, according to these parameters, the diversity of the strains was higher on day 35 than it was initially, suggesting the absence of selection during in vitro culturing. In contrast, the diversity of the strains recovered from the brain tended to decrease over time, suggesting that selection of more adapted strains had occurred. The strains recovered on day 35 from the spleen and the lungs had different phenotypes than the strains isolated from the brain of the same mouse on the same day, thus strongly suggesting that there is organ specificity for C. neoformans strain selection. Fingerprinting of the strains recovered in vitro and in vivo over time confirmed that genotypes evolved very differently in vitro and in vivo, depending on the environment. Overall, our results suggest that organ-specific selection can occur during cryptococcosis.     

Cryptococcus neoformans is a facultative intracellular pathogen in murine pulmonary infection

To produce chronic infection, microbial pathogens must escape host immune defenses. Infection with the human pathogenic fungus Cryptococcus neoformans is typically chronic. To understand the mechanism by which C. neoformans survives in tissue after the infection of immunocompetent hosts, we systematically studied the course of pulmonary infection in mice by electron microscopy. The macrophage was the primary phagocytic cell at all times of infection, but neutrophils also ingested yeast. Alveolar macrophages rapidly internalized yeast cells after intratracheal infection, and intracellular yeast cells were noted at all times of infection from 2 h through 28 days. However, the proportion of yeast cells in the intracellular and extracellular spaces varied with the time of infection. Early in infection, yeast cells were found predominantly in the intracellular compartment. A shift toward extracellular predominance occurred by 24 h that was accompanied by macrophage cytotoxicity and disruption. Later in infection, intracellular persistence in vivo was associated with replication, residence in a membrane-bound phagosome, polysaccharide accumulation inside cells, and cytotoxicity to macrophages, despite phagolysosomal fusion. Many phagocytic vacuoles with intracellular yeast had discontinuous membranes. Macrophage infection resulted in cells with a distinctive appearance characterized by large numbers of vacuoles filled with polysaccharide antigen. Similar results were observed in vitro using a macrophage-like cell line. Our results show that C. neoformans is a facultative intracellular pathogen in vivo. Furthermore, our observations suggest that C. neoformans occupies a unique niche among the intracellular pathogens whereby survival in phagocytic cells is accompanied by intracellular polysaccharide production.     

Diversity of the T-cell response to pulmonary Cryptococcus neoformans infection

Cell-mediated immunity plays an important role in immunity to the pathogenic fungus Cryptococcus neoformans. However, the antigen specificity of the T-cell response to C. neoformans remains largely unknown. In this study, we used two approaches to determine the antigen specificity of the T-cell response to C. neoformans. We report here that a diverse T-cell receptor (TCR) Vbeta repertoire was maintained throughout the primary response to pulmonary C. neoformans infection in immunocompetent mice. CD4+ T-cell deficiency resulted in relative expansion of all CD8+ T-cell subsets. During a secondary immune response, preferential usage of a TCR Vbeta subset in CD4+ T cells occurred in single individuals, but the preferences were "private" and not shared between individuals. Both CD4+ and CD8+ T cells from the secondary lymphoid tissues of immunized mice proliferated in response to a variety of C. neoformans antigens, including heat-killed whole C. neoformans, culture filtrate antigen, C. neoformans lysate, and purified cryptococcal mannoprotein. CD4+ and CD8+ T cells from the secondary lymphoid tissues of mice undergoing a primary response to C. neoformans proliferated in response to C. neoformans lysate. In response to stimulation with C. neoformans lysate, lung CD4+ and CD8+ T cells produced the effector cytokines tumor necrosis factor alpha and gamma interferon. These results demonstrate that a diverse T-cell response is generated in response to pulmonary C. neoformans infection.     

Disseminated pulmonary infection due to Cryptococcus neoformans in a non immunocompromised patient

We report a case of a primary pulmonary infection due to Cryptococcus neoformans developed in a 40 Year old immunocompetent and HIV negative man. Radiologic findings consisted in diffuse, bilateral reticular and nodular opacities. Bronchoscopy was normal and bronchoalveolar lavage showed numerous macrophages without associated pathogens. A thoracovideoscopy with an open lung biopsy showed numerous cryptococci, free in the alveoli or located within the macrophages. They were associated with an inflammatory infiltrate in the interalveolar spaces, predominantly composed of mononuclear cells. Ultrastructural study showed yeasts with numerous intracytoplasmic organites, a nucleus, a wall and a thick capsule. Pulmonary cryptococcosis is rare in immunocompetent hosts and can be difficult to diagnose since clinicoradiologic features observed in this cryptococcal infection mimic other infectious or neoplastic diseases.     

Life-threatening community-acquired methicillin-resistant Staphylococcus aureus infection in Australia

Eight patients with invasive bacteremic community-acquired methicillin-resistant Staphylococcus aureus infection in southeast Queensland, Australia, are reported. One patient died of septic shock. Haematogenous seeding to lungs, bone, and other sites was common. All isolates carried the virulence factor Panton-Valentine leukocidin and were either the southwest Pacific clone or the newly described Queensland clone. Clinicians should consider community-acquired methicillin-resistant Staphylococcus aureus infection in any patient presenting to hospital with severe staphylococcal sepsis or pneumonia.     

Role of the mannose receptor in a murine model of Cryptococcus neoformans infection

Cryptococcus neoformans is an encapsulated fungal pathogen with a predilection to infect persons with suppressed T-cell function. Cryptococcal mannoproteins (MP) are highly mannosylated antigens which elicit T-cell responses in infected mice and in convalescent patients. Key to the immunogenicity of MP is its capacity to bind to the conserved mannose receptor (MR), CD206, on dendritic cells (DCs). To test the role of the MR in the immune response to C. neoformans, wild-type and MR knockout (MR KO) mice were compared by using in vivo and ex vivo models of cryptococcosis. Following a pulmonary challenge with C. neoformans, MR KO mice died significantly faster than wild-type mice and had higher lung fungal burdens after 4 weeks of infection. Uptake of MP was similar when DCs obtained from wild-type and MR KO mice were compared. Additionally, MP did not upregulate the maturation markers major histocompatibility complex class II, CD86, and CD40 in either wild-type or MR KO DCs. However, MP stimulated lymphoproliferation in CD4(+) T cells obtained from the peripheral lymph nodes of infected wild-type but not MR KO mice. These studies demonstrate a nonredundant role for the MR in the development of CD4(+) T-cell responses to MP and protection from C. neoformans.