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PubMed1990

Cytoplasmic components of natural killer cells limit the growth of Cryptococcus neoformans.

Murine natural killer (NK) cell-mediated inhibition of growth of a yeast-like target cell, Cryptococcus neoformans, was completely abrogated by blocking the effector cell secretory process with monensin. Therefore, further studies were performed to determine the ability of various cytoplasmic fractions of NK cells to mediate inhibition of cryptococcal growth. Percoll-fractionated homogenates of rat LGL tumor cells demonstrated that the granule-containing fractions plus three additional sets of less dense cytoplasmic fractions displayed anti-cryptococcal activity; whereas only the cytoplasmic granule-containing fractions had cytotoxic activity against YAC-1 tumor cell and sheep erythrocyte targets. Maximal cryptococcal growth inhibition induced by LGL granules occurred after a 1 h incubation, required the presence of Ca2+ (1.0 mM) or Mg2+ (0.5 mM or 5.0 mM), and was completely abrogated in the presence of rabbit anti-LGL granule IgG. Cytolysin, the granule component which mediates tumor cell and sheep erythrocyte lysis, effectively limited the growth of cryptococci. Since Percoll gradient fractionation of the LGL homogenates demonstrated three separate peaks of anti-cryptococcal activity other than the granule peak, it is possible that the cytolysin-containing granules are not the only subcellular component of NK cells playing a role in inhibition of C. neoformans growth.

Animals↗
PubMed1986

[Cryptococcus neoformans meningoencephalitis in AIDS].

The risk for AIDS patients from Cryptococcus neoformans is outlined on the basis of a case report on a 28-year old male patient whose disease was complicated by cryptococcosis. Beside the description of the diagnosis of cryptococcosis (demonstration of the agent and its antigen), epidemiological associations (habitat of Cr. neoformans in fecal matter of birds) and the clinically, mostly not recognized, route of infection via the lungs is stressed. The effective therapy with the combination of amphotericin B and 5-flucytosine, which also in this case has been successful is described from the clinical and microbiological angles. Finally, proposals for the prevention of Cr. neoformans infections in AIDS patients and for a special mycological surveillance directed at this fungus are made.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Intracellular crystal formation as a mechanism of cytotoxicity in murine pulmonary Cryptococcus neoformans infection.

Rod-like crystalline structures formed during eosinophilic Cryptococcus neoformans pneumonia in C57BL/6 mice. Crystals were found associated with yeast cells and free in host cell cytoplasm. The crystals apparently formed because of the interaction of a host protein with the cryptococcal polysaccharide. Crystal formation likely contributes to pathogenesis by causing cellular damage.

Animals↗
PubMed2001

Cutaneous cryptococcosis due to Cryptococcus neoformans var. gattii.

A case of cutaneous cryptococcosis due to Cryptococcus neoformans var. gattii in an immunocompetent host is presented. In addition a review of the literature on this subject was carried out and a brief comment made on occurrence of the variety gattii in Brazil.

Journal Article↗
PubMed1993

A strain of urease negative Cryptococcus neoformans isolated from the environment in China.

This is the first report of a strain of urease negative Cryptococcus neoformans isolated from the environment in China. The colonies of this isolate showed brown pigmentation on cornmeal agar with 300 micrograms/ml caffeic acid, but failed to hydrolyze urea. Microbiological identification and pathogenicity tests in mice confirmed this as a strain of C. neoformans. A similar strain had reportedly been isolated from an AIDS patient.

Animals↗
PubMed1999

In vitro and in vivo stability of a Cryptococcus neoformans [corrected] glucuronoxylomannan epitope that elicits protective antibodies.

The monoclonal antibody (MAb) 2H1 defines an epitope in Cryptococcus neoformans capsular glucuronoxylomannan (GXM) that can elicit protective antibodies. In murine models of cryptococcosis, MAb 2H1 administration prolongs survival and reduces fungal burden but seldom clears the infection. The mechanism by which C. neoformans persists and escape antibody-mediated clearance is not understood. One possibility is that variants that do not bind MAb 2H1 emerge in the course of infection. Using an agglutination-sedimentation protocol, we recovered a variant of strain 24067 that did not agglutinate, could not be serotyped, and had marked reduction in GXM O-acetyl groups. Binding of MAb 2H1 to 24067 variant cells produced a different immunofluorescence pattern and lower fluorescence intensity relative to the parent 24067 cells. Addition of MAb 2H1 to 24067 variant cells had no effect on cell charge. Phagocytic assays demonstrated that MAb 2H1 was not an effective opsonin for the 24067 variant. The 24067 variant was less virulent than the 24067 parent strain in mice, and MAb 2H1 administration did not prolong survival in animals infected with the variant strain. To investigate whether variants which do not bind MAb 2H1 are selected in experimental infection, three C. neoformans strains were serially passaged in mice given either MAb 2H1 or no antibody. Analysis of passaged isolates by agglutination assay, flow cytometry, and indirect immunofluorescence revealed changes in MAb 2H1 epitope expression but no clear trend with regards to gain or loss of MAb 2H1 epitope. C. neoformans variants with reduced MAb 2H1 epitope content can be isolated in vitro, but persistence of infection in mice given MAb 2H1 does not appear to be a result of selection of escape variants that lack the MAb 2H1 epitope.

Animals↗
PubMed2006

Cryptococcus neoformans population includes hybrid strains homozygous at mating-type locus.

Recent attempts to characterise the hybrid strains of Cryptococcus neoformans have led to the identification of a cryptic population of hybrid strains ('H strains') with double DNA content but only a single mating-type allele. To verify a set of hypotheses concerning their origin, we investigated 14 previously isolated H strains and ten F1-progeny strains arising from H99 and JEC20 mating. The double DNA content was tested by flow cytometry; the presence of only one mating type was tested by amplifying 12 mating-type-specific genes and one gene unlinked with the mating-type locus (URA5). Analysis of the F1 progeny identified two H strains, and electrophoretic karyotyping confirmed the occurrence of genetic recombination. The simultaneous presence of the homozygous and heterozygous loci, and the fact that all of the F1-progeny strains presented a recombinant karyotype, suggest that the H strains originated from the post-meiotic random fusion of two of the four recombinant nuclei. Further studies are required to elucidate the role of the homozygous mating-type loci in the virulence of C. neoformans.

Crosses, Genetic↗
PubMed1994

Cryptococcus neoformans infection can elicit protective antibodies in mice.

An IgG1 monoclonal antibody generated from a mouse infected with Cryptococcus neoformans modified the course of intravenous cryptococcal infection in A/J mice by prolonging survival and reducing lung fungal burden, brain mass, and serum polysaccharide levels. The results demonstrate that C. neoformans infection can elicit useful antibodies.

Animals↗
PubMed1993

Conditions affecting the adherence of Cryptococcus neoformans to rat glial and lung cells in vitro.

Conditions affecting the adherence of clinical isolates of Cryptococcus neoformans to rat glial and lung cell cultures were studied. Adherence to glial cells was a time-dependent process that was affected by the yeast culture age and growth temperature. The most adherent yeasts were those from 48 h cultures grown at 37 degrees C. Formalin-treating the yeasts did not affect adherence but formalin-treating the glial monolayers prevented yeast binding. Treating the yeasts with trypsin reduced adherence to glial monolayers, indicating that the yeast adhesin had a trypsin-labile protein component. Certain carbohydrates inhibited cryptococcal adherence to glial and lung cells in a time and concentration-dependent manner. Of the carbohydrates tested, N-acetyl-D-glucosamine, sucrose, lactose, sorbitol and myo-inositol were the most inhibitory, while mannose, galactose and xylose were the least inhibitory. The results collectively indicated that the mechanisms of adherence of C. neoformans to lung cells were similar to those of glial cells and that both involved a protein-containing adhesin on the cryptococcal surface that was expressed only after growth at 37 degrees C. Carbohydrate receptors also appeared to be involved with these interactions.

Animals↗
PubMed1999

In-vitro and in-vivo activities of SCH56592 against Cryptococcus neoformans.

The in-vitro and in-vivo activities of SCH56592, a triazole antifungal agent, against Cryptococcus neoformans were studied. MIC(90)s for 16 strains of C. neoformans measured by microdilution method (NCCLS M27-A) were 1 mg/L of SCH56592, 16 mg/L of fluconazole, 32 mg/L of flucytosine, and 0.5 mg/L of amphotericin B. In a murine model of pulmonary cryptococcosis, 10 mg/kg of SCH56592 was more effective than fluconazole. The fungal burden of the lung of animals treated with SCH56592 was significantly reduced (7.40 +/- 0.21 log(10) cfu/g), as compared with fluconazole (7.77 +/- 0.07 log(10) cfu/g) and control (7.79 +/- 0.1 log(10) cfu/g) (P < 0.01). For C. neoformans-infected mice following 7 days treatment with 10 mg/kg of SCH56592 there was a higher concentration in lung (3.36 +/- 0.62 ng/ml) than in plasma (2.16 +/- 0.86 ng/mL), and this was maintained for 12 h after administration.

Animals↗
PubMed2004

B cell response during infection with the MAT a and MAT alpha mating types of Cryptococcus neoformans.

In the present study, we compared the B cell response of BALB/c and C57Bl/6 mice during Cryptococcus neoformans infection. This response was investigated using virulent serotype D forms of mating types alpha and a (MAT alpha and MAT a). C57Bl/6 mice showed massive (mainly cerebral) infection by both types, while BALB/c were resistant to infection. Some resistance of C57Bl/6 mice was induced by previous immunization with the capsular polysaccharide from MAT alpha. Passive immunization of C57Bl/6 mice with purified antibody (Ab) obtained from capsular polysaccharide-immunized mice also increased resistance to infection. Both mouse strains showed comparable low IgM response to the capsular polysaccharide from MAT alpha, and only C57Bl/6 mice produced IgM to the polysaccharide of MAT a. Comparable levels of different immunoglobulin (Ig) isotypes against capsular components of MAT alpha and MAT a were detected, and the response of C57Bl/6 mice was higher when compared to that of BALB/c mice. FACS analysis indicated an increase in the percentage of a high-granulosity (side-scatter) splenic subpopulation and in the percentage of splenic Gr-1+ cells in infected C57Bl/6 mice. In addition, the percentage of follicular splenic B cells was decreased after C. neoformans infection of C57Bl/6 mice. This response was more pronounced when we investigated infection induced by the MAT a mating type. Taken together, our results indicate that capsular polysaccharide derived from MAT alpha and MAT a types of C. neoformans have a stimulatory effect upon B cells but that there is no correlation between resistance of BALB/c mice and Ab production. However, the increase in resistance of C57Bl/6 mice parallels the production of Abs and a major change in splenic cell populations.

Animals↗
PubMed1981

Roles of macrophage Fc and C3b receptors in phagocytosis of immunologically coated Cryptococcus neoformans.

I have studied the roles of macrophage Fc and C3b receptors in the cell's interaction with encapsulated Cryptococcus neoformans and have defined the effects of a lymphokine that enhances macrophage complement receptor function, the effects of ingestion of soluble immune complexes, and the effects of corticosteroid treatment upon the ability of macrophages to phagocytize cryptococci via these receptors. Neither uncoated nor C3-coated cryptococci were phagocytized, whereas IgG-coated cryptococci were avidly phagocytized by mouse peritoneal macrophages. Treatment of macrophages with the lymphokine enabled them to ingest C3-coated cryptococci. Prior ingestion of soluble immune complexes severely compromised macrophages' ability to phagocytize cryptococci via their Fc receptors but did not affect their ability to ingest cryptococci via their complement receptors. Corticosteroid treatment severely impaired the ability of macrophages to respond to the lymphokine. Based upon these experimental observations, I have constructed a model for normal host defense mechanisms against disease due to C. neoformans.

Animals↗
PubMed1998

Analysis of HLA association in susceptibility to infection with Cryptococcus neoformans var. gattii in a Papua New Guinean population.

The possible association between susceptibility to infection with Cryptococcus neoformans var. gattii and HLA phenotype was examined in a group of Papua New Guinean patients. There was no evidence for a statistically significant association between susceptibility to infection and HLA class I and HLA class II phenotypes, although analysis of data which had not been subjected to the appropriate Bonferroni correction factor suggested a trend for susceptibility linked to HLA B*5601.

Cryptococcosis↗
PubMed1998

Meningitis due to a combined infection with Cryptococcus neoformans and Streptococcus pneumoniae in an AIDS patient.

We report on a case of dual infection with Cryptococcus neoformans and Streptococcus pneumoniae in the cerebrospinal fluid of a patient with AIDS. To our knowledge this represents the first case to be reported in the English literature. In immunocompromised patients the importance of performing both the Gram- and India-ink stain and cryptococcal antigen test on CSF specimens with completely normal biochemical and cellular parameters is emphasized.

AIDS-Related Opportunistic Infections↗
PubMed2005

Structural and functional characterization of glycosylation in an immunoglobulin G1 to Cryptococcus neoformans glucuronoxylomannan.

Analysis of the N-linked oligosaccharides of the murine IgG1 monoclonal antibody (mAb) to Cryptococcus neoformans by LC/MS revealed five different core fucosylated, biantennary complex-type oligosaccharides at Asn-293, with the major species being a mono-galactosylated oligosaccharide with the glycosyl composition of Hex4HexNAc4Fuc (39% of the total glycan pool). The primary sequence predicted from nucleic acid sequencing differed from that measured by mass spectrometry at position 33 (ASN to ASP), a finding that may represent post-translational modification caused by spontaneous ASP deamination. Analysis of mAb 18B7 from three hybridoma clones revealed the same heterogenous N-glycan pattern, indicating that diversity in oligosaccharide structures originated from individual cells. The binding of native and de-glycosylated mAb 18B7 to cryptococcal Ag was comparable but the de-glycosylated 18B7 had shorter serum half-life and did not activate complement (C). De-glycosylated mAb 18B7 was opsonic for C. neoformans with murine macrophages through a mechanism that involved C-independent ingestion through the C receptor. Passive administration of de-glycosylated mAb 18B7 mediated comparable protective efficacy to the native mAb in mice with lethal infection. The results imply that the contribution of N-glycan structure to immunoglobulin function varies depending on the Ag-Ab system.

Amino Acid Sequence↗
PubMed2000

A rapid method for detecting extracellular proteinase activity in Cryptococcus neoformans and a survey of 63 isolates.

A rapid method to detect extracellular proteolytic activity around colonies of Cryptococcus neoformans was developed with tannic acid used to complex with residual protein in a solid medium. A survey was conducted with 32 isolates of C. neoformans var. gattii and 31 isolates of C. neoformans var. neoformans which were cultured on medium containing gelatin as the sole nitrogen source. The annulus of clearing around fungal colonies was > 1.2 mm in 24 (77%) isolates of C. neoformans var. neoformans compared with only 7 (22%) isolates of C. neoformans var. gattii. There was no difference in proteolytic activity between environmental and human clinical isolates of C. neoformans. However, there was a difference between the size of the annulus around animal isolates of C. neoformans var. neoformans and isolates of the same variety from other sources. The annuli around the 14 animal isolates were all >1.2 mm, while 7 (70%) of 10 human clinical isolates and only 3 (43%) of 7 environmental isolates were scored in the high proteinase range. A difference between the genetic types (as characterised by RAPD typing) of C. neoformans var. gattii was also evident with 17 (77%) of 22 VG-I isolates having a small annulus compared with only 1 (17%) of 6 VG-II and VG-III isolates with annuli of similar size. Relatively low proteinase production by C. neoformans var. gattii may reduce local and systemic spread of infection in mammalian hosts.

Animals↗
PubMed1977

Evaluation of a caffeic acid-ferric citrate test for rapid identification of Cryptococcus neoformans.

An evaluation of a rapid caffeic acid-ferric citrate paper disk test for the identification of Cryptococcus neoformans, using 474 isolates of yeasts and yeastlike organisms, showed that 96.6, 97.7, and 98.3% of 176 isolates of C. neoformans produced brown to dark-brown pigment on disks incubated for 6 h at room temperature, 30 degrees C, and 37 degrees C, respectively. All C. neoformans produced brown to dark-brown pigment within 24 h. However, nonspecific pigmentation was encountered at all temperatures of incubation with one isolate of Trichosporon cutaneum and, at room temperature only, with one isolate of C. luteolus after 6 h. Other genera of yeasts produced similar pigmentation after 24 h at all temperatures. The age of the cultures tested or the types of media used before testing did not significantly affect the ability of C. neoformans to produce pigmentation at 37 degrees C. A positive test may prove useful for presumptive identification of C. neoformans, but a negative reaction should not be used to rule out an identification of this yeast. Since a number of false-negative and false-positive tests occur, it is necessary to confirm, by other biochemical tests, the identification of all organisms suspected of being C. neoformans, to reduct the serious risk of missing or misidentifying this important pathogen.

Caffeic Acids↗