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PubMed1992

Cloning the Cryptococcus neoformans TRP1 gene by complementation in Saccharomyces cerevisiae.

We have cloned the phosphoribosyl anthranilate isomerase (PRAI)-encoding gene (TRP1) of Cryptococcus neoformans by genetic complementation in Saccharomyces cerevisiae. Sequence analysis of this gene revealed it to be 939 bp in length, and without known promoter or termination sequences. Unlike some of the filamentous fungi, where PRAI enzymatic activity is controlled by a trifunctional gene product, the C. neoformans PRAI appears to be unifunctional. PRAI of C. neoformans exhibits 39% amino acid (aa) sequence identity compared to the S. cerevisiae counterpart. The TRP1 gene of C. neoformans maps to different size chromosomes in strains with different serotypes. The cloning of this gene for vector constructions, and the demonstration that S. cerevisiae can be used as a surrogate for C. neoformans gene expression, should help with the molecular studies of this significant fungal pathogen in our increasing immunocompromised population.

Aldose-Ketose Isomerases↗
PubMed2006

Indinavir-treated Cryptococcus neoformans promotes an efficient antifungal immune response in immunosuppressed hosts.

A previous paper demonstrated that indinavir affects the virulence of Cryptococcus neoformans, thereby rendering the fungus more susceptible to killing by natural effector cells. This study demonstrates that inoculation of immunosuppressed mice with C. neoformans previously exposed to indinavir, in comparison to untreated C. neoformans, results in: (i) a more pronounced secretion of interleukin-12 by splenic dendritic cells; (ii) reduction of CD14 and Fc gammaRs expression on splenic dendritic cells, and upregulation of CD86 and CD40 molecules; (iii) enhancement of interferon-y and interleukin-2 production by splenic T cells and increase of their proliferation in response to fungal antigens; and (iv) survival from an otherwise lethal challenge, correlated with a drastic decrease in colony forming units from brain and liver. In conclusion, these data indicate that indinavir interaction with C. neoformans could be beneficial because of its direct influence on fungal virulence and blunting of the deleterious effects exerted by C. neoformans on host immune response. Thus, indinavir could be crucial in addressing the outcome of cryptococcosis in immunocompromised hosts.

Animals↗
PubMed1993

Analysis of ploidy and sexual characteristics of natural isolates of Cryptococcus neoformans.

We report here an extensive examination of the ploidy of a basidiomycetous yeast. The ploidy of 34 strains of Cryptococcus neoformans var. neoformans, isolated mostly from Japanese patients, was determined by means of quantitative fluorescence microscopy after DNA staining with propidium iodide. The sexual characteristics of the strains including the two tester strains were as follows. Twenty-four strains were of the heterothallic alpha type, 1 was of the heterothallic a type, and 2 were self fertile; the remaining 7 showed no sexual response. The following strains were found to be haploid: the heterothallic a strain, 20 of the 24 heterothallic alpha strains, and 3 of the 7 asexual strains. Thus, the C. neoformans strains were mostly haploid, as the sexual response of this organism suggests. Both of the self-fertile strains and four of the seven asexual strains were diploid. Unexpectedly, 4 of the 24 heterothallic alpha strains were diploid.

Cryptococcus neoformans↗
PubMed1994

Comparison of broth dilution and semisolid agar dilution for in vitro susceptibility testing of Cryptococcus neoformans.

We compared the in vitro activity of amphotericin B, flucytosine, itraconazole, fluconazole, ketoconazole and miconazole against 18 strains of Cryptococcus neoformans by using two methods: microbroth dilution and semisolid agar dilution. By both of the methods minimum inhibitory concentrations (MICs) showed a wide range for all antifungal agents but not for amphotericin B. Statistically significant differences between the two methods were observed only with amphotericin B and flucytosine, p = 0.048 and p = 0.045 respectively. Our study suggests that azole susceptibility testing for C. neoformans may be performed by the broth microdilution as well as the semisolid agar test. The choice of the method when testing amphotericin B and flucytosine is more problematic.

Amphotericin B↗
PubMed1997

Induction of human immunodeficiency virus type 1 expression in monocytic cells by Cryptococcus neoformans and Candida albicans.

Because candidiasis and cryptococcosis are common in human immunodeficiency virus (HIV)-infected persons, the effect of Cryptococcus neoformans and Candida albicans on HIV expression in monocytic cells was examined. Stimulation of the latently HIV-infected myelomonocytic cell line OM-10.1 with C. neoformans and C. albicans in the presence of pooled human serum caused a ratio-dependent increase in HIV production. Induction of HIV by C. neoformans was enhanced by anti-capsular antibody, while induction by both organisms was inhibited by anti-TNF-alpha antibody. In THP-1 cells transfected with HIV plasmid constructs, both organisms induced transcription from the HIV long terminal repeat that was dependent on intact NF-kappaB binding sequences. Thus, C. neoformans and C. albicans enhance HIV expression in monocytic cells through a TNF-alpha- and NF-kappaB-dependent mechanism. In HIV-infected patients, such enhancement may further impair host immunity and could accelerate the course of HIV disease.

Binding Sites↗
PubMed1970

Cryptococcus neoformans IV. The Not-So-Encapsulated Yeast.

Nonencapsulated cells of Cryptococcus neoformans which may have a diameter of less than 4 mum are capable of producing experimental cryptococcosis in mice. It has been established that this relatively small, nonencapsulated yeast can exist in soil. In this form, the organism could be more readily disseminated by air currents, and it is more likely to be inhaled into the lungs than the larger encapsulated yeast. Nonencapsulated cells produce sufficient capsular material to inhibit phagocytosis by 50% when incubated for 5 to 10 hr with human lung tissue in vitro. The general assumption that the encapsulated cells are the etiological agent of naturally acquired cryptococcosis may have to be revised.

Journal Article↗
PubMed2004

Steroid responsive late deterioration in Cryptococcus neoformans variety gattii meningitis.

The authors describe the clinical course of Cryptococcus neoformans variety gattii infection in a young immunocompetent man who had a late deterioration characterized by headaches, subarachnoid inflammation, hydrocephalus, and stroke that reproducibly responded to steroids. These findings, in combination with declining markers of CSF infection, are consistent with the late deterioration being caused by sterile arachnoiditis rather than ongoing infection.

Acetazolamide↗
PubMed2000

Extracellular activity in Cryptococcus neoformans strains isolated from AIDS patients and from environmental sources.

Nineteen Cryptococcus neoformans strains isolated from AIDS patients and 16 from bird droppings were tested for their extracellular activity. Typical enzymatic activity that was different from other medically important yeasts was found. The results obtained may indicate that there are new extracellular enzymatic activities that imply a relationship between C. neoformans and its virulence. A correlation among the different enzymatic activities was also investigated and according to the results obtained no relationship was observed among any of the recorded extracellular enzymatic activities. Research on C. neoformans extracellular enzymatic activity is useful not only to better understand its metabolism but in particular to establish a possible relationship between its virulence and pathogenicity.

Journal Article↗
PubMed1985

Detection of a Trichosporon beigelii antigen cross-reactive with Cryptococcus neoformans capsular polysaccharide in serum from a patient with disseminated Trichosporon infection.

Latex beads coated with anti-Cryptococcus neoformans antibody were agglutinated by serum from a bone marrow transplant recipient having a disseminated infection caused by Trichosporon beigelii. The cryptococcal latex agglutination titer in the serum of the patient rose to 1:2,560 by the time of his death. Necropsy confirmed the disseminated Trichosporon infection and absence of C. neoformans. Cell wall extracts of the isolate of the patient and two additional strains of T. beigelii agglutinated anti-Cryptococcus-coated latex beads. The antigen in the serum of the patient and in the extracts responsible for the agglutination was not destroyed by proteolytic enzymes or heat. A single antigen reactive with rabbit anti-Trichosporon serum could be identified in the serum of the patient and the cell wall extracts by rocket immunoelectrophoresis and crossed immunoelectrophoresis. Rocket immunoelectrophoresis and indirect fluorescent-antibody staining demonstrated that anti-Trichosporon antibody recognized the capsular polysaccharide of C. neoformans.

Adult↗
PubMed1997

In vitro activity of fluvastatin, a cholesterol-lowering agent, and synergy with flucanazole and itraconazole against Candida species and Cryptococcus neoformans.

Fluvastatin, a cholesterol-lowering drug, exhibited minimal activity (MICs of 64 to >128 microg/ml) against Candida species and Cryptococcus neoformans. When fluvastatin was combined with fluconazole or itraconazole, both synergistic and additive effects were noted (fractional inhibitory concentration indices of < or = 0.156 to 0.625; fractional lethal concentration indices of < or = 0.156 to 0.75). This combined fungicidal activity was confirmed by time-versus-killing studies.

Anticholesteremic Agents↗
PubMed1968

Fluorescent-antibody reagent for the identification of Cryptococcus neoformans.

A sensitive and diagnostically applicable conjugate for the rapid and accurate detection and identification of Cryptococcus neoformans has been developed. C. neoformans rabbit antisera were produced by 14 daily intravenous injections of 36 million cells for a total dosage of approximately 500 million cells. Cross-staining reactions with species of Cryptococcus other than C. neoformans, as well as with Candida species, were eliminated by adsorption of the C. neoformans conjugate with cells of C. diffluens and C. krusei.

Adsorption↗
PubMed1981

Distribution of Cryptococcus neoformans in a natural site.

Pigeon droppings in a vacant tower were assayed for the number and size of viable cells of Cryptococcus neoformans. The dry, thinly scattered floor debris contained 2.6 x 10(6) viable cells per g--300 times more cells than were cultured from a large, compact pile of pigeon droppings (7.4 x 10(3) cells per g). Aerosols generated from floor debris containing pigeon droppings had an average of 360 viable cells in 31 liters of air; 27 of these cells (7.5%) were 1.1 to 3.3 micrometers in diameter and, therefore, capable of human lung deposition. Environmental factors which may influence the distribution, survival, and proliferation of C. neoformans in nature are discussed.

Aerosols↗
PubMed2003

In vitro interaction of flucytosine with conventional and new antifungals against Cryptococcus neoformans clinical isolates.

Combinations of flucytosine with conventional and new antifungals were evaluated in vitro against 30 clinical isolates of Cryptococcus neoformans. Synergy determined by checkerboard analysis was observed with combinations of fluconazole, itraconazole, voriconazole, amphotericin B, and caspofungin with flucytosine against 77, 60, 80, 77, and 67% of the isolates, respectively. Antagonism was never observed. Killing curves showed indifferent interactions between triazoles and flucytosine and synergy between amphotericin B and flucytosine.

Antifungal Agents↗
PubMed1993

Susceptibilities of serial Cryptococcus neoformans isolates from patients with recurrent cryptococcal meningitis to amphotericin B and fluconazole.

Amphotericin B and fluconazole susceptibilities of 13 Cryptococcus neoformans isolates from five patients with recurrent cryptococcal meningitis were determined. For each patient, serial isolates showed no increase in antibiotic resistance relative to the initial isolate. For these patients, recurrent disease was not due to drug resistance but may reflect changes in immune function and/or poor compliance.

AIDS-Related Opportunistic Infections↗
PubMed1995

Monoclonal antibody mediated capsular reactions (Quellung) in Cryptococcus neoformans.

Capsular reactions ('Quellung') visible by light microscopy were observed when capsule-binding monoclonal antibody (mAb) was added to Cryptococcus neoformans yeast cells. Capsular reactions were observed with capsule-binding IgM, IgG1, IgG2a, IgG2b, IgG3 and IgA mAbs. Scanning electron microscopy revealed that mAb binding produced a structural change in the fibrillar network of the capsule. The occurrence of capsular reactions with mAbs indicate that this phenomenon can be produced by the binding of antibody to a single epitope.

Animals↗
PubMed1973

Variables influencing susceptibility testing of Cryptococcus neoformans to 5-fluorocytosine.

The minimum inhibitory concentration (MIC) of 5-fluorocytosine (5-FC) was determined for 65 isolates of Cryptococcus neoformans by using a twofold serial tube dilution method. The MIC was profoundly influenced by incubation temperature, inoculum size, and duration of incubation. By using a standard set of test conditions, 100% of 49 pretreatment isolates of C. neoformans were susceptible to 10 mug of 5-FC per ml or less, and 9 (56%) of 16 isolates recovered during or after 5-FC therapy were massively drug resistant (MIC > 320 mug/ml). With the standard test conditions recommended here, the tube dilution method was found to be both accurate and reproducible, and the results correlated with the treatment status of patients.

Antifungal Agents↗
PubMed1998

Specific antibody to Cryptococcus neoformans alters human leukocyte cytokine synthesis and promotes T-cell proliferation.

Addition of a monoclonal antibody which binds the Cryptococcus neoformans capsule to suspensions of human monocytes, T lymphocytes, and cryptococcal cells (i) enhances interleukin-1beta (IL-1beta), tumor necrosis factor alpha, and IL-2 production; (ii) reduces IL-10 secretion; and (iii) promotes T-cell proliferation. The ability of specific antibody to influence cytokine production and lymphoproliferation suggests a mechanism by which humoral immunity can influence cell-mediated immunity.

Antibodies, Fungal↗
PubMed1998

[The evaluation of the specific type of capsular polysaccharide of Cryptococcus neoformans as an immunogen and positive-control antigen].

The specific type of capsular polysaccharide of an autochthonous strain of Cryptococcus neoformans var. neoformans was obtained by using the method of selective precipitation with hexadimethrine bromide. The capsular polysaccharide was matched to lamb's erythrocytes and it was used as an immunogen in rabbits. Antibody titres of up to 1:32 were attained. Doble serial dilutions of the capsular polysaccharide were evaluated as positive control antigen by contraimmunoelectrophoresis, latex and ELISA techniques, showing biological activity.

Animals↗