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Biomedical subjects

A Cassone

Publications and source records attributed to A Cassone.

At least 109 records · Page 6Linked to original sources
PubMed1992

The secretion of aspartyl proteinase, a virulence enzyme, by isolates of Candida albicans from the oral cavity of HIV-infected subjects.

Prevalence, serotype and in vitro secretion of aspartyl proteinase, a virulence enzyme, were studied in Candida isolates from the oral cavity of 337 HIV-infected subjects. Controls were 95 age-sex-matched HIV- (seronegative) subjects, belonging to either HIV-risk categories (47) or to the normal, general population (48). Fungi were isolated from 155 HIV+ subjects. C. albicans was the most prevalent species (85.8% of all isolates). 94.6% of C. albicans isolates were serotype A and all were agglutinated by a monoclonal antibody (AF1) directed against a major mannoprotein immunogen of the candidal cell wall, confirming previous results with C. albicans isolates from non-immunodeficient subjects. With regard to the stage of HIV infection, there were no statistically significant differences in the incidence of oral Candida carriage between asymptomatic (stage II) HIV+ and HIV- subjects, and between stage II and lymphadenopathic (stage III) individuals. Also, the low (3.8%) incidence of oral candidiasis in the subjects of the latter stage was insignificant with respect to stage II subjects. However, the incidence of C. albicans in stage IV (AIDS) subjects (46.8%) was significantly higher than in all other subjects, and in almost all cases, fungal isolation was accompanied by oral thrush and lower CD4+ lymphocyte counts (less than 400 x 10(6)/L). All isolates of C. albicans were proteolytic in vitro, as assessed by scoring the proteinase activity on BSA agar and monitoring the secreted proteinase antigen by a highly sensitive (1 ng) and specific immunoenzymatic assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1992

Glucan synthesis and its inhibition by cilofungin in susceptible and resistant strains of Candida albicans.

The lipopeptide antimycotic agent, cilofungin, at a dose of 20 micrograms ml-1, inhibited beta 1-3 glucan synthesis in a drug-susceptible strain (3153; minimum inhibitory concentration (MIC) < 1 microgram ml-1) as well as in a drug-resistant strain of Candida albicans (CA-2, derived from 3153 by nitrosoguanidine mutagenesis; MIC > 50 micrograms ml-1). This was demonstrated for both whole cells under growing and non-growing conditions, and during protoplast regeneration. However, time-effect experiments, during growth of a CA-2 culture initially exposed to an inhibitory dose of cilofungin, showed that this strain was able to progressively regain both glucan synthesis and a growth rate comparable to that of cultures that had not been treated with the drug. This recovery was not attributable to cilofungin instability or degradation within the CA-2 culture. Our study suggests the existence of an as yet unknown drug-related and/or cell-related factor(s) modulating the inhibition of glucan synthesis, and then contributing to the actual inhibitory effects of cilofungin in C. albicans.

Antifungal Agents↗
PubMed1992

Fluconazole treatment of catheter-related right-sided endocarditis caused by Candida albicans and associated with endophthalmitis and folliculitis.

An unusual case of catheter-related right-sided endocarditis, endophthalmitis, and extensive folliculitis, apparently caused by a single DNA biotype of Candida albicans, was successfully treated with a 6-month course of fluconazole plus two intravitreous doses of amphotericin B. The patient was a 21-year-old man who underwent colectomy for diffuse polyposis and developed the clinical syndrome just described following total parenteral nutrition for the treatment of purulent anal fistulas. Fluconazole was initially administered at a daily dose of 200 mg, with 600 mg daily given after 4 weeks. Clinical improvement resulted, with no relapse during 14 months of follow-up. Sequential measurements by an enzyme-linked immunosorbent inhibition assay demonstrated that levels of circulating mannoprotein antigen of C. albicans fell from 75 ng/mL to less than 1 ng/mL after the institution of fluconazole therapy. These observations seem to confirm previous reports on the efficacy of fluconazole as sole therapy for candidal endocarditis and suggest a role for serological studies in clinical monitoring of severe candidal infections.

Adult↗
PubMed1992

Identification of a mannoprotein fraction from Candida albicans that enhances human polymorphonuclear leukocyte (PMNL) functions and stimulates lactoferrin in PMNL inhibition of candidal growth.

Mannoprotein fractions of Candida albicans were assayed for their effects on the anticandidal activity of human polymorphonuclear leukocytes (PMNL). One fraction, MP-F2, enhanced PMNL inhibition of candidal growth in vitro as potently as bacterial lipopolysaccharide (LPS), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-8. MP-F2-mediated PMNL activation was manifested on yeast and mycelial forms of the fungus, required the integrity of the mannan, and was due to an increase in the actual number of phagocytic PMNL rather than to a greater ingestion of fungal cells by each individual neutrophil. While not inducing augmented O2 production or degranulation of azurophilic granules, MP-F2 strongly stimulated the release of lactoferrin. Lactoferrin inhibited candidal growth in the absence of PMNL, and anti-lactoferrin antibodies reversed both this inhibition and the PMNL activation by MP-F2, GM-CSF, and LPS. Thus, PMNL may be activated by relevant candidal mannoproteins, and release of lactoferrin may add to other antimicrobial mechanisms of PMNL for the control of candidal infections.

Antibodies↗
PubMed1992

Lactoferrin release and interleukin-1, interleukin-6, and tumor necrosis factor production by human polymorphonuclear cells stimulated by various lipopolysaccharides: relationship to growth inhibition of Candida albicans.

Lipopolysaccharides (LPSs) from Escherichia coli, Serratia marcescens, and Salmonella typhimurium, at doses from 1 to 100 ng/ml, strongly enhanced growth inhibition of Candida albicans by human polymorphonuclear leukocytes (PMN) in vitro. Flow cytometry analysis demonstrated that LPS markedly augmented phagocytosis of Candida cells by increasing the number of yeasts ingested per neutrophil as well as the number of neutrophils capable of ingesting fungal cells. LPS activation caused augmented release of lactoferrin, an iron-binding protein which itself could inhibit the growth of C. albicans in vitro. Antibodies against lactoferrin effectively and specifically reduced the anti-C. albicans activity of both LPS-stimulated and unstimulated PMN. Northern (RNA blot) analysis showed enhanced production of mRNAs for interleukin-1 beta, tumor necrosis factor alpha, and interleukin-6 and in neutrophils within 1 h of stimulation with LPS. The cytokines were also detected in the supernatant of the activated PMN, and their synthesis was prevented by pretreatment of LPS-stimulated PMN with protein synthesis inhibitors, such as emetine and cycloheximide. These inhibitors, however, did not block either lactoferrin release or the anti-Candida activity of LPS-stimulated PMN. These results demonstrate the ability of various bacterial LPSs to augment neutrophil function against C. albicans and suggest that the release of a candidastatic, iron-binding protein, lactoferrin, may contribute to the antifungal effect of PMN. Moreover, the ability to produce cytokines upon stimulation by ubiquitous microbial products such as the endotoxins points to an extraphagocytic, immunomodulatory role of PMN during infection.

Candida albicans↗
PubMed1991

In vitro production of tumor necrosis factor by murine splenic macrophages stimulated with mannoprotein constituents of Candida albicans cell wall.

Mannoprotein components from Candida albicans were investigated for their ability to induce production of tumor necrosis factor (TNF) by cultured splenocytes from naive or Candida-infected mice. Two chromatographically separated mannoproteins preparations, designated F1 and F2, were as able as the heat-inactivated Candida cells to induce the production of TNF from splenocytes of naive animals. In addition, they caused a significant augmentation of basic TNF secretion by splenocytes of Candida-infected animals. Experiments using plastic and/or nylon wool adherence, as well as treatments with antibodies depleting T or NK cells, consistently indicated that most if not all TNF was produced by splenic macrophages. In cultures of splenocytes from Candida-infected mice, mannoprotein addition also stimulated interferon-gamma (IFN-gamma) production by Thy 1.2 positive cells. Depletion of these cells or addition of anti-IFN-gamma antibodies abolished IFN production and reduced TNF secretion by adherent cells to the levels found in the cultures of mannoprotein-stimulated spleen cells from naive mice. These data add further evidence to the immunomodulatory properties possessed by some cell wall constituents of the human commensal microorganism C. albicans and suggest that IFN-gamma is endowed with a regulatory role in TNF production by mouse macrophages in vitro.

Animals↗
PubMed1991

Interferon induction in rabbits after intraduodenal administration of a phosphorylated glucomannan-protein fraction of the cell wall of Candida albicans.

The aim of this work was to demonstrate whether a glucomannan protein fraction (GMP) of Candida albicans cell wall could induce interferon after intraduodenal administration in normal rabbits and rabbits immunized against C. albicans. For this purpose we collected simultaneously plasma and abdominal lymph for 10 h after the administration of the inducer. We observed a peak of antiviral activity in the lymph 4 h after intraduodenal administration of 20 mg GMP dissolved in saline to 6 normal rabbits. Immunized rabbits (anti-GMP titres greater than 1024) responded earlier (peak after 2 h) and more intensely; analysis of the values of the areas under the curve indicated that the IFN response in the lymph of immunized rabbits was significantly higher (P less than 0.0025) than in normal rabbits. Antiviral activity was absent in plasma in all cases. Preliminary characterization of the IFN activity has shown it to be trypsin-sensitive, acid and heat stable, and species-specific.

Animals↗
PubMed1991

Cell mediated cytotoxicity and cytokine production in peripheral blood mononuclear cells of glioma patients.

A mannoprotein preparation (MP) from Candida albicans induced MHC-unrestricted cytotoxicity in peripheral blood mononuclear cells (PBMC) from healthy subjects, but not in those from glioma-bearing subjects. The two groups of subjects did not significantly differ in the number of cells bearing typical natural killer (NK) markers (both in resting and MP stimulated PBMC) and NK activity. However, interferon gamma (IFN-gamma) production was in tumour patients minimal or significantly reduced, as compared to healthy subjects, following PBMC stimulation by MP or phytohaemoagglutinin, respectively. In addition, minimal, if any, stimulation of interleukin-2 (IL-2) production was achieved in MP stimulated PBMC from glioma patients. Considering the pivotal role of the above cytokines in immune responses, particularly in those concerning generation of antitumour effectors, our results consistently suggest that defective cytokine production is one possible mechanism of immunological impairment in glioma patients. They also provide indirect support for a possible clinical use of IFN-gamma as an immunopotentiating agent in gliomatous subjects.

Adult↗
PubMed1991

Biochemical and antigenic characterization of mannoprotein constituents released from yeast and mycelial forms of Candida albicans.

Yeast or mycelial cultures of Candida albicans released comparable amounts of Concanavalin A-reactive mannoprotein material after 24-h of growth, and in both cases this material showed a qualitatively similar SDS-PAGE pattern, with predominantly polydisperse constituents of high molecular mass. The two secretion mixtures also showed similar reactivity by ELISA with serum from a subject with high titre anti-Candida antibodies, as well as with an anti-Candida hyperimmune antiserum raised in rabbits. Both secreted extracts were separated by ion-exchange chromatography into two major fractions (designated F1 and F2), each containing mannoprotein antigens recognized by rabbit and human sera, although the immunoreactivity of the two fractions from the two growth forms was not uniform. The mannoproteins released from mycelial cultures, in particular those present in the F1 fraction, were poorly reactive or not reactive at all in ELISA with a monoclonal antibody (mAbAF1) which strongly recognized the material released from yeast cultures. Immunoblots of the more acidic, more antigenic F2 fractions with mAbAF1 and polyclonal anti-Candida antisera demonstrated that the monoclonal antibody did not recognize several mannoprotein molecules which were recognized by the polyclonal antibodies, in particular a 45-47 kDa component present only in the secreted extract from mycelium. A quantitative ELISA-inhibition method showed that the rate of release of mannoprotein antigen during growth in the yeast form was either constant (as assayed with polyclonal antibodies) or fluctuated without any definite trend (as seen with mAbAF1). On the other hand, cultures of mycelial cells exhibited an early (90 min) peak of antigen release, followed by either a decrease to a rate corresponding to that of yeast cells (with polyclonal antibodies) or a total lack of secretion (with mAbAF1). This modulation in the secretion of mAbAF1 reactive molecules was temporarily associated with germ tube emergence-elongation, and was not observed in an agerminative mutant of C. albicans grown under germination permissive conditions. These results highlight the dynamic aspects of the secretion of specific mannoprotein epitopes released from C. albicans during hyphal growth, and the direct relationship between this release and the dynamic expression of the same epitopes on the cell surface demonstrated previously.

Antigens, Fungal↗
PubMed1991

Proliferative and cytotoxic responses to mannoproteins of Candida albicans by peripheral blood lymphocytes of HIV-infected subjects.

Mucosal candidiasis is one of the first opportunistic diseases in HIV-infected subjects. In order to understand the relationship between this disease and immunodeficiency to chemically defined, immunodominant Candida antigens, a mannoprotein fraction from C. albicans cell wall (GMP) was used to analyse proliferative and non-MHC-restricted cytotoxic responses of peripheral blood mononuclear cells (PBMC) from normal and HIV-infected subjects. In the former, GMP induced extensive blastogenesis, generation of powerful cytotoxicity against a tumour cell line (K562), and production of substantial amounts of interferon-gamma (IFN-gamma). Cultured PBMC from HIV-infected subjects manifested an early decreased ability for proliferative as well as differentiative cytotoxic responses to the candidal mannoproteins. This inability became clearly evident in subjects with stage III (CDC) of the disease, was total in CDC stage IV and occurred even in some subjects with a normal number of CD4+ cells. Low or absent response to GMP correlated with lack of response to tetanus toxoid. In contrast, both lymphoproliferative and cytotoxic responses to exogenous IL-2 was highly preserved at all stages of infection. The production of IFN-gamma in GMP-stimulated PBMC cultures critically fell to negligible values in most of the subjects in CDC stages II and III. Thus, the lowered or absent cell-mediated immune responses to candidal mannoprotein may be one factor to explain the early, elevated susceptibility of HIV-infected subjects to mucosal candidiasis. This study also shows that our mannoprotein preparation may be used as a probe to detect the overall efficiency of T cell responses in the above subjects.

Acquired Immunodeficiency Syndrome↗
PubMed1991

DNA fingerprinting and electrophoretic karyotype of environmental and clinical isolates of Candida parapsilosis.

The endonuclease restriction pattern (DNA fingerprinting) and the electrophoretic karyotype of 16 Candida parapsilosis isolates from environmental and clinical sources were investigated. DNA from both whole cells and separated mitochondria was digested with enzymes, including EcoRI, BamHI, KpnI, BglII, HpaII, PvuII, and HindIII. Regardless of their source and pathogenic properties, all isolates showed a uniform, reproducible, and overlapping whole-cell DNA fingerprinting with each endonuclease digest. Mitochondrial DNA fragments were, in all cases, major contributors to the total cellular DNA restriction pattern. In contrast, the electrophoretic karyotype generated by rotating field gel electrophoresis (RFGE) or contour clamped homogeneous field electrophoresis (CHEF) showed a remarkable polymorphism among the isolates. This polymorphism concerned the smaller molecular size section of the karyotype (range, 1.8 to 0.7 Mb), where at least two to five chromosomal bands could be consistently detected by both RFGE and CHEF. Larger (greater than or equal to 3.0 to 1.9 Mb) chromosome-sized DNA bands (four in CHEF and three in RFGE) were quite distinct and common to all isolates. Thus, seven karyotype classes could be defined, on the basis of both the number and size of putative chromosomes. The three categories of isolates (soil, vaginal, and hematological) were not randomly distributed among the seven classes. In particular, the four hematological isolates had a karyotype pattern which was clearly distinct from that shown by the three environmental isolates, and of the nine vaginal isolates only one shared a class with isolates from another source (soil). Although tentative, the classification was totally consistent with the independent and reproducible results obtained by the two pulse-field electrophoretic techniques employed. It is suggested that the electrophoretic analysis of the karyotype might be particularly useful for epidemiological and pathogenicity studies on biotypes of C. parapsilosis.

Candida↗
PubMed1991

Vaginopathic and proteolytic Candida species in outpatients attending a gynaecology clinic.

Non-pregnant, non-diabetic outpatients were examined for the presence of pathogenic vaginal yeasts to determine if a correlation existed between a specific yeast and clinical disease. Yeasts were isolated as single vaginal species from 186 of 228 subjects with clinically diagnosed candidal vaginitis, as well as from 122 out of 380 asymptomatic, age-matched controls. Apart from Candida albicans and C glabrata, other prevalent species were C krusei, C parapsilosis and Saccharomyces cerevisiae which accounted for 9.2%, 6.0% and 5.4%, and 9.0%, 2.4% and 19.7%, of yeasts from patients and carriers, respectively. Only C albicans and C parapsilosis were significantly more common in those with vaginitis. Only the isolates of these two species secreted aspartyl proteinase in vitro, and the amount of the enzymes secreted by the isolates from patients was significantly higher than that secreted by the isolates from carriers. These two species consistently produced vaginal infection in pseudoestrus rats, whereas none of the non-proteolytic species tested (C glabrata, C krusei, and S cerevisiae) colonised the vagina in these rats. Proteinase secretion correlated with experimental vaginal infection; it could also be a reliable factor for distinguishing clinically active infection from asymptomatic fungal carriage.

Adult↗
PubMed1990

Induction of LAK-like cells in the peritoneal cavity of mice by inactivated Candida albicans.

We have investigated the effect of multiple administrations of inactivated Candida albicans (CA) cells on induction of non-MHC-restricted antitumor cytotoxic responses both in normal and congenitally athymic (nude) mice. Intraperitoneal inoculation of CD2F1 mice with five doses of 2 x 10(7) CA cells over a 2-week interval was associated with the induction of peritoneal exudate cells (PEC) that mediated natural killer cell activity. These cells, in contrast to those elicited by a single dose of CA, killed both NK-sensitive and NK-resistant tumor target cells in vitro. This broad-spectrum, antitumor cytotoxicity peaked 1 day after the last injection of CA, and decreased to control values within 6 (NK-resistant) or 14 (NK-sensitive target cells) days. Cytotoxicity could be recalled to a high level by a boosting injection of CA or a major mannoprotein-soluble antigen (MP) from the Candida cell wall, given 30 days after multiple CA treatment. Upon a 24-hr in vitro incubation, CA-induced peritoneal immunoeffectors lost their killing activity unless human recombinant interleukin-2 (rIL-2) was added to cultures. The non-MHC-restricted cytotoxic PEC activity induced by CA was mainly associated with nonadherent, nonphagocytic large granular lymphocytes (LGL) which exhibited the following phenotypes: (i) asialo GM1+, Lyt 2.2-, and partially Thy 1.2+ (effectors active against NK-sensitive targets) and (ii) asialo GM1+, Lyt 2.2-, and Thy 1.2+ (effectors active against NK-resistant targets). Nude mice also responded to multiple CA inoculations by displaying high cytotoxic activity against NK-sensitive targets and significant cytotoxicity against NK-resistant targets. This cytotoxicity could be recalled on Day +30, and the cytotoxic effectors involved were highly sensitive to anti-asialo GM1 plus complement treatment. Overall, the results add further experimental evidence to the wide range of immunomodulatory properties possessed by C. albicans, and demonstrate that the majority of antitumor cytotoxic activity induced by fungal cells was due to lymphokine-activated killer (LAK)-like effectors.

Animals↗
PubMed1990

Experimental pathogenicity and acid proteinase secretion of vaginal isolates of Candida parapsilosis.

Isolates of Candida parapsilosis from women with or without candidal vaginitis were compared for their ability to produce secretory aspartate (acid) proteinase and their virulence for normal or cyclophosphamide-immunodepressed mice. Although all isolates were strongly proteolytic in vitro, only those from candidosis-affected subjects were appreciably pathogenic for neutropenic mice. In these animals, organ invasion was monitored after challenge with representative isolates of each category. The number of yeast cells in the kidneys of animals infected with an isolate from a subject without candidal vaginitis was approximately one order of magnitude less than that in mice infected with either one of two isolates from patients with candidal vaginitis. Mice infected with either category of C. parapsilosis isolates developed antibodies against a mannoprotein-rich extract of the cell wall, and these antibodies did not cross-react with a chemically similar preparation from Candida albicans. However, only those animals which had been challenged with one of the isolates from a candidosis subject produced a low level of antibodies, detectable by ELISA, against an acid proteinase of C. parapsilosis. These antibodies cross-reacted with a highly purified enzyme preparation of C. albicans. The data demonstrate differences in the potential virulence of different isolates of C. parapsilosis and suggest that the ability to express the acid proteinase in vivo may be related to differences in pathogenicity.

Adult↗
PubMed1990

The effect of antimycotics on secretory acid proteinase of Candida albicans.

The effect of antimycotics on secretory aspartate (acid) proteinase, a virulence enzyme of Candida albicans, was investigated. The conditions of the study were such as to induce proteinase production in the stationary phase of growth (25-40 hours), when no antifungal tested, except the polyene derivative methyl partricin, significantly reduced the viability of the culture. Among azole derivatives, fenticonazole (FZ) but not miconazole, fluconazole or ketoconazole, exerted strong inhibition on proteinase, in typical dose-diphasic pattern, (0.01 microgram/ml; 1-10 micrograms/ml). 5-fluorocytosine (5-FC) was also inhibitory at a dose interval 1-10 micrograms/ml. In all cases, the inhibition concerned the synthesis of the enzyme rather that its activity as suggested by the results of comparative ELISA, SDS-PAGE and spectrophotometric methods of proteinase detection. Finally, the inhibition of proteinase production by FZ and 5-FC mainly reflected the effect of these antimycotics on general protein synthesis.

Antifungal Agents↗