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J Pontón

Publications and source records attributed to J Pontón.

At least 19 recordsLinked to original sources
PubMed2001

Serological differentiation of experimentally induced Candida dubliniensis and Candida albicans infections.

Using a rabbit model of systemic infection, we show that it is possible to differentiate infections caused by Candida dubliniensis and other Candida species by detecting the antibody response mounted by the infected animals. These results confirm our previous observation in a patient with C. dubliniensis candidemia and suggest that detection of C. dubliniensis-specific antibodies is useful in the diagnosis of invasive candidiasis caused by this yeast.

Animals↗
PubMed2001

Immunoreactivity of the fungal cell wall.

The cell wall is the major fungal structure involved in the interaction with the host and most of the immunological effects observed with intact fungal cells have been reproduced with cell-wall components. As a result of the exposure to fungal antigens, most individuals develop both cellular and antibody responses intended to limit the invasiveness or to eradicate the fungus from the infected tissues. However, a number of fungi including Candida albicans, Cryptococcus neoformans, Blastomyces dermatitidis, Coccidioides immitis, Trichophyton spp. and Histoplasma capsulatum can also induce T- and B-suppressive activities. A wide diversity of immunodominant cell-wall antigens for both cell-mediated and humoral responses have been identified in the most important fungal pathogens, although considerable differences exist in the information available at the molecular level among the different mycoses. Cellular responses require macrophage and Th1 activation, whereas humoral responses comprise the activation of the complement system and the induction of antibodies. The ability of fungal cell-wall components to elicit cellular or humoral immune responses has been traditionally used in the serodiagnosis of mycoses, the identification of fungal organisms and the development of vaccines for the prevention of mycoses. In the future, the analysis of such molecules will provide critical information in understanding the nature of host-fungus interactions.

Antibodies, Fungal↗
PubMed2000

Emerging pathogens.

The ever increasing numbers of immunosuppressed individuals has led to a significant increase in the incidence of opportunistic infections, particularly those caused by fungi. The epidemiology of infections caused by the common fungal pathogens such as Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus has been well documented. However, in addition to these, a number of species which have previously been unrecognized (e.g., C. dubliniensis) or have previously been assumed to be non-pathogenic (e.g., Saccharomyces cerevisiae, Scedosporium spp. and Fusarium spp.) have emerged as agents of human disease. Since these species have only been identified recently as human pathogens, their role in disease is poorly understood. In most cases, identification of these species is problematic and therefore their epidemiology has yet to be elucidated adequately. In addition, several of these species fail to respond to conventional antifungal therapies. In this article, we describe the emergence of two separate yeast species (C. dubliniensis and S. cerevisiae) and two separate groups of moulds (Scedosporium prolificans and Fusarium spp.), as human pathogens. It is apparent from what we already know, that much work has yet to be performed before we have a clear understanding of how these species cause disease and most importantly how they can be controlled.

Candida↗
PubMed2000

Influence of environmental pH on the reactivity of Candida albicans with salivary IgA.

Salivary secretory IgA reacts with a group of heat-shock mannoproteins preferentially expressed on Candida albicans yeast cells and germ tubes grown at 37 degrees C. Since other environmental factors can also modulate the expression of those antigens, we have investigated the influence of the pH of the culture medium on the expression of the antigens reacting with human salivary IgA by C. albicans. By indirect immunofluorescence, yeast cells grown in Sabouraud glucose broth at 37 degrees C showed a statistically significant increase in reactivity with salivary IgA (p < 0.0001) when compared with cells grown at 25 degrees C at the 4 pH values studied (3.3, 5.9, 7.5, and 9.5), the highest reactivity and the major heat-shock effect being observed at pH 5.9. The decrease in reactivity with salivary IgA observed in C. albicans cells grown at pH values of 3.3 and 9.5 was confirmed by Western blotting. Salivary IgA reacted with polydispersed materials from the cell walls of molecular masses > 55 kDa, which were more expressed at neutral pH than at acidic or alkaline pH values. A similar reactivity was observed when the antigenic extracts were stained with an antiserum directed against oligosaccharides present in antigen 6 of C. albicans serotype A. The differences in reactivity presented by salivary IgA may be related to a decrease in the expression of polysaccharides present on the surfaces of the yeast cells of C. albicans grown at acidic or alkaline pH values. The low reactivity of salivary IgA with C. albicans cells grown at acidic pH values may help to explain the association between acidic saliva and the carriage of Candida in the oral cavity, as well as with oral candidiasis.

Analysis of Variance↗
PubMed1999

The nuclear pore complex protein Nup88 is overexpressed in tumor cells.

It has been previously shown (J. Schneider et al., Br. J. Cancer, 77: 1015-1020, 1998) that an antibody directed against Candida albicans proteins (C6) recognizes specifically a protein in human ovarian tumors. We have now performed an immunoscreening of a human cDNA library using this antibody and identified the antigen as Nup88, a protein localized preferentially at the nuclear membrane and probably implicated in nucleocytoplasmic transport. Our results show that Nup88 is strongly expressed in a series of human tumor cell lines compared with nontransformed cell lines at the RNA and the protein levels. Furthermore, we observed that in 76% of 21 ovarian tumors analyzed, the protein is also overexpressed in malignant tissue when compared with healthy adjacent tissue. Nup88 may, therefore, be considered as a putative marker for tumor growth and is probably related to increased cell cycling.

Antibodies, Monoclonal↗
PubMed1999

Characterization of Candida albicans antigenic determinants by two-dimensional polyacrylamide gel electrophoresis and enhanced chemiluminescence.

The use of a two-dimensional polyacrylamide gel electrophoresis joined with Western blotting allowed us to investigate the reactivities of antibodies present in sera from mice and humans to antigens of Candida albicans blastoconidia. The analysis of the antibody response in the two models studied and the comparison between the antibody response in infected and noninfected individuals showed that the infection by C. albicans produces changes in the antibody response which may be of relevance in the serodiagnosis of invasive candidiasis. These changes include the induction of antibodies against new antigens, the disappearance of antibodies against a group of antigens and variations in the reactivity of antibodies directed to a different group of antigens. The technique used resolved the isoforms of several antigens including enolase. It is concluded that the antibody response in humans and mice with candidiasis is not homogeneously directed to all the isoforms of an antigen.

Animals↗
PubMed1998

Factors influencing the expression in vitro of Candida albicans stress mannoproteins reactive with salivary secretory IgA.

We have examined the influence of subinhibitory concentrations of several antifungals, the different glucose and ammonium sulphate concentrations in the culture medium as well as the strain variability on the expression in vitro of stress mannoproteins reactive with salivary sIgA in C. albicans and other Candida spp isolates. Irrespective of the conditions used, no reactivity with salivary sIgA was observed in yeast cells grown at 25 degrees C. However, when grown at 37 degrees C, all of the 10 C. albicans strains, but only 9 out of 28 non-C. albicans isolates studied showed reactivity with salivary sIgA. Cells grown at 37 degrees C in medium containing maximum concentrations of glucose and ammonium sulphate expressed the antigens reactive with sIgA during longer periods of time than the cells grown in medium with minimal concentrations of the same compounds. The regulatory role showed by the concentration of glucose and ammonium sulphate on the antigenic expression was subordinated, nevertheless, to the most important factor, the temperature of incubation. Only isolates showing low susceptibility expressed the antigens reactive with sIgA under the influence of subinhibitory concentration of antifungals. However, induced resistance to one of the antifungals tested (5 fluorocytosine) allowed the antigenic expression at elevated subinhibitory concentrations even in previous susceptible strains. In conclusion, in addition to the temperature, factors such as characteristics of the strain, the concentration of glucose and ammonium sulphate in the culture medium and the resistance to antifungals played a role on the expression of C. albicans antigens reactive with sIgA, which could be of clinical relevance in the course of infection.

Antifungal Agents↗
PubMed1998

Cross-reactivity between Candida albicans and human ovarian carcinoma as revealed by monoclonal antibodies PA10F and C6.

Summary Antibodies against Candida albicans antigenic determinants have been reported to cross-react with human tumour cells. We have found that two monoclonal antibodies, C6 and PA1OF, developed at our laboratory against C. albicans antigenic determinants, cross-react with human ovarian cancer on Western blots and immunohistochemistry. We have subsequently used one of them, PA10OF, to test by means of immunohistochemistry a series of 37 human ovarian carcinomas. Out of 37 tumours, 25 (67.6%) expressed the antigen recognized by PA1OF. The reactivity, however, was concentrated on the subgroup of particularly aggressive, invasive carcinomas in advanced stages of the disease (19 out of 24 positive), whereas the antigen was expressed significantly less (P=0.0007) in the subgroup of much less aggressive stage I tumours of low malignant potential, also called borderline carcinomas (2 out of 13 positive). This cross-reactivity between C. albicans and ovarian carcinoma seems to be attributable to a common antigenic determinant related to tumour aggressiveness.

Animals↗
PubMed1998

Detection of antibodies to Candida albicans germ tubes during experimental infections by different Candida species.

Identification and characterization of Candida albicans germ tube-specific antigens may be of relevance for the serodiagnosis of invasive candidiasis since they could be the basis for the development of new diagnostic tests. In this study, we have identified two antigens of 180 and >200 kDa in the cell wall of C. albicans germ tubes which are responsible for the induction of antibodies to C. albicans germ tubes. Antigens of similar molecular masses have been demonstrated in the cell walls of the Candida species C. stellatoidea, C. parapsilosis, C. guilliermondii, C. tropicalis, and C. krusei, but not C. glabrata. The kinetics of the antibody responses to C. albicans germ tubes were studied in rabbits infected with different Candida species. Although these antibodies were detected in rabbits infected with all Candida species except C. glabrata, the kinetics of the antibody responses to C. albicans germ tubes induced by the Candida species studied were different. Both the highest titer and the earliest response of antibodies to C. albicans germ tubes were observed in rabbits infected with either of the two serotypes of C. albicans used. However, the time needed to elicit the antibodies to C. albicans germ tubes can be reduced as the result of an anamnestic antibody response. The results presented in this study show that a test designed to detect antibodies against C. albicans germ tube antigens may be suitable for the diagnosis of infections caused by most of the medically important Candida species.

Animals↗
PubMed1998

Rapid identification of Candida dubliniensis by indirect immunofluorescence based on differential localization of antigens on C. dubliniensis blastospores and Candida albicans germ tubes.

There is a clear need for the development of a rapid and reliable test for the identification of Candida dubliniensis and for the discrimination of this species from Candida albicans. In the present study we have investigated the potential use of C. dubliniensis-specific antigens as a basis for its identification. We produced an anti-C. dubliniensis serum which, after adsorption with C. albicans blastospores, was found to differentially label C. dubliniensis isolates in an indirect immunofluorescence test. In this test, the antiserum reacted with blastospores and germ tubes of C. dubliniensis and with blastospores of Candida krusei and Rhodotorula rubra but did not react with blastospores of several other Candida species including C. albicans. The antiserum also reacted with C. albicans germ tubes. The anti-C. dubliniensis adsorbed serum reacted with specific components of 25, 28, 37, 40, 52, and 62 kDa in the C. dubliniensis extract and with a variety of antigens from other yeast species. The antigens from non-C. dubliniensis yeasts showing reactivity with the anti-C. dubliniensis adsorbed serum are mostly expressed within the cell walls of these yeast species, and this reactivity does not interfere with the use of the anti-C. dubliniensis adsorbed serum in an indirect immunofluorescence test for the rapid identification of C. dubliniensis.

AIDS-Related Opportunistic Infections↗
PubMed1997

Comparison of morphotypic and genotypic methods for strain delineation in Candida.

We compared two phenotypic methods, colony morphotyping on Sabouraudtripheniltetrazolium agar (STTZ) and serotyping, with two genotypic methods, karyotyping and Random Amplified Polymorphic DNA bands obtained by PCR amplification (RAPD-PCR), for strain delineation in 33 Candida clinical isolates and two C. albicans strains from culture collections. Analysis of isolates on STTZ showed 11 different morphotypes. In two patients there was a switch in the morphotype coincidential with a change in the susceptibility of the isolates to azole antifungals. C. albicans isolates were divided into two serotypes. Sixteen and 18 different patterns were identified among the Candida isolates by karyotyping and RAPD-PCR, respectively. No relationship was found between any of the typing methods used and the source of the isolates. The combination of karyotyping and morphotyping on STTZ yielded useful epidemiological information, since it allowed the differentiation among the Candida species studied and the discrimination of clusters within C. albicans as well as to check the capacity of a strain to generate variants with different susceptibility to some antifungals.

Candida↗
PubMed1997

Resistance to candidiasis and macrophage activity in chitin-treated mice.

The effect of chitin, a polysaccharide of the cell wall of Candida albicans, on both the survival of C. albicans infected mice and the activity of the murine peritoneal macrophages has been studied. Pretreatment of mice with 30 mg kg(-1) C. albicans chitin enhanced the survival of the infected animals. The protective effect was concomitant with an enhancement of both phagocytic and candidacidal activities of the peritoneal macrophages. Chitin by itself did not induce the nitric oxide (NO) synthase in the macrophages, which remained at a level similar to that shown by the macrophages from untreated animals. The administration of 10 mg kg(-1) C. albicans chitin diminished the long term survival of the infected animals. This effect was coincident with a lower candidacidal activity and NO production by the macrophages of the chitin treated and infected animals, compared to the untreated infected animals.

Animals↗
PubMed1997

Detection of antibodies to Candida albicans germ tubes for diagnosis and therapeutic monitoring of invasive candidiasis in patients with hematologic malignancies.

We prospectively investigated the ability of detection of antibodies to Candida albicans germ tubes (CAGT) to diagnose invasive candidiasis in 95 consecutive admissions of 73 patients with hematologic disorders undergoing intensive chemotherapy. The episodes were divided into three groups according to clinical and microbiological diagnosis. Group 1 comprised eight admissions of eight patients with invasive candidiasis. Group 2 comprised 42 admissions of 34 patients without evidence of invasive candidiasis. Group 3 comprised the remaining 45 admissions of 37 patients with febrile episodes which were not diagnosed by microbiological culture. Antibodies to CAGT were detected in 87.5% of group 1 patients. Detection of antibodies to CAGT in patients with Candida fungemia was delayed somewhat relative to the time the blood culture was positive, but antibodies to CAGT were detected earlier than a diagnosis was made in patients with deep-tissue candidiasis. Sera from 2 admissions in group 2 and 12 admissions in group 3 revealed antibodies to CAGT. At a titer of > or = 1:20, detection of antibodies to CAGT had a sensitivity of 87.5%, specificity of 95.2%, positive predictive value of 77.8%, and negative predictive value of 97.6%. Antibodies to CAGT were usually detected before beginning of empiric antifungal therapy. Titers of antibodies to CAGT were maintained in most patients who died but declined and eventually disappeared in the patients who survived. Since antibodies to CAGT were detected in all patients with tissue-proven invasive candidiasis but negative by blood culture, detection of antibodies to CAGT complemented blood cultures for diagnosis and therapeutic monitoring of patients with hematologic malignancies and invasive candidiasis.

Adolescent↗
PubMed1997

Characterization of Scedosporium prolificans clinical isolates by randomly amplified polymorphic DNA analysis.

Fingerprinting by randomly amplified polymorphic DNA (RAPD) analysis was used to differentiate Scedosporium prolificans isolates. A total of 59 arbitrary primers were screened with six unrelated S. prolificans isolates, and a panel of 12 primers was selected. The 12 primers were then used to detect DNA polymorphisms among 17 S. prolificans isolates from 11 patients with systemic S. prolificans infections diagnosed in three hospitals located in geographically different areas of Spain. Eight patients were diagnosed with S. prolificans infection in a single institution over a 6-year period, and two other patients were diagnosed with S. prolificans infection in a different hospital over a 1-year period. No single primer allowed for the discrimination of all the isolates from different patients, but this was possible by combining the RAPD patterns from three primers (UBC 701, AB1.08, and AB1.11 or UBC 701, AB1.08, and UBC 707). However, multiple isolates from the same patient were identical. In this study, we also compared a visual method and a computerized method for the analysis of the RAPD patterns. Both methods were satisfactory and gave few discordances, but given the advantages and disadvantages of each method, both systems should be used together. RAPD analysis provided a fast and economical means of typing S. prolificans isolates, with a high level of discrimination among unrelated isolates. Typing by RAPD analysis confirmed that the S. prolificans infections were epidemiologically unrelated.

DNA Primers↗
PubMed1996

A new method of antibiotyping yeasts for subspecies discrimination and distribution in human clinical specimens.

A study of the antibiotypes of 764 isolates of the genera Candida and Torulopsis from different clinical specimens is reported. The typing method was based on the susceptibility results obtained by the standardized and partially automated kit ATB-Fungus (API-bioMérieux), giving to each strain a code of six figures, according to these criteria: susceptibility to 5-fluorocytosine, amphotericin B, nystatin, miconazole, econazole, and ketoconazole. Candida albicans serotypes were determined by the Candida Check test (Iatron, Japan). Twenty-six antibiotypes were found in C. albicans (482 isolates), 21 types in serotype A, and 15 in serotype B strains. Candida parapsilosis (115 isolates) was divided into 11 antibiotypes, Torulopsis glabrata (53 isolates) into five, Candida guilliermondii (36 isolates) into 10 and Candida tropicalis (31 isolates) into eight. Depending on the sample origin, 000000 (susceptibility to all the antifungals tested) was the predominant C. albicans antibiotype (92.9% of blood isolates, 41.2% of vaginal isolates, 33.3% of respiratory isolates, isolates, 31.01% or oral and digestive tract isolates, and 25.0% of nail and skin isolates). No predominant antibiotypes were found in strains from respiratory tract, skin ad nails. A reproducibility close to 99% was found with the test. Simplicity and standardization could make this method useful for typing Candida and Torulopsis isolates.

Antibodies, Fungal↗