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D Poulain

Publications and source records attributed to D Poulain.

At least 19 recordsLinked to original sources
PubMed2006

Comparative analysis of cell wall surface glycan expression in Candida albicans and Saccharomyces cerevisiae yeasts by flow cytometry.

The yeast Candida albicans is an opportunistic pathogen, part of the normal human microbial flora that causes infections in immunocompromised individuals with a high morbidity and mortality levels. Recognition of yeasts by host cells is based on components of the yeast cell wall, which are considered part of its virulence attributes. Cell wall glycans play an important role in the continuous interchange that regulates the balance between saprophytism and parasitism, and also between resistance and infection. Some of these molecular entities are expressed both by the pathogenic yeast C. albicans and by Saccharomyces cerevisiae, a related non-pathogenic yeast, involving similar molecular mechanisms and receptors for recognition. In this work we have exploited flow cytometry methods for probing surface glycans of the yeasts. We compared glycan expression by C. albicans and by S. cerevisiae, and studied the effect of culture conditions. Our results show that the expression levels of alpha- and beta-linked mannosides as well as beta-glucans can be successfully evaluated by flow cytometry methods using different antibodies independent of agglutination reactions. We also found that the surface expression pattern of beta-mannosides detected by monoclonal or polyclonal antibodies are differently modulated during the growth course. These data indicate that the yeast beta-mannosides exposed on mannoproteins and/or phospholipomannan are increased in stationary phase, whereas those linked to mannan are not affected by the yeast growth phase. The cytometric method described here represents a useful tool to investigate to what extent C. albicans is able to regulate its glycan surface expression and therefore modify its virulence properties.

Antibodies↗
PubMed2006

Multilocus sequence typing reveals intrafamilial transmission and microevolutions of Candida albicans isolates from the human digestive tract.

Candida albicans is a human commensal that is also responsible for superficial and systemic infections. Little is known about the carriage of C. albicans in the digestive tract and the genome dynamics that occur during commensalisms of this diploid species. The aim of this study was to evaluate the prevalence, diversity, and genetic relationships among C. albicans isolates recovered during natural colonization of the digestive tract of humans, with emphasis on Crohn's disease patients who produce anti-yeast antibodies and may have altered Candida sp. carriage. Candida sp. isolates were recovered from 234 subjects within 25 families with multiple cases of Crohn's disease and 10 control families, sampled at the oral and fecal sites. Prevalences of Candida sp. and C. albicans carriage were 53.4% and 46.5%, respectively, indicating frequent commensal carriage. No differences in prevalence of carriage could be observed between Crohn's disease patients and healthy subjects. Multilocus sequence typing (MLST) of C. albicans isolates revealed frequent colonization of a subject or several members of the same family by genetically indistinguishable or genetically close isolates. These latter isolates differed by loss-of-heterozygosity events at one or several of the MLST loci. These loss-of-heterozygosity events could be due to either chromosome loss followed by duplication or large mitotic recombination events between complementary chromosomes. This study was the first to jointly assess commensal carriage of C. albicans, intrafamilial transmission, and microevolution. The high frequency of each of these events suggests that the digestive tract provides an important and natural niche for microevolutions of diploid C. albicans through the loss of heterozygosity.

Bacterial Typing Techniques↗
PubMed2005

Anti-Saccharomyces cerevisiae antibodies in twins with inflammatory bowel disease.

BACKGROUND AND AIMS: An increased occurrence of anti-Saccharomyces cerevisiae antibodies (ASCA) is reported in unaffected members of families with Crohn's disease. Whether ASCA is a familial trait due to genetic factors or is caused by exposure to environmental factors is unknown. To assess the genetic influence of ASCA we studied its occurrence in a twin population. PATIENTS AND METHODS: ASCA were analysed in 98 twin pairs with inflammatory bowel disease and were related to clinical phenotype and CARD15/NOD2 genotype. RESULTS: ASCA were more common in Crohn's disease than in ulcerative colitis (40/70 (57%) twins v 5/43 (12%) twins). Associations with ileal Crohn's disease, stricturing/penetrating behaviour, and young age, but not CARD15/NOD2 were confirmed. ASCA were found in 1/20 (5%) healthy siblings in discordant monozygotic pairs with Crohn's disease compared with 7/27 (26%) in discordant dizygotic pairs. Using the intraclass correlation coefficient (ICC), no agreement in ASCA titres was observed in discordant twin pairs with Crohn's disease, in monozygotic (ICC = -0.02) or dizygotic (ICC = -0.26) pairs. In contrast, strong agreement was seen within concordant monozygotic twin pairs with Crohn's disease (ICC = 0.76). CONCLUSIONS: These findings question the concept of ASCA as a marker of genetic susceptibility for Crohn's disease. The agreement in ASCA titres within concordant monozygotic twin pairs with Crohn's disease, suggests that the level of increase is genetically determined. We propose that ASCA are a marker of a response to an environmental antigen and that a specific gene(s) other than CARD15/NOD2 determines the level of response and perhaps also specific phenotypic characteristics.

Adult↗
PubMed2004

Anti-Saccharomyces cerevisiae mannan antibodies in inflammatory bowel disease: comparison of different assays and correlation with clinical features.

BACKGROUND: Anti-Saccharomyces cerevisiae mannan antibodies have been proposed as a new serological marker associated with Crohn's disease. However, their clinical value is still unclear; furthermore, a standardization of anti-S. cerevisiae mannan measurements is lacking. AIM: In this study, we aimed to assess the correlation between anti-S. cerevisiae mannan detection and specific clinical features in Crohn's disease and ulcerative colitis. Moreover, we tested the concordance of four different anti-S. cerevisiae mannan assays. MATERIALS AND METHODS: Serum samples from 196 patients with Crohn's disease, 197 patients with ulcerative colitis and 100 unrelated healthy controls were tested for anti-S. cerevisiae mannan with a standard enzyme-linked immunosorbent assay method (Lille) by one of the authors (VP). Subsequently, 60 randomly selected serum samples (27 Crohn's disease, 28 ulcerative colitis and five healthy controls) were tested for anti-S. cerevisiae mannan with three different commercial kits. RESULTS: With the Lille assay, anti-S. cerevisiae mannan were detected in 100 of 196 patients with Crohn's disease (51%; P < 0.0001 vs. controls), 32 of 197 patients with ulcerative colitis (16%; P < 0.02 vs. controls), and six of 100 controls (6%). No correlation between presence of anti-S. cerevisiae mannan and specific clinical features was found in both ulcerative colitis and Crohn's disease patients. The percentages of anti-S. cerevisiae mannan detected with four different assays ranged from 28 (Bouty) up to 43% (Inova), but these differences did not reach statistical significance. The concordance rate of anti-S. cerevisiae mannan detection in the four assays was very low (11 concordant results of 60 samples, 18.3%) (k = 0.15). No improvement of the concordance rate was obtained by modifying the suggested cut-off values (k = 0.20). CONCLUSION: In this study, we confirm that anti-S. cerevisiae mannan are significantly more frequent in Crohn's disease patients compared with ulcerative colitis patients (P < 0.0001) and controls. However, no correlation with clinical features was found in both ulcerative colitis and Crohn's disease. The low prevalence of anti-S. cerevisiae mannan, at least in our population, and the low concordance rate between different assays, makes the clinical role of this marker questionable.

Adolescent↗
PubMed2004

Polymicrobial candidaemia revealed by peripheral blood smear and chromogenic medium.

Candida spp are the fourth most common group of nosocomial pathogens isolated from patients on medical, surgical, and intensive care wards. Polymicrobial candidaemia has rarely been described. The diagnosis of candidaemia from peripheral blood smears has not been widely reported. This report describes the case of a young woman suffering from Ewing's sarcoma who developed a syndrome of septic shock. Deep fungal infection was diagnosed from a systematic peripheral blood smear and yeasts were isolated within 24 hours. A subculture on CHROMagar Candida allowed the differentiation and presumptive identification of Candida tropicalis and Candida krusei. Species identification was confirmed by the ID 32C system. This report underlines the usefulness of peripheral blood smears in the diagnosis of fulminant deep fungal infections, and of a differential isolation medium in the rapid presumptive identification of clinically important yeast species from clinical samples. This medium is particularly useful for the detection of mixed fungal infections, allowing early and better adapted antifungal treatment.

Adolescent↗
PubMed2002

Serological markers for prediction of response to anti-tumor necrosis factor treatment in Crohn's disease.

OBJECTIVES: The use of monoclonal anti-tumor necrosis factor (TNF) antibodies (infliximab, Remicade) is a new therapeutic approach for severe refractory luminal or fistulizing, Crohn's disease (CD). However, up to 30% of patients do not respond to this treatment. So far, no parameters predictive of response to anti-TNF have been identified. Our aim was to determine whether serological markers ASCA (anti-Saccharomyces cerevisiae antibodies) or pANCA (perinuclear antineutrophil cytoplasmic antibodies) could identify Crohn's patients likely to benefit from anti-TNF therapy. METHODS: Serum samples of 279 CD patients were analyzed for ASCA and pANCA before anti-TNF therapy. A blinded physician determined clinical response at week 4 (refractory luminal CD) or week 10 (fistulizing CD) after the first infusion of infliximab (5 mg/kg). RESULTS: Overall, there was no relationship between ASCA or pANCA and response to therapy. However, lower response rates were observed for patients with refractory intestinal disease carrying the pANCA+/ASCA- combination, although this lacked significance (p = 0.067). CONCLUSIONS: In this cohort of infliximab-treated patients, neither ASCA nor pANCA could predict response to treatment. However, the combination pANCA+/ASCA- might warrant further investigation for its value in predicting nonresponse in patients with refractory luminal disease.

Adolescent↗
PubMed2002

Contribution of phospholipomannan to the surface expression of beta-1,2-oligomannosides in Candida albicans and its presence in cell wall extracts.

beta-1,2-Oligomannosides (beta-1,2-Man) derived from Candida albicans mannan have been shown to act as adhesins and to induce protective antibodies. We used monoclonal antibodies specific for beta-1,2-Man in electron, confocal, and fluorescence microscopy to study the surface expression of beta-1,2-Man epitopes. These monoclonal antibodies were also used for Western blotting of cell surface extracts to study the nature of the molecules expressing the beta-Man epitopes. Evidence was obtained for the contribution of a glycolipid, phospholipomannan (PLM), to the complex expression of beta-1,2-Man epitopes at the cell wall surfaces of yeasts grown on solid media. PLM was present in intercellular matrixes of colonies grown on agar and was detected as a contaminant in mannan batches prepared by conventional methods.

Candida albicans↗
PubMed2002

Beta-1,2-mannosylation of Candida albicans mannoproteins and glycolipids differs with growth temperature and serotype.

Increasing the growth temperature from 28 to 37 degrees C reduced the expression of beta-1,2-oligomannoside epitopes on mannoproteins of Candida albicans serotypes A and B. In contrast, beta-1,2-mannosylation of phospholipomannan (PLM) remained constant despite a slight decrease in the relative molecular weight (M(r)) of this compound. At all growth temperatures investigated, serotype A PLM displayed an M(r) and an antigenicity different from those of serotype B PLM when they were tested with a panel of monoclonal antibodies.

Antibodies, Monoclonal↗
PubMed2001

Contribution of serological tests and blood culture to the early diagnosis of systemic candidiasis.

The isolation of Candida species from a single blood culture is considered sufficient evidence for the initiation of systemic antifungal therapy. However, blood cultures still lack sensitivity. Previous reports have suggested that the combined serological detection of mannanemia and anti-mannan antibodies may be useful for the diagnosis of systemic candidiasis caused by Candida albicans (specificity and sensitivity 93% and 80%, respectively). In this study, serological tests to detect Candida albicans mannan and Candida albicans antibodies (Platelia Candida Antigen and Antibody tests; Bio-Rad, France) were applied retrospectively to a series of patients with at least one Candida-positive blood culture and from whom at least one serum sample, taken before or on the day of blood culture, was available. Forty-five patients were selected, including 23 infected by Candida albicans, 4 by Candida glabrata, 9 by Candida tropicalis, 5 by Candida parapsilosis, and 4 by Candida krusei. Serological tests were positive in 73% of patients at least 2 days, and in some patients, up to 15 days before blood cultures became positive. These data suggest that serological surveillance of at-risk patients using the Platelia Candida tests could result in earlier initiation of antifungal therapy, especially when used in conjunction with blood cultures. In this way, more efficient management of nosocomial infections caused by Candida species can be achieved.

Candidiasis↗
PubMed2001

Peptides that mimic Candida albicans-derived beta-1,2-linked mannosides.

Beta-1,2-linked mannosides from Candida albicans phosphopeptidomannan (PPM) bind to macrophages through a receptor independent from the macrophage alpha-linked mannose receptor and stimulate these cells to secrete immune mediators. Anti-beta-1,2-linked mannoside but not anti-alpha-linked mannoside antibodies produced after immunization with neoglycoproteins protect animals from disseminated candidiasis. In this study, peptides that mimic beta-1,2-linked mannosides were isolated using phage display methodology. A phage library expressing random peptides was panned with an anti-beta-1,2-linked mannoside monoclonal antibody (mAb). After three rounds of biopanning, the isolated phages were able to inhibit recognition of C. albicans by the mAb. Sixty percent of the phages had an identical DNA insert corresponding to the peptide sequence FHENWPS that was recognized specifically by the mAb. Injection of KLH-coupled peptide into mice generated high titers of polyclonal antibodies against C. albicans yeast cell walls. The anti-FHENWPS antibodies bound to C. albicans PPM and were inhibited by soluble beta-1,2-mannotetraose. Together, these data provide evidence for mimotopic activity of the peptide selected by biopanning with the anti-beta-1,2-oligomannoside mAb.

Amino Acid Sequence↗
PubMed2001

Familial expression of anti-Saccharomyces cerevisiae Mannan antibodies in Crohn's disease and ulcerative colitis: a GISC study.

OBJECTIVES: Recent studies in familial Crohn's disease (CD) have suggested that anti-Saccharomyces cerevisiae mannan antibodies (ASCAs) may represent a new specific marker of genetic susceptibility. In this study we aimed to assess the importance of ASCAs by comparing their presence in a large number of patients with sporadic and familial occurrence of CD or ulcerative colitis (UC) and their unaffected relatives. METHODS: Serum samples from 96 patients with sporadic CD, 97 patients with sporadic UC, and 50 unrelated healthy controls were tested for ASCAs by a standard ELISA method. Moreover, 73 families with two or more members affected by CD and/or UC were recruited. From these families 58 CD patients, 84 UC patients, and 216 unaffected first degree relatives were investigated. RESULTS: ASCAs were detected in 34 of 96 patients with sporadic CD (35%, p < 0.01 vs controls), 11 of 97 patients with sporadic UC (12%), and two of 50 controls (4%). ASCAs were significantly (p < 0.04) more frequent in patients with familial CD (55%) and familial UC (25%) than in sporadic cases. Moreover, ASCAs were found in 25% of unaffected relatives, and this rate did not significantly differ in CD, UC, and mixed families (28%, 26%, and 22%, respectively). CONCLUSIONS: In this study we confirm that ASCAs occur particularly frequently in CD patients, especially with the presence of a positive family history. However, they are also significantly increased in UC patients with a family history and in a considerable number of unaffected relatives of inflammatory bowel disease families, irrespective of the characteristics of their families (UC, CD, mixed, ASCA positive, and ASCA negative). The presence of ASCAs in unaffected relatives might point toward a genetic predisposition to either CD or UC.

Adolescent↗
PubMed2001

Role of extracellular signal-regulated protein kinase cascade in macrophage killing of Candida albicans.

The pathogenic yeast Candida albicans and its derived molecules stimulate a wide range of macrophage secretory functions and may adapt to escape being killed by this phagocyte. In this study, phagocytosis of C. albicans and of the nonpathogenic yeast Saccharomyces cerevisiae was shown to be associated with phosphorylation of the mitogen-activated protein kinase (MAPK)/extracellularly regulated kinase (ERK) pathway in the absence of significant activation of either p38MAPK or stress-activated protein kinase/c-Jun N-terminal kinase. However, although 80% of endocytosed C. albicans survived after 1 h, 80% of S. cerevisiae cells were killed. Considerable quantitative differences were observed between the two species in the sequential phosphorylation of MAPK/ERK kinase (MEK), extracellularly regulated kinase-1, and 90-kDa-ribosomal S6 kinases. A lower level of activation of the pathway by C. albicans was associated with a species-specific overexpression of the MEK phosphatase MAPK phosphatase (MKP)-1. Killing of both C. albicans and S. cerevisiae could be reduced using PD98059, which mimics MKP-1 and inhibits MEK phosphorylation, suggesting that specific MKP-1 activation by C. albicans could contribute to its ability to escape the yeast lytic potential of macrophages.

Animals↗
PubMed2000

Synthesis and antifungal activity of a ferrocene-fluconazole analogue.

A novel ferrocene fluconazole analogue was synthesized and its antifungal properties investigated against yeast strains of medical importance, including those intrinsically resistant to fluconazole. In vitro tests revealed a slight increase in fungal growth and a reversal of the effect of fluconazole at minimal inhibitory concentrations.

Antifungal Agents↗
PubMed2000

Candida albicans-derived beta-1,2-linked mannooligosaccharides induce desensitization of macrophages.

Candida albicans beta-1,2-oligomannosides stimulate macrophage tumor necrosis factor alpha (TNF-alpha) but not NO release. This stimulation desensitized macrophages by altering beta-1, 2-oligomannoside-dependent TNF-alpha production and lipopolysaccharide-dependent TNF-alpha and NO secretion. Desensitization was not related to tyrosine phosphorylation signal transduction but was transferred by culture supernatants in which arachidonic acid derivatives were evidenced.

Animals↗
PubMed2000

beta-1,2-linked oligomannosides from Candida albicans bind to a 32-kilodalton macrophage membrane protein homologous to the mammalian lectin galectin-3.

beta-1,2-linked oligomannoside residues are present, associated with mannan and a glycolipid, the phospholipomannan, at the Candida albicans cell wall surface. beta-1,2-linked oligomannoside residues act as adhesins for macrophages and stimulate these cells to undergo cytokine production. To characterize the macrophage receptor involved in the recognition of C. albicans beta-1,2-oligomannoside we used the J774 mouse cell line, which is devoid of the receptor specific for alpha-linked mannose residues. A series of experiments based on affinity binding on either C. albicans yeast cells or beta-1,2-oligomannoside-conjugated bovine serum albumin (BSA) and subsequent disclosure with biotinylated conjugated BSA repeatedly led to the detection of a 32-kDa macrophage protein. An antiserum specific for this 32-kDa protein inhibited C. albicans binding to macrophages and was used to immunoprecipitate the molecule. Two high-pressure liquid chromatography-purified peptides from the 32-kDa tryptic digest showed complete homology to galectin-3 (previously designated Mac-2 antigen), an endogenous lectin with pleiotropic functions which is expressed in a wide variety of cell types with which C. albicans interacts as a saprophyte or a parasite.

Animals↗