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Marie Gauthier

Publications and source records attributed to Marie Gauthier.

9 recordsLinked to original sources

Crystal structure of the complex between the monomeric form of Toxoplasma gondii surface antigen 1 (SAG1) and a monoclonal antibody that mimics the human immune response.

Toxoplasma gondii, the intracellular parasite responsible for toxoplasmosis infects more than one-third of the world population and can be life-threatening for fetuses and immunocompromised patients. The surface protein SAG1 is an important immune target, which provides a strong immune response against the invasive tachyzoite while the other forms of the parasite, devoid of SAG1 at their surface, are multiplying. In addition to this role as a "hot spot" decoy, SAG1 is predicted to act as an adhesin during host-cell attachment through its binding to proteoglycans. To begin to understand the relationships between SAG1 epitopes and the ligand-binding site, we have solved the crystal structure of the monomeric form of T.gondii SAG1 complexed to a Fab derived from a monoclonal antibody raised against tachyzoite particles. This antibody competes strongly with human Toxoplasma-specific sera, suggesting that its epitope is part of an immunodominant region present on the surface of SAG1. The structure reveals that this conformational epitope, located within the SAG1 N-terminal domain, does not overlap with the proposed ligand-binding pocket. This study provides the first structural description of the monomeric form of SAG1, and significant insights into its dual role of adhesin and immune target during parasite infection.

Amino Acid Sequence↗

Gene expression during early ascidian metamorphosis requires signalling by Hemps, an EGF-like protein.

Hemps, a novel epidermal growth factor (EGF)-like protein, is expressed during larval development and early metamorphosis in the ascidian Herdmania curvata and plays a direct role in triggering metamorphosis. In order to identify downstream genes in the Hemps pathway we used a gene expression profiling approach, in which we compared post-larvae undergoing normal metamorphosis with larval metamorphosis blocked with an anti-Hemps antibody. Molecular profiling revealed that there are dynamic changes in gene expression within the first 30 minutes of normal metamorphosis with a significant portion of the genome (approximately 49%) being activated or repressed. A more detailed analysis of the expression of 15 of these differentially expressed genes through embryogenesis, larval development and metamorphosis revealed that while there is a diversity of temporal expression patterns, a number of genes are transiently expressed during larval development and metamorphosis. These and other differentially expressed genes were localised to a range of specific cell and tissue types in Herdmania larvae and post-larvae. The expression of approximately 24% of the genes that were differentially expressed during early metamorphosis was affected in larvae treated with the anti-Hemps antibody. Knockdown of Hemps activity affected the expression of a range of genes within 30 minutes of induction, suggesting that the Hemps pathway directly regulates early response genes at metamorphosis. In most cases, it appears that the Hemps pathway contributes to the modulation of gene expression, rather than initial gene activation or repression. A total of 151 genes that displayed the greatest alterations in expression in response to anti-Hemps antibody were sequenced. These genes were implicated in a range of developmental and physiological roles, including innate immunity, signal transduction and in the regulation of gene transcription. These results suggest that there is significant gene activity during the very early stages of H. curvata metamorphosis and that the Hemps pathway plays a key role in regulating the expression of many of these genes.

Animals↗

Treatment of urinary tract infections among febrile young children with daily intravenous antibiotic therapy at a day treatment center.

OBJECTIVE: Urinary tract infections (UTIs) are common among infants and toddlers. Children can be treated effectively with short courses (2-4 days) of intravenous (IV) therapy followed by oral therapy. If IV therapy is chosen, use of once-daily dosing may allow outpatient management instead of hospital admission. However, no description of ambulatory treatment with IV antibiotics of UTI among febrile children has been reported to date. We aimed to describe the feasibility and complications of outpatient management with IV antibiotics of UTI among febrile children, at the day treatment center (DTC) of a tertiary-care pediatric hospital. METHODS: Between April 1, 2002, and March 31, 2003, a prospective cohort of patients 3 months to 5 years of age who were examined in the emergency department (ED) and diagnosed as having presumed febrile UTI were treated according to a clinical protocol. Patients were treated at the DTC unless they met exclusion criteria, in which case they were hospitalized. The DTC was open 7 days per week, including holidays, from 8:30 am to 4:30 pm. At the DTC, patients were initially treated with a daily dose of IV gentamicin, until the child had been afebrile for at least 24 hours, and with oral amoxicillin, until preliminary urine culture results were available. Children allergic to penicillin received gentamicin only. IV antibiotics were administered through peripheral IV access; the IV catheter's patency was maintained with injection of 50 U of heparin once daily throughout the treatment period. Parental satisfaction with the DTC experience was assessed with an anonymous, self-administered questionnaire. RESULTS: Two hundred ninety-one episodes of presumed febrile UTI were diagnosed in the ED, of which 212 (72.9%) were sent to the DTC. There were 71 hospital admissions (24.4%); in 9 of these instances, the child was admitted because parents refused or were unable to comply with DTC treatment. Adherence to the treatment protocol in the ED was excellent; in 92.1% of presumed febrile UTI episodes (268 of 291 episodes), the patient was referred to the appropriate setting for treatment. In 8 instances, patients who met an exclusion criterion were sent to the DTC. They should have been hospitalized, according to the protocol. At the DTC, a final diagnosis of UTI was made in 178 of the 212 episodes (84%). Patients treated at the DTC, with a final diagnosis of UTI, had a median age of 12.0 months (range: 3-68 months), and their mean initial temperature was 39.2 degrees C (SD: 1.1 degrees C). Patients were afebrile by 24 hours in 52% of UTI episodes and by 48 hours in 82%. Minor problems with IV access occurred in 9.0% of cases. The duration of IV antibiotic therapy at the DTC was 1.9 days (SD: 0.9 day). The mean number of visits to the DTC, including appointments for renal ultrasound and voiding cystourethrography evaluations, was 3.5 (SD: 0.9). Parents were present at all scheduled visits in 98.9% of cases. Four patients needed to be hospitalized from the DTC, but in only 1 case was hospital admission related to UTI treatment. Four patients with UTI treated in the DTC had positive blood cultures, 2 with Escherichia coli (both successfully treated at the DTC) and 2 with contaminants. For 4 children treated at the DTC, UTI was caused by gentamicin-resistant E coli. One patient became afebrile within 24 hours after treatment initiation with IV gentamicin; he was then treated with oral cefixime. A second patient was treated with IV ceftriaxone, administered at the DTC once culture results were available, and remained febrile for <72 hours. The last 2 patients were hospitalized; one, who was also allergic to cephalosporins, had been febrile for 72 hours at the time of hospitalization (once hospitalized, he was treated with IV amikacin), and the other was admitted to the hospital for an unrelated problem, namely, scalp cellulitis. None of these 4 patients was initially bacteremic or became bacteremic during the treatment period. Repeat urine culture was performed within 14 days after treatment initiation in 146 instances, and results were negative in all cases. At telephone follow-up assessments 14 days after discharge, no patient had been rehospitalized because of UTI. Successful treatment at the DTC (defined as attendance at all visits, normalization of temperature within 96 hours, negative control urine cultures, if performed, and absence of hospitalization from the DTC) was observed in 96.6% of the 178 UTI episodes. Overall adherence of physicians to the protocol at the DTC was 87.1% (95% confidence interval: 82.2-92.0%). One hundred seventy-two satisfaction questionnaires were returned and revealed good, very good, or excellent parental satisfaction in 98.8% of cases. CONCLUSIONS: Our data show that ambulatory treatment with IV antibiotics, at a DTC, may be used for at least three-fourths of UTIs among febrile children 3 months to 5 years of age. It is safe and feasible and appears very satisfactory to parents. Although ambulatory treatment with IV antibiotics is more invasive than oral therapy during the initiation of UTI treatment, it ensures almost full compliance, allows close medical supervision, and facilitates investigations related to the UTI. It is an interesting alternative to hospitalization.

Administration, Oral↗

Characterization and diagnostic potential of hepatitis B virus nucleocapsid expressed in E. coli and P. pastoris.

The hepatitis B core antigen (HBcAg) was expressed in Escherichia coli and in Pichia pastoris. A hexahistidine tag was introduced at the C terminus of the E. coli expressed protein allowing its purification by Ni(2+)-chelate affinity chromatography. The P. pastoris expressed HBcAg was isolated following heat treatment. The two recombinant HBcAgs were purified further on a sucrose gradient. Mass spectrometry analysis suggested that HBcAg was N-acetylated only in P. pastoris and reaction with Ellman's reagent allowed the measurement respectively, of 0.37 and 0.23 mole of free sulfydryl groups per mole of HBcAg monomer expressed in E. coli or P. pastoris. Electron microscopy indicated that the E. coli and the P. pastoris proteins formed capsid-like particles with respectively, a diameter of 34 and 28-nm. Nucleic acid components were found entrapped in both particles but protected from enzymatic treatment only in the P. pastoris derived particles suggesting structural discrepancies between the two recombinant molecules. The high purity of these recombinant antigens allowed the development of a sandwich immunoassay to detect anti-HBc antibodies in human serum. The preliminary results indicate that the P. pastoris HBcAg produced intracellularly is more suitable than the renatured E. coli HBcAg for detection of anti-HBc in this diagnostic assay.

Amino Acid Sequence↗

Erratum to "characterization and diagnostic potential of hepatitis B virus nucleocapsid expressed in E. coli and P. pastoris".

The hepatitis B core antigen (HBcAg) was expressed in Escherichia coli and in Pichia pastoris. A hexa-histidine tag was introduced at the C terminus of the E. coli expressed protein allowing its purification by Ni2+-chelate affinity chromatography. The P. pastoris expressed HBcAg was isolated following heat treatment. The two recombinant HBcAgs were purified further on a sucrose gradient. Mass spectrometry analysis suggested that HBcAg was N-acetylated only in P. pastoris and reaction with Ellman's reagent allowed the measurement, respectively, of 0.37 and 0.23 mole of free sulfydryl groups per mole of HBcAg monomer expressed in E. coli or P. pastoris. Electron microscopy indicated that the E. coli and the P. pastoris proteins formed capsid-like particles with, respectively, a diameter of 34 and 28 nm. Nucleic acid components were found entrapped in both particles but protected from enzymatic treatment only in the P. pastoris derived particles suggesting structural discrepancies between the two recombinant molecules. The high purity of these recombinant antigens allowed the development of a sandwich immunoassay to detect antibodies to HBcAg (anti-HBc) in human serum. The preliminary results indicate that the P. pastoris HBcAg produced intracellularly is more suitable than the renatured E. coli HBcAg for detection of anti-HBc in this diagnostic assay.

Amino Acid Sequence↗

Acute adenitis in children: clinical course and factors predictive of surgical drainage.

OBJECTIVES: To describe clinical course of children hospitalized for a first episode of acute unilateral infectious adenitis and to identify factors predictive of surgical lymph node drainage. METHODS: We reviewed medical records of children from 0 to 17 years of age discharged from a tertiary care pediatric center with a diagnosis of adenitis between 1 April 1996 and 31 March 2001. Patients were included if they had acute (< or = 10 days) unilateral lymph node swelling greater or equal to 2.5 cm on initial physical examination. Exclusion criteria were: bilateral adenitis or adenitis at more than one site; prior adenitis; underlying chronic disease. RESULTS: Two hundred and eighty-four patients were included in this study. The mean age was 4.0 years (3.1 SD). Twenty-three per cent of infected nodes were > 5 cm in size and 92.6% were cervical. Thirteen of 252 blood cultures were positive (5.2%), of which one showed Streptococcus pneumoniae and 12 contaminants. Mean length of stay was 4.2 days (2.2 SD). Surgical node drainage was performed in 60 (21.1%) patients. Factors significantly associated with increased risk of surgical drainage were age < 1 year (adjusted OR: 14.5; 95% CI: 5.0-42.2) and node involvement > 48 h (adjusted OR: 2.9; 95% CI: 1.2-7.2). There were no major complications. Follow-up was documented in 183 patients, of whom 92.3% achieved complete healing. CONCLUSIONS: Children hospitalized for a first episode of acute unilateral infectious adenitis generally do well. Younger patients and those with longer duration of node involvement before admission have an increased risk of surgical node drainage.

Abscess↗

Developmental expression of transcription factor genes in a demosponge: insights into the origin of metazoan multicellularity.

Demosponges are considered part of the most basal evolutionary lineage in the animal kingdom. Although the sponge body plan fundamentally differs from that of other metazoans, their development includes many of the hallmarks of bilaterian and eumetazoan embryogenesis, namely fertilization followed by a period of cell division yielding distinct cell populations, which through a gastrulation-like process become allocated into different cell layers and patterned within these layers. These observations suggest that the last common ancestor (LCA) to all living animals was developmentally more sophisticated than is widely appreciated and used asymmetric cell division and morphogen gradients to establish localized populations of specified cells within the embryo. Here we demonstrate that members of a range of transcription factor gene classes, many of which appear to be metazoan-specific, are expressed during the development of the demosponge Reniera, including ANTP, Pax, POU, LIM-HD, Sox, nuclear receptor, Fox (forkhead), T-box, Mef2, and Ets genes. Phylogenetic analysis of these genes suggests that not only the origin but the diversification of some of the major developmental metazoan transcription factor classes took place before sponges diverged from the rest of the Metazoa. Their expression during demosponge development suggests that, as in today's sophisticated metazoans, these genes may have functioned in the regulatory network of the metazoan LCA to control cell specification and regionalized gene expression during embryogenesis.

Amino Acid Sequence↗