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G Dupuis

Publications and source records attributed to G Dupuis.

At least 73 records · Page 4Linked to original sources
PubMed1988

Lectin interactions with the Jurkat leukemic T-cell line: quantitative binding studies and interleukin-2 production.

Phytohemagglutinin (PHA), concanavalin A (Con A), pea lectin, and wheat germ agglutinin (WGA) have been used to investigate their binding properties to Jurkat 77 6.8 leukemic human T cells and their ability to induce these cells to produce interleukin-2 (IL-2). Binding studies showed that the Jurkat cells fixed 0.82 +/- 0.11 microgram pea lectin, 2.02 +/- 0.17 micrograms Con A, 1.85 +/- 0.07 micrograms PHA and 8.88 +/- 0.61 micrograms WGA. Scatchard plots were linear, indicating that the binding process was homogeneous with respect to the binding constant. PHA and Con A bound with the highest affinity [Kass (apparent) approximately equal to 9 x 10(9) M-1], followed by pea lectin and WGA [Kass (apparent) approximately equal to 3 x 10(9) M-1]. The number of lectin binding sites was in agreement with the results of saturation experiments. We also evaluated the effect of the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the binding process. Results show that there were no gross alterations in the value of (apparent) Kass in the case of PHA and WGA. In contrast, the presence of TPA decreased the affinity of Con A and modified the Scatchard profile for pea lectin, which was curvilinear with a concavity turned upward. In this case, data were (apparent) K1 = 17.7 x 10(9) M-1 ("high-affinity" sites) and (apparent) K2 = 2.6 x 10(9) M-1 ("low-affinity" sites). The four lectins shared the ability to stimulate Jurkat 77 6.8 cells to secrete IL-2. Optimal lectin concentrations were 20 micrograms/ml (PHA) and 50 micrograms/ml (WGA and Con A). Pea lectin failed to display a dose-response relationship, and IL-2 production increased proportionally with lectin concentration. Con A was the most efficient stimulator (250 U/ml), followed by WGA (160 U/ml) and PHA (108 U/ml). Addition of TPA potentiated Jurkat cell response. In this case, Con A and pea lectin were the most efficient stimulators (470 U/ml), followed by PHA (316 U/ml) and WGA (271 U/ml). Here, also, pea lectin failed to show a dose-response relationship. Our data do not reveal an obvious relationship between the binding parameters and the ability of the lectins to induce IL-2 production. We suggest that the efficiency of the four lectins to stimulate IL-2 production in the case of the Jurkat 77 6.8 variant is most likely related to the nature of their specific cell surface receptor(s).

Binding Sites↗
PubMed1988

Enzyme-linked immunosorbent assay for diagnosis of chronic Q fever.

From 1982 through 1987 we diagnosed 13 chronic Q fever cases. Clinically these patients presented a culture-negative endocarditis, and all but two had high complement-fixing antibody titers to Coxiella burnetii phase I (reciprocal titer above 200). With the enzyme-linked immunosorbent assay (ELISA), titers of immunoglobulin G (IgG) to phases I and II of C. burnetii averaged 158,000 and 69,900, respectively, whereas they reached 300 and 3,200 in acute Q fever cases. Similarly, IgA to both phases of C. burnetii and IgM to phase I were consistently higher during chronic than acute Q fever. The serological follow-up of one patient with chronic Q fever over a 4-year period showed a good correlation between the titers of IgG and IgM antibody titers detected by ELISA and indirect fluorescent-antibody test (IFA) to both phases of C. burnetii. Few discrepancies appeared with IgA. Shortly after initiation of antibiotic treatment, a slow and steady decrease of the antibody titers to C. burnetii phases I and II was observed. The complement fixation, IFA, and ELISA tests showed the same type of antibody response. The ELISA proved to be an excellent diagnostic test for chronic Q fever. It distinguished negative from positive reactions clearly, and results were highly reproducible. The reading is objective, and the test is simple to perform and more sensitive than the IFA and complement fixation tests. The ELISA is recommended for serologic evaluation of patients with chronic Q fever.

Antibodies, Bacterial↗
PubMed1987

An important outbreak of human Q fever in a Swiss Alpine valley.

We describe an important Q fever human epidemic involving 415 serologically confirmed cases in the Val de Bagnes (Valais, Switzerland) during the autumn of 1983. The ages of the 415 cases with acute Q fever ranged from 8 to 82 years with a mean of 35 years, of whom 58% (240) were men and 42% (175) were women. This outbreak started about three weeks after 12 flocks of sheep (between 850 and 900 animals) descended from the alpine pastures to the valley. Geographically, the epidemic reached all the villages in the lower part of the Val de Bagnes located along the road followed by the sheep. As a result, 21.1% of the population of these villages contracted Q fever during this period. In contrast (p less than 0.001), the inhabitants of the higher villages away from the road followed by the sheep were only slightly affected (2.9%). Better collaboration between physicians and veterinarians would prevent such outbreaks in the future.

Adolescent↗
PubMed1987

B lymphocytes respond specifically to phytohaemagglutinin after liposome-dependent transfer of purified phytohaemagglutinin receptors.

Phytohaemagglutinin (PHA) receptor glycoproteins purified by affinity chromatography from porcine splenic lymphocytes, were reconstituted into vesicles made of phosphatidylcholine and phosphatidylserine, concomitantly with Sendai virus fusogenic proteins HN and F. The vesicles were used as a vehicle to insert the PHA receptor glycoproteins into a highly enriched population of porcine B lymphocytes. Fluorescence analyses showed that 52 +/- 2% of the reconstituted B cells had incorporated the lectin receptors. The modified B lymphocytes were assayed for their response (tritiated thymidine incorporation into nucleic acids) to PHA, concanavalin A (Con A), or to lipopolysaccharide (LPS). The results showed that porcine B cells fused with vesicles containing only viral fusogenic proteins failed to respond to either PHA or Con A. Tritiated thymidine incorporation was similar to background values. The cells did, however, respond to LPS with values of label incorporation similar to those observed in the case of pre-fused B lymphocytes. When purified B lymphocytes were fused with vesicles containing PHA receptors and viral fusogenic proteins, assays of thymidine incorporation showed a statistically significant (P less than 0.001) and specific response of the modified cells to PHA stimulation. Reconstituted cells cultured in the presence of PHA incorporated approximately nine times more radioactive label than pre-fused cells or cells fused with vesicles containing only fusogenic viral proteins. In marked contrast, reconstituted B lymphocytes did not show any significant label incorporation above background level in response to Con A, but they retained their ability to respond to LPS. Our findings suggest that B lymphocytes can be made to respond specifically to PHA by insertion of appropriate lymphocyte-derived receptors.

Animals↗
PubMed1987

Comparison of enzyme-linked immunosorbent assay and complement fixation and indirect fluorescent-antibody tests for detection of Coxiella burnetii antibody.

An enzyme-linked immunosorbent assay (ELISA) was developed to detect immunoglobulin G to Coxiella burnetii phase II. Serum samples from 213 patients who had had Q fever 1 year previously and from 301 blood donors from six localities in Switzerland were tested by ELISA and by indirect fluorescent-antibody (IFA) and complement fixation (CF) tests. The ELISA and the IFA and CF tests detected antibody to C. burnetii in 202 (94.8%), 193 (90.6%), and 166 (77.8%) of the 213 Q fever patients, respectively. With the serum samples from blood donors, the ELISA yielded a higher percentage of positive sera than did the IFA and CF tests. The high specificity of the three tests was confirmed by analyzing paired serum samples from 36 patients suffering from acute pneumonia of viral or bacterial origin. In these cases, the serological results were negative by the three tests, except for three Q-fever cases included as positive control.

Antibodies, Bacterial↗
PubMed1987

Functional incorporation and preferred orientation of phytohemagglutinin receptor glycoproteins in phospholipid vesicles.

Porcine lymphocyte Phaseolus vulgaris phytohemagglutinin (PHA) receptor glycoproteins purified by affinity chromatography have been reassembled into vesicles made of phosphatidylcholine and phosphatidylserine by detergent (dodecyltrimethylammonium bromide) dialysis. The receptor glycoproteins were incorporated into the lipid vesicles in a nonselective manner with a yield of 65-70%. Vesicles containing the glycoproteins were sealed as evidenced by their impermeability to calcium ions, using quin 2 trapped inside the vesicles. The vesicles were agglutinated by PHA, suggesting that the saccharidic moiety of the reconstituted glycoproteins was, at least in part, oriented towards the extravesicular medium. This observation was further supported by the fact that the vesicles bound 125I-labeled PHA in a specific and saturable manner. At maximum amount of lectin bound, a ratio of 1.01 +/- 0.05 microgram of PHA per microgram glycoprotein incorporated was measured. When the binding data were analyzed by Scatchard plot, a downward concave profile was observed, suggestive of a positive cooperativity at low concentrations of lectin. The orientation of the reconstituted lectin receptor glycoproteins was determined by proteolytic treatments of labeled glycoproteins. The combined action of trypsin and chymotrypsin released, in the 120,000 X g supernatant, approximately 80% of label when 125I-tagged PHA receptor glycoproteins were incorporated into the vesicles. When the oligosaccharidic moieties of the receptor glycoproteins were specifically labeled, the simultaneous action of the two enzymes released approximately 70% of tritium labeling present in the reconstituted system. Taken together, these results suggest that the reconstituted PHA receptors are preferentially oriented into the phospholipid vesicles. The reconstituted PHA receptor glycoproteins competed effectively with cellular receptors in the assay of PHA-induced porcine lymphocyte activation. A 50% inhibition of [3H]thymidine incorporation was observed when 1 microgram of glycoproteins in vesicles was added to the cultured cells, whereas vesicles alone had no effect at this (equivalent) concentration.

Animals↗
PubMed1986

[Seroprevalence of human Q fever in Switzerland].

In current practice, only serology, by the titration of anti-Coxiella burnetii antibodies, permits the diagnosis of acute or chronic Q fever. New serological techniques have also made it possible to more accurately determine the number of people in a community who have been affected by this infectious agent. We have thus been able to compare the results of 1437 specimens from the whole of Switzerland with 4009 taken in the Valais. The analysis of these sera by indirect microimmunofluorescence now shows that Q fever is much more prevalent than was generally estimated. However, these results vary greatly from one area and another, between 6.7% and 31.7% depending on the locality. Normally the lowest percentages were found in the big cities (from 9.5% to 12.2% in Berne, Geneva and Zurich) whilst the highest incidences were found in mountain regions (from 23.6% to 31.7% in the Tessin, Uri or the Valais). Regarding sex distribution, it was found that the incidence of Q fever is on average slightly lower (between 3% and 5%) in women than in men. It was also noted that the percentage of people having anti-Coxiella burnetii antibodies increases with age. The high incidence of Q fever in Switzerland is also of concern because of a severe and chronic form of this infection: endocarditis.

Adolescent↗
PubMed1986

Serological diagnosis of Q fever endocarditis.

The diagnosis of Q fever endocarditis cannot be made by bacterial cultures and necessitates serological identification of specific antibodies to Coxiella burnetii which stimulates mainly the production of anti-phase II antibodies during the acute disease, but primarily anti-phase I antibodies in endocarditis. Indirect microimmunofluorescence allows rapid detection of specific IgA, IgG and IgM. The results of serological analyses of 191 acute cases of Q fever were compared with those of 8 cases of Coxiella burnetii endocarditis. All sera were evaluated by complement fixation and microimmunofluorescence tests. The highest titre differences between primary Q fever and Q fever endocarditis were observed with anti-phase I IgA and IgG antibodies measured by microimmunofluorescence followed by anti-phase I antibodies measured by complement fixation tests. Antiphase I IgG and IgM titres were consistently higher than anti-phase II titres in endocarditis. The reverse is true in acute Q fever. In addition, anti-phase I IgA appeared to be diagnostic for Coxiella burnetii endocarditis. Accordingly we recommend the testing of these specific IgA, IgG, and IgM by microimmunofluorescence in cases of culture-negative endocarditis. These tests could also prove useful for following the development of Coxiella burnetii endocarditis in patients under treatment.

Antibodies, Bacterial↗
PubMed1985

Phytohemagglutinin (PHA)-resistant Chinese hamster ovary cell mutants acquire sensitivity to the lectin after fusion with liposomes containing PHA receptor glycoproteins.

Phytohemagglutinin receptor glycoproteins have been inserted into phospholipid vesicles and these have been fused with phytohemagglutinin-resistant chinese hamster ovary cells. Our results show that the fused cells acquire "neoreceptors" for the lectin phytohemagglutinin. Fluorescence activated cell sorting analyses show that approximately 40% of the cells fused with the receptor-containing vesicles. Studies with 125I-labelled lectin showed that fused cells bound three times more ligand than untreated mutant cells. Furthermore, lectin receptors were functionally inserted in the mutant cell plasma membrane. Fused cells cultured in the presence of lectin (200 micrograms ml-1) lost rapidly (8 hours or less) their ability to incorporate [3H] thymidine. Whereas mutant cells cultured for 16 hours in the presence of 50-400 micrograms ml-1 of lectin remained viable, fused cells showed a 45% decrease in 3H-labelled nucleotide incorporation. The method described here should be of general applicability for the study of lectin-dependent cytotoxicity in chinese hamster ovary cell lines.

Animals↗
PubMed1985

[Clinical aspects observed during an epidemic of 415 cases of Q fever].

The clinical findings during a major epidemic of Q-fever which affected 415 people in the Val de Bagnes (Valais, Switzerland) in the autumn of 1983 are reported. Q-fever symptoms were evident in 191 cases but inconspicuous or absent in 224 cases. The symptoms most frequently reported were prolonged high fever, headaches, severe exhaustion, loss of appetite, cough and myalgia. Amongst disorders which accompany acute Q-fever, pneumonia and granulomatous hepatitis are very frequent, while myopericarditis and glomerulonephritis are less frequently observed. Endocarditis, a later complication of Q-fever, is a severe illness which more frequently affects patients with underlying valvular lesions. New serological techniques now permit more rapid and more accurate diagnosis of both acute and chronic Q-fever.

Adolescent↗
PubMed1985

Evaluation of the Cobasbact automated antimicrobial susceptibility testing system.

The Cobasbact is an automated system for use in the microbiological laboratory which is capable of performing antimicrobial susceptibility tests within five hours. The performance of the Cobasbact system was evaluated using 2000 non-fastidious, facultative and aerobic clinical bacterial isolates. The standard Kirby-Bauer disk diffusion test served as reference method. For gram-positive isolates, the rate of overall full and essential agreement between Cobasbact and reference antibiograms was 90% and 95.5% respectively, for Enterobacteriaceae 91% and 95.5% and for Pseudomonas spp. 90% and 96%. Reproducibility studies yielded an essential agreement rate of 98%. On the basis of this preliminary evaluation it would seem that the Cobasbact system can rapidly produce reasonably accurate and reproducible results of antimicrobial susceptibility tests for gram-positive cocci, Enterobacteriaceae and Pseudomonas spp.

Automation↗
PubMed1985

Evaluation of the complement fixation and indirect immunofluorescence tests in the early diagnosis of primary Q fever.

A comparison was made of the performance of the commonly used complement fixation test and the more recently developed indirect immunofluorescence test in the early diagnosis of Q fever. The 303 sera tested were from 181 patients who contracted Q fever during an outbreak in Switzerland in 1983. Specific IgM antibodies were detected by the immunofluorescence test in 53% and 89% of sera obtained during the first and second week respectively after onset of illness. With the complement fixation test, the diagnosis could not be made until the second week of illness. The immunofluorescence test proved to be superior to the complement fixation test in the early detection of Q fever. Not only was it more specific but also faster and simpler to perform, permitting an earlier diagnosis on the basis of results obtained with a single serum specimen.

Antigens, Bacterial↗
PubMed1985

Immunoglobulin responses in acute Q fever.

Knowledge of the development of different classes of antibody during the course of acute Q fever is important to the clinician for interpreting a patient's serological test results. In the present study, the appearance of antibodies to Coxiella burnetii phases I and II was determined for a period of 1 year. A total of 683 sera from 191 patients with symptomatic Q fever were evaluated by the complement fixation and indirect immunofluorescence (immunoglobulins M and G [IgM, IgG]) tests. These patients had contracted acute Q fever in the fall of 1983 during an epidemic that resulted in 415 serologically confirmed cases of Q fever. As demonstrated by the complement fixation test, antibodies to C. burnetii phase II remained elevated throughout the entire study period, whereas antibodies to phase I were barely detectable. Although the immunofluorescence test was more sensitive than the complement fixation test, the specific anti-IgG response to C. burnetii to phases I and II gave the same general antibody profiles as did the complement fixation test. IgM anti-phase I and II titers appeared earlier but disappeared after 10 to 12 weeks. During this period, anti-phase II antibody levels were generally much higher than anti-phase I antibody levels.

Antibodies, Bacterial↗
PubMed1985

Affinity chromatography purification and partial characterization of phytohemagglutinin-receptor glycoproteins from porcine splenic lymphocytes.

We describe the isolation of pig spleen lymphocyte glycoproteins that interact with phytohemagglutinin (PHA), the lectin from Phaseolus vulgaris. Purification was achieved by affinity chromatography of a Nonidet P-40 extract of the cells on a PHA--Affi-Gel 10 column. The retained glycoproteins were eluted with an acidic (pH 3.0) glycine buffer and represented 1.9-2.4% of the amount of protein applied to the column. They contained 20 +/- 1.3% hexose and 1.7 +/- 0.7% fatty acids, on a weight basis. Electrophoretic analyses (sodium dodecyl sulfate--polyacrylamide gel electrophoresis) showed the presence of major Coomassie blue positive bands with apparent molecular masses of 50-55, 75, 95, 130, and 155 kdaltons along with minor bands of 20-40, 42, 45, 60-65, 175, and 200-250 kdaltons. The purified PHA-receptor glycoproteins inhibited, in a dose-dependent manner, the incorporation of [3H]thymidine in pig lymphocytes cultured at a concentration of 10(6) cells/mL in the presence of PHA. A 50% inhibition was observed when 20 micrograms/mL of the glycoproteins was added to the lymphocyte cultures containing 0.5 microgram/mL of PHA. Scatchard analysis of the binding of 125I-labelled PHA, in the presence of increasing amounts of the purified glycoproteins, showed a suppression of the binding of the lectin to high affinity sites of the cells, as evidenced by a change from biphasic to a linear profile. Results of binding suggested a competitive inhibition by a population of purified glycoproteins with a similar affinity for the lectin. The purified glycoproteins decreased PHA-dependent interleukin 2 (IL-2) production by pig lymphocytes as assayed with a IL-2 dependent murine cell line.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Binding of phytohemagglutinin to porcine lymphocyte receptors. Time-course studies and comparative binding isotherms using whole cells or cellular receptors incorporated into phospholipid vesicles.

We have studied the binding of 125I-labeled phytohemagglutinin (PHA) to porcine splenic lymphocytes (10(7) cells . mL-1) at 37 degrees C. Our data show that PHA binding is dependent on the incubation period and that a maximum quantity of 4.53 +/- 0.13 micrograms is bound when 200 micrograms of PHA is added. The binding process is rapid and saturation can readily be achieved in less than 2 min. These observations suggest, in accordance with the mass-action principle, that the binding equilibrium can be rapidly displaced towards PHA-receptor complex formation when sufficient amounts of PHA are added. Our data further suggest that receptor sites are exposed at the cell surface and that putative cryptic receptor sites are unlikely to play a major role in the initial part of the binding process. We have studied this aspect by comparing Scatchard plots for PHA binding to receptors in intact lymphocytes and to lymphocyte-derived receptors incorporated into liposomes. In one case, partially purified plasma membranes were solubilized and incorporated into phosphatidylcholine-phosphatidylserine (PC-PS) vesicles prepared by detergent dialysis. In another case, PHA-receptor glycoproteins were purified by affinity chromatography and reassembled into PC-PS vesicles, using the same technique. Scatchard plot analyses showed nonlinear profiles with a concavity turned upward for PHA binding to receptors of intact cells or of PC-PS vesicles with plasma membranes, and a concavity turned downward for vesicles with purified glycoproteins. These observations suggest that PHA-receptor environment plays a determining role in the binding process of the lectin. Numerical data from binding experiments were obtained by computer-assisted nonlinear regression analysis, using a one ligand--two sites model. The (apparent) high-affinity constant (K1) for intact lymphocytes or partially purified plasma membrane components reassembled into liposomes was 4.6 X 10(7) M-1 and the (apparent) low-affinity constants (K2) were 4.4 X 10(6) +/- 1.5 X 10(6) M-1 (intact lymphocytes) and 1.7 X 10(6) +/- 0.6 X 10(6) M-1 (plasma membranes constituents reassembled into liposomes). The value obtained for reconstituted PHA-glycoprotein receptors (K) was 0.70 X 10(7) +/- 0.10 X 10(7) M-1. The apparent number of sites was n1 = 0.19 X 10(6) +/- 0.05 X 10(6) (high affinity) and n2 = 2.50 X 10(6) +/- 0.50 X 10(6) (low affinity) sites per intact lymphocyte cell.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗