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Biomedical subjects

C Hannoun

Publications and source records attributed to C Hannoun.

At least 55 records · Page 3Linked to original sources
PubMed1992

A nylon membrane enzyme immunoassay for rapid diagnosis of influenza A infection.

A new membrane-enzyme immunofiltration assay (MIFA) was developed for rapid diagnosis of influenza A infection. The pretreated specimens were dispensed into a 1.2 micron Biodyne B nylon membrane-bottomed microplate and vacuum filtration was applied. Blocking solution, peroxidase-conjugated anti-influenza A nucleoprotein monoclonal antibody, washing buffer and substrate were added in that order. The assay was completed within 30 min. Out of 103 nasopharyngeal swabs collected in transport medium, 31 isolates of influenza A virus were obtained and 22 specimens were detected directly by the MIFA technique. The 9 isolation-positive MIFA-negative specimens required 6 days or more for viral detection in cell culture, and probably contained a very low quantity of virus. The 72 cell culture negative specimens were also negative by MIFA. Comparison with a classical immunocapture assay (ICA) gave a better sensitivity for MIFA, as only 15/103 specimens were positive by ICA. MIFA is a rapid test with 71% sensitivity and 100% specificity. It was also very useful to test the cell culture supernatants, as a sensitivity of 100% was obtained with MIFA when the immunofluorescence technique was positive. The same technique could be readily carried out on the same plate for other respiratory viruses since capture antibody is not used.

Adolescent↗
PubMed1991

Analytical detection of 9(4)-O-acetylated sialoglycoproteins and gangliosides using influenza C virus.

The unique glycoprotein of influenza C virus, designated hemagglutinin (HEF), exhibits three functions: hemagglutination, esterase activity, and fusion factor. As the virus uses 9-O-acetylated sialic acid as a high-affinity receptor determinant for attachment to cells, its binding activity was used to reveal O-acetylated sialic acid residues after polyacrylamide gel electrophoresis and transfer onto nitrocellulose sheets of proteins and thin-layer chromatography of lipids. The specificity of the binding for O-acetylated sialoglycoconjugates was investigated. Our results showed that influenza C virus could detect the different forms of the two murine glycophorins which are known to be O-acetylated sialoglycoconjugates. The virus also bound to O-acetylated gangliosides isolated from embryonic chicken brain such as purified O-acetylated NeuAc alpha (2-8)NeuAc alpha (2-8)NeuAc alpha (2-3)Gal beta (1-4)Glc beta (1-1)ceramide (GT3). The esterase activity of the HEF protein of influenza C virus was used to unmask the sialic acid. After its deacetylation by the virus enzyme, the O-acetylated GT3 was recognized by a monoclonal antibody which binds only to the nonacetylated derivative. The results presented here show that influenza C virus is a discriminating analytical probe for identifying O-acetylated sialoglycoconjugates directly after Western blotting of proteins and thin-layer chromatography of lipids, thus providing a new analytical tool.

Acetylation↗
PubMed1991

Activity of influenza C virus O-acetylesterase with O-acetyl-containing compounds.

Influenza C virus (strain C/Johannesburg/1/66) was grown, harvested, purified and used as source for the enzyme O-acetylesterase (N-acyl-O-acetylneuraminate O-acetylhydrolase; EC 3.1.1.53). This activity was studied and characterized with regard to some new substrates. The pH optimum of the enzyme is around 7.6, its stability at different pH values shows a result similar to that of the pH optimum, and its activity is well maintained in the pH range from 7.0 to 8.5 (all these tests were performed with 4-nitrophenyl acetate as substrate). Remarkable differences were found in the values of both Km and Vmax, with the synthetic substrates 4-nitrophenyl acetate, 2-nitrophenyl acetate, 4-methylumbelliferyl acetate, 1-naphthyl acetate and fluorescein diacetate. The use of 4-nitrophenyl acetate, 4-methylumbelliferyl acetate or 1-naphthyl acetate as substrate seems to be convenient for routine work, but it is better to carry out the measurements in parallel with those on bovine submandibular gland mucin (the latter is a natural and commercially available substrate). It was found that 4-acetoxybenzoic acid, as well as the methyl ester of 2-acetoxybenzoic acid, but not 2-acetoxybenzoic acid itself, are cleaved by this enzyme. Triacetin, di-O-acetyladenosine, tri-O-acetyladenosine, and di-O-acetyl-N-acetyladenosine phosphate, hitherto unreported as substrates for this viral esterase, are hydrolysed at different rates by this enzyme. We conclude that the O-acetylesterase from influenza C virus has a broad specificity towards both synthetic and natural non-sialic acid-containing substrates. Zn2+, Mn2+ and Pb2+ (as their chloride salts), N-acetylneuraminic acid, 4-methyl-umbelliferone and 2-acetoxybenzoic acid (acetylsalicylic acid) did not act as inhibitors.

Acetylesterase↗
PubMed1991

A new influenza surveillance system in France: the Ile-de-France "GROG". 2. Validity of indicators (1984-1989).

The evaluation of the validity of the GROG's indicators is based on the first five years of activity, four of which being epidemic ones. A virological criterion for identifying epidemics is used as the gold standard. For each non-specific indicator, the ratio of epidemic weeks to non-epidemic weeks is outlined. Therefore we can define four epidemic situations in relation with the strains circulating and the non-specific indicators. Influenza A epidemics, which are known as a mortality problem can also be described according to its impact upon morbidity. As a result, it is possible to set up a sensitive and specific surveillance system for early detection of influenza epidemics. This objective is achieved by combining both the weekly collection of virological data as well as the collection of other available indicators either in routine practice or as provided by a network of sentinel practitioners. Such detection can pave the way for an improvement in preventive measures against the harmful effects on health of influenza epidemics.

Antiviral Agents↗
PubMed1990

[Prevention of influenza A. Effectiveness and tolerance of rimantadine hydrochloride].

The prophylactic effectiveness of rimantadine hydrochloride (RH) during an outbreak of influenza A was evaluated in a double-blind study versus placebo (P). After identification of 111 homes with one affected member, 301 household contacts were enrolled and given either RH (151 contacts from 56 households) or a placebo (150 contacts from 55 households). Each treatment was given for ten days. Overall, at least one contact developed influenza in 8 of the 56 RH group households and 19 of the 55 placebo group households (p = 0.013). Numbers of contacts who developed influenza were 8/151 in the RH group and 26/150 in the placebo group. When only the 49 homes where influenza was confirmed by virological studies were considered, these numbers were 4/28 in the RH group and 10/21 in the placebo group (p = 0.011). Adverse effects were seen in 18 of the 151 subjects given RH (11.9 per cent) and 6 of the 150 subjects given the placebo (4 per cent). RH appeared as an effective prophylactic agent in a confirmed influenza A outbreak and was satisfactorily tolerated.

Adamantane↗
PubMed1990

In vitro human cytotoxic T cell responses against influenza A virus can be induced and selected by synthetic peptides.

Studies on human anti-influenza cytolytic activities have demonstrated that cytotoxic T lymphocytes (CTL) from HLA-B37 individuals react preferentially with the peptide corresponding to residues 335-349 of the nucleoprotein, whereas CTL from HLA-A2 donors recognize peptide 57-68 from the viral matrix as a dominant epitope. We studied the secondary CTL response, obtained from peripheral blood mononuclear cells, of an HLA-A2+,B37+ individual stimulated either by infectious virus or by synthetic peptides. Only an HLA-B37-restricted response was detected after stimulation by the whole virus, showing an immunodominance of this activity over that restricted by HLA-A2. Moreover, human cytotoxic cell lines were successfully obtained after stimulation of peripheral blood mononuclear cells with synthetic peptides. Under these conditions, it was possible to selectively reveal the existence of an HLA-A2-restricted activity directed against the matrix peptide. These results demonstrate that, at least in vitro, it is possible to stimulate a latent repertoire by using synthetic peptides. Nevertheless, we could not induce a response against the matrix or the nucleoprotein peptides in HLA-A2- or B37- individuals, suggesting that a finer selection of synthetic peptides would be necessary for their possible utilization to induce CTL during vaccination.

Amino Acid Sequence↗
PubMed1990

Carbohydrates inhibit the potentiating effect of bacteria, endotoxin and virus on basophil histamine release.

Histamine release caused by calcium ionophore A23187 and anti-IgE was examined in leukocyte suspensions from 8 healthy individuals. Staphylococcus aureus, lipopolysaccharide (LPS) from Salmonella typhimurium and influenza A virus were found to enhance the histamine release but did not release histamine per se. The potentiation of mediator release depends on a non-transient signal since the potentiating effect was also obtained by preincubation of the cells with LPS followed by wash-out and stimulation of the cells with anti-IgE. The potentiation was abolished or reduced by galactose, N-acetyl-glucosamine, alpha-methyl-D-glucoside, alpha-methyl-D-mannoside, N-acetylneuraminic acid and lactose, but not by glucose. These findings indicate that the enhancement of mediator release by bacteria, endotoxin, and virus depends on a sugar-mediated reaction.

Basophils↗
PubMed1990

Comparison of neuraminidases of the same subtype but from different species using a new method of titration.

Neuraminidase is one of the two surface glycoproteins of influenza virions. In order to compare neuraminidases of the same subtype but isolated from different species (man, birds, pig), a new and simple method was adapted and optimized using peanut hemagglutinin. Results were very similar to those obtained with the classical method recommended by the WHO, using fetuin as a substrate. The technique was used to examine the relationship between animal and human neuraminidases belonging to serotypes N1 and N2. The results confirm the possible role of ducks as a reservoir for influenza viruses and the eventuality of interspecific exchanges.

Animals↗
PubMed1990

Effects of iron deficiency upon the antibody response to influenza virus in rats.

The effects of severe and moderate iron deficiency upon the antibody response to influenza virus were investigated in rats. Three groups of weanling male Wistar rats were fed one of two iron-deficient diets (5 mg and 15 mg iron/kg diet) or a normal iron-containing diet (35 mg iron/kg diet). A group of individually pair-fed rats was introduced with the low iron-consuming rats. The effects of the diets upon various iron status parameters were followed during the 4th, 5th, 6th, and 7th week of diet. After 4 weeks of feeding different diets, an intraperitoneal injection of inactivated influenza virus A/New Jersey/76 was performed and a recall injection was done at 5 weeks. Primary and secondary antibody responses were assayed. Rats were sacrificed at 7 weeks of diet. After 4 weeks of feeding different diets, the rats fed the 5 mg iron/kg diet were severely anemic and rats fed 15 mg iron/kg diet were moderately iron-deficient, as shown by their iron status parameters. Growth was delayed in anemic and matched pair-fed rats. A primary antibody response was almost nonexistent in all groups. Secondary antibody titers were significantly weaker in anemic rats than in ad libitum controls, but were not different from those of pair-fed rats. This response was similar in moderately iron-deficient, ad libitum, and pair-fed rats. These results show that antibody synthesis in response to the influenza virus vaccine is preserved in moderate iron deficiency but is reduced in severe anemia. The reduction in energy consumption associated with severe iron deficiency in the rat could play a part in the altered humoral response.

Journal Article↗
PubMed1990

Influenza A virus enhances basophil histamine release and the enhancement is abolished by carbohydrates.

Basophil histamine release was studied in leukocyte suspensions from normal individuals and from patients allergic to house dust mite or birch pollen. Mediator release caused by IgE-mediated reactions was examined by stimulating the cells with anti-IgE or specific antigens, and the calcium ionophore A23187 was used for a non-immunological histamine release. In all experiments influenza A virus caused a synergic enhancement of the mediator release and the potentiation was abolished by galactose (10(-7) to 10(-6) M) and by 10(-6) to 10(-5) M of N-acetylglucosamine, alpha-methyl-D-glucoside, alpha-methyl-D-mannoside, N-acetylneuraminic acid and lactose, but not by glucose. Wash-out experiments show that the sugars prevent the aggravation of mediator release by a binding of sugar to the basophil cell membrane, thereby causing a blockade of binding sites responsible for the potentiating effect of virus.

Adult↗
PubMed1990

Sialidase activity in rimantadine-resistant and -sensitive influenza A viruses.

Rimantadine-resistant and -sensitive influenza A variants were assayed for their sialidase (neuraminidase, EC 3.2.1.18) activity. The kinetic parameters determined (pH optimum, stability against different pH values, thermal stability, activity on methylumbelliferyl-alpha-D-N-acetylneuraminic acid, N-acetylneuraminyl-lactose, fetuin and bovine submandibular gland mucin as substrates, Km with the former substrate, inhibition by two competitive inhibitors, and behavior towards amantadine) revealed the same results for both variants of the virus. Thus, it can be deduced that resistance to rimantadine does not influence the sialidase activity of influenza A virus.

Animals↗
PubMed1989

A new influenza surveillance system in France: the Ile-de-France "GROG". 1. Principles and methodology.

The aims of influenza surveillance have changed over the years. The early detection of epidemics is essential for practical decisions on vaccine development, strategy of vaccine prophylaxis, chemoprophylaxis or chemotherapy. A new surveillance system is presented which combines the classical specific data related to the isolations, direct detection of virus as well as serological findings, with non-specific indices. The rationale for definition and elaboration of such indices is discussed: selected parameters deal with medical activity of a panel of sentinel doctors (general practitioners and pediatricians), notifications of diagnosed acute respiratory viral infections, measure of emergency doctors activity, absence from work (as seen by physicians, insurance agencies or industrial personnel), selected drug prescription and consumption, hospital admissions. The sentinel physicians also cooperate in taking samples from cases, thereby extending the field of specific surveillance since they have contact with standard cases of the disease and not only hospitalized patients. A weekly comparison of time variations of specific and non-specific indices should permit a reliable evaluation of the epidemic situation and therefore be of great help for practical decisions. The system has operated since 1984, and the initial hypothesis of the sensitivity of some of the indices has already been verified.

Disease Outbreaks↗
PubMed1989

Kinetic studies on the sialidase of three influenza B and three influenza A virus strains.

Sialidase of influenza virus type A has been extensively studied through structural and kinetic approaches. However, sialidase of influenza virus type B has been less investigated. In this work, we have studied the activity and some properties (optimal pH, KM, Vmax, thermal stability) of sialidase in three influenza virus strains of type B (circulating in the period 1983-86) and also the activity and properties of sialidase from three virus strains of type A circulating at the same period of time. The results show that the activity and the Vmax was always higher for sialidase of type A viruses relative to those values of type B. Differences were also found for optimal pH and, in some cases, for thermal stability of the sialidase between strains belonging to the influenza viruses type A and B. However, the behaviour for the sialidase in all strains was very similar towards two competitive inhibitors. Thus, it could be suggested that the evolution pattern of the sialidase of both types of influenza viruses determines some modifications which result in a higher efficiency for sialidase of some strains of influenza virus type A, but maintaining in the two types of viruses a similar behaviour towards competitive inhibitors.

Animals↗
PubMed1989

Influenza A virus enhances IgE-mediated histamine release from human basophil leukocytes. Examination of the effect of viral neuraminidase and haemagglutinin.

Histamine release caused by anti-IgE was examined in leukocyte suspensions from 10 healthy individuals. Influenza A virus was found to enhance the histamine release but did not release histamine per se. When monoclonal antibodies directed against the viral neuraminidase were included in the samples, the potentiating effect of the virus was completely abolished. The same occurred using a neuraminidase inhibitor. However, monoclonal antibodies directed against the viral haemagglutinin also abolished the potentiation. A binding of virus to the basophil cell surface by haemagglutinin therefore seems to be necessary for the viral neuraminidase to cause potentiation of mediator release.

Antibodies, Anti-Idiotypic↗
PubMed1989

Influenza A virus enhances allergic histamine release. Effect of neuraminidase.

Histamine release was examined in leukocyte suspensions from patients allergic to house dust mite, grass pollen, birch pollen or cat dander. Influenza A virus was found to enhance the antigen-induced mediator release, but did not cause release of histamine from the cells per se. Also histamine release induced by anti-IgE in cell suspensions from normal individuals was enhanced by virus. The potentiating effect of influenza A virus might be due to neuraminidase on the surface of virus, since a similar effect was caused by a purified neuraminidase obtained from Vibrio cholerae, and the effect of virus as well as the neuraminidase was completely abolished by a potent neuraminidase inhibitor. The synergistic enhancement in IgE-mediated histamine release by virus could be of significance for the conversion from latent to manifest asthma.

Adult↗
PubMed1989

Influenza A virus enhances Staphylococcus aureus-induced basophil histamine release in normal individuals and patients with intrinsic asthma.

Influenza A virus was found to enhance Staphylococcus aureus-induced histamine release in human leukocyte suspensions, but did not per se release histamine. This potentiating effect was found to be similar in cells from normal individuals and from patients with intrinsic asthma. The enhancement of mediator release could be due to viral neuraminidase on the surface of the virus, since a similar potentiating effect was caused by a purified neuraminidase preparation obtained from Vibrio cholerae, and the effect of virus as well as of the purified neuraminidase was completely abolished by a potent neuraminidase inhibitor. The potentiating effect of virus on bacteria-induced mediator release might be of importance for the conversion from latent to manifest asthma in upper respiratory tract infections.

Adult↗