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Red blood cells (RBCs) in pathological situations undergo biochemical and conformational changes, leading to alterations in rheology involved in cardiovascular events. The shape of RBCs in volunteers and stable and exacerbated chronic obstructive pulmonary disease (COPD) patients was analyzed. The effects of RBC spherization on platelet transport (displacement in the flow field caused by their interaction with RBCs) were studied in vitro and by numerical simulations. RBC spherization was observed in COPD patients compared with volunteers. In in vitro experiments at a shear rate of 100 s-1 , treatment of RBCs with neuraminidase induced greater sphericity, which mainly affected platelet aggregates without changing aggregate size. At 400 s-1 , neuraminidase treatment changes both the size of the aggregates and the number of platelet aggregates. Numerical simulations indicated that RBC spherization induces an increase of the platelet mean square displacement, which is traditionally linked to the platelet diffusion coefficient. RBCs of COPD patients are more spherical than healthy volunteers. Experimentally, RBC spherization induces increased platelet transport to the wall. Additional studies are needed to understand the link between the effect of RBCs on platelet transport and the increased cardiovascular events observed in COPD patients.

The transmission of Influenza A viruses (IAV), either airborne in mammals or oro-faecal in aquatic birds, submits viral particle to a wide range of environmental conditions. These environmental conditions modulate IAV survival outside the host, which is also dependent on the viral subtype or strains. To date, the molecular drivers of IAV environmental persistence remain to be identified. In order to identify IAV molecular drivers of the environmental persistence, we generated different reassortant viruses between two H1N1 viruses that do not have the same stability outside the host. To this purpose, we performed survival kinetic and compared the inactivation slope of generated reassortant viruses in our controlledenvironment, using a real time cell analysis system. Our results demonstrate that the hemagglutinin (HA) and the neuraminidase (NA) are the main viral segments driving IAV environmental persistence. In addition, mutations driving viral stability in the environment were identified in the HA and NA amino-acid sequences. We also demonstrated that synonymous mutations introduced in the HA, using a codon-optimization strategy, drive the environmental persistence of IAV. The HA stability at low pH, HA surface expression levels in infected cells and the number of calcium binding sites of the NA were alternately changed by the mutations described in our study, indicating that these are stability determinants of IAV survival outside the host. Then, the sequential events of viral entry were analysed with fluorescence microscopy assays, showing that viral particles being exposed for a long period in saline water at 35°C are still able to bind their cellular receptor whereas the HA-mediated fusion within the endosome is not possible anymore. These two steps of the viral cycle are mainly mediated by the HA protein. Altogether, these result highlight the importance of the HA and the NA proteins, driving the environmental persistence of IAV. Given the known diversity of these two proteins in nature, this arouses interest in studying IAV environmental persistence at a more global scale. Such study could improve our knowledge on IAV ecology and epidemiology. Epidemiologic and climatic data analyse of human seasonal influenza viruses during 5 years and from 13 countries revealed that H1N1 virus and H3N2 virus distribution differs according to the mean weekly temperature in these countries. We then compared the H1N1 virus and H3N2 virus persistence on stainless steel surface at 4 °C and 20 °C, and the preliminary results suggest that IAV seasonal subtypes distribution might be partly regulated by their stability according to the temperature; La transmission des virus grippaux de type A s’effectue via l’eau, l’air ou les surfaces. Elle implique donc toujours une étape dans l’environnement, durant laquelle les virus sont inactivés plus ou moins rapidement en fonction du sous-type ou de la souche virale analysés. Cependant, à ce jour, les facteurs moléculaires déterminant la stabilité des particules virales en dehors de l’hôte restent largement méconnus. Dans le but d’identifier ces déterminants, nous avons généré différentes combinaisons de réassortiments entre deux virus grippaux de sous-types H1N1 possédant un phénotype de stabilité différent. Les stabilités respectives de ces virus réassortants ont été évaluées dans un environnement-modèle, puis comparées entre elles. Pour cela, nous avons utilisé un système d’analyse en temps réel des cultures cellulaires, permettant de calculer, pour chacun des virus testés, une pente d’inactivation moyenne et, in fine, de mesurer l’influence respective de chacun des segments viraux sur le phénotype de stabilité des virus. D’après nos résultats, le phénotype de stabilité des virus grippaux est majoritairement déterminé par l’hémagglutinine (HA) et la neuraminidase (NA), qui sont les principales glycoprotéines de surface de ces virus. De plus, nous avons identifié des changements d’acides aminés dans la HA et dans la NA, qui ont pour effet une diminution ou une augmentation de la stabilité des particules virales dans l’environnement. Nous avons également montré qu’un virus avec un gène de la HA codons-optimisés, et donc porteur de mutations synonymes, suffit pour augmenter significativement la stabilité des particules virales dans l’environnement. La stabilité de la HA à pH acide, le taux d’expression de la HA dans les cellules infectées, et le nombre de sites de fixation aux ions calcium dans la NA sont modifiés par les mutations décrites dans cette étude, et sont donc des facteurs de stabilité des particules virales. De plus, une analyse en microscopie a permis de montrer que les virus inactivés dans l’environnement peuvent fixer leurs récepteurs cellulaires, mais sont incompétents pour induire l’étape de fusion dans l’endosome nécessaire à l’entrée des virus dans la cellule. Ces deux étapes du cycle viral sont dépendantes de la HA. Dans l’ensemble, nos résultats montrent l’importance de la HA et de la NA des virus grippaux dans la détermination du phénotype de stabilité des virus grippaux dans l’environnement. Par conséquent, la diversité connue des HA et NA dans la nature laisse supposer des variations fréquentes du phénotype de stabilité de ces virus. Leur étude pourrait permettre de mieux décrire l’écologie et l’épidémiologie de ces virus. L’analyse des données épidémiologiques et climatiques des épidémies de grippe saisonnière, sur 5 ans et dans 13 pays, a ainsi révélé une différence de distribution des virus H1N1 et H3N2, en fonction de la température hebdomadaire dans ces pays. La comparaison de la stabilité de ces virus sur des surfaces, à 4 °C et à 20 °C, suggère que la distribution des sous-types viraux au début des épidémies est en partie régulée par leur stabilité en fonction de la température

National audience; One of the host-range determinants that favor the multiplication of influenza viruses in domestic poultry is the length of the neuraminidase (NA) stalk: a deletion of about 20 amino acids in the NA-stalk is frequently detected upon transmission of influenza A viruses from waterfowl to domestic poultry and was recently associated with increased virulence in chicken. Whether this modification has any effect in ducks is currently unknown. Using reverse genetics, a recombinant virus derived from a turkey H7N1 influenza virus isolate with a short-stalk neuraminidase, A/turkey/Italy/977/1999, and an NA stalk insertion variant (insNA) were produced. Four-week-old chickens that were inoculated via the intratracheal and oral routes with the insNA virus showed a better survival and a lower oro-pharyngeal excretion than those inoculated with the wt-virus. The two viruses did not differ as regards viral loads in the lungs, kidneys and caeca, but the short-stalk NA virus induced more necrotic lesions in the bronchial epithelium. Conversely, the insNA virus showed a higher cloacal excretion when inoculated to 4-wk-old ducks. Chickens inoculated with the less pathogenic, long-stalk NA-virus showed, at 2 d.p.i. in the lungs, significantly increased levels of mRNAs encoding IFNγ, IL-8, IL-15, IL-6, and to a lesser extent CCL5, when compared with their wt virus-inoculated counterparts. Both viruses infected efficiently a lung epithelial chicken cell line, in which they induced similar levels of transcription of the IFN-α and -β, Mx, and IL-8 genes. At the molecular level, the neuraminidase activity, which was null for the short-stalk NA virus in the chicken erythrocytes elution assay, was fully restored in the long-stalk NA virus. Overall, our data confirm that a shortened NA stalk is a strong determinant of adaptation and virulence of influenza viruses in chickens, and suggest reciprocally that a virus with a short-stalk NA is less fit for replication and shedding in ducks.

The purpose of this study is to describe the perception of neuraminidase inhibitors (NAIs) during the pandemic A(H1N1)2009 influenza among general practitioners. A survey was conducted between 15 July and 15 September 2010 among a random sample of metropolitan French GPs. Among the 161 respondents, only 6% reported that they "often" prescribed NAIs during the pandemic A(H1N1)2009 influenza, while 69% reported that they prescribed NAIs "from time to time". The main objectives of GPs were to limit the risk of complications and the duration of symptoms. The main predictor of prescription of neuraminidase inhibitors during the pandemic A(H1N1)2009 influenza was the prescription of NAIs during epidemic seasonal periods (OR = 3.23 [95% CI 1.3 to 8.8]). Barriers to the prescription of NAIs were an estimated lack of efficacy (64%) and a negative benefit/risk balance (52%). Among the GPs surveyed in this research, 62% reported that they had been vaccinated against influenza A(H1N1)2009, while 73% recommended vaccination. GPs who prescribed NAIs during the pandemic A(H1N1)2009 influenza were those who prescribed NAIs during a seasonal influenza epidemic. To improve the outpatient prescription of NAIs during pandemic outbreaks, more knowledge about NAIs is required during seasonal influenza.

International audience

Résumé La grippe saisonnière est due aux virus influenza A et B. Il s’agit de virus enveloppés dont le génome est constitué de sept à huit fragments d’ARN. Les différents sous-types sont déterminés par la nature des deux glycoprotéines de surface HA et NA. La grippe saisonnière est une maladie épidémique et hivernale dans les zones à climat tempéré. Son épidémiologie est liée à la grande variabilité du virus au cours du temps, nécessitant la mise en place d’un système d’alerte détectant chaque année les variants circulants dominant et déterminant la composition vaccinale. Les symptômes cliniques de la grippe ne sont pas suffisamment spécifiques pour permettre le diagnostic sans examen virologique. Cela est particulièrement vrai en période non épidémique, chez les sujets de plus de 65 ans et chez les enfants de moins de cinq ans. L’enfant représente une cible privilégiée des infections à virus influenza. Le recours à l’hospitalisation est d’autant plus élevé que l’enfant est jeune. Chez le nourrisson, l’infection peut être paucisymptomatique et s’accompagner de manifestations non respiratoires (léthargie, convulsions, malaises). Le diagnostic virologique de la grippe est justifié chez tous les sujets hospitalisés pour un syndrome respiratoire compatible avec une infection à virus influenza. Il existe plusieurs outils permettant une recherche directe du virus dans les sécrétions respiratoires : isolement du virus en culture, détection d’antigènes, détection moléculaire de l’ARN. Le choix de la méthode se fait selon les caractéristiques du test : sensibilité, spécificité, rapidité et simplicité de réalisation, coût.

Anti-influenza chemotherapies The recent outbreaks of avian influenza A (H5N1) virus have called attention to the need for antiviral treatments to use in the event of pandemic influenza. The goal of antiviral treatments is also to reduce symptoms and complications associated with seasonal epidemics. Two classes of antiviral drugs, M2 proton channel inhibitors (amantadine, rimantadine) and neuraminidase inhibitors (zanamivir, oseltamivir), are effective for the chemoprophylaxis and treatment of influenza. Antiviral resistance is especially frequent with treatment with M2 inhibitors, and limits their clinical use. Resistance to oseltamivir during treatment has been described recently in several Vietnamese patients infected with H5N1. A close monitoring of antiviral resistance is needed, as is further research into the development of new agents, potentially targeting other viral proteins such as hemagglutinin or polymerase, and which could be used in combination chemotherapies., L’actuelle épizootie de grippe A (H5N1) souligne la nécessité de traitements antiviraux pour faire face à une éventuelle pandémie grippale. Les traitements anti-influenza ont aussi pour objectif de réduire les symptômes et complications survenant lors des épidémies saisonnières. Deux classes d’antiviraux, les inhibiteurs du canal à protons M2 (amantadine, rimantadine), et les inhibiteurs de neuraminidase (zanamivir, oseltamivir), ont une efficacité prophylactique et thérapeutique. L’émergence de virus résistants est particulièrement fréquente lors du traitement avec les inhibiteurs de M2, et limite leur utilisation. Le développement d’une résistance à l’oseltamivir a été décrit chez plusieurs patients infectés avec le virus H5N1. Une surveillance étroite de la résistance aux anti-viraux s’impose, ainsi que le développement de nouveaux composés, pouvant cibler éventuellement d’autres protéines virales telles que l’hémagglutinine ou la polymérase, et pouvant être utilisés en polychimiothérapies., Naffakh Nadia, Rameix-Welti Marie-Anne, Van der Werf Sylvie. Chimiothérapies anti-influenza. In: Bulletin de l'Académie Vétérinaire de France tome 161 n°1, 2008. Séances exceptionnelles : Le médicament vétérinaire. pp. 13-17.

It has been recently demonstrated that influenza is not predominantly an adult disease but affects massively the children and spreads to the community from them. Affected children may be admitted to hospital and the maximal risk concerns those younger than 1 year and mainly6 months of age. For them, the risk to be admitted is equivalent to that observed in elderly and adults with underlying conditions. Asthma and chronic diseases enhance the risk in children in the same proportions as observed in adults. Influenza may lead to death, infants aged 0-6 months being the most affected. Young children with influenza exhibit a non specific respiratory illness and often non respiratory manifestations (isolated fever, GI tract illness, convulsions). Influenza rapid "doctor tests" are now available and may be used at the physician's surgery. Treating fever is the most important purpose. Aspirin use should be avoided due to an increased risk of Reye syndrome. Antibiotic prescription is not indicated, except in case of bacterial super infection. Neuraminidase inhibitors may be used for treatment of influenza in children from 1 year (oseltamivir) or 5 years (zanamivir). These medications may also be used for prophylaxis of the disease.

Oseltamivir and zanamivir are highly potent inhibitors of influenza A and B neuraminidase and operate by inhibiting viral replication, and more specifically, the release and the movement of the virus through mucus. Neuraminidase inhibitors reduce the severity and duration of symptoms, and prevent clinical influenza as post-exposure and seasonal prophylaxis. Both have similar efficacy; oseltamivir has a more convenient route of administration, and zanamivir a more favourable resistance profile. Pending availability of effective vaccines, neuraminidase inhibitors are the only specific antiviral drugs which might be opposed to a possible pandemic that could emerge from the current highly pathogenic H5N1 virus. Although the effectiveness of oseltamivir and zanamivir for the therapy of clinical H5N1 influenza is questionable, simulation models suggest that a combination of targeted antiviral prophylaxis and quarantine might be able to contain an emerging influenza strain at the source. As a consequence, after an initial lack of commercial success probably related to the mild intensity of seasonal influenza during the last winters, neuraminidase inhibitors are now stockpiled by many countries to prepare for an outbreak.

Acute respiratory bacterial infection is the most common complication of influenza and a leading cause for excess rate of outpatient visits, hospitalization, and death (pneumonia). Influenza promotes bacterial infection as stated by epidemiologic evidence of temporal association between outbreaks or peaks of both influenza and bacterial pneumonia. The bacteria involved are Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus. However, Gram-negative rods, Klebsiella pneumoniae, Pseudomonas aeruginosa, anaerobes and methicillin resistant S. aureus may be involved in institutionalized elderly patients. Various studies confirm that antibiotics are over-prescribed in patients with influenza or influenza like illness, even in the absence of bacterial infection signs, and in patients without comorbidity. No data has proven the benefice of antibiotic prescription in influenza-infected patients without bacterial infection. Neuraminidase inhibitors may be of interest for the management of influenza infected patients, because they can decrease the risk of bacterial complications and the use of antibiotics.

This paper describes antivirals active against Myxovirus influenzae (influenza vaccine excluded), together with their indications in inter-pandemic and pandemic situations. Three kinds of antiviral drug, with different mechanisms of action, are active against Myxovirus influenzae: the adamantanes (amantadine and rimantadine); ribavirin; and neuraminidase inhibitors (zanamivir and oseltamivir). Amantadine is available in France but its indications are limited by its inactivity against influenza B virus, its adverse effects, and rapid onset of resistance. Ribavirin is administered by nebulization, exclusively in hospital, for severe cases. Neuraminidase inhibitors are effective on benign influenza; they are also well tolerated, active against subtypes A and B, and rarely elicit resistant mutants in vivo (exclusively seen with oseltamivir, mainly among children). According to their licensing terms, antivirals may be prescribed during epidemics, within 24-48 hours of typical symptom onset. They must not be used prophylactically in place of influenza vaccine, but may be useful when there is a familial or institutional index case, or during pandemics. Use in this latter situation would raise supply problems and, thus, the question of who should be treated first.

To describe in real-life conditions the flu therapeutic management, motivations to prescribe or not NAI (General Practitioners' (GPs) characteristics, decisional factors) and treated patients' course.A prospective, longitudinal, pharmacoepidemiological study involved 305 GPs in France during 2002-2003 winter epidemic peak. All patientsor=1 year old, with a clinical diagnostic of flu were included.One hundred and eighty-five GPs (150 NAI prescribing and 30 non-prescribing physicians) have included at least 1 patient. Prescribing physicians were the best informed on flu and NAI. 660 patients were analysed (250 NAI+ and 410 NAI-). 66% of NAI+ and 40% of NAI- attended to a consultation within 24 h (P0.001). 31% of NAI+ and 20% of NAI- had a visit at home (P=0.002). Among the patients without complication at inclusion (N=585), 3% of NAI+ received an antibiotherapy vs 13% of NAI- (P0.001). 43% of the patients had a sick leave, shorter for the NAI+ than NAI- (respectively, 3.7+/-1.7 vs 4.2+/-1.7 days, p=0.017). NAI was taken within 3 hours (median) after prescription by the 78% of the patients who returned their diary cards. The NAI+ patients had a faster improvement of symptoms than NAI- (within 24 h, respectively: 18 vs 5%, P0.001) and they returned faster to routine activities (within 48 h, respectively: 27 vs 11%, P0.001).This study evidenced the good use of NAI by the physicians. It confirms their therapeutic efficacy in real-life conditions and suggests their prescription allows decreasing antibiotic co-prescriptions and sick leaves duration, profits to consider in NAI benefit/risk ratio.

Prevention of influenza for persons at risk with inactivated vaccine remains the best way for attenuating the impact of influenza epidemics if persons to be vaccinated are correctly identified. In current recommendations, the lower cut off age is controversial, but new arguments on mortality associated with influenza suggest to lower the age to 45 for vaccination. Moreover immunization of health care workers is essential by decreasing transmission to susceptible patients and by reducing absenteeism of essential people during epidemics. Intranasal attenuated live vaccine seems to be of particular importance essentially in children and could replace the current vaccine in a near future. The role of chemoprophylaxis by inhibitors of neuraminidase needs further studies, but preliminary controlled trials have demonstrated a certain efficacy by controlling outbreaks in health care institutions. Treatment of influenza by these latter antivirals already has defined indications and a larger use currently lies on convincing arguments. By reducing inappropriate use of antibiotics, an extended use of neuraminidase inhibitors is of particular interest even if it is not a valuable argument, stricto sensu, for good medical practices.

Influenza is an infection of human beings and several animal species. It is caused by influenza viruses which belong to the Orthomyxoviridae family. Type A influenza viruses are the most important as they cause severe epidemics and are responsible of important pathological troubles. Type A influenza viruses are classified in different sub-types depending of the nature of their surface glycoproteins: haemagglutinin (H) and neuraminidase (N). The nature of the genome and the mode of replication of influenza viruses account for the high variability of these two proteins which are responsible for the immunity to the virus. The continuous appearance of point mutations in the gene coding for the H protein, leads to the progressive emergence of new viral strains. This event which is called antigenic drift makes it necessary to annually assess the composition of the human flue vaccine. Genetic reassortment is another mechanism of antigenic variation. When the gene coding for the H protein, or when both genes coding for H and N proteins are involved in genetic reassortment, a new viral sub-type occurs which replace the precedent. This event, which is termed antigenic shift, occurs occasionally every 10 to 30 years, and it is responsible of the great human pandemics. The role of the animals and particularly the importance of pigs and poultry in the emergence of these new viruses is discussed.

NEURAMINIDASE INHIBITORS: Zanamivir, the leading neuraminidase inhibitor has been awarded marketing approval in France for curative treatment of flu. It has been demonstrated that zanamivir reduces the duration of symptoms and the frequency of recourse to antibiotics. INDICATIONS FOR ZANAMIVIR: Besides early prescription for curative treatment of flu, as soon as the first symptoms occur, particularly in vaccinated elderly patients (vaccination is effective in only 70 to 80% of cases), zanamivir could also be used as a preventive treatment in subjects exposed to an index case. EARLY TRIALS WITH PLECONARIL: Pleconaril is active against picomaviruses and appears to have interesting efficacy against exceptionally severe enterovirus infections. Conversely, trials conducted in cases of upper respiratory tract infections and meningitis caused by enteroviruses have shown modest results.

For improving the anti-influenza vaccination efficacy, the choice of strains carrying up dated neuraminidase antigen (NA) and the introduction of the optimal amount of NA antigen in the vaccine are critical. Monoclonal antibodies prepared against the neuraminidase N2 of A/Beijing/32/92 showed NA inhibition (NI) and neutralized (Nt) the cells infection by influenza virus either at an early stage (group 2 antibodies inhibit virus binding to cells) or at a late stage of infection (group 1 antibodies inhibit virus release). The specificity of the neutralization test is restricted to the homologous variant whereas the NI specificity is much broader. When both group 1 and group 2 antibodies are tested together, their neutralizing activity is significantly increased. The emergence in 1997 of an avian strain H5N1 in humans influenza infections at Hong Kong (Strain A/Hong-Kong/156/97) rose the threat of pandemic. The H5N1 strain carried H5 HA which is not recognized by the human immune system, but N1 might be related to other N1 antigens belonging to avian, swine and human strains. So we 1) characterized the N1 antigen from H5N1 in comparison with other known antigens, 2) we looked for anti N1 (H5N1) antibodies in humans according to the age and the vaccination status, 3) we checked the neutralizing activity of anti N1 antibodies. The N1 antigen (H5N1) appeared closely related to N1 from swine strains: Sw/31 correlated itself to the pandemic spanish virus (1918-19), and more recent swine isolates from 1982 and 1989. The anti N1 (H5N1) antibodies were present in sera collected from 75+ years old persons and these N1 antibodies were neutralizing H5N1 cells infection. Consequently, 75+ years old persons do not represent a priority group for vaccination in the case of H5N1 pandemic conditions.

Expression of carcinoembryonic Tn antigen studied with VVA-B4 and GSI-A4 lectins with the monoclonal antibody 83D4 and of T antigen with LDL and PNA lectins with the monoclonal antibody ZCMO4, were examined in 54 malignant or benign human breast tumors and for MCF-7, T47D and MCF-10A cell lines of human breast tumors origin. For breast tissues, positive membrane labelling with D-GalNAc alpha-O-ser/thr (Tn-antigen) specific lectins and 83D4 MAb occurred in benign cases indicating that modification of glycoconjugates may precede the cytologic anomalies. In fibroadenoma, fibrocystic dystrophy, ductal hyperplasia and grade I invasive ductal carcinomas, the binding sites for lectins and 83D4 MAb were essentially on the cell membrane with labelling of both apical and basolateral compartments. In grade II and III, the labelling involved the cytoplasma, and cell heterogeneity appeared. The disappearance of reactivity observed for a large proportion of cells at grade III may be due either to the loss of glycosyltransferase, or to the lack of synthesis of the protein back-bone. Invasive lobular carcinomas showed labelling both on apical membrane and the outermost part of the cytoplasm with a distinct cell polarity. Lectin receptors are present at the surface of metastatic cells, possibly related to their involvement in adhesion. In all cases, T or sialosyl-T antigens are present at the surface of tumors cells. All cell lines from breast tumors cultured in vitro were labelled with lectins and monoclonal antibodies. The simultaneous presence of Tn and T antigens on the cells, indicates that the expression of Tn antigen is due to a partial but non total deficiency in the beta-1-3 galactosyltransferase involved in T-antigen synthesis.

The case of a 4 year-old boy presenting with dysmorphic facies, hepatomegaly, splenomegaly, growth and psychomotor retardation is reported. Radiological pattern suggested a storage disease. Bone marrow differential cell count showed numerous storage cells with vacuolated lymphocytes. Enzymatic studies showed decreased beta-galactosidase and neuraminidase levels, leading to the diagnosis of galactosialidosis. This is the first Tunisian case reported, which differs from the other cases published by the presence of a Kayser-Fleischer ring.

The main contributions of the author and collaborators about sialidase (EC 3.2.1.18) of influenza virus types A and B and O-acetylesterase (EC 3.1.1.53) of type C are summarized. After a short introduction on the topic, the negative results obtained by the author on inhibitors are commented. Then, the peculiarities of the three procedures assayed, based on the NADH determination as a measurement for the sialidase activity, are discussed. The spectrofluorimetric measurement of NADH concentration is a more sensitive and convenient procedure than that by spectrophotometry, although it is less sensitive than that based on bioluminiscence. Sialidase activity is generally higher in influenza virus type A than in type B; however, some differences have been found between the three sub-types A analysed. Furthermore, thermal stability and stability against changes in the pH values are higher for influenza virus from ducks, followed by those from humans and, finally, by those from pigs. O-acetylesterase of influenza virus type C shows a broad specificity; it acts on O-acetyl-containing compounds which may not be sialic acids. It seems that this enzyme might contribute to facilitate the action of sialidase of influenza virus types A and B. The peculiarities of influenza virus type C suggest to include this type as a new genus in the future classification of viruses.

The authors report a case of infantile sialidosis with hydrops fetalis and heart failure. At birth the baby presented a dysmorphic syndrome with histological anomalies. A storage disease with deficiency of neuraminidase activity, sialidosis type II, was confirmed. Amniocentesis with sialic-acid dosage or thin-layed chromatography seems necessary in hydrops fetalis with heart failure of unknown origin.

Isolation of pure neuraminidase and hemagglutinin from influenza virus A/Hong Kong 1/68 (H3N2) can be achieved using the coupled action of a new carboxypolypeptidase from Streptomyces fradiae and sodium dodecyl sulfate (SDS). Biochemical, physical and physico-chemical studies showed that the two molecules are in pure form and of glycoproteic nature.

A total of 145 influenza A viruses were isolated from ducks, geese and passerine birds in Ontario, Québec and the Maritimes in July-August 1977. Antigenic characterization of these isolates included five hemagglutinin (Hsw1, Hav4, Hav5, Hav6, Hav7) and five neuraminidase subtypes (N1, N2, Neq1, Neq2, Nav1) in nine different combinations; one combination Hav7 Neq1 had not been previously reported. The majority of these viruses were Hsw1 N1, antigenically related to influenza viruses in pigs and humans. This large reservoir of influenza A viruses circulating in ducks may well be involved in the appearance of new viruses in other species, including humans.