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.

Simple method for detection of mutations causing hereditary fructose intolerance

Aldolase B is critical for sugar metabolism, and a catalytic deficiency due to mutations in its gene may result in hereditary fructose intolerance (HFI) syndrome, with hypoglycaemia and severe abdominal symptoms. This report describes two cases of HFI, which were identified by intravenous fructose tolerance test and a new RFLP (restriction fragment length polymorphism) test that detects the two most common mutations, A149P and A174D. The method includes PCR of a 224-base-pair segment of exon 5, a subsequent 3 h incubation with Cac8I and agarose electrophoresis, which reveals either or both of the mutations in one single reaction. The method might be useful for screening of these mutations, which may account for more than 70% of the mutations causing HFI.

Perspectives on influenza surveillance in Europe: European scientific working group on influenza, Brussels

Although influenza surveillance has reached a high level of sensitivity, it is not given the same priority in all European countries. A recent survey has shown the diversity of the surveillance and diagnostic methods. Suggestions are made to encourage homogenisation of techniques, assistance to less active laboratories, training of personnel, evaluation, and co-operation in the field of animal influenza.

Hepatitis B virus genotypes in Mongols and Australian Aborigines

Hepatitis B virus (HBV) is spread worldwide. Seven genotypes, A-G, have been described, differing by more than 8% of the genome. In eastern Asia and Oceania genotypes B and C are predominant. However, little is known about genotypes in Mongolia and Australian aborigines. We analysed the preS and S regions of HBV from 9 Mongols and 5 Australian Aborigines. All Mongolian strains were of genotype D and were most similar to Central Asian sequences. All the Australian strains were genetically of serotype ayw3, and could not be reliably classified by the S region analysis, but placed on a separate branch. By preS analysis, they were however clearly of genotype C. The 6-7% nucleotide difference from published Asian genotype C sequences suggests that they diverged from Asian genotype C branch more than 1000 years ago.

Phylogenetic origin of hepatitis B virus strains with precore C-1858 variant

Mutations that prevent the expression of the hepatitis B e antigen frequently emerge in the immunoreactive phase of infection. The predominant mutation, the precore G-->A-1896 mutation, is restricted by the variability at position 1858 and is rare in strains with cytosine at nucleotide 1858. The C-1858 variant is characteristic of genotype A. It also occurs in genotypes C and F, but not in B, D, or E, explaining the geographical variation in the prevalence of precore mutants. C-1858 strains have been frequently observed in southeast Asia, but have not been phylogenetically characterized. By sequencing eight complete hepatitis B virus genomes, C-1858 variants of east Asian origin were found to constitute a phylogenetic entity within genotype C that probably diverged several hundred years ago. Further study of the distribution of this variant is warranted.

Virological response to interferon therapy of chronic hepatitis B as measured by a highly sensitive assay

In the interferon (IFN) treatment of chronic hepatitis B, there is no accepted definition of virological response as measured by highly sensitive HBV DNA assays. In the present study of 98 patients given IFN (10 MU/day for 1 week, then 10 MU TIW for 11 weeks) with or without prednisolone priming, a virological response was identified as log HBV DNA/mL below 6.0 (by Amplicor Monitor, Roche) 6 months post-treatment. At this time, 92% (33/36) of the sustained responders (SR) still had detectable viraemia with log HBV DNA/mL at 4.30 +/- 0.15 (+/- SEM), as compared with 8.69 +/- 0.097 in nonsustained responders. Pretreatment viraemia below a threshold at 500 million copies/mL was associated with higher chance of response (P=0.023). Prednisolone enhanced the sustained response (53% vs. 30%, P=0.025), and in particular end-of-treatment response (ETR, 50% vs. 10%, P < 0.0001). ETR was predictive for SR (P < 0.0001), especially when log HBV DNA/mL was < 4.0 (PPV=92%). The potential value of differentiating the therapy of chronic hepatitis B on the basis of viraemia levels, as measured by highly sensitive assays, should be further investigated.

Reactivation of hepatitis B virus replication accompanied by acute hepatitis in patients receiving highly active antiretroviral therapy

We describe 2 patients who were initially positive for antibodies to hepatitis B surface antigen and who experienced a strong and sudden increase of hepatitis B virus (HBV) replication during highly active antiretroviral therapy (HAART). We found that reactivation of HBV replication during HAART can occur independently of lamivudine resistance or withdrawal of lamivudine, and in spite of increasing CD4(+) cell counts.

Survey on influenza laboratory diagnostic and surveillance methods in Europe. European Scientific Working Group on Influenza

The survey was undertaken by ESWI in order to investigate the comparability of the laboratory diagnostic methods and the influenza surveillance systems used in 24 European countries. The results indicate considerable consensus in the general approaches to collection and use of clinical specimens, rapid diagnostic techniques, virus isolation techniques in eggs or/and MDCK cell lines, virus identification and use of inhibition of hemagglutination (IHA) and complement fixation (CF) tests for serological diagnostics. However, the details of the techniques used are somewhat heterogeneous: antigen detection methods (immunofluorescence versus immuno adsorbent assay), isolation methods (eggs versus tissue culture), reagents (locally produced, WHO, commercial) are not always equivalent and results are therefore not really comparable. Some of these discrepancies are due to a lack of resources or a lack of priority for influenza in the country. The greatest differences between individual countries exist in the epidemiological part of surveillance programmes. The mode of collection of influenza related mortality and absentism from work varies considerably in different countries. These findings indicate the need to harmonize viral procedures and surveillance systems in European countries in order to improve validity and comparability of results and as a prerequisite for early information on influenza etiology and spread.

Long-term mutation rates in the hepatitis B virus genome

Mutations in the hepatitis B virus (HBV) genome have so far been investigated in cross-sectional or short-term longitudinal studies. Information about long-term changes is lacking due to the difficulty of sampling over long observation periods. In this study, a retrospective approach was used that allowed the analysis of changes in the viral genome from transmission to late stages of infection without the requirement for sampling early during this period. The entire viral genome was sequenced from serum samples of three mothers and their 10 adult children, who presumably had been infected vertically. The emergence of mutations between birth and sampling (mean 26.5 years) was assessed by comparing the individual sequences with the sequence of the strain assumed to have been transmitted. The mean differences from this sequence were 0.02 and 0. 28% in seven asymptomatic and one symptomatic hepatitis B e antigen (HBeAg)-positive carriers, respectively, and 0.62 % in five HBeAg-negative carriers. Mutations occurred throughout the genome and 88% of the mutations caused amino acid substitutions spread over all genes. In HBeAg-negative carriers, the number of nucleotide and amino acid changes was independent of the severity of liver disease and, except the (1762)AGG(1764)-->TGA changes, no specific mutation was associated with liver disease. In conclusion, by using a novel method it was found that the entire HBV genome is extremely stable over long periods of time during the HBeAg-positive phase if the immune response (inflammation) is weak, whereas an average of 20 mutations emerged after development of hepatitis and/or loss of HBeAg without association with clinical outcome.

Production of influenza virus in serum-free mammalian cell cultures

Human influenza viruses are routinely isolated and grown in a variety of mammalian cell substrates. However, influenza viruses for use as inactivated vaccine are still produced in embryonated eggs. Using a perfusion culture-based bioreactor process using serum-free medium, both human and equine influenza viruses of different types and subtypes could be produced to high titres. Classical DEAE-dextran microcarriers were found to be more suitable than polyester sponge carriers for virus production. In addition, MDCK cells grown in serum-free medium were further validated as the most suitable cell substrate compared to Vero and BHK-21 C13 cells for large scale virus production of influenza virus. Finally, to minimize potential contamination by adventitious agents, it was demonstrated that a new serum-free medium in which all animal-derived products are replaced by a plant extract, efficiently supports the growth of MDCK cells as well as the production of influenza virus in the presence of trypsin when using the perfusion bioreactor process.

Core promoter mutations and genotypes in relation to viral replication and liver damage in East Asian hepatitis B virus carriers

Virus load and liver damage, as measured by quantitative polymerase chain reaction and histology activity index, were related to genotype and core promoter mutations in 43 chronic hepatitis B virus (HBV) carriers of East Asian origin. T-1762 mutants were more frequent in genotype C strains and were associated with more inflammation (P=.0036) and fibrosis (P=.0088) of the liver but not with hepatitis B e antigen (HBeAg) status or virus load. Conversely, precore mutations were associated with less liver inflammation (P=. 08), which was linked to HBeAg negativity and lower viral replication. Carriers with genotype C were more often HBeAg positive (P=.03) with precore wild type strains and more-severe liver inflammation (P=.009) than were those with genotype B. These findings suggest that pathogenic differences between genotypes may exist and that the T-1762 mutation may be useful as a marker for progressive liver damage but seem to contradict that down-regulation of HBeAg production is the major effect of this mutation.

Effective prophylaxis of influenza A virus pneumonia in mice by topical passive immunotherapy with polyvalent human immunoglobulins or F(ab')2 fragments

The effectiveness of polyvalent plasma-derived human immunoglobulins (IVIG) in passive immunotherapy of influenza virus pneumonia was assessed, using the Strain Scotland (A/Scotland/74 (H3N2)) adapted to BALB/c mice by repeated lung passages. Haemagglutinin antibodies in two batches of IVIG at 10 mg/ml had a titre of 1/16. Intravenous injection of 1000-5000 microg of IVIG, 3 h after infection, gave 60-70% protection, whereas intranasal injection of 25-50 microg protected 90% of mice infected with a lethal dose of influenza virus. F(ab')2 fragments were at least as protective as intact IVIG, suggesting that complement or Fcgamma receptor-bearing cells were not required. Topical passive immunotherapy with IVIG or F(ab')2 gave protection up to 8 h after infection, but not at 24 h, suggesting that anti-influenza A antibodies in IVIG, delivered locally, are only effective at early stages of the infectious process. The potential value of topical administration of IVIG or F(ab')2 fragments for influenza A pneumonia prophylaxis was further demonstrated by the protective effects of their intranasal administration 24 h before challenge.

Plans against influenza pandemics in Europe: history and principles

Antigenic variation, New Jersey porcine influenza, Pandemic planning: Berlin 1993, Pandemics, Principles of action, H5N1 avian influenza in Hong Kong.

Study of the O-acetylesterase activity of five influenza C virus strains

Four influenza C virus strains, isolated in France in 1991, were used as a source for a kinetic study of the enzyme O-acetylesterase (EC 3.1.1.53) related to another strain, C/JHB/1/66, considered as the reference strain. Similarities, but also differences, in their haemagglutination titres were detected. Remarkable differences were found for enzyme activity and the K(m), Vmax, and the Vmax/K(m) ratio between certain strains, as well as for their thermostability at 40 degrees C when methylumbelliferyl acetate was used as substrate. By contrast, their optimum pH, stability at different pH values, and stability at 4 degrees C over 14 days were very similar. The effect of some compounds on O-acetylesterase activity was studied. The peculiarities of these factors are discussed in relation to the functional variation of the virus.

Influenza vaccination in 22 developed countries: an update to 1995

This study expands and updates through 1995 our earlier report on influenza vaccine use in 18 developed countries. Five of the six countries with high levels of vaccine use in 1992 (> or = 130 doses/1000 population) showed little change or slight declines over the subsequent 3 years. The exception was the United States, where a new federal program for vaccination reimbursement for the elderly helped to increase vaccine distribution from 144 to 239 doses/1000 population. The six countries with medium levels of vaccine use in 1992 (76-96 doses/1000 population) increased to > or = 100 doses/1000 population by 1995. Among the six low-use countries in 1992 (< or = 65 doses/1000 population), only Finland showed substantial improvement (96 doses/1000 population) in 1995. Four new countries were added to the study. In Germany, vaccine use increased to 80 doses/1000 population in 1995, but in Ireland it remained at a low level (48 doses/1000 population). In Korea, vaccine use increased from 17 to 95 doses/ 1000 population during the period 1987-1995. In Japan, very high levels of vaccine use (approximately 280 doses/1000 population) in the early 1980s were associated with vaccination programs for school children. However, vaccine use fell precipitously when these programs were discontinued, and only 2 and 8 doses/1000 population were used in 1994 and 1995, respectively. In all 22 countries, higher levels of vaccine use were associated with vaccination reimbursement programs under national or social health insurance and were not correlated with different levels of economic development. Excluding Japan, in 1995 there was still a greater than fourfold difference between the highest and lowest levels of vaccine use among the other 21 countries in the study. Given its well established clinical effectiveness and cost-effectiveness, none of these countries has yet achieved the full benefits of its programs for influenza vaccination.

[Influenza: interspecies transmissions and viral rearrangement]

Influenza is an infection of humans beings and many animal species. It is caused by viruses which belong to the Orthomyxoviridae family. There are three types of influenza viruses A, B and C. The type A is the most pathogenic of all. The type is determined mainly by the nature of the nucleoprotein (NP), an antigen which does not greatly vary. On the contrary, the surface antigens, among which the haemagglutinin is the most important, are highly variable and their nature determines the sub-type of virus within the type A. The expressed mutations affecting the haemagglutinin are referred as antigenic drift and make virological surveillance necessary in order to annually assess the composition of the vaccine strains. The segmented nature of the genome of influenza viruses, makes possible the genetic reassortment of two different influenza viruses co-infecting one cell and produces a new hybrid virus. When such an event affects the haemagglutinin, the reassortment leads to an antigenic shift. In nature, it most certainly takes place in swine, between human and avian viruses. Whereas antigenic drift is a continuous and progressive phenomenon, antigenic shift occurs occasionally every 10 to 30 years. The emergence of a hybrid virus bearing a new haemagglutinin and thus belonging to a new human subtype, can be the starting point of the genesis of a pandemic, generally associated with a high mortality rate in humans. The participation of the pig is specially mentioned.

Antigenic and genetic analyses of H1N1 influenza A viruses from European pigs

H1N1 influenza A viruses isolated from pigs in Europe since 1981 were examined both antigenically and genetically and compared with H1N1 viruses from other sources. H1N1 viruses from pigs and birds could be divided into three groups: avian, classical swine and 'avian-like' swine viruses. Low or no reactivity of 'avian-like' swine viruses in HI tests with monoclonal antibodies raised against classical swine viruses was associated with amino acid substitutions within antigenic sites of the haemagglutinin (HA). Phylogenetic analysis of the HA gene revealed that classical swine viruses from European pigs are most similar to each other and are closely related to North American swine strains, whilst the 'avian-like' swine viruses cluster with avian viruses. 'Avian-like' viruses introduced into pigs in the UK in 1992 apparently originated directly from strains in pigs in continental Europe at that time. The HA genes of the swine viruses examined had undergone limited variation in antigenic sites and also contained fewer potential glycosylation sites compared to human H1N1 viruses. The HA exhibited antigenic drift which was more marked in 'avian-like' swine viruses than in classical swine strains. Genetic analyses of two recent 'avian-like' swine viruses indicated that all the RNA segments are related most closely to those of avian influenza A viruses.

Production of influenza virus in cell cultures for vaccine preparation

Influenza virus strains of different types for use as an inactivated vaccine have been successfully grown in different cell lines. Increasing titres were obtained with BHK-21/BRS, VERO and MDCK cells. Cultures in stationary flasks, in spinner cultures or in large bioreactor systems were tested and the optimal conditions were studied. MDCK cells grown in serum-free medium before and during the virus production phase were found to yield high titres in the presence of trypsin. Satisfactory results were obtained with egg-adapted strains of human and equine origin as well as with strains just isolated from human patients without any further passages in eggs or cell culture.

Influenza vaccination in 18 developed countries, 1980-1992

Influenza continues to be an important cause of preventable morbidity and mortality. Although influenza vaccine is widely recommended for older high-risk individuals, no studies have compared its use in different countries. We gathered information on influenza vaccine distribution in 18 developed countries for the period 1980-1992. During the 1980s there was a > or = 10-fold difference in annual per capita vaccine distribution among these countries, and in 1992 the difference was still more than 7-fold. Several countries demonstrated large increases in vaccine use over the study period, some showing substantial increases in specific years. Thirteen of the 18 countries recommend influenza vaccination for all elderly persons and 11 countries provide reimbursement for vaccination through national or social health insurance. These countries tend to have higher levels of vaccine use. Historical, economic and political factors also affect vaccination practices and policies, but their relationships to differences in vaccine use between countries are not known. A better understanding of why the use of influenza vaccine varies among countries will be important if its protective benefits are to be fully realized.

Sensitivity, specificity and predictive values of health service based indicators for the surveillance of influenza A epidemics

BACKGROUND

The Regional Influenza Surveillance Group (GROG) is a French surveillance network set up in 1984. It collects virological specimens and health service based indicators on a weekly basis. Our aim was to assess the predictive value of the health service based indicators for the detection of influenza A epidemics.

METHODS

Virological data were used as a gold standard for defining the epidemics. For each health service based indicator, a statistical threshold was used as a test for the identification of epidemic weeks. Finally, an epidemiological criterion was defined in order to improve the specificity and the speed of detection of outbreaks.

RESULTS

Health service based indicators have a positive predictive value of around 0.80. They also advance the detection of outbreaks by between 1 and 4 weeks.

CONCLUSIONS

These indicators are easy to collect and are useful for the surveillance of influenza epidemics. Such a system is the prerequisite for the rational use of preventive tools.

Adjuvant activity of polar glycopeptidolipids of Mycobacterium chelonae (pGPL-Mc) on the immunogenic and protective effects of an inactivated influenza vaccine

Mice injected intraperitoneally with 2.5 or 25 mg/kg of pGPL-Mc, before, during or after the administration of a monovalent inactivated influenza vaccine (8 IU of A/New Jersey/X53), exhibited significantly very high haemagglutination inhibition (HI) antibody titers (up to 8 fold) as compared to vaccine controls. Treatment with pGPL-Mc has increased the protective effect of the vaccine by completely abolishing, in certain treatment groups, the onset of symptoms of disease and mortality after a lethal challenge with 5 LD50 of A/PR/8/34 virus, 60 days after the first vaccination. Moreover, the development of visible pulmonary lesions significantly decreased in surviving vaccinated mice treated with 25 mg/kg of pGPL-Mc on day D0. These results suggest that pGPL-Mc is a potent adjuvant to the immunogenic and protective effect of inactivated influenza vaccines.

Sero-epidemiological survey of influenza C virus infection in Spain

From an overall point of view, the epidemiological situation of influenza C virus infections in western Europe is hardly known. In some countries like Spain, no epidemiological survey has been carried out to determine whether influenza C virus does or does not circulate and cause infection in the considered geographical area. We thus decided to perform such a study. A total of 191 serum samples was collected from people (from 1.5 to 80 years old) living in Spain in October 1990. These sera were tested for the presence of antibodies to influenza C virus by hemagglutination-inhibition (HI) tests. Significant HI activity was found in 59.3 to 64.9% of the 191 tested sera and titres ranged from 20 to 320. The high prevalence of antibody as well as the highly significant titres indicate an intense circulation of influenza C virus in Spain. A significant difference was found between children/teenagers and adults.

Influenza virus vaccine in B-cell chronic lymphocytic leukaemia patients

The clinical reaction and the immunological response to influenza virus vaccine were studied in 43 B-cell chronic lymphocytic leukaemia patients. The Vaxigrip vaccine was administered containing the antigens A/Ghizhou/54/89, A/Singapore/6/86, and B/Yamagata/16/88. The side-effects observed were minimal and well tolerated. Antibody production with titres > 1:20 on day 15 was observed at least for one antigen in 35 patients (81%). In 23 of them (63%) this response was retained on days 30 and 60. Patients with IgG levels (< 700 mg/dl) responded less well as compared to those having normal IgG levels (> 700 mg/dl).

Natural infection of dogs by influenza C virus: a serological survey in Spain

Two seroepidemiological surveys carried out so far, one in Japan, the other in France, gave a strong indication that dogs may be naturally infected by influenza C virus, considered to be exclusively human until recently. In this work, 101 serum samples were collected during winter 1989/1990 from dogs in Castilla y León, Spain. Sera were tested for the presence of antibodies to influenza C virus by Hemagglutination Inhibition (HI) test. Using antibody absorption by staphylococcal protein A, we demonstrated the specificity of the results. Significant HI activity was found in 56.3% of the 101 tested sera and titres ranged from 25 to 200.

Genic amplification of the entire coding region of the HEF RNA segment of influenza C virus

In order to provide an easy and powerful analysis of influenza C viral HEF RNA segment of a recent strain, a combination of reverse transcription and the polymerase chain reaction was used. We amplified the entire coding region of the HEF gene of a laboratory strain of virus called C/Johannesburg/1/66, widely used for binding and esterase activity studies as well as that of a strain isolated in 1991 (C/Paris/145/91) from a patient suffering from severe flu syndrome. The sequences we amplified were about 2 kilobases long. In this work, we show that the forward 'universal primer' Uni1, which has been used for influenza A and B viruses cDNA syntheses can also be used for influenza C virus. The PCR primers were designed to contain restriction sites to make the PCR products ready to be used for further purposes. A restriction analysis of the PCR products combined with analyses of all the human influenza C virus HEF gene sequences published so far permitted the design of sets of oligonucleotides which can prime PCR on cDNA of unknown influenza C virus for cloning.

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.

Increased influenza A virus sialidase activity with N-acetyl-9-O-acetylneuraminic acid-containing substrates resulting from influenza C virus O-acetylesterase action

Influenza virus type C (Johannesburg/1/66) was used as a source for the enzyme O-acetylesterase (EC 3.1.1.53) with several natural sialoglycoconjugates as substrates. The resulting products were immediately employed as substrates using influenza virus type A [(Singapore/6/86) (H1N1) or Shanghai/11/87 (H3N2)] as a source for sialidase (neuraminidase, EC 3.2.1.18). A significant increase in the percentage of sialic acid released was found when the O-acetyl group was cleaved by O-acetylesterase activity from certain substrates (bovine submandibular gland mucin, rat serum glycoproteins, human saliva glycoproteins, mouse erythrocyte stroma, chick embryonic brain gangliosides and bovine brain gangliosides). A common feature of all these substrates is that they contain N-acetyl-9-O-acetylneuraminic acid residues. By contrast, no significant increase in the release of sialic acid was detected when certain other substrates could not be de-O-acetylated by the action of influenza C esterase, either because they lacked O-acetylsialic acid (human glycophorin A, alpha 1-acid glycoprotein from human serum, fetuin and porcine submandibular gland mucin) or because the 4-O-acetyl group was scarcely cleaved by the viral O-acetylesterase (equine submandibular gland mucin). The biological significance of these facts is discussed, relative to the infective capacity of influenza C virus.

Natural infection of dogs by influenza C virus

To date, only one seroepidemiological survey, carried out in Japan, gave a strong indication that dogs may be naturally infected by the influenza C virus, long considered to be exclusively human. In the present work, 134 serum samples were collected during the winter of 1988/89 from dogs aged 6 months to 16 years in northern France. Samples were tested for the presence of antibodies to influenza C virus by both haemagglutination inhibition (HI) and ELISA. Using antibody absorption by staphylococcal protein A, we demonstrated the specificity of the results. In 62% of cases, the results were identical using the two methods. Significant HI activity was found in 32% of the 134 tested sera and titres ranged from 20 to 320. Of the sera tested, 42% were positive by ELISA and titres ranged from 500 to 8,000. The discordant results are discussed. The population tested was divided into five age groups: less than 4 years, 4 to 6 years, 7 to 9 years, 10 to 11 years and greater than 12 years. The distribution of antibodies in the tested canine population, in contrast to that of humans, did not show a significant degree of association with age.

The Alsatian tick-borne encephalitis focus: presence of the virus among ticks and small mammals

An extensive epidemiologic survey was carried out from 1970 to 1974 in order to understand the condition of circulation of tick-borne encephalitis virus between ticks and small mammals in the Alsatian focus, France. The virus has been isolated from Ixodes ricinus adult ticks (30 lots out of 369, representing a total of 5617 ticks), and from Ixodes ricinus nymphs (4 lots out of 251, representing a total of 8587 ticks). The virus has also been isolated from 11 pools of rodent organs (out of 3361 rodents), and HI antibodies were detected in 21 out of 8735 rodent specimens. The virus has never been detected in rodent blood, nor in 10,298 ticks collected engorged from 1505 vertebrate hosts. These results show that Alsatian tick-borne encephalitis focus is stable since the activity of the virus is detected every year, and that the focus is an extended one since the virus is isolated from 5 of 6 study sites, as well as in several control sites.

Influenza C virus infection in France

Little is known of the epidemiology of influenza C virus infections in western Europe and of the exact role of this agent in acute viral respiratory infections. Several tests may be used for detecting antibodies against this agent but the significance of their respective results is not clear. A total of 301 samples of serum was collected from persons aged from 4 months to 88 years living in France in 1988. The samples were tested for the presence of antibodies to influenza C virus by haemagglutination-inhibition (HI) tests and ELISA. The specificity of the results was checked by immunoblotting and by antibody absorption with staphylococcal protein A. Significant HI activity was found in 61% of the 301 samples tested, titres ranging from 20-320; 70% were positive by ELISA with titres ranging from 500 to 32,000. The population tested was divided into four age groups: 0-15 years; 16-30 years; 31-50 years and 51-88 years. The highest rates for positive samples were found in the 16-30 year group (76 and 79% by HI tests and ELISA respectively) as well as significant HI and ELISA geometric mean titres. Positive samples were less common in young children (46 and 50% by HI tests and ELISA respectively) and in the oldest group (44 and 54% respectively). The 31-50 years age group formed an intermediate class. The high prevalence of antibody as well as the significant titres indicate intense circulation of influenza C virus, especially among young adults.

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.

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.

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.

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.

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.

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.