http://repub.eur.nl/res/aut/770/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/39045/ 2012-09-01T00:00:00Z Each year, influenza viruses cause epidemics by evading pre-existing humoral immunity through mutations in the major glycoproteins: the haemagglutinin (HA) and the neuraminidase (NA). In 2004, the antigenic evolution of HA of human influenza A (H3N2) viruses was mapped (Smith et al., Science 305, 371-376, 2004) from its introduction in humans in 1968 until 2003. The current study focused on the genetic evolution of NA and compared it with HA using the dataset of Smith and colleagues, updated to the epidemic of the 2009/2010 season. Phylogenetic trees and genetic maps were constructed to visualize the genetic evolution of NA and HA. The results revealed multiple reassortment events over the years. Overall rates of evolutionary change were lower for NA than for HA1 at the nucleotide level. Selection pressures were estimated, revealing an abundance of negatively selected sites and sparse positively selected sites. The differences found between the evolution of NA and HA1 warrant further analysis of the evolution of NA at the phenotypic level, as has been done previously for HA. http://repub.eur.nl/res/pub/29482/ 2008-09-12T00:00:00Z Annual influenza epidemics in humans affect 5-15% of the population, causing an estimated half million deaths worldwide per year [Stohr K. Influenza-WHO cares. Lancet Infectious Diseases 2002;2(9):517]. The virus can infect this proportion of people year after year because the virus has an extensive capacity to evolve and thus evade the immune response. For example, since the influenza A(H3N2) subtype entered the human population in 1968 the A(H3N2) component of the influenza vaccine has had to be updated almost 30 times to track the evolution of the viruses and remain effective. The World Health Organization Global Influenza Surveillance Network (WHO GISN) tracks and analyzes the evolution and epidemiology of influenza viruses for the primary purpose of vaccine strain selection and to improve the strain selection process through studies aimed at better understanding virus evolution and epidemiology. Here we give an overview of the strain selection process and outline recent investigations into the global migration of seasonal influenza viruses. http://repub.eur.nl/res/pub/29240/ 2008-04-18T00:00:00Z Antigenic and genetic analysis of the hemagglutinin of ∼13,000 human influenza A (H3N2) viruses from six continents during 2002-2007 revealed that there was continuous circulation in east and Southeast Asia (E-SE Asia) via a region-wide network of temporally overlapping epidemics and that epidemics in the temperate regions were seeded from this network each year. Seed strains generally first reached Oceania, North America, and Europe, and later South America. This evidence suggests that once A (H3N2) viruses leave E-SE Asia, they are unlikely to contribute to long-term viral evolution. If the trends observed during this period are an accurate representation of overall patterns of spread, then the antigenic characteristics of A (H3N2) viruses outside E-SE Asia may be forecast each year based on surveillance within E-SE Asia, with consequent improvements to vaccine strain selection. http://repub.eur.nl/res/pub/35517/ 2007-04-01T00:00:00Z In the early 1970s, a human influenza A/Port Chalmers/1/73 (H3N2)-like virus colonized the European swine population. Analyses of swine influenza A (H3N2) viruses isolated in The Netherlands and Belgium revealed that in the early 1990s, antigenic drift had occurred, away from A/Port Chalmers/1/73, the strain commonly used in influenza vaccines for pigs. Here we show that Italian swine influenza A (H3N2) viruses displayed antigenic and genetic changes similar to those observed in Northern European viruses in the same period. We used antigenic cartography methods for quantitative analyses of the antigenic evolution of European swine II3N2 viruses and observed a clustered virus evolution as seen for human viruses. Although the antigenic drift of swine and human H3N2 viruses has followed distinct evolutionary paths, potential cluster-differentiating amino acid substitutions in the influenza virus surface protein hemagglutinin (HA) were in part the same. The antigenic evolution of swine viruses occurred at a rate approximately sis times slower than the rate in human viruses, even though the rates of genetic evolution of the HA at the nucleotide and amino acid level were similar for human and swine H3N2 viruses. Continuous monitoring of antigenic changes is recommended to give a first indication as to whether vaccine strains may need updating. Our data suggest that humoral immunity in the population plays a smaller role in the evolutionary selection processes of swine II3N2 viruses than in human H3N2 viruses. Copyright http://repub.eur.nl/res/pub/15074/ 2005-01-01T00:00:00Z There are two objections to the guideline 'Influenza prevention in nursing homes and care homes' issued by the Dutch Society of Nursing Home Specialists. First there is insufficient experimental evidence for recommending doubling the dose of influenza vaccine for the elderly and secondly the guideline does not present a clear preliminary conclusion on the effectiveness of oseltamivir prophylaxis. http://repub.eur.nl/res/pub/13361/ 2004-04-20T00:00:00Z The etiology of acute respiratory tract illnesses is sometimes unclear due to limitations of diagnostic tests or the existence of as-yet-unidentified pathogens. Here we describe the identification and characterization of a not previously recognized coronavirus obtained from an 8-mo-old boy suffering from pneumonia. This coronavirus replicated efficiently in tertiary monkey kidney cells and Vero cells, in contrast to human coronaviruses (HCoV) 229E and OC43. The entire cDNA genome sequence of the previously undescribed coronavirus was determined, revealing that it is most closely related to porcine epidemic diarrhea virus and HCoV 229E. The maximum amino acid sequence identity between ORFs of the newly discovered coronavirus and related group 1 coronaviruses ranged from 43% to 67%. Real-time RT-PCR assays were designed to test for the prevalence of the previously undescribed coronavirus in humans. Using these tests, the virus was detected in four of 139 individuals (3%) who were suffering from respiratory illness with unknown etiology. All four patients suffered from fever, runny nose, and dry cough, and all four had underlying or additional morbidity. Our data will enable the development of diagnostic tests to study the prevalence and clinical impact of this virus in humans in more detail. Moreover, it will be important to discriminate this previously undescribed coronavirus from HCoV 229E and OC43 and the severe acute respiratory syndrome coronavirus. http://repub.eur.nl/res/pub/3989/ 2004-01-01T00:00:00Z Recently two new neuraminidase inhibitors zanamivir and oseltamivir have been marketed. They appear to considerably reduce morbidity and mortality from influenza. Their adverse effects are infrequent and mild and the chance of development of pathogenically significant resistant mutants appears to be small. During the first six months of a pandemic, neuraminidase inhibitors are the only defence against the virus. It is therefore important to stockpile in each country sufficient quantities of these drugs. During the usual influenza epidemics the main value of neuraminidase inhibitors lies in their use for therapy, prophylaxis and post-exposure prophylaxis in long-term care institutions for the elderly (for prophylaxis only oseltamivir is licensed). Although data on the effectiveness against complications of influenza and on the effect on people with an increased risk of (fatal) complications as a result of an influenza virus infection are limited, the available information on the effects of the neuraminidinase inhibitors indicates that these drugs will also protect against complications and that high-risk groups will benefit from the rapid deployment of these products. The cost-effectiveness of treatment and post-exposure prophylaxis with neuraminidinase inhibitors is probably not favourable for healthy children and adults but seems to be favourable for the high-risk groups (vaccinated or not) in winter. http://repub.eur.nl/res/pub/3931/ 2003-01-01T00:00:00Z http://repub.eur.nl/res/pub/3845/ 2002-01-31T00:00:00Z Since the 1940s, influenza vaccines are inactivated and purified virus or virus subunit preparations (IIV) administered by the intramuscular route. Since decades, attempts have been made to construct, as an alternative, attenuated live influenza vaccines (LIV) for intranasal administration. Presently, the most successful LIV is derived from the cold-adapted master strains A/Ann Arbor/6/60 (H2N2) and B/Ann Arbor/1/66 (AA-LIV, for Ann-Arbor-derived live influenza vaccine). It has been claimed that AA-LIV is more efficacious than IIV. In order to assess differences between the two vaccines with respect to systemic reactogenicity, antibody response, and efficacy, we performed a meta-analysis on eighteen randomised comparative clinical trials involving a total of 5000 vaccinees of all ages. Pooled odds ratios (AA-LIV versus IIV) were calculated according to the random effects model. The two vaccines were associated with similarly low frequencies of systemic vaccine reactions (pooled odds ratio: 0.96, 95% confidence interval: 0.74-1.24). AA-LIV induced significantly lower levels of serum haemagglutination inhibiting antibody and significantly greater levels of local IgA antibody (influenza virus-specific respiratory IgA assayed by ELISA in nasal wash specimens) than IIV. Yet, although they predominantly stimulate different antibody compartments, the two vaccines were similarly efficacious in preventing culture-positive influenza illness. In all trials assessing clinical efficacy, the odds ratios were not significantly different from one (point of equivalence). The pooled odds ratio for influenza A-H3N2 was 1.50 (95% CI: 0.80-2.82), and for A-H1N1, 1.03 (95% CI: 0.58-1.82). The choice between the two vaccine types should be based on weighing the advantage of the attractive non-invasive mode of administration of AA-LIV, against serious concerns about the biological risks inherent to large-scale use of infectious influenza virus, in particular the hazard of gene reassortment with non-human influenza virus strains. http://repub.eur.nl/res/pub/3802/ 2001-08-14T00:00:00Z In order to explore the occurrence of antigenic drift in swine influenza A(H1N1) viruses and the match between epidemic and vaccine strains, 26 virus isolates from outbreaks of respiratory disease among finishing pigs in the Netherlands in the 1995/1996 season and reference strains from earlier outbreaks were examined using serological and molecular methods. In contrast to swine H3N2 viruses, no significant antigenic drift was observed in swine H1N1 viruses isolated from the late 1980s up to 1996 inclusive. However, a marked antigenic and genetic heterogeneity in haemagglutination inhibition tests and nucleotide sequence analyses was detected among the 26 recent swine H1N1 virus strains. Interestingly, the observed antigenic and molecular variants were not randomly distributed over the farms. This finding indicates independent introductions of different swine H1N1 virus variants at the various farms of the study and points to a marked difference between the epidemiologies of human and swine influenza viruses. The observed heterogeneity may hamper the control of swine influenza by vaccination and indicates that the efficacy of current swine influenza vaccines requires re-evaluation and that the antigenic reactivity of swine influenza viruses should be monitored on a regular basis. http://repub.eur.nl/res/pub/3798/ 2001-07-09T00:00:00Z From 28 young children in the Netherlands, we isolated a paramyxovirus that was identified as a tentative new member of the Metapneumovirus genus based on virological data, sequence homology and gene constellation. Previously, avian pneumovirus was the sole member of this recently assigned genus, hence the provisional name for the newly discovered virus: human metapneumovirus. The clinical symptoms of the children from whom the virus was isolated were similar to those caused by human respiratory syncytial virus infection, ranging from upper respiratory tract disease to severe bronchiolitis and pneumonia. Serological studies showed that by the age of five years, virtually all children in the Netherlands have been exposed to human metapneumovirus and that the virus has been circulating in humans for at least 50 years. http://repub.eur.nl/res/pub/3791/ 2001-04-10T00:00:00Z It is generally believed that pigs can serve as an intermediate host for the transmission of avian influenza viruses to humans or as mixing vessels for the generation of avian-human reassortant viruses. Here we describe the antigenic and genetic characterization of two influenza A (H1N1) viruses, which were isolated in The Netherlands from two patients who suffered from pneumonia. Both viruses proved to be antigenically and genetically similar to avian-like swine influenza A (H1N1) viruses which currently circulate in European pigs. It is concluded that European swine H1N1 viruses can infect humans directly, causing serious disease without the need for any reassortment event. http://repub.eur.nl/res/pub/3820/ 2001-01-01T00:00:00Z Background: The vigour of immune responses declines at higher ages. The present study examined sera from influenza vaccinees to assess the magnitude of this effect in case of an antigenic mismatch. Methods: Sera taken in mid-1997 from influenza vaccinees of various ages, including residents of nursing homes, were used in haemagglutination inhibition (HI) tests. In the following influenza season of 1997/1998, a major antigenic mismatch of the H3N2 vaccine component occurred. Results: At advanced age, the homologous antibody response was lowered, starting above 60 years. Also, the cross-reactivity of the formed antibodies to the drifted field virus decreased with age, starting above 70 years. Conclusion: The effect of ageing on the induction of "protective" titres (>=40) of HI antibodies against an emerging deviant strain can be severe: in the 1997/1998 season, above 80 years, the percentage of vaccinees acquiring such titres against the major epidemic H3N2 virus was only about 15%. http://repub.eur.nl/res/pub/3832/ 2001-01-01T00:00:00Z In the 2000/01 season, the size of the influenza epidemic in the Netherlands was exceptionally small. Since the start of the Continuous Morbidity Registration of the Netherlands Institute of Primary Health Care (NIVEL) in 1970, the peak incidence of influenza-like illnesses has never been so low. The aetiology of the epidemic was also unusual. Most remarkable was the relatively extensive circulation of subtype H1N1 and the low activity of subtype H3N2. The epidemic started in week 1 of 2001 and ended in week 8. The antigenic properties of the influenza A (H1N1) viruses closely resembled those of the vaccine strain A/New Caledonia/20/99. This new variant of subtype H1N1 was first isolated in Asia in 1995 and was only (sporadically) detected in the Netherlands in the 1999/2000 season. Phylogenetic analysis showed that these viruses represent a new line of subtype H1N1. Following the influenza-activity caused by H1N1 viruses in the 2000/01 season, a small number of B and H3N2 viruses were also isolated up to week 19. Antigenically, these viruses were identical to those obtained in the previous years. On the basis of the antigenetic analyses presented, it can be concluded that the vaccine provided good protection against the circulating influenza viruses in the 2000/01 season. The World Health Organization recommends that influenza vaccines intended for use in the 2001/02 season of the northern hemisphere should contain the following, or antigenically similar, strains: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1), and B/Sichuan/379/99. http://repub.eur.nl/res/pub/3720/ 2000-01-01T00:00:00Z The success of influenza vaccination depends largely on the antigenic match between the influenza vaccine strains and the virus strains actually circulating during the season. In the past, this match has proved to be satisfactory in most seasons. In the 1997/1998 season, however, hemagglutination inhibition (HI) assays with ferret antisera indicated a considerable mismatch between the H3N2 vaccine component and the most prevalent epidemic influenza A(H3N2) virus. The results from antigenic analyses using pre- and postvaccination serum samples from volunteers of various ages, including residents of nursing homes who were more than 60 years of age, were in good agreement with the results obtained with ferret antisera. Homologous serum antibody responses to the H3N2 vaccine component as well as the cross-reactivity of the induced antibodies to the epidemic H3N2 strain, declined with increasing age of the vaccinees. As a consequence of these two effects, 84% of the vaccinees over 75 years of age did not develop HI antibody titers >/= 40 against the major H3N2 virus variant of 1997/1998, suggesting that they were not protected against infection with this virus variant. These findings support the current policy of the World Health Organization (WHO), which is to base worldwide influenza virus surveillance on results predominantly obtained by antigenic analyses of influenza virus isolates with ferret antisera in HI tests. If an antigenic mismatch is observed, the protective efficacy of the vaccine, especially for the elderly, may be insufficient. The observations also support the current policy to include the elderly in serologic efficacy trials. http://repub.eur.nl/res/pub/3669/ 1999-03-01T00:00:00Z In order to explore the occurrence of antigenic drift in swine influenza A(H3N2) virus, we examined virus strains from outbreaks of respiratory disease among finishing pigs in the Netherlands in 1996 and 1997 and from earlier outbreaks. In contrast to swine H3N2 strains from the 1980s, the recent isolates did not show significant cross-reactivity with human influenza A(H3N2) viruses from 1972-1975 in haemagglutination inhibition tests. These new strains form a separate branch in the phylogenetic trec of the HA1 parts of HA. We conclude that recently there has been considerable antigenic drift within the swine H3N2 viruses in the Netherlands and Belgium and recommend replacement of the A/Port Chalmers/1/73 (H3N2) strain in the current vaccine by a more recent swine H3N2 isolate. http://repub.eur.nl/res/pub/3609/ 1997-01-01T00:00:00Z The first indication of flu activity in the Netherlands in the 1996/'97 season was the isolation of an A/H3N2 influenza virus in week 48 of 1996. In subsequent weeks influenza viruses were isolated sporadically. The clinical influenza activity increased from week I of 1997 and reached its peak in week 4 of 1997. Simultaneously with the increase of clinical influenza activity, an increasing number of influenza viruses were isolated. The epidemic had a relatively small extent. Initially, A/H3N2 influenza viruses were predominant, but in the second half of the epidemic an increasing number of influenza B viruses were isolated as well. The A/H3N2 viruses were antigenically fairly strongly distinct from the variants prevalent in the preceding years. This season influenza A/HINI viruses did not play a significant role and only one virus of this subtype was isolated. All influenza A/H3N2, A/HINI and B viruses isolated were antigenically similar to the vaccine strains. http://repub.eur.nl/res/pub/3614/ 1997-01-01T00:00:00Z Letter http://repub.eur.nl/res/pub/3541/ 1995-01-01T00:00:00Z http://repub.eur.nl/res/pub/3557/ 1995-01-01T00:00:00Z http://repub.eur.nl/res/pub/3509/ 1994-01-01T00:00:00Z The influenza season 1993/'94 in the Netherlands and the rest of Northwestern Europe was marked by an influenza A/H3N2 epidemic. The morbidity of this epidemic was moderate, but a high mortality rate was observed. The epidemic viruses, represented by A/Netherlands/241/93 (H3N2), were characterised by haemagglutination inhibition assays and nucleotide sequence analysis. The viruses were related to A/Beijing/32/92 (H3N2), the vaccine strain for 1993/'94, but clear antigenic differences were detected. Therefore, the WHO has recommended a new A/H3N2 component, A/Shangdong/9/93, for the vaccine of 1994/'95. The onset of the epidemic was unusually early in the influenza season. An increase in the influenza activity was already noticed in the second week of November and it reached its peak in week 49. As a result of the early epidemic, the influenza vaccination programme had not been completed yet. Therefore, the point of time for vaccinating people at risk may have to be reconsidered and moved up in order to complete the vaccination programme earlier. http://repub.eur.nl/res/pub/3472/ 1993-01-01T00:00:00Z Monoclonal antibody (MAb) preparations specific for the enteric adenoviruses of subgenus F (AdF) were generated and evaluated as typing reagents in virus neutralization tests and enzyme-linked immunosorbent assays (ELISAs). A panel of 11 genome types of adenovirus 40 (Ad40), 24 genome types of Ad41, and 47 adenovirus prototype strains was used to determine the specificities of the MAbs in the two assays. In this way two MAbs, MAb 40-1 (anti-Ad40) and MAb 41-1 (anti-Ad41) were selected. These two MAbs showed strict type specificity in both assays. A third MAb reacted in an ELISA with all 47 human adenovirus types. With two other MAbs, three antigenic subtypes of Ad41 could be distinguished by their reactivities in virus neutralization tests and ELISAs. On the basis of the five selected MAbs, a sensitive ELISA system was developed for the direct detection and simultaneous typing and subtyping of Ad40 and Ad41 present in stool specimens. The five MAbs were also used to study the epidemiology of infections with Ad40 and Ad41 in The Netherlands in the period 1981 through 1989. It was shown that there were no significant fluctuations in the annual incidence of the cluster of enteric adenoviruses as a whole. This cluster should therefore be considered to belong to the "endemic" rather than the "epidemic" adenoviruses. The relative incidence of Ad40 infections compared with that of Ad41 infections changed considerably during the period studied; the proportion of Ad41 infections rose from about 30% in 1981 to about 95% in 1986, after which it stabilized at 90 to 95%. The proportion of one of the subtypes of Ad41 (Ad41 subtype M3) increased from about 40 to 80% in the same period. http://repub.eur.nl/res/pub/3357/ 1989-01-01T00:00:00Z The DNA of 48 strains of adenovirus type 40 (Ad40) and of 128 strains of adenovirus type 41 (Ad41), isolated between 1971 and 1986 from various countries, was characterized by restriction enzyme analysis using nine and ten restriction endonucleases respectively. Five new DNA variants of Ad40 and 18 new DNA variants of Ad41 were detected. Most of the restriction sites which differed among the various DNA variants appeared to be distributed at random over the entire length of the viral genomes of the two serotypes. The number of restriction sites by which two DNA variants differed from each other was used as a measure of their relatedness. Several clusters of closely related DNA variants were observed for each of the two serotypes. The 35 DNA variants of Ad40 and Ad41 were used to test monoclonal antibody preparations for their range of reactivity in a neutralization assay. One monoclonal antibody (5-8), raised against Ad40 strain Dugan, showed type-specific neutralization of all 11 Ad40 DNA variants tested. Six monoclonal antibodies, raised against Ad41 strain Tak, neutralized different proportions of the variants of Ad41. Two of these preparations (1-21 and 3-19) neutralized all 24 Ad41 DNA variants, while a third (1-23) reacted with only 12 Ad41 variants. Three other monoclonal antibody preparations (3-10, 3-18, 7-14) reacted specifically with only 6 of these 12 variants. The patterns of reactivity with the monoclonal antibody preparations correlated with the presence or absence of a HindIII restriction site at 56 map units and of an EcoRI restriction site at 52 map units on the Ad41 DNA. This region of the adenovirus DNA codes for the hexon protein, which is known to contain the type-specific neutralizing antigenic determinants. http://repub.eur.nl/res/pub/3293/ 1985-01-01T00:00:00Z Hemagglutination inhibiting (HI) monoclonal antibody preparations (MA) were raised against six influenza A (H3N2) strains from the period 1977-1982. Twenty-three hybridomas were selected and titrated in HI assays against these strains and against 18 influenza A (H3N2) viruses isolated in The Netherlands during the seasons 1981-1982 and 1982-1983. Similar HI tests were performed with conventional post-infection ferret antisera and with ferret antisera adsorbed with heterologous strains of influenza A (H3N2) virus. The resulting serological data were subjected to a computerized taxonomic cluster procedure based on the Euclidean distance between viruses. With respect to the degree of separation between clusters the unadsorbed ferret antisera were inferior to the adsorbed antisera whereas the MA were superior to both. Our results demonstrate that computer programs based on numerical taxonomy can be helpful in processing large numbers of serological data and that MA are indispensable in epidemiological and diagnostic influenza studies. http://repub.eur.nl/res/pub/3285/ 1984-01-01T00:00:00Z Hybridomas producing haemagglutination inhibiting monoclonal antibodies against influenza A/Texas/1/77 H3N2 were developed. One hybridoma producing antibodies reacting with Victoria/3/75, Texas/1/77 Bangkok/1/79 and England/496/80 was selected to determine the potency of influenza virusvaccines. Tests were performed in a newly developed Enzyme Linked Immunosorbent Assay (ELISA). For this purpose microtiter plates were successively coated with the monoclonal antibody, washed, incubated with vaccine or standard, washed, incubated with the peroxidase conjugated monoclonal antibody, washed and finally incubated with a substrate. Samples of the vaccine and of a standard containing 25-100 ng of antigen were assayed in the ELISA and the results were compared with those obtained in a rocket electrophoresis method. Linear regression analysis of the results showed that the correlation coefficients obtained with standards and vaccines for both methods were greater than or equal to 0.96. The comparison of vaccine potencies determined in the ELISA and the rocket electrophoresis method will be discussed. http://repub.eur.nl/res/pub/3282/ 1984-01-01T00:00:00Z Three successive fusions of mouse myeloma cells and spleen lymphocytes of a mouse immunized with Treponema Pallidum resulted in one hybridoma producing anti T. pallidum antibodies for each fusion. The mice were immunized with live pallidum cells respectively 1, 3 and 5 months before fusion and with antigen purified on density gradients 4, 3 and 2 days before fusion. Hybridomas cultures were tested for antibody production with an Enzyme Linked Immunosorbent Assay (ELISA) and a Western blotting technique. Two of the three anti T. pallidum antibody producing hybridomas were found with the ELISA, the third was found with a Western blotting technique. These hybridomas were also tested for the production of antibodies to rabbit antigens and T. phagedenis antigens in the ELISA: none appeared to be positive. Two of the hybridomas produce antibodies to a T. pallidum protein antigen of a molecular weight of 46 000: one hybridoma produces antibodies to a T. pallidum protein antigen of a molecular weight of 44 000 as determined by the Western blotting. Antibodies against these antigens are found during almost all stages of syphilis in man. One of the hybridomas produces monoclonal antibodies that react with treponemal antigen from E. coli cells, prepared by recombinant DNA technology as appeared in the Western blotting technique and this antibody will be used for purification of the 44 000 protein.