http://repub.eur.nl/res/aut/9144/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/38989/ 2012-12-07T00:00:00Z Annual vaccination of healthy children >6 months of age against seasonal influenza has been recommended by public health authorities of some countries. However, currently used seasonal vaccines provide only limited protection against (potentially) pandemic influenza viruses. Furthermore, we recently hypothesized that annual vaccination may hamper the development of cross-reactive immunity against influenza A viruses of novel subtypes, that would otherwise be induced by natural infection. Here we summarize our findings in animal models in which we demonstrated that vaccination against influenza A/H3N2 virus reduced the induction of heterosubtypic immunity against highly pathogenic avian influenza A/H5N1 virus, otherwise induced by a prior infection with influenza A/H3N2 virus. The reduction of heterosubtypic immunity correlated with reduced virus-specific CD8+ T cell responses. An additional study was performed in humans, in which we collected peripheral blood mononuclear cells from annually vaccinated children with cystic fibrosis (CF) and age-matched unvaccinated healthy control children to study the virus-specific T cell response. An age-related increase of the virus-specific CD8+ T cell response was observed in unvaccinated children that was absent in vaccinated children with CF. These findings highlight the importance of the development of vaccines that provide protection against influenza A viruses of all subtypes. http://repub.eur.nl/res/pub/33226/ 2011-11-01T00:00:00Z Infection with seasonal influenza A viruses induces immunity to potentially pandemic influenza A viruses of other subtypes (heterosubtypic immunity). We recently demonstrated that vaccination against seasonal influenza prevented the induction of heterosubtypic immunity against influenza A/H5N1 virus induced by infection with seasonal influenza in animal models, which correlated with the absence of virus-specific CD8+T cell responses. Annual vaccination of all healthy children against influenza has been recommended, but the impact of vaccination on the development of the virus-specific CD8+T cell immunity in children is currently unknown. Here we compared the virus-specific CD8+T cell immunity in children vaccinated annually with that in unvaccinated children. In the present study, we compared influenza A virus-specific cellular and humoral responses of unvaccinated healthy control children with those of children with cystic fibrosis (CF) who were vaccinated annually. Similar virus-specific CD4+T cell and antibody responses were observed, while an age-dependent increase of the virus-specific CD8+T cell response that was absent in vaccinated CF children was observed in unvaccinated healthy control children. Our results indicate that annual influenza vaccination is effective against seasonal influenza but hampers the development of virus-specific CD8+T cell responses. The consequences of these findings are discussed in the light of the development of protective immunity to seasonal and future pandemic influenza viruses. http://repub.eur.nl/res/pub/33263/ 2011-10-01T00:00:00Z Influenza A (H1N1) viruses of swine origin were introduced into the human population in 2009 and caused a pandemic. The disease burden in the elderly was relatively low, which was attributed to the presence of cross-reacting serum antibodies in this age group, which were raised against seasonal influenza A (H1N1) viruses that circulated before 1957. It has also been described how infection with heterosubtypic influenza viruses can induce some degree of protection against infection by a novel strain of influenza virus. Here, we assess the extent of protective immunity against infection with the 2009 influenza A (H1N1) pandemic influenza virus that is afforded by infection with a seasonal influenza A (H3N2) virus in mice. Mice that experienced a primary A (H3N2) influenza virus infection displayed reduced weight loss after challenge infection and cleared the 2009 influenza A (H1N1) virus infection more rapidly. To elucidate the correlates of protection of this heterosubtypic immunity to pandemic H1N1 virus infection, adoptive transfer experiments were carried out by using selected post-infection lymphocyte populations. Virusspecific CD8+T-cells in concert with CD4+T-cells were responsible for the observed protection. These findings may not only provide an explanation for epidemiological differences in the incidence of severe pandemic H1N1 infections, they also indicate that the induction of crossreactive virus-specific CD8+and CD4+T-cell responses may be a suitable approach for the development of universal influenza vaccines. http://repub.eur.nl/res/pub/33515/ 2011-03-01T00:00:00Z Infection with seasonal influenza viruses induces a certain extent of protective immunity against potentially pandemic viruses of novel subtypes, also known as heterosubtypic immunity. Here we demonstrate that infection with a recent influenza A/H3N2 virus strain induces robust protection in ferrets against infection with a highly pathogenic avian influenza virus of the H5N1 subtype. Prior H3N2 virus infection reduced H5N1 virus replication in the upper respiratory tract, as well as clinical signs, mortality, and histopathological changes associated with virus replication in the brain. This protective immunity correlated with the induction of T cells that cross-reacted with H5N1 viral antigen. We also demonstrated that prior vaccination against influenza A/H3N2 virus reduced the induction of heterosubtypic immunity otherwise induced by infection with the influenza A/H3N2 virus. The implications of these findings are discussed in the context of vaccination strategies and vaccine development aiming at the induction of immunity to pandemic influenza. Copyright http://repub.eur.nl/res/pub/33722/ 2011-01-01T00:00:00Z During the 1993-1994 flu season, influenza A/H3N2 viruses emerged with an amino acid substitution (R384G) at the anchor residue of the HLA-B*2705 restricted NP383-391epitope located in the nucleoprotein (NP). The R384G substitution reached fixation rapidly and abrogated recognition of A/H3N2 viruses by NP383-391-specific CD8+ T cytotoxic T lymphocytes (CTL) completely. To test the impact of the R384G substitution in the immunodominant NP383-391epitope in vivo, influenza A viruses that differ at position 384 of the NP only were generated by reverse genetics. These viruses with an arginin (384R) or a glycin (384G) at position 384 were used to inoculate HLA-B*2705-transgenic mice and C57Bl/6 mice. Infection of naïve C57Bl/6 and HLA-B*2705 mice with influenza virus containing the NP383-391epitope (384R) caused more weight loss compared to infection with the virus without the epitope (384G). In contrast, HLA-B*2705 transgenic mice primed for a secondary CTL response by infection with a heterosubtypic influenza A virus, did not display this difference in virulence and the outcome of infection with the 384R virus was somewhat reduced. This phenotype of the 384R-virus was not observed in primed C57Bl/6 mice lacking HLA-B*2705. The relative reduction of weight loss after infection of primed HLA-B*2705+ mice with the 384R virus correlated with the CTL response to the NP383-391. However, no differences were observed in the kinetics of viral clearance between the two viruses in immune HLA-B*2705+ mice, which may be attributed at least partially to CTL responses to other HLA-B*2705 restricted epitopes that were similar in magnitude. http://repub.eur.nl/res/pub/27671/ 2010-08-01T00:00:00Z Highly pathogenic avian influenza A viruses of the H5N1 subtype continue to circulate in poultry, and zoonotic transmissions are reported frequently. Since a pandemic caused by these highly pathogenic viruses is still feared, there is interest in the development of influenza A/H5N1 virus vaccines that can protect humans against infection, preferably after a single vaccination with a low dose of antigen. Here we describe the induction of humoral and cellular immune responses in ferrets after vaccination with a cell culture-derived whole inactivated influenza A virus vaccine in combination with the novel adjuvant CoVaccine HT. The addition of CoVaccine HT to the influenza A virus vaccine increased antibody responses to homologous and heterologous influenza A/H5N1 viruses and increased virus-specific cell-mediated immune responses. Ferrets vaccinated once with a whole-virus equivalent of 3.8 μg hemagglutinin (HA) and CoVaccine HT were protected against homologous challenge infection with influenza virus A/VN/1194/04. Furthermore, ferrets vaccinated once with the same vaccine/adjuvant combination were partially protected against infection with a heterologous virus derived from clade 2.1 of H5N1 influenza viruses. Thus, the use of the novel adjuvant CoVaccine HT with cell culture-derived inactivated influenza A/H5N1 virus antigen is a promising and dose-sparing vaccine approach warranting further clinical evaluation. Copyright http://repub.eur.nl/res/pub/20134/ 2010-07-01T00:00:00Z It was recently shown that the use of an experimental subunit vaccine protected mice against infection with a human A/H3N2 influenza virus, but consequently affected the induction of heterosubtypic immunity to a highly pathogenic A/H5N1 influenza virus, which was otherwise induced by the A/H3N2 infection. As whole inactivated virus (WIV) vaccines are widely used to protect against seasonal influenza and also contain inner viral proteins such as the nucleoprotein (NP), the potential of a WIV vaccine to induce protective immunity against infection was tested with a homologous A/H3N2 (A/Hong Kong/2/68) and a heterosubtypic A/H5N1 influenza virus (A/Indonesia/5/05). As expected, the vaccine afforded protection against infection with the A/H3N2 virus only. In addition, it was demonstrated that the use of WIV vaccine for protection against A/H3N2 infection affected the induction of heterosubtypic immunity that was otherwise afforded by A/H3N2 influenza virus infection. The reduction in protective immunity correlated with changes in the immunodominance patterns of the CD8+ T-cell responses directed to the epitopes located in the acid polymerase subunit of the viral RNA polymerase (PA224-233) and the NP (NP366-374). In unvaccinated mice that experienced infection with the A/H3N2 influenza virus, the magnitude of the CD8+ T-cell response to both peptides was similar on secondary infection with A/H5N1 influenza virus. In contrast, prior vaccination with WIV affected the immunodominance pattern and skewed the response after infection with influenza virus A/ Indonesia/5/05 towards a dominant NP366-374-specific response. These findings may have implications for vaccination strategies aimed at the induction of protective immunity to seasonal and/or pandemic influenza. http://repub.eur.nl/res/pub/24525/ 2009-11-16T00:00:00Z A candidate influenza H5N1 vaccine based on cell-culture-derived whole inactivated virus and the novel adjuvant CoVaccineHT™ was evaluated in vitro and in vivo. To this end, mice were vaccinated with the whole inactivated influenza A/H5N1 virus vaccine with and without CoVaccineHT™ and virus-specific antibody and cellular immune responses were assessed. The addition of CoVaccineHT™ increased virus specific primary and secondary antibody responses against the homologous and an antigenically distinct heterologous influenza A/H5N1 strain. The superior antibody responses induced with the CoVaccineHT™-adjuvanted vaccine correlated with the magnitude of the virus-specific CD4+ T helper cell responses. CoVaccineHT™ did not have an effect on the magnitude of the CD8+ T cell response. In vitro, CoVaccineHT™ upregulated the expression of co-stimulatory molecules both on mouse and human dendritic cells and induced the secretion of pro-inflammatory cytokines TNF-α, IL-6, IL-1β and IL-12p70 in mouse- and IL-6 in human dendritic cells. Inhibition experiments indicated that the effect of CoVaccineHT™ is mediated through TLR4 signaling. These data suggest that CoVaccineHT™ also will increase the immunogenicity of an influenza A/H5N1 vaccine in humans. http://repub.eur.nl/res/pub/24985/ 2009-05-14T00:00:00Z Annual vaccination against seasonal influenza viruses is recommended for certain individuals that have a high risk for complications resulting from infection with these viruses. Recently it was recommended in a number of countries including the USA to vaccinate all healthy children between 6 and 59 months of age as well. However, vaccination of immunologically naïve subjects against seasonal influenza may prevent the induction of heterosubtypic immunity against potentially pandemic strains of an alternative subtype, otherwise induced by infection with the seasonal strains. Here we show in a mouse model that the induction of protective heterosubtypic immunity by infection with a human A/H3N2 influenza virus is prevented by effective vaccination against the A/H3N2 strain. Consequently, vaccinated mice were no longer protected against a lethal infection with an avian A/H5N1 influenza virus. As a result H3N2-vaccinated mice continued to loose body weight after A/H5N1 infection, had 100-fold higher lung virus titers on day 7 post infection and more severe histopathological changes than mice that were not protected by vaccination against A/H3N2 influenza. The lack of protection correlated with reduced virus-specific CD8+ T cell responses after A/H5N1 virus challenge infection. These findings may have implications for the general recommendation to vaccinate all healthy children against seasonal influenza in the light of the current pandemic threat caused by highly pathogenic avian A/H5N1 influenza viruses. http://repub.eur.nl/res/pub/35795/ 2007-06-01T00:00:00Z Influenza virus-specific CD4+T-helper cells were cloned that recognized a virus strain isolated in 1981, but that failed to recognize more recent strains. The HLA-DR*1601-restricted epitope recognized was located in the hemagglutinin (HA99-113) and the naturally occurring A → V substitution at position 106 was responsible for abrogating the recognition by HA99-113-specific CD4+T-cells. This amino acid substitution was found in influenza A/H3N2 viruses that circulated between 1999 and 2005 and did not affect recognition by virus-specific antibodies. It was speculated that influenza viruses could evade recognition by virus-specific CD4+T-cells, at least temporarily. http://repub.eur.nl/res/pub/35453/ 2007-05-01T00:00:00Z In the present study, we examined the effect of the loss of the human leucocyte antigen (HLA)-B*3501-restricted nucleoprotein (NP)418-426epitope on interferon (IFN)-γ-production and lytic activity of the human cytotoxic T lymphocyte (CTL) response in vitro. Extensive amino acid variation at T cell receptor contact residues of the NP418-426epitope has led to repeated evasion from specific CTL. We generated recombinant influenza viruses with variants of the NP418-426epitope, which were used to stimulate peripheral blood mononuclear cells obtained from six HLA-B*3501-positive study subjects in order to expand virus-specific CTL. Loss of the NP418-426epitope resulted in a significant reduction of IFN-γ-expressing CD8+T cells, similar to that observed previously after the loss of the HLA-B*2705-restricted NP383-391epitope. In addition, the effect of the loss of the NP418-426epitope on the lytic activity of the virus-specific CTL response was assessed. Also this functional property of the virus-specific CTL response was affected significantly by the loss of this and the NP383-391epitope, as determined using the newly developed fluorescent antigen-transfected target cell (FATT)-CTL assay. These findings indicate that the loss of single immunodominant epitopes affects the functionality of the virus-specific CTL response significantly. http://repub.eur.nl/res/pub/35591/ 2007-02-01T00:00:00Z The influenza A virus nucleoprotein (NP) and matrix protein are major targets for human virus-specific cytotoxic T-lymphocyte (CTL) responses. Most of the CTL epitopes that have been identified so far are conserved. However, sequence variation in CTL epitopes of the NP has recently been demonstrated to be associated with escape from virus-specific CTLs. To assess the extent of variation in CTL epitopes during influenza A virus evolution, 304 CTL clones derived from six study subjects were obtained with specificity for an influenza A/H3N2 virus isolated in 1981. Subsequently, the frequency of the CTL clones that failed to recognize a more recent influenza virus strain isolated in 2003 was determined. In four of six study subjects, CTLs were found to be specific for variable epitopes, accounting for 2.6 % of all CTL clones. For some of these CTL clones, the minimal epitope and the residues responsible for abrogation of T-cell recognition were identified. http://repub.eur.nl/res/pub/13889/ 2005-09-01T00:00:00Z Viruses can exploit a variety of strategies to evade immune surveillance by cytotoxic T lymphocytes (CTL), including the acquisition of mutations in CTL epitopes. Also for influenza A viruses a number of amino acid substitutions in the nucleoprotein (NP) have been associated with escape from CTL. However, other previously identified influenza A virus CTL epitopes are highly conserved, including the immunodominant HLA-A*0201-restricted epitope from the matrix protein, M1(58-66). We hypothesized that functional constraints were responsible for the conserved nature of influenza A virus CTL epitopes, limiting escape from CTL. To assess the impact of amino acid substitutions in conserved epitopes on viral fitness and recognition by specific CTL, we performed a mutational analysis of CTL epitopes. Both alanine replacements and more conservative substitutions were introduced at various positions of different influenza A virus CTL epitopes. Alanine replacements for each of the nine amino acids of the M1(58-66) epitope were tolerated to various extents, except for the anchor residue at the second position. Substitution of anchor residues in other influenza A virus CTL epitopes also affected viral fitness. Viable mutant viruses were used in CTL recognition experiments. The results are discussed in the light of the possibility of influenza viruses to escape from specific CTL. It was speculated that functional constraints limit variation in certain epitopes, especially at anchor residues, explaining the conserved nature of these epitopes.