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Passage of influenza A/H3N2 viruses in human airway cells removes artefactual variants associated with neuraminidase-mediated binding.

ABSTRACT: Serological assays with modern influenza A/H3N2 viruses have become problematic due to the progressive reduction in the ability of viruses of this subtype to bind and agglutinate red blood cells (RBCs). This is due to reduced ability of the viral haemagglutinin (HA) glycoprotein to bind to the sialic acid-containing receptors presented by these cells. Additionally, as a result of reduced HA-mediated binding in cell culture, modern A/H3N2 viruses often acquire compensatory mutations during propagation that enable binding of cellular receptors through their neuraminidase (NA) surface protein. Viruses that have acquired this NA-mediated binding agglutinate RBCs through their NA, confusing the results of serological assays designed to assess HA antigenicity. Here we confirm with a large dataset that the acquisition of mutations that confer NA binding of RBCs is a culture artefact, and demonstrate that modern A/H3N2 isolates with acquired NA-binding mutations revert to a clinical-like NA sequence after a single passage in human airway epithelial (HAE) cells.

SUBMITTER: Brown JC

PROVIDER: S-EPMC7414449 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Passage of influenza A/H3N2 viruses in human airway cells removes artefactual variants associated with neuraminidase-mediated binding.

Brown Jonathan C JC Barclay Wendy S WS Galiano Monica M Harvey Ruth R

The Journal of general virology 20191106 5

Serological assays with modern influenza A/H3N2 viruses have become problematic due to the progressive reduction in the ability of viruses of this subtype to bind and agglutinate red blood cells (RBCs). This is due to reduced ability of the viral haemagglutinin (HA) glycoprotein to bind to the sialic acid-containing receptors presented by these cells. Additionally, as a result of reduced HA-mediated binding in cell culture, modern A/H3N2 viruses often acquire compensatory mutations during propag ...[more]

PMID: 31702542

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Project description:BackgroundHuman influenza viruses are known to bind to sialic acid linked alpha2-6 to galactose, but the binding specificity beyond that linkage has not been systematically examined. H3N2 human influenza isolates lost binding to chicken red cells in the 1990s but viruses isolated since 2003 have re-acquired the ability to agglutinate chicken erythrocytes. We have investigated specificity of binding, changes in hemagglutinin sequence of the recent viruses and the role of sialic acid in productive infection.ResultsViruses that agglutinate, or do not agglutinate, chicken red cells show identical binding to a Glycan Array of 264 oligosaccharides, binding exclusively to a subset of alpha2-6-sialylsaccharides. We identified an amino acid change in hemagglutinin that seemed to correlate with chicken red cell binding but when tested by mutagenesis there was no effect. Recombinant hemagglutinins expressed on Sf-9 cells bound chicken red cells but the released recombinant baculoviruses agglutinated only human red cells. Similarly, an isolate that does not agglutinate chicken red cells show hemadsorption of chicken red cells to infected MDCK cells. We suggest that binding of chicken red cells to cell surface hemagglutinin but not to virions is due to a more favorable hemagglutinin density on the cell surface. We investigated whether a virus specific for alpha2-6 sialyloligosaccharides shows differential entry into cells that have varying proportions of alpha2-6 and alpha2-3 sialic acids, including human A549 and HeLa cells with high levels of alpha2-6 sialic acid, and CHO cells that have only alpha2-3 sialic acid. We found that the virus enters all cell types tested and synthesizes viral nucleoprotein, localized in the nucleus, and hemagglutinin, transported to the cell surface, but infectious progeny viruses were released only from MDCK cells.ConclusionAgglutination of chicken red cells does not correlate with altered binding to any oligosaccharide on the Glycan Array, and may result from increased avidity due to density of hemagglutinin and not increased affinity. Absence of alpha2-6 sialic acid does not protect a cell from influenza infection and the presence of high levels of alpha2-6-sialic acids on a cell surface does not guarantee productive replication of a virus with alpha2-6 receptor specificity.

Project description:The vast majority of people already have preexisting immune responses to influenza viruses from one or more subtypes. However, almost all preclinical studies evaluate new influenza vaccine candidates in immunologically naive animals. Recently, our group demonstrated that priming naive ferrets with broadly reactive H1 COBRA HA-based vaccines boosted preexisting antibodies induced by wild-type H1N1 virus infections. These H1 COBRA hemagglutinin (HA) antigens induced antibodies with HAI activity against multiple antigenically different H1N1 viral variants. In this study, ferrets, preimmune to historical H3N2 viruses, were vaccinated with virus-like particle (VLP) vaccines expressing either an HA from a wild-type H3 influenza virus or a COBRA H3 HA antigen (T6, T7, T10, or T11). The elicited antisera had the ability to neutralize virus infection against either a panel of viruses representing vaccine strains selected by the World Health Organization or a set of viral variants that cocirculated during the same time period. Preimmune animals vaccinated with H3 COBRA T10 HA antigen elicited sera with higher hemagglutination inhibition (HAI) antibody titers than antisera elicited by VLP vaccines with wild-type HA VLPs in preimmune ferrets. However, while the T11 COBRA vaccine did not elicit HAI activity, the elicited antibodies did neutralize antigenically distinct H3N2 influenza viruses. Overall, H3 COBRA-based HA vaccines were able to neutralize both historical H3 and contemporary, as well as future, H3N2 viruses with higher titers than vaccines with wild-type H3 HA antigens. This is the first report demonstrating the effectiveness of a broadly reactive H3N3 vaccine in a preimmune ferret model.IMPORTANCE After exposure to influenza virus, the host generates neutralizing anti-hemagglutinin (anti-HA) antibodies against that specific infecting influenza strain. These antibodies can also neutralize some, but not all, cocirculating strains. The goal of next-generation influenza vaccines, such as HA head-based COBRA, is to stimulate broadly protective neutralizing antibodies against all strains circulating within a subtype, in particular those that persist over multiple influenza seasons, without requiring an update to the vaccine. To mimic the human condition, COBRA HA virus-like particle vaccines were tested in ferrets that were previously exposed to historical H3N2 influenza viruses. In this model, these vaccines elicited broadly protective antibodies that neutralized cocirculating H3N2 influenza viruses isolated over a 20-year period. This is the first study to show the effectiveness of H3N3 COBRA HA vaccines in a host with preexisting immunity to influenza.

Project description:BACKGROUND: In pandemic and epidemic forms, avian and human influenza viruses often cause significant damage to human society and economics. Gradually accumulated mutations on hemagglutinin (HA) cause immunologically distinct circulating strains, which lead to the antigenic drift (named as antigenic variants). The "antigenic variants" often requires a new vaccine to be formulated before each annual epidemic. Mapping the genetic evolution to the antigenic drift of influenza viruses is an emergent issue to public health and vaccine development RESULTS: We developed a method for identifying antigenic critical amino acid positions, rules, and co-mutated positions for antigenic variants. The information gain (IG) and the entropy are used to measure the score of an amino acid position on hemagglutinin (HA) for discriminating between antigenic variants and similar viruses. A position with high IG and entropy implied that this position is highly correlated to an antigenic drift. Nineteen positions with high IG and high genetic diversity are identified as antigenic critical positions on the HA proteins. Most of these antigenic critical positions are located on five epitopes or on the surface based on the HA structure. Based on IG values and entropies of these 19 positions on the HA, the decision tree was applied to create a rule-based model and to identify rules for predicting antigenic variants of a given two HA sequences which are often a vaccine strain and a circulating strain. The predicting accuracies of this model on two sets, which consist of a training set (181 hemagglutination inhibition (HI) assays) and an independent test set (31,878 HI assays), are 91.2% and 96.2% respectively. CONCLUSION: Our method is able to identify critical positions, rules, and co-mutated positions on HA for predicting the antigenic variants. The information gains and the entropies of HA positions provide insight to the antigenic drift and co-evolution positions for influenza seasons. We believe that our method is robust and is potential useful for studying influenza virus evolution and vaccine development.

Dataset Information

Passage of influenza A/H3N2 viruses in human airway cells removes artefactual variants associated with neuraminidase-mediated binding.

Publications

Passage of influenza A/H3N2 viruses in human airway cells removes artefactual variants associated with neuraminidase-mediated binding.

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