RESUMO
Antigenic drift forces us to frequently update influenza vaccines; however, the genetic basis for antigenic variation remains largely unknown. In this study, we used clade 7.2 H5 viruses as models to explore the molecular determinants of influenza virus antigenic variation. We generated eight monoclonal antibodies (MAbs) targeted to the hemagglutinin (HA) protein of the index virus A/chicken/Shanxi/2/2006 and found that two representative antigenically drifted clade 7.2 viruses did not react with six of the eight MAbs. The E131N mutation and insertion of leucine at position 134 in the HA protein of the antigenically drifted strains eliminated the reactivity of the virus with the MAbs. We also found that the amino acid N131 in the H5 HA protein is glycosylated. Our results provide experimental evidence that glycosylation and an amino acid insertion or deletion in HA influence antigenic variation.
Assuntos
Aminoácidos/imunologia , Antígenos Virais/imunologia , Glicoproteínas de Hemaglutininação de Vírus da Influenza/imunologia , Virus da Influenza A Subtipo H5N1/imunologia , Sequência de Aminoácidos , Aminoácidos/genética , Aminoácidos/metabolismo , Animais , Anticorpos Monoclonais/imunologia , Anticorpos Antivirais/genética , Anticorpos Antivirais/imunologia , Anticorpos Antivirais/metabolismo , Antígenos Virais/genética , Antígenos Virais/metabolismo , Galinhas/virologia , Glicosilação , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Glicoproteínas de Hemaglutininação de Vírus da Influenza/metabolismo , Humanos , Virus da Influenza A Subtipo H5N1/genética , Virus da Influenza A Subtipo H5N1/metabolismo , Vacinas contra Influenza/genética , Vacinas contra Influenza/imunologia , Vacinas contra Influenza/metabolismo , Influenza Aviária/genética , Influenza Aviária/imunologia , Influenza Aviária/virologia , Influenza Humana/genética , Influenza Humana/imunologia , Influenza Humana/virologia , Homologia de Sequência de AminoácidosRESUMO
Influenza A viruses (IAVs), particularly H1N1, H5N1 and H7N9, pose a substantial threat to public health worldwide. Here, we report that MIR2911, a honeysuckle (HS)-encoded atypical microRNA, directly targets IAVs with a broad spectrum. MIR2911 is highly stable in HS decoction, and continuous drinking or gavage feeding of HS decoction leads to a significant elevation of the MIR2911 level in mouse peripheral blood and lung. Bioinformatics prediction and a luciferase reporter assay showed that MIR2911 could target various IAVs, including H1N1, H5N1 and H7N9. Synthetic MIR2911 significantly inhibited H1N1-encoded PB2 and NS1 protein expression, but did not affect mutants in which the MIR2911-binding nucleotide sequences were altered. Synthetic MIR2911, extracted RNA from HS decoction and HS decoction all significantly inhibited H1N1 viral replication and rescued viral infection-induced mouse weight loss, but did not affect infection with a mutant virus in which the MIR2911-binding nucleotide sequences of PB2 and NS1 were altered. Importantly, the inhibitory effect of HS decoction on viral replication was abolished by an anti-MIR2911 antagomir, indicating that the physiological concentration of MIR2911 in HS decoction could directly and sufficiently suppress H1N1 viral replication. MIR2911 also inhibited H5N1 and H7N9 viral replication in vitro and in vivo. Strikingly, administration of MIR2911 or HS decoction dramatically reduced mouse mortality caused by H5N1 infection. Our results demonstrate that MIR2911 is the first active component identified in Traditional Chinese Medicine to directly target various IAVs and may represent a novel type of natural product that effectively suppresses viral infection.