Disaster Planning ; Disease Outbreaks ; Humans ; Influenza A Virus, H1N1 Subtype ; metabolism ; Influenza, Human ; epidemiology ; transmission ; Travel

Since March 2009, pandemic A/H1N1/2009 influenza virus has been spreading throughout many countries including China. The emerged virus caused great harm to human health and social economy. Hemagglutinin (HA) is the most important viral surface glycoprotein, mainly possessing three kinds of functions: (1) binding to host cell receptor, (2) triggering the fusion between viral envelop and target cell membrane, (3) stimulating the body to generate the neutralizing antibody. Advances in the structure, primary function, evolution and antigenicity of pandemic A/H1N1/2009 influenza virus HA protein are reviewed in this paper.
Animals ; Evolution, Molecular ; Hemagglutinin Glycoproteins, Influenza Virus ; chemistry ; genetics ; immunology ; metabolism ; Humans ; Influenza A Virus, H1N1 Subtype ; genetics ; immunology ; pathogenicity ; physiology ; Influenza, Human ; epidemiology ; virology ; Pandemics

This study aims to investigate the virological impact of the stalk region and cysteine (C) in neuraminidase (NA) of influenza A/Anhui/1/05 (H5N1) and A/Ohio/07/2009 (H1N1) viruses. The NA of A/ Anhui/1/05 (H5N1), defined as AH N1, lacked 20 amino acids (including C, defined as s20) as compared with NA of A/Ohio/07/2009 (H1N1) (defined as 09N1). We deleted s20 of 09N1 to construct 09N1-s20, and inserted s20 into AH N1 to construct AH N1+s20. To investigate the impact of C on the biological function of NA, we deleted C in 09N1 to construct 09N1-C and inserted C into AH N1 to construct AH N1-C. The pseudo-type viral particle (pp) system was used to evaluate the impact of these mutants on virology. The combination of 09N1-C and 09H1 (defined as 09H1::09N1-C) showed an infectivity 8 times that of the wild type 09H1::09N1, while the infectivity of the combination of AH N1+C and AH H5 (defined as AH H5::AH N1+C) was much lower than that of the wild type AH H5::AH N1. The infectivity of the combination of 09N1-s20 and 09H1 (defined as 09H1::09N1-s20) was 4 times that of the wild type 09H1::09N1; the infectivity of the combination of AH N1+s20 and AH H5 (defined as AH H5:: AH N1+s20) was 1/7 that of the wild type AH H5::AH N1. The co-existence of 09N1-C and AH H5 displayed 6 times the infectivity of AH H5::09N1, while the infectivity of 09H1::AH N1+C was very low. Multimer analysis showed that in the wild type 09N1, the forms of NA were dimer > tetramer > monomer; the major component of NA in 09N1-C was monomer; in 09N1-s20, the forms of NA were monomer > dimer. AH N1 was mainly composed of monomer; in AH N1+s20, the forms of NA were dimer > monomer > tetramer; in AH N1+C, the forms of NA were dimer > tetramer. Deletion of C or s20 from 09N1 did not change the expression of NA. The study suggested that deletion of C from the stalk region of NA in A/Ohio/07/2009 (H1N1) increases infectivity. Insertion of C into NA's stalk region of A/ Anhui/1/05 (H5N1) significantly decreases infectivity. Cysteine deletion in the stalk region is important for the infectivity of A/Anhui/1/05 (H5N1) and A/Ohio/07/2009 (H1N1). It may interfere with the infectivity via changes in NA polymerization.
Amino Acid Motifs ; Humans ; Influenza A Virus, H1N1 Subtype ; chemistry ; enzymology ; genetics ; pathogenicity ; Influenza A Virus, H5N1 Subtype ; chemistry ; enzymology ; genetics ; pathogenicity ; Influenza, Human ; virology ; Neuraminidase ; chemistry ; genetics ; metabolism ; Viral Proteins ; chemistry ; genetics ; metabolism ; Virulence

Animals ; Global Health ; History, 20th Century ; Humans ; Influenza A Virus, H1N1 Subtype ; genetics ; isolation & purification ; metabolism ; pathogenicity ; Influenza, Human ; epidemiology ; history ; virology ; Spain ; epidemiology ; Viral Proteins ; genetics ; metabolism

We aimed to understand the molecular changes in host cells that accompany infection by the seasonal influenza A H1N1 virus because the initial response rapidly changes owing to the fact that the virus has a robust initial propagation phase. Human epithelial alveolar A549 cells were infected and total RNA was extracted at 30 min, 1 h, 2 h, 4 h, 8 h, 24 h, and 48 h post infection (h.p.i.). The differentially expressed host genes were clustered into two distinct sets of genes as the infection progressed over time. The patterns of expression were significantly different at the early stages of infection. One of the responses showed roles similar to those associated with the enrichment gene sets to known ‘gp120 pathway in HIV.’ This gene set contains genes known to play roles in preventing the progress of apoptosis, which infected cells undergo as a response to viral infection. The other gene set showed enrichment of ‘Drug Metabolism Enzymes (DMEs).’ The identification of two distinct gene sets indicates that the virus regulates the cell's mechanisms to create a favorable environment for its stable replication and protection of gene metabolites within 8 h.
Apoptosis ; Epithelial Cells* ; Gene Expression Regulation ; High-Throughput Nucleotide Sequencing ; Humans* ; Influenza A Virus, H1N1 Subtype ; Influenza, Human* ; Lung* ; Metabolism ; RNA ; Seasons

To analyze influenza pathogen spectrum in Yunnan province during 2009-2014 years, and analyze HA and NA genes of influenza A H1N1. Analysis was made on the monitoring date of influenza cases in Yunnan province in recent 6 years, 23 strains of influenza virus of HA and NA gene was sequenced and analyzed by MEGA 5 software to construct phylogenetic tree. 4 times of influenza AH1N1 epidemic peak were monitored from 2009-2014 years in Yunnan Province, as the nucleic acid detection results of influenza A H1N1 accounted for 28.8% of the total. The sequencing result showed that HA and NA gene were divided into 3 groups, one was detected with H275Y mutation strains. Influenza A H1N1 is one of the important subtypes in Yunnan province and their genes have divided into three branches during the period of 2009-2014 years, the vast majority of influenza a H1N1 are still sensitive to neuraminidase inhibitors.
China ; epidemiology ; Hemagglutinin Glycoproteins, Influenza Virus ; genetics ; metabolism ; Humans ; Influenza A Virus, H1N1 Subtype ; classification ; enzymology ; genetics ; isolation & purification ; Influenza, Human ; epidemiology ; virology ; Molecular Sequence Data ; Mutation ; Neuraminidase ; genetics ; metabolism ; Phylogeny ; Viral Proteins ; genetics ; metabolism

Catalytic Domain ; Enzyme Inhibitors ; metabolism ; pharmacology ; Influenza A Virus, H1N1 Subtype ; enzymology ; Models, Molecular ; Mutation ; Neuraminidase ; antagonists & inhibitors ; chemistry ; genetics ; metabolism ; Protein Binding

OBJECTIVEBoth the 2, 6 linkage and its topology on target cells are critical for the recognition by human influenza virus. The binding preference of avian flu virus H5N1 HA to the 2, 3-linked sialylated glycans is considered the major factor limiting its efficient infection and transmission in humans. To monitor potential adaptation of H5N1 virus in human population, the surveillance of receptor-binding specificity was undertaken in China.

METHODSThe binding specificity of 32 human H5N1 virus strains isolated from 2003 to 2009 was tested by 2, 3-specific sialidase-treated chicken red blood cell (CRBC) agglutination assay and a solid-phase direct binding assay with synthetic sialylglycopolymers.

RESULTSDual binding preference to 2, 3 and 2, 6-glycans were found in two strains: A/Guangdong/1/06 (A/GD/1/06) and A/Guangxi/1/08 (A/GX/1/08). Though minor effect of short-2, 6-binding was detected in A/GX/1/08 at a low virus titer, both showed high affinity to the oligosaccharide at a high load. Notably both are of the long-2, 6-recognition, with the same topology as that of human H1N1 and H3N2 viruses.

CONCLUSIONThe findings suggest that human H5N1 virus in China likely acquired the potential human-adaptation ability. Further research and surveillance on receptor-binding specificity of H5N1 viruses are required.

Adaptation, Biological ; Animals ; Chickens ; China ; epidemiology ; Hemagglutination Tests ; Humans ; Influenza A Virus, H1N1 Subtype ; metabolism ; Influenza, Human ; epidemiology ; Polysaccharides ; metabolism ; Receptors, Cell Surface ; metabolism ; Receptors, Virus ; metabolism ; Sialic Acids ; metabolism

On the basis of successful cloning the full length hemagglulinin (HA) and neuramidinase (NA) gene and sequence analysis of influenza virus H1N1, part of the gene was ligated into pMETA. Expression vectors pMETA/HA (52-1 557 bp) and pMETA/NA (121-1 263 bp) were constructed and expressed in pMAD16 induced by methanol. Recombinant protein was purified through Ni2+ affinity chromatography. Western blotting and ELISA were used to determine the antigenic activity of the recombinant protein. SDS-PAGE showed that the recombinant capsid gene could be overexpressed in Pichia methanolica. ELISA and Western blotting showed that the recombinant protein had antigenicity.
Cloning, Molecular ; Genetic Vectors ; genetics ; Hemagglutinins ; biosynthesis ; genetics ; Influenza A Virus, H1N1 Subtype ; genetics ; Neuraminidase ; biosynthesis ; genetics ; Pichia ; genetics ; metabolism ; Recombinant Proteins ; biosynthesis ; genetics ; immunology

To observe the inhibitive effect of Baicalin against influenza A H1N1 virus infection in epithelial cell line A549, the cell proliferation and cytotoxicity were assayed by MTT, the cell cycle and the apoptosis were analyzed by flowcytometer using PI staining, the morphology of cellular nucleolus was observed by Hoechst 33258 staining and the effects of activation on caspase 3 and caspase 8/9 were also detected by immunofluorescent staining with a fluorescence microscope. The results showed that Baicalin exerted an inhibitive effect on CPE after influenza A H1N1 virus infection. The FACS with PI staining showed that the cell cycle of the infected cell was arrested at S phase, the Baicalin-treated group decreased S phase cell ratio and subG0 phase peak in comparison with the control (P < 0.05) and significantly promoted cell proliferation (# P < 0.05). Hoechst33258 staining suggested that Baicalin protected the cellular nucleolus against the influenza virus-induced apoptosis. Observation under the immunofluorescent microscope suggested that the activities of caspase-8 and caspase-3 were enhanced at 36 h post the influenza virus infection, but 100 microg/mL Baicalin suppressing the activation of caspase-8 and caspase-3 rather than that of caspase-9. In summary, this research confirmed that Baicalin inhibited the influenza A H1N1 virus strain infection in vitro, the drug obviously protected cells from apoptosis damages through regulating cell cycle and suppressed the activation of caspase-8 and caspase-3. The down-regulation was significant and showed a dose-dependent relationship.
Antiviral Agents ; pharmacology ; Apoptosis ; drug effects ; Caspases ; metabolism ; Cell Cycle ; drug effects ; Cell Line, Tumor ; Flavonoids ; pharmacology ; Flow Cytometry ; Humans ; Influenza A Virus, H1N1 Subtype ; drug effects ; physiology