Influenza B virus (IBV) is more likely to cause complications than influenza A virus (IAV) and even causes higher disease burden than IAV in a certain season, but IBV has received less attention. In order to analyze the genetic evolution characteristics of the clinical strain IBV (B/Guangxi-Jiangzhou/1352/2018), we constructed genetic evolution trees and analyzed the homology and different amino acids of hemagglutinin and neuraminidase referring to the vaccine strains recommended by World Health Organization (WHO). We found that strain B/Guangxi-Jiangzhou/1352/2018 was free of interlineage reassortment and poorly matched with the vaccine strain B/Colorado/06/2017 of the same year. We also determined the median lethal dose (LD₅₀) and the pathogenicity of strain B/Guangxi-Jiangzhou/1352/2018 in mice. The results showed that the LD₅₀ was 10^5.9 TCID₅₀ (median tissue culture infective dose), the IBV titer in the lungs reached peak 1 d post infection and the mRNA level of the most of inflammatory cytokines in the lungs reached peak 12 h post infection. The alveoli in the lungs were severely damaged and a large number of inflammatory cells were infiltrated post infection. The study demonstrated that the clinical strain IBV (B/Guangxi-Jiangzhou/1352/2018) could infect mice and induce typical lung inflammation. This will facilitate the research on the pathogenesis and transmission mechanism of IBV, and provide an ideal animal model for evaluation of new vaccines, antiviral and anti-inflammatory drug.
Amino Acids/genetics* ; Animals ; Antiviral Agents/pharmacology* ; China ; Cytokines/metabolism* ; Hemagglutinins/metabolism* ; Humans ; Influenza B virus/pathogenicity* ; Influenza, Human/virology* ; Mice ; Neuraminidase/genetics* ; Orthomyxoviridae Infections/virology* ; Phylogeny ; RNA, Messenger/metabolism* ; Virulence/genetics*

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

Data based on the antiviral-resistant phenotyping characteristics of 884 influenza B viruses circulating in mainland China from October 2013 to March 2014 were analyzed to assess the susceptibility of influenza B viruses to neuraminidase inhibitors. All 884 viruses were sensitive to oseltamivir; two viruses (0.23%) had reduced sensitivity to zanamivir and all other viruses were sensitive to zanamivir. Among the 38 viruses with a B/Victoria lineage, B/Shandong-Kuiwen/1195/2014 exhibited a half-maximal inhibitory concentration (IC50) for zanamivir that was elevated by 5. 12-fold (1.78 nM) compared with neuraminidase inhibitors sensitive to the reference virus (0.34 nM), suggesting that it exhibited reduced inhibition by zanamivir. D35G, N59D and S402T (39, 64 and 399 with N2 number) amino-acid substitutions in the NA gene were detected with no previously reported antiviral-resistant substitutions. Among viruses with the 846 B/Yamagata lineage, B/Hunan-Lingling/350/2013 exhibited a 7.99-fold elevated IC50 for zanamivir (2.72 nM) compared with neuraminidase inhibitors sensitive to the reference virus (0.34 nM), suggesting that it exhibited reduced inhibition by zanamivir. D197N (N2 number), a previously reported antiviral resistant-related amino-acid substitution in the NA gene, was detected in B/Hunan-Lingling/350/2013. These data suggest that recently circulating influenza B viruses in mainland China have retained susceptibility to neuraminidase inhibitors.
Amino Acid Substitution ; Antiviral Agents ; pharmacology ; China ; epidemiology ; Drug Resistance, Viral ; Enzyme Inhibitors ; pharmacology ; Humans ; Influenza B virus ; drug effects ; enzymology ; genetics ; isolation & purification ; Influenza, Human ; epidemiology ; virology ; Microbial Sensitivity Tests ; Neuraminidase ; antagonists & inhibitors ; genetics ; metabolism ; Viral Proteins ; antagonists & inhibitors ; 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

This study aimed to investigate the drug susceptibility of wild-type and mutant avian influenza A (H7N9) virus neuraminidase (NA) to oseltamivir and zanamivir. Codon optimized DNA of H7N9 (A/ Hangzhou/1/2013) NA was synthesized and constructed into the pcDNA3.1/His vector (NA(H7N9-WT)). Mutant NA(H7N9-H274Y) and NA(H7N9-R292K) plasmids were constructed by directed mutagenesis PCR using NA(H7N9-WT) plasmid as the template followed by sequencing. NA plasmids were transfected into 293T cells and cell lysates containing NAs were collected 48 h post-transfection. Wild-type and mutant NAs were analyzed by Western blotting and their activities were tested by the 4-MUNANA-based assay. All three NAs were expressed and enzymatic activities were confirmed. The effects of oseltamivir and zanamivir on all three NAs were then tested. It showed that the half maximal inhibitory concentrations (IC50s) of oseltamivir carboxylate on NA(H7N9-WT), NA(H7N9-H274Y) and NA(H7N9-R292K) were 1.6 nM, 15.1 nM, and > 1 000 nM with fold changes of 9 and > 625, respectively. The IC50 values of zanamivir on NA(H7N9-WT), NA(H7N9-H274Y), and NA(H7N9-R292K) were 1.1 nM, 1.4 nM, and 38.0 nM with fold changes of 1.3 and 34, respectively. These results indicated that oseltamivir and zanamivir could significantly inhibit NA(H7N9-WT). NA(H7N9-R292K) showed high-level resistance to both drugs (34-fold and 625-fold) and NA(H7N9-H274Y) was sensitive to both (1.3-fold and 9-fold). These results indicated that both oseltamivir and zanamivir could be used for patients infected with the H7N9 virus. However, when patients carried the H7N9 virus with a NA R292K mutation, other medications would be preferred over oseltamivir or zanamivir.
Antiviral Agents ; pharmacology ; Humans ; Influenza A Virus, H7N9 Subtype ; drug effects ; enzymology ; genetics ; Influenza, Human ; virology ; Microbial Sensitivity Tests ; Mutation ; Neuraminidase ; antagonists & inhibitors ; genetics ; metabolism ; Oseltamivir ; pharmacology ; Viral Proteins ; antagonists & inhibitors ; genetics ; metabolism ; Zanamivir ; pharmacology

OBJECTIVETo prepare the 4 candidate vaccine strains of H5N1 avian influenza virus isolated in China.

METHODSRecombinant viruses were rescued using reverse genetics. Neuraminidase (NA) and hemagglutinin (HA) segments of the A/Xinjiang/1/2006, A/Guangxi/1/2009, A/Hubei/1/2010, and A/Guangdong/1/2011 viruses were amplified by RT-PCR. Multibasic amino acid cleavage site of HA was removed and ligated into the pCIpolI vector for virus rescue. The recombinant viruses were evaluated by trypsin dependent assays. Their embryonate survival and antigenicity were compared with those of the respective wild-type viruses.

RESULTSThe 4 recombinant viruses showed similar antigenicity compared with wild-type viruses, chicken embryo survival and trypsin-dependent characteristics.

CONCLUSIONThe 4 recombinant viruses rescued using reverse genetics meet the criteria for classification of low pathogenic avian influenza strains, thus supporting the use of them for the development of seeds and production of pre-pandemic vaccines.

Animals ; Chick Embryo ; Chickens ; China ; Hemagglutinin Glycoproteins, Influenza Virus ; genetics ; metabolism ; Influenza A Virus, H5N1 Subtype ; immunology ; Influenza Vaccines ; immunology ; Influenza in Birds ; prevention & control ; virology ; Neuraminidase ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Vaccines, Synthetic ; immunology

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

To investigate the N-glycosylation characteristics of recombinant human erythropoietin (rhEPO) produced by an industrial Chinese hamster ovary (CHO) cell line that is currently used in a large scale manufacturing process, we cultured this cell strain in static mode. The produced rhEPO in the culture supernatant was analyzed using isoelectric focusing (IEF) and Ricinus communis agglutinin-I (RCA-I) lectin precipitation. The lactate dehydrogenase (LDH) and sialidase activity in the serum-free supernatant were assayed as well. The analyses revealed that this cell strain could produce rhEPO with high sialic acid content, but during prolonged culture, cell viability decreased with time whilst the activity of sialidase present in the supernatant increased. The loss in rhEPO quality was due to a decrease in terminal sialic acid on the N-glycans, caused by sialidase degradation. The methods and findings in this paper serve as basis for further investigation of industrial production process.
Animals ; CHO Cells ; metabolism ; Cell Culture Techniques ; methods ; Cricetinae ; Cricetulus ; Erythropoietin ; biosynthesis ; genetics ; metabolism ; Genetic Engineering ; Humans ; N-Acetylneuraminic Acid ; metabolism ; Neuraminidase ; metabolism ; Proteolysis ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism

Influenza virus assembly requires the completion of viral protein and vRNP transport to the assembly site at the plasma membrane. Therefore, efficient regulation of intracellular transport of the viral proteins and vRNPs to the surface of the host cell is especially important for virus morphogenesis. Influenza A virus uses the machineries of host cells to transport its own components including ribonucleoproteins (vRNPs) and three transmembrane proteins hemagglutinin (HA), neuraminidase (NA) and matrix 2 protein (M2). It has been shown that newly synthesized vRNPs are associated with active form of Rab11 and accumulate at recycling endosomes adjacent to the microtubule organizing center (MTOC) following nuclear export. Subsequently, they are transported along the microtubule network toward the plasma membranes in cargo vesicles. The viral transmembrane proteins are translated on the rough endoplasmic reticulum and transported to the virus assembly site at the plasma membrane. It has been found that several host factors such as ARHGAP21 and GTPase Cdc42 are involved in regulation of intracellular trafficking of influenza A virus transmembrane proteins including NA. In this review, we will highlight the current knowledge about anterograde transport and its regulation of the influenza A virus transmembrane proteins and genome in the host cytoplasm.
Cytoplasm ; metabolism ; GTP Phosphohydrolases ; metabolism ; GTPase-Activating Proteins ; metabolism ; Genome, Viral ; Hemagglutinin Glycoproteins, Influenza Virus ; metabolism ; Humans ; Influenza A virus ; genetics ; pathogenicity ; physiology ; Neuraminidase ; metabolism ; Protein Transport ; Ribonucleoproteins ; metabolism ; Viral Matrix Proteins ; metabolism ; cdc42 GTP-Binding Protein ; metabolism

Influenza viruses are highly contagious for human population and result in acute respiratory infectious diseases ranging from mild to severe. Neuraminidase (NA) inhibitors (NAIs) (oseltamivir, zanamivir, peramivir and laninamivir), which target the NA glycoproteins of influenza A and B viruses are widely used in the prophylaxis and treatment of influenza virus infection. However, the substitutions of amino acids in NA or HA gene may lead to resistances to NAIs. NAI-resistance-related substitutions are typically specific to certain NA type or subtype. The sensitivity for NAI-resistance detection is affected by different assays used.
Animals ; Antiviral Agents ; pharmacology ; Drug Resistance, Viral ; Enzyme Inhibitors ; pharmacology ; Humans ; Influenza, Human ; drug therapy ; virology ; Neuraminidase ; antagonists & inhibitors ; genetics ; metabolism ; Orthomyxoviridae ; drug effects ; enzymology ; genetics ; physiology ; Viral Proteins ; antagonists & inhibitors ; genetics ; metabolism