ABSTRACT
The number of H7N9 bird flu cases was high and the situation was grim in guizhou province in 2017. To understand the molecular characteristics of the hemagglutinin gene (HA) and the risk of human infection with avian influenza virus A(H7N9) in Guizhou Province, 2017. Homology, genetic evolution and pivotal sites related to receptor binding regions, pathogenicity and potential glycosylation of 14 avian influenza viruses A(H7N9) were analyzed by a series of bioinformation softwares. It was cleared that there was 95.9%-100% similarity among 14 strains in nucleotide of the HA gene, and there were 96.8%-97.8% and 96.8%-97.9% similarities with vaccine strains A/Shanghai/2/2013 and A/Anhui/1/2013 recommended by WHO, respectively. Phylogenetic analysis showed that 14 HA genes were directly evolved in the Yangtze River Delta evolution branch, but they could be derived from five diffenrent strains. Then 13 of 14 strains cleavage site sequences of HA protein revealed they were low pathogenic avian influenza viruses, while A/Guizhou-Weining/CSY01/2017 was high pathogenic avian influenza virus. Mutation G186V at the receptor binding sites in the HA was found in all 14 strains, and mutation Q226L in 13 strains besides A/Guizhou-Weining/CSY01/2017. All five potential glycosylation motifs in the HA were conservative.
ABSTRACT
Objective To predict and identify liner B-cell epitopes in the hemagglutinin ( HA) of human-infected avian-origin H7N9 influenza virus and analyze the specificity of H7 subtype.Methods Three serum samples collected at different times from the same patient who was confirmed to be infected with H7N9 influenza virus were provided by Shaoxing People’s Hospital, and one serum sample from healthy person was collected as the control.The extracellular region of HA protein was predicted by TMHMM Sever v.2.0.The potential B-cell epitopes were predicted by DNAStar Lasergene’ s Protean, BcePred and ABCpred tools, and the immunogenicity of the predicted B cell antigen epitopes was assessed by indirect enzyme-linked immunosordent assay ( ELISA ) .H7 subtype specificity was analyzed by comparing HA protein amino acid sequence with H7N9 and H1-H16 subtype influenza virus from Genbank using Clustal X 2.1 software, and Cn3D 4.3.1 software was used to detect the distribution and 3D structure of predicted epitopes on the HA protein of H7N9.Results The potential B-cell epitopes may be located in 172-183, 363-380, 452-472 and 491-506 of extracellular N-terminus of HA protein.ELISA showed that four predicted eptiopes specifically reacted with positive serums from patient.Multi-sequence alignment demonstrated that peptide 172-183 and 363-380 had higher H7 subtype specificity compared with amino acid sequences of other subtypes.Moreover, the predicted linear B-cell epitopes all located on the surface of HA protein according to the 3D structure analysis.Conclusion Four potential B-cell epitopes were identified, in which peptide 172-183 and 363-380 have higher H7 subtype specificity, and may be used in the design of epitope-based vaccines and diagnostics tests.
ABSTRACT
Objective To obtain the information of the 2009 influenza outbreak and the variations of influenza virus strains in quanzhou, and explore the relationship between the genetic variation of influenza virus and influenza epidemic. Methods During the influenza outbreak in quanzhou,one hundred and ninetyeight throat swabs specimens from the patients with influenza were collected. Viruses were isolated with MDCK cells and identified with serological test, followed by real-time RT-PCR. RNA of four influenza virus strains were extracted, then HA1 gene was amplified by RT-PCR. The purified PCR products were sequenced. The data were analyzed with the software DNAstar megalign. Results Total 98 pieces of H3N2 subtype influenza virus nucleic acid were detected in 198 throat swabs specimens,among which 62 influenza virus strains were identified as subtype influenza A( H3N2 ). The sequencing results of HA1 gene in these positive strains showed that their genetic characterization were more closed to strains A/Ningbo/333/2008 with a nucleotide homology of 98.7%, which was 96.8% as compared with A/Xiamen/70/2004. The amino acids sequences deduced from the nucleotide sequences in HA1 region of the isolated strain had 7 mutant sites compared with A/Brisbane/10/2007 vaccine strain. One variant amino acids were found located in the antigenic determinant sites A( 144 ), two were in the sites B( 158,189 ). Phylogenetic analysis also confirmed the difference in HAl domain. Conclusion The influenza virus strains causing the flu outbreak among some communities of quanzhou in 2009 are subtype influenza A ( H3N2 ), whose genetic characterization and antigenicity were different from the vaccine strain.