Epidemiological, clinical, and virologic features of two family clusters of avian influenza A (H7N9) virus infections in Southeast China.

This study aimed to investigate the epidemiological, clinical, and virologic characteristics of avian influenza A (H7N9) confirmed cases from two family clusters in Southeast China. Epidemiological data of the H7N9 confirmed cases and their close contacts were obtained through interviews and reviews of medical records. Of the four patients in these two family clusters, two cases had mild symptoms, one had severe symptoms, and one died. Three of the four patients had a history of exposure to live poultry or contaminated environments. The complete genome sequences of the H7N9 viruses from the same family cluster were highly homologous, and the four isolated viruses from the two family clusters exhibited the virologic features of the H7N9 virus, in terms of transmissibility, pathogenicity, host adaptation, and antiviral drug resistance. In addition, our findings indicated that the A/Fujian/18/2015 viral strain contained an additional hemagglutinin G225D substitution, which preferentially binds α2,6-linked sialic acids. The results of this study demonstrate that one family cluster was infected through common exposure to live poultry or contaminated environments, and the other was more likely to be infected through the human-to-human route.

[Characteristics of complete genome of pandemic A/H1N1/2009 influenza virus isolated in Fujian Province, China].

This study aims to investigate the characteristics of genomic variation of pandemic A/H1N1/2009 influenza virus isolated in Fujian Province, China. Complete genome sequence analysis was performed on 14 strains of pandemic A/H1N1/2009 influenza virus isolated from Fujian during 2009-2012. All virus strains were typical low-pathogenic influenza viruses, with resistance to amantadine and sensitivity to neuraminidase inhibitors. Eight genome fragments of all strains were closely related to those of A/California/07/2009 (H1N1) vaccine strain, with > or = 98.2% homology. Compared with the vaccine strain, the influenza strains from Fujian had relatively large variation, and variation was identified at 11 amino acid sites of the HA gene of A/Fujiangulou/SWL1155/2012 strain, including 4 sites (H138R, L161I, S185T, and S203T) involved inthree antigen determinants (Ca, Sa, and Sb). In conclusion, the influenza vaccine has a satisfactory protective effect on Fujian population, but the influenza strains from Fujian in 2012 has antigenic drift compared with the vaccine strain, more attention should therefore be paid to the surveillance of mutations of pandemic A/H1N1/2009 influenza virus.

[Sequencing and analysis of the complete genome sequence of WU polyomavirus in Fuzhou, China].

WU polyomavirus (WUPyV), a new member of the genus Polyomavirus in the family Polyomaviridae, is recently found in patients with respiratory tract infections. In our study, the complete genome of the two WUPyV isolates (FZ18, FZTF) were sequenced and deposited in GenBank (accession nos. FJ890981, FJ890982). The two sequences of the WUPyV isolates in this study varied little from each other. Compared with other complete genome sequences of WUPyV in GenBank (strain B0, S1-S4, CLFF, accession nos. EF444549, EF444550, EF444551, EF444552, EF444553, EU296475 respectively), the sequence length in nucleotides is 5228bp, 1bp shorter than the known sequences. The deleted base pair was at nucleotide position 4536 in the non-coding region of large T antigen (LTAg). The genome of the WUPyV encoded for five proteins. They were three capsid proteins: VP2, VP1, VP3 and LTAg, small T antigen (STAg), respectively. To investigate whether these nucleotide sequences had any unique features, we compared the genome sequence of the 2 WUPyV isolates in Fuzhou, China to those documented in the GenBank database by using PHYLIP software version 3.65 and the neighbor-joining method. The 2 WUPyV strains in our study were clustered together. Strain FZTF was more closed to the reference strain B0 of Australian than strain FZ18.

Molecular evolution of influenza A (H3N2) viruses circulated in Fujian Province, China during the 1996-2004 period.

We studied the genetic and epidemic characteristics of influenza A (H3N2) viruses circulated in human in Fujian Province, south of China from 1996 to 2004. Phylogenetic analysis was carried out for genes encoding hemagglutinin1 (HA1) of influenza A virus (14 new and 11 previously reported reference sequences). Our studies revealed that in the 8 flu seasons, the mutations of HA1 genes occurred from time to time, which were responsible for about four times of antigenic drift of influenza H3N2 viruses in Fujian, China. The data demonstrated that amino acid changes were limited to some key codons at or near antibody binding sites A through E on the HA1 molecule. The changes at the antibody binding site B or A or sialic acid receptor binding site 226 were critical for antigenic drift. But the antigenic sites might change and the key codons for antigenic drift might change as influenza viruses evolve. It seems important to monitor new H3 isolates for mutations in the positively selected codons of HA1 gene in south of Asia.

[Analysis of the amino acid changes of the hemagglutinin of H5 avian influenza virus].

We introduced 38 single-point amino acid changes into the hemagglutinin (HA) protein of the reassortmented A/Duck/Mongolia/54/01 (H5N2) strain by a PCR random mutation method. The percentage of amino acid changes on the HA domain that did not abrogate hemadsorption activity was calculated to be 89%. Changes in the amino acids of the HA2 domain were observed to be about half of those in the HA1 domain of these mutants. We assumed that amino acid changes in the HA1 domain afforded more flexibility in maintaining the functions of the HA protein than did those in the HA2 domain. Changes at two positions allowed the mutants to have same characteristics with respect to HA function despite the difference in the substituted amino acid. The results suggested that the effect on hemadsorption activity of an amino acid change on the HA protein primarily depends on the position rather than the species of substituted amino acid. An amino acid change at residue 122 from Trp to Arg and 179 from His to Arg resulted in the loss of hemadsorption activity of the HA protein. Site 122 is near the antibody binding site A, and site 179 is in the receptor binding domain (RBD) of HSHA. So that we suggest residue position 179 or 122 is very important to maintain the structure of RBD or antigenic site of H5HA. Position 4 in HA1 changed from Cys to Arg and position 148 in HA2 changed from Cys to Tyr also resulted in the loss of hemadsorption activity of the HA protein. Cys plays an important role in maintaining the structure of HA protein by means of S-S bonds. 3 potential glycosylation sites (Asn-X-Ser/Thr) were lost in our experiment that did not lose the hemadsorption activity of HA. Some interesting positions need to be analyzed more finely. Some amino acid changes identified in vitro experiment may serve as molecular markers for assessing the pandemic potential of H5N1 field isolates.