ABSTRACT
Objective@#To understand the viral etiology of a clustered case of human infection outbreak in the middle school of Huai’an city.@*Methods@#Nasopharyngeal swab samples from patients were collected and rapidly detected by Real-time RT-PCR and the target virus isolated in cells. Furthermore, HA1 segments of target virus were amplified by RT-PCR and sequenced. The genetic and phylogenetic analysis based on HA1 genes was computed.@*Results@#Influenza A(H1N1)pdm09 viral nucleic acid in 11 nasopharyngeal swab samples from patients in the outbreak were positive. Compared to the vaccine strains A/California/07/2009, the Huai’an isolates, nucleotide identity was 97.7%-98.1%, and amino acid identity was 96.6%-97.4%. Phylogenetic analysis of HA1 segment sequences indicated that the Huai’an strains from the outbreak were related closely to the viruses isolated in the year of 2014. Sequence analysis indicated that the Huai’an isolates had no amino acid substitution in the receptor binding sites and glycosylation sites, while in the Ca1 of antigenic determinant of HA1 the Huai’an isolates had an amino acid substitution of S for T at 220.@*Conclusions@#The pathogen of the clustered case of human infection was Influenza A(H1N1)pdm09 virus. Though the Huai’an isolates had one animo acid substitution in the Ca1 of antigenic determinant, the antigenicity characteristic remained unchanged.
ABSTRACT
Objective To investigate the mutation of hemagglutinin gene and amino acid variation of influenza B.Methods Influenza B virus was isolated from throat swab samples in sentinel surveillance of Yunnan province from 2009 to 2014.HA1 gene sequence analysis was applied to determine 12 randomly-selected strains of influenza B virus.The results were analyzed,MEGA software was used to do homology comparison and HA gene phylogenetic tree was established.Results Differences on the serotype and genotype identification of influenza strains were found and it might be caused by inadequate gene mutation accumulation.Amino acid variations were found in 3 important regions of antigenic determinants in HA1 protein:ring 120,ring 150 and ring 160.The amino acid variation of position 131 in ring 120 was N131K,and in position 137 was N137H.Two strains had P187S mutation in position 187.Conclusion There are some important variations in the hemagglutinin gene of influenza B strains in Yunnan Province,with some variations being the same as vaccine strains and some being not.
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Objective To study the evolutionary characteristics and rules of two lineages on influenza B virus.Methods A total of 126 HA1 sequences of strains isolated during 1940 to 2012were downloaded from the GenBank.Time of the most recent common ancestor (TMRCA) and divergence of the two lineages were calculated based on the data from phylogenetic analysis of HA1gene,using Bayesian Markov Chain Monte Carlo (Bayesian-MCMC) and molecular clock method.Results The average amino acid variant ratios were ranged from 5.4％ to 10.2％ within the strains of influenza B virus isolated during 1978 to 2010.Compared with the Victoria-like strains,all Yamagatalike strains showed an amino acid deletion at 163th site,while some of them showing a deletion at position 166.HA1 gene of influenza B virus seemed not have been affected by positive selection except a few sites.The evolutionary average rate on HA1 gene was 2.138 × 10-3 substitutions/site/year (95％HPD:1.833 × 10-3-2.437 × 10-3 substitutions/site/year).The estimated dates for TMRCA of the two lineages of influenza B virus could be dated back to 1971 (95％ HPD:1969-1972),while the divergence times of the two lineages were 1973 (95％ HPD:1971-1974) and 1977 (95％ HPD:1975-1978) respectively.Conclusion Significant differences were found on HA1 gene between earlier and recent identified strains of Victoria and Yamagata lineage.Differences between the two lineages increased and showing the potential of dividing themselves into different subtypes in the future.More attention should be paid to these trends and the related epidemiological significance.