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Objective:To investigate the phylogenetic and antigenic characteristics of hemagglutinin (HA) gene of influenza B/Victoria lineage (BV) viruses in Beijing during the 2021-2022 influenza surveillance season, and to analyze whether the circulating BV viruses match the vaccine strain.Methods:Pharyngeal swab specimens from influenza like-illness (ILI) cases in the 2021-2022 influenza surveillance season were collected from surveillance network labs in Beijing and cultured in MDCK cells and chicken embryo to isolate BV viruses. Nucleic acids of the viruses were extracted, and the HA gene was amplified and sequenced. The nucleotide and amino acid sequence identity of the HA gene was analyzed using MEGA5.0 software. A phylogenetic tree of HA gene was constructed using the maximum likelihood method. The N-glycosylation sites in HA were predicted online. Three-dimensional structure of HA was constructed using SWISS-MODEL homologous modeling. Hemagglutination inhibition (HI) test was performed to analyze the antigenicity of BV viruses.Results:A total of 402 BV viruses were collected and 58 strains with full-length HA gene sequences were chosen for further analysis. Compared with the HA gene of this year′s vaccine strain (B/Washington/02/2019), there were 27 amino acid mutations, 11 of which were located in four different antigenic determinants. The phylogenetic analysis revealed that three subgroups of 1A.3, 1A.3a1, and 1A.3a2 co-circulated in Beijing with 54 strains (54/58, 93.10%) clustered to the Clade 1A.3a2, two strains (2/58, 3.45%) clustered to the Clade 1A.3a1, and two strains (2/58, 3.45%) in the same subgroup (Clade 1A.3) as the vaccine component BV strain in 2021-2022. Compared with the vaccine strain (B/Washington/02/2019), two BV strains had an additional N-glycosylation site at residue 197, while the other 56 strains showed no change in N-glycosylation sites. Antigenic analysis showed that 35 BV strains (35/58, 60.34%) were antigenically similar to the vaccine strain and 23 strains (23/58, 39.66%) were low-response strains.Conclusions:Three subgroups of BV viruses co-circulated in Beijing during the 2021-2022 influenza surveillance season. The predominant subgroup was Clade 1A.3a2 (93.10%), showing a certain genetic distance with the vaccine strain (B/Washington/02/2019). Nearly 40% (39.66%) of the viruses were low-response strains. This study indicated that continuous monitoring of the variations of influenza epidemic strains and timely providing laboratory basis for screening vaccine component strains were the basic technical guarantee for coping with influenza pandemic.
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Objective@#To understand the epidemiological characteristics of outbreaks and analyze the genetic characteristics of the whole genome of influenza H3N2 virus among avian-human-swine, and to elaborate the source of influenza virus.@*Methods@#The epidemic information was collected using the case investigation, the pharyngeal swab samples from influenza-like-illness cases were detected by real-time PCR and virus isolation. The phylogeny and molecular features of whole-genome were analyzed with EditSeq and MEGA 5.05 software.@*Results@#The prevalence rate of this outbreak was 34.88%, 15 samples of throat swabs were collected, the positive rate of nucleic acid detection was 73.33%, 5 strains of seasonal influenza A (H3N2) influenza viruses were isolated. The phylogenetic analysis showed the eight gene segments of the isolated influenza viruses belonged to the same cluster with 2015-2016 influenza vaccine strain A/Switzerland/9715293/2013(H3N2), and no recombination was found. Compared with vaccine strain, 14 variant amino acids of protein of HA were identified, and 8 of them were located in antigenic sites. All strains were sensitive to neuraminidase inhibitors while they showed resistance to blockers of M2 ion channel. The glycosylation sites analysis showed that two new glycosylation sites NRT151-153 and NAT245-247were added.@*Conclusions@#The outbreak was caused by seasonal influenza A (H3N2) virus which had an antigenic drift and no genetic avian-human-swine recombination was found.
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Antigenic analysis of 10 strains of Coxsackievirus type A 24 (CA24) was carried out by monoclonal antibodies (McAbs) prepared with a China isolate of Coxsackievirus A 24 variant (CA24v).8 McAbs which were positive in indirect immunofluorescent test reacted to 9 CA 24 v detected. Of them, 4 McAbs could react to both CA 24v and CA 24 prototype (Joseph strain),and the others did not react to CA 24 prototype. 5 McAbs possessing virus-neutralizing activity did not neutralized CA 24 prototype (Joseph strain)and only one of them could neutralize EH 24/70 strain weakly, three of them neutralize 2 isolate from Japan in 1985-86 (J140/85 and J 60/86) and one isolate Fujian of China in 1986. However, all 5 McAbs above could neutralize isolate from Henan and Shanghai of China in 1986 as well as Beijing, Liaoning and Fujian of China in 1988.