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

Objective To analyze the phenotypic characteristics of antiviral-resistant influenza B viruses circulating in mainland China and to analyze the susceptibility of influenza B viruses to neuraminidase inhibitors ( NAIs) . Methods Antiviral-resistant phenotyping test was performed to analyze the NAI suscep-tibility of 1 386 influenza B viruses isolated in mainland China from April 2014 to March 2015, including the test of susceptibility to oseltamivir and zanamivir. Results All of the 94 B-Victoria lineage viruses were sensitive to oseltamivir and zanamivir. Of all 1 292 B-Yamagata lineage viruses tested, 1 virus showed re-duced sensitivity to oseltamivir with NA gene containing I221T amino acid mutation, 10 viruses showed re-duced sensitivity to zanamivir with 4 having D197N amino acid mutation in NA gene, 3 viruses showed re-duced sensitivity to both oseltamivir and zanamivir with NA gene possessing D197N amino acid mutation and 1 virus carrying the A245T amino acid mutation in NA gene showed reduced sensitivity to oseltamivir and highly reduced sensitivity to zanamivir. Conclusion The majority of influenza B viruses circulating in main-land China during 2014 to 2015 were sensitive to NAIs, which indicated that NAIs could be used continually for clinical treatment of patients with influenza. Sustained monitoring of antiviral susceptibility of influenza B viruses should be emphasized for timely detection of antiviral resistant viruses and more attention should be paid to the D197N mutations in NA gene of influenza B viruses.

To analyze the antigenic and genetic characteristics of the influenza A (H3N2) virus in mainland China during the surveillance year of 2013-2014, the antigenic characteristics of H3N2 virus were analyzed using reference ferret anti-sera. The nucleotide sequences of the viruses were determined by Sanger dideoxy sequencing, phylogenetic trees were constructed with the neighbor-joining method, and the genetic characteristics of the viruses were determined in comparison to current vaccine strains. The results showed that most of the H3N2 viruses were antigenically closely related to the A/Victoria/361/2011 vaccine strain cell-propagated prototype virus (99.6%). Using the A/Texas/50/2012 egg isolate as the reference antigen, 15.1% of the viruses were found to be closely antigenically related to it, while 11.9% of strains were closely antigenically related to the egg-propagated epidemic strain, A/Shanghai-Changning/1507/2012. Phylogenetic analysis of HA genes indicated that the A(H3N2) viruses in this surveillance year were in the same clade, but no drug resistant mutation was identified in the NA genes. During the 2013-2014 influenza surveillance year, no significant genetic change was detected in either the HA or NA genes of the A(H3N2) viruses, while significant mutations were found in egg isolates resulting from their adaptation during propagation in eggs. The antigenic and genetic changes should be investigated in a timely manner to enable the selection of an appropriate vaccine strain in China.
Animals ; Antigenic Variation ; Base Sequence ; Chick Embryo ; China ; Genetic Variation ; Hemagglutinin Glycoproteins, Influenza Virus ; genetics ; immunology ; Humans ; Influenza A Virus, H3N2 Subtype ; genetics ; immunology ; isolation & purification ; Influenza, Human ; virology ; Molecular Sequence Data ; Mutation ; Phylogeny

Objective Assess and determine inactivation effect of heat,.ultraviolet (UV) light and three disinfectants against human infected H9N2 avian influenza virus in laboratory.Methods Suspension containing with 1010.67 TCID50/ml viral was exposed to 50 ℃,56 ℃,60 ℃,65 ℃ for 10 to 60 minutes and UV every 10 interval minutes from 10 to 80 minutes.The residual viruses after physical treatment were determined through half of tissue culture infective dose (TCID50) with MDCK cells and calculated by Reed-Muench method.Suspension with 1010.37EID50/ml quantitative virus was applied to equal volume of 10％ 84 sanitizer,75％ ethanol,1％ Virkon solution and incubated for 1 minute to 15 minutes respectively.The residual viral activity would be evaluated by inoculating in SPF chicken embryo.When the virus titer dropped by 4 lgTCID50/ml or virus in chicken embryo culture was observed to be negative,the physical and chemical treatment was considered effective.Results Human infected H9N2 avian influenza virus titer decreased by 4.02 lgTCID50 at 56 ℃ for 15 minutes,and after 30 minutes at 56 ℃ or 10 minutes at 60 ℃/65 ℃,the post-viral titer would decline below the detection level.20 minutes of UV irradiation would lead to a 5.67 log reduction,and after 70 minutes lighted,the virus titer fell below the detection level.Virus proliferation was not detected after 3 minutes of disinfection with 10％ 84 sanitizer,75％ ethanol and 1％ Virkon.Conclusions We should note that it is necessary to meet the specific condition to effectively inactivate the human infected H9N2 avian influenza virus.Our study provides an experimental basis for the biosafety operation of human infected H9N2 avian influenza virus.

Objective:To analyze the antigenicity and genetic characteristics of two strains of Eurasian avian H1N1 swine influenza virus (EAS-H1N1) isolated from 2 human cases found in Gansu province to provide scientific reference for disease prevention and control.Methods:Two cases of human infection with EAS-H1N1 discovered in Gansu province since February 2021 were analyzed for antigenicity and genome comparison, and their genome characteristics were analyzed using software such as Mega7.0.Results:Two human infections with EAS-H1N1 had related environmental exposure history. Two strains were obtained: A/Gansu-Xifeng/1143/2021 and A/Gansu-Xifeng/1194/2021. The two strains of HA, NA genes were all from the Eurasian avian H1N1 swine influenza virus, and are closely related to the human infection EAS-H1N1 virus in Hebei and Tianjin and the EAS-H1N1 virus isolated from the mink in Shandong; the HA receptor binding sites of 2 strains E190D and D225E mutations occurred in all spots, and there were no H274Y and N294S mutations in NA protein.Conclusions:Some important molecular mutations occurred in the genome of people infected with EAS-H1N1 virus in Gansu province, which may lead to increased virulence and potential human-to-human transmission. Strengthening the research and analysis of EAS-H1N1 gene characteristics will help to monitor the mutation and mutation of the virus at the molecular level and scientifically prevent and control the epidemic.

Objective:The antigenic and genetic characteristics of influenza A(H1N1)pdm09 virus isolated from the mainland of China during the 2018-2019 influenza surveillance year were analyzed.Methods:Two thousand nine hundred and fifty-eight influenza A(H1N1)pdm09 virus strains in the 2018-2019 influenza surveillance year were analyzed by hemagglutination inhibition test. The hemagglutinin(HA) gene of 279 influenza A(H1N1)pdm09 virus strains was sequenced and analyzed. The representative strains of the dominant clades were performed for antigenic characteristics using post-vaccination human antisera.Results:Two thousand eight hundred and sixty-one (97%, 2 861/2 958) viruses characterized were antigenically similar to A/Michigan/45/2015. All HA gene of the sequenced viruses belonged to 6B.1 clade, and 269(96%, 269/279) viruses belonged to 6B.1A subclade. Compared with the vaccine virus, it had the common amino acid substitutions of S74R, S164T and I295V in the HA protein. There were several small groups with common amino acid substitutions in the 6B.1A subclade, and 51% sequenced viruses had S183P amino acid substitution in this subclade. The result of antigenic analysis using post-vaccination human antiserums showed that most of the representative strains were well inhibited by the sera.Conclusions:The antigenicity of influenza A(H1N1)pdm09 viruses in the mainland of China in 2018-2019 influenza surveillance year matched well with the corresponding vaccine strain, but the HA gene had genetically diverse characteristic.

OBJECTIVETo analyze the susceptibility of influenza A (H3N2) viruses to neuraminidase inhibitors during 2011-2012 in Mainland China.

METHODSAll the tested viruses were obtained from the Chinese National Influenza Surveillance Network, which covers 31 provinces in mainland China, including 408 network laboratories and 554 sentinel hospitals. In total 1 903 viruses were selected with isolation date from January 1, 2011 to December 31, 2012 in Mainland China, among these viruses, 721 were confirmed to be influenza A (H3N2) virus by Chinese National Influenza Center and tested for the susceptibility to oseltamivir and zanamivir using chemiluminescence-based assay. The neuraminidase inhibitor sensitive reference virus A/Washington/01/2007 (119E) and oseltamivir resistant virus A/Texas/12/2007 (E119V) were used as control in this study. The t -test was used to compare the difference of NAI susceptibility of viruses isolated from different years.

RESULTSThe half maximal inhibitory concentration (IC₅₀) of A/Washington/01/2007 for oseltamivir and zanamivir was (0.10 ± 0.02) and (0.30 ± 0.05) nmol/L, respectively. The IC₅₀ of A/Texas/12/2007 for oseltamivir and zanamivir was (4.27 ± 1.60) and (0.20 ± 0.03) nmol/L, respectively. Among the 721 influenza A (H3N2) viruses, 132 influenza A (H3N2) viruses were isolated in 2011 and 589 influenza A (H3N2) viruses were isolated in 2012. The IC50 for oseltamivir ranged from 0.04 to 0.62 nmol/L for viruses isolated in 2011 and ranged from 0.02 to 0.95 nmol/L for viruses in 2012, and the IC₅₀ of all the viruses tested was within 10-fold IC₅₀ (1.0 nmol/L) of the neuraminidase inhibitor sensitive reference virus A/Washington/01/2007. The IC50 of zanamivir ranged from 0.12 to 0.80 nmol/L for viruses in 2011 and ranged from 0.04 to 0.72 nmol/L for viruses in 2012, and was within 10-fold IC₅₀ (3.0 nmol/L) of the neuraminidase inhibitor sensitive reference virus A/Washington/01/2007.

CONCLUSIONThe influenza A(H3N2) viruses isolated during 2011-2012 in Mainland China were tested to be sensitive to oseltamivir and zanamivir.

Antiviral Agents ; China ; Drug Resistance, Viral ; Enzyme Inhibitors ; Epidemiological Monitoring ; Humans ; Influenza A Virus, H3N2 Subtype ; Influenza, Human ; Neuraminidase ; Oseltamivir ; Zanamivir