Objective: To analyze the spatial and temporal distribution characteristics of seasonal A(H3N2) influenza [influenza A(H3N2)] in China and to provide a reference for scientific prevention and control. Methods: The influenza A(H3N2) surveillance data in 2014-2019 was derived from China Influenza Surveillance Information System. A line chart described the epidemic trend analyzed and plotted. Spatial autocorrelation analysis was conducted using ArcGIS 10.7, and spatiotemporal scanning analysis was conducted using SaTScan 10.1. Results: A total of 2 603 209 influenza-like case sample specimens were detected from March 31, 2014, to March 31, 2019, and the influenza A(H3N2) positive rate was 5.96%(155 259/2 603 209). The positive rate of influenza A(H3N2) was statistically significant in the north and southern provinces in each surveillance year (all P<0.05). The high incidence seasons of influenza A (H3N2) were in winter in northern provinces and summer or winter in southern provinces. Influenza A (H3N2) clustered in 31 provinces in 2014-2015 and 2016-2017. High-high clusters were distributed in eight provinces, including Beijing, Tianjin, Hebei, Shandong, Shanxi, Henan, Shaanxi, and Ningxia Hui Autonomous Region in 2014-2015, and high-high clusters were distributed in five provinces including Shanxi, Shandong, Henan, Anhui, and Shanghai in 2016-2017. Spatiotemporal scanning analysis from 2014 to 2019 showed that Shandong and its surrounding twelve provinces clustered from November 2016 to February 2017 (RR=3.59, LLR=9 875.74, P<0.001). Conclusion: Influenza A (H3N2) has high incidence seasons with northern provinces in winter and southern provinces in summer or winter and obvious spatial and temporal clustering characteristics in China from 2014-2019.
Humans ; Influenza, Human/epidemiology* ; China/epidemiology* ; Influenza A Virus, H3N2 Subtype ; Seasons ; Cluster Analysis

OBJECTIVETo evaluate the safety and immunological effect of domestic split influenza virus vaccine.

METHODSAll 606 subjects were divided into three groups by under 6, 16-60 and above 60 years old. Each age group was divided as study group (n = 213), control group 1 (n = 195) and control group 2 (n= 198) by Table of Random Number, one domestic vaccine and two imported vaccines were respectively inoculated in three group people. The differences of clinical side effect rate, antibody positive rate, protective rate and geometric mean titer (GMT) of these three vaccines were compared by using the statistical software with statistical significance of P < 0.05.

RESULTSThe side effect rate of study group, control group 1 and control group 2 was 3.76% (8/213), 4.10% (8/195), and 3.54% (7/198), respectively without statistical significance(chi2 = 0.87, P =0.93). The positive seroconversion rates of H1N1, H3N2 and B in these three groups were respectively 89.2% (190/213), 63.4% (135/213), 86.4% (184/213), 88.7% (173/195), 61.5% (120/195), 87.2% (170/195), 87.9% (174/198), 61.6% (122/198) and 84.8% (168/198). There were no statistical significance in the total positive seroconversion rate of each antibody type (chi2(H1N1) = 0.94, P(H1N1) = 0.63; chi2(H3N2) = 0.94, P(H3N2) = 0.63; chi2(B) = 0.75, P(B) = 0.69). The average growth multiple of H1N1, H3N2 and B in these three groups were 10.7, 7.3, 8.4, 10.5, 6.3, 8.3, 10.2, 7.1, 8.8 times. There were no statistical significances in the GMT growth multiple of each antibody type (F(H1N1) = 0.35, P(H1N1) = 0.70; F(H3N2) = 2.22, P(H3N2) = 0.11; F(B) = 1.51, P(B) = 0.35). The antibody protective rates of H1N1, H3N2 and B were 100% (213/213), 70.0% (149/213), 95.3% (203/213), 100% (195/195), 66.7% (130/195), 97.9% (191/195), 99.5% (197/198), 66.2% (131/198), 96.5% (191/198) respectively. There was no statistical difference among the three vaccines (chi2(H1N1) = 2.04, P(H1N1) = 0.36; chi2(H3N2) = 0.74, P(H3N2) = 0.69; chi2(B) = 0.42, P(B) = 0.82).

CONCLUSIONThe domestic influenza split vaccine might be suitable for colony vaccination for its having clinical safety and immunological effect.

Adolescent ; Adult ; Child ; Humans ; Influenza A Virus, H1N1 Subtype ; immunology ; Influenza A Virus, H3N2 Subtype ; immunology ; Influenza Vaccines ; adverse effects ; immunology ; Influenza, Human ; prevention & control ; Middle Aged ; Young Adult

The NA genes of 395 strains of human H3N2 influenza virus isolated from 1996 to 2005 in China were sequenced, analyzed with bioinformatics tools. The NA nucleotide sequence of phylogenetic tree showed a main evolution branch with multiple short side branches. The strains in the same year may be divided into several branches. There was an obvious lag between vaccine strains recommended by WHO and the Chinese circulating strains in phylogenetic tree of the NA nucleotide. The result also showed no amino acid deletion and insertion in the NA. In NA antigen sites, where including residues 197-199 aa, 431-434 aa and 339-347aa the mutation was higher, in contrast, the residues including 153 aa, 328-336 aa, 367-370aa and 400-403 aa, the mutation was lower. Besides the antigenic determinant sites, there also had the other amino acid mutated highly, such as 18, 23, 30, 93, 143, 208, 216, 221, 249, 265, 267, 307, 385 and 437 aa, among them 143 and 267 mutation were higher than that in antigenic determinant sites, their biological significance are not clear yet. The neuraminidase active-site residues in NA were highly conservative and the same were the disulphide bond and the glycosylation sites in NA. In conclusion, our analysis provides some information for influenza prevention and control and the NA inhibitor medicine application.
China ; Genes, Viral ; Humans ; Influenza A Virus, H3N2 Subtype ; genetics ; Mutation ; Neuraminidase ; genetics ; Phylogeny ; Time Factors

High-yield H3N2 subtype swine influenza virus for large-scale vaccine production in cell culture was generated by reverse genetics. The rescued H3N2 (rH3N2) candidate virus contained hemagglutinin (HA) and neuraminidase (NA) genes derived from a field isolate A/Swine/Henan/S4/01 (H3N2), PB2 gene from A/PR/8/34, and the other five internal genes from A/Goose/Dalian/3/01 (H9N2). The rH3N2 virus titer in MDCK cell culture were measured by hemagglutination assay and the maximum virus titre of 1:512 hemagglutination unit was obtained after infection of MDCK cell for 60 h. The results of the present study indicated that rH3N2 virus was suitable for growth in MDCK cell culture and is feasible to be used for the production of cell grown influenza vaccine.
Animals ; Cell Line ; Dogs ; Hemagglutination Tests ; Influenza A Virus, H3N2 Subtype ; classification ; genetics ; growth & development ; Influenza Vaccines ; Plasmids ; Virus Cultivation

BACKGROUND: The new emerging avian influenza A H7N9 virus, causing severe human infection with a mortality rate of around 41%. This study aims to provide a novel treatment option for the prevention and control of H7N9. METHODS: H7 hemagglutinin (HA)-specific B cells were isolated from peripheral blood plasma cells of the patients previously infected by H7N9 in Jiangsu Province, China. The human monoclonal antibodies (mAbs) were generated by amplification and cloning of these HA-specific B cells. First, all human mAbs were screened for binding activity by enzyme-linked immunosorbent assay. Then, those mAbs, exhibiting potent affinity to recognize H7 HAs were further evaluated by hemagglutination-inhibiting (HAI) and microneutralization in vitro assays. Finally, the lead mAb candidate was selected and tested against the lethal challenge of the H7N9 virus using murine models. RESULTS: The mAb 6-137 was able to recognize a panel of H7 HAs with high affinity but not HA of other subtypes, including H1N1 and H3N2. The mAb 6-137 can efficiently inhibit the HA activity in the inactivated H7N9 virus and neutralize 100 tissue culture infectious dose 50 (TCID50) of H7N9 virus (influenza A/Nanjing/1/2013) in vitro, with neutralizing activity as low as 78 ng/mL. In addition, the mAb 6-137 protected the mice against the lethal challenge of H7N9 prophylactically and therapeutically. CONCLUSION The mAb 6-137 could be an effective antibody as a prophylactic or therapeutic biological treatment for the H7N9 exposure or infection.
Animals ; Antibodies, Monoclonal/therapeutic use* ; Antibodies, Neutralizing/therapeutic use* ; Antibodies, Viral ; Hemagglutinins ; Humans ; Influenza A Virus, H1N1 Subtype ; Influenza A Virus, H3N2 Subtype ; Influenza A Virus, H7N9 Subtype ; Influenza Vaccines ; Influenza in Birds ; Influenza, Human/prevention & control* ; Mice

Global Health ; History, 20th Century ; Humans ; Influenza A Virus, H1N1 Subtype ; genetics ; isolation & purification ; Influenza A Virus, H3N2 Subtype ; genetics ; isolation & purification ; Influenza, Human ; epidemiology ; history ; therapy ; virology ; Russia ; epidemiology

Global Health ; History, 20th Century ; Humans ; Influenza A Virus, H2N2 Subtype ; genetics ; isolation & purification ; Influenza A Virus, H3N2 Subtype ; genetics ; isolation & purification ; Influenza, Human ; epidemiology ; history ; mortality ; virology

BACKGROUNDPB1-F2 protein has been proven to increase the pathogenicity of influenza A virus (IAV) strains in primary infection and in secondary bacterial infection. It can also regulate the activity of viral polymerase. However, it was shown in another retrospective study that a portion of IAVs do not express full-length PB1-F2 protein during virus development; different kinds of stop codons cause exits in the open reading frames and form PB1-F2 gene products with the corresponding genotypes. Truncated PB1-F2 in human H3N2 IAVs has long been detected in North America but its evolution in China is still unclear.

METHODSInfluenza-like illnesses (ILIs) from the whole of Jiangsu Province were collected and inspected to determine the type and subtype of the viruses. A portion of isolates collected in the epidemic period were selected as samples for later whole-genome sequencing, and the exact sequences were determined and analyzed.

RESULTSH3N2 influenza virus was one of the epidemical strains which had been prevalent during 2009-2010, in Jiangsu. Five H3N2 isolates with truncated PB1-F2 protein (25aa) were detected in influenza samples from Nanjing and Xuzhou, while seven similar H3N2 isolates were also reported in Niigata, Japan.

CONCLUSIONThis emergence indicates the possibility that there has been transmission of the H3N2 virus between the two countries.

China ; epidemiology ; Humans ; Influenza A Virus, H3N2 Subtype ; genetics ; metabolism ; Influenza, Human ; virology ; Viral Proteins ; chemistry ; genetics ; metabolism

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

OBJECTIVETo elucidate the evolution pattern of human influenza virus A H3 subtype by detecting positive selected codons in hemagglutinin gene.

METHODSAll H3 sequences in NCBI GenBank and influenza sequence database were downloaded and two step cluster method was applied to divide sequences into six groups, which were corresponding to different period by turns. Fixed Effect Model was applied to detect positive selected codons in each group, and two step cluster method was then used again to summarize variation patterns of selective pressure among sites.

RESULTSPositive selected codons were different in groups corresponding different periods. 50 amino acid codons had been identified as positive selected sites in at least one time span. Among them, 42 codons belonged to one of the five known antigen-combinng regions. A larger amount of sites as well as relatively higher selection pressure were identified in antibody combining regions A and B. Results showed that the 50 sites could be divided into seven different patterns. While other six patterns corresponding to positive selected codons at only one time span, the sites of the seventh pattern were under positive selection in several periods.

CONCLUSIONPositive selection codons in evolution of H3A1 strains were alternated in different time period whereas antibody combining regions A and B played more important roles in the evolution process. Other 8 identified codons out of the antibody combining regions might belong to unknown antigen regions.

Amino Acid Sequence ; Codon ; Hemagglutinins ; genetics ; Humans ; Influenza A Virus, H3N2 Subtype ; genetics ; Influenza, Human ; genetics ; Selection, Genetic