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Influenza virus

Influenza virus

Epidemiological and evolutionary characteristics of influenza B viruses in Hubei, 2010-2015

FANG Bin;LIU Lin-lin;LI Xiang;YE Guo-jun;YU Xiao;SONG Yi

Disease Surveillance,Vol 31,No. 07

【Abstract】 Objective To understand the epidemiologic and evolutionary characteristics of influenza B viruses in Hubei during 2010–2015. Methods The sequences of HA and NA genes of influenza B viruses isolated in Hubei were obtained from sequencing and GISAID’s database during this period. The phylogenetic trees and amino acid mutations of HA and NA protein were analyzed respectively, besides the homology modeling structures of the NA protein were constructed and analyzed. The epidemiological dynamics of influenza B virus was described by using phylogenetic data. Results When the first intra-lineage or inter-lineage reassortant influenza B virus was found in Hubei during 2010–2015, the virus cause epidemic in Hubei during this period. Amino acid substitutions of the viruses, such as N116K, N129S, A146T, K162R and N197S, were detected on four major epitopes of HA protein. D197N substitution was found on the enzyme active locus of NA protein, which was not directly in contact with substrate or neuraminidase inhibitors on homology modeling structure. Conclusions There was a close relationship between epidemiological dynamics and genetic evolution of influenza B viruses in Hubei during 2010–2015. It would facilitate the understanding of evolutionary characteristics of influenza B virus by monitoring amino acid substitutions on the epitopes of HA protein and drug resistance loci.

Passage Stability of a High-yield Strain of the Influenza B Virus in Vero Cells

CUN Yina;SONG Shaohui;ZHOU Jian;LIU Ze;GUO Qi;GAO Jingxia;MA Lei;LI Weidong;LIAO Guoyang

Chinese Journal of Virology,Vol 35,No. 02

【Abstract】 Cellular influenza vaccines (CIVs) are being developed because they can be produced rapidly and in large quantities to cope with a possible outbreak of influenza. Selecting the high-yield adaptive strains of the influenza virus in Vero cells is very important for CIV development. We studied the passage stability of the high-yield strain BX-51BVa (By) of an influenza virus in Vero cells to ascertain if this strain could be used as a seed lot for preparing an influenza vaccine in Vero cells. The Vero cell-adapted BX-51BVa (By) was passaged continuously for 50 generations in Vero cells to determine its hemagglutination titer and infectious titer. The stability of biological characteristics during passage was examined by type identification and gene sequencing. The hemagglutination titer was maintained at 256–512. The infectious titer was stable at about 1 × 10 7 TCID 50/mL, and the type did not change. The sequence of HA and NA amino acids did not change compared with the prevalent strain (BX-51B). These data suggest that the influenza B virus reassortant strains can be passaged continuously in Vero cells and used as a seed lot for the preparation of influenza vaccines in Vero cells.

Analyses of Surveillance Results for Influenza B Virus and the Characteristics of Its Hemagglutinin Gene in Yunnan Province, China, 2017

LI Duo;XU Wen;FU Xiaoqing;LUO Chunrui

Chinese Journal of Virology,Vol 35,No. 04

【Abstract】 Between 2017 and 2018, the influenza virus was very prevalent in China. In particular, the influenza B virus (IBV) with the Yamagata (By) lineage and the H1N1 and H3N2 subtypes were prevalent in China. To evaluate the monitoring results for IBV and the molecular characteristics of the hemagglutinin (HA) gene of the IBV in Yunnan Province, China, 2017, a total of 21 672 specimens were collected from the Influenza Surveillance Hospital of Yunnan Province, China, in 2017 and processed using real-time reverse transcription polymerase chain reaction. The nucleic acid-positive specimens were isolated by MDCK cells using the HA agglutination test and inhibition test for IBV identification. Twenty four IBV strains were selected randomly for high-throughput sequencing. The characteristics of their HA genes were analyzed using MEGA software. In 2017, the data (monitoring and outbreak monitoring) of sentinel hospitals in Yunnan Province, China showed that IBV was one of the dominant strains for the influenza epidemic. Nine outbreaks (42.86%) caused by the Victoria (Bv) lineage and four outbreaks (19.05%) by the By lineage were detected. The HA gene of IBV showed no obvious variation. Strengthening monitoring, improving monitoring sensitivity, and providing timely warnings are crucial to lessen the risk of influenza epidemics.

Study on Methods for Detecting Susceptibility of Influenza Virus to Polymerase Inhibitors

FANG Qiongqiong;LI Zi;CHENG Yanhui;HUANG Weijuan;ZHAO Xiang;MENG Yao;LI Duo;TAN Minju;WEI Hejiang;WANG Dayan

Chinese Journal of Virology,Vol 35,No. 05

【Abstract】 Influenza virus is the main pathogen for seasonal flu epidemics and influenza pandemics. Anti-influenza drugs are one of the critical pathways in the control of influenza virus infection. Now, the polymerase inhibitors of influenza viruses are a promising category. To optimize the method for detecting the susceptibility of influenza virus to polymerase inhibitors, the incubation time, drug concentration and other test conditions were determined when different types/subtypes of seasonal influenza viruses were inoculated in different culture plates, and immuno-staining and crystal violet staining were compared. The susceptibility of seasonal influenza viruses to T-705 was evaluated by plaque reduction assay. The results showed that in 12-well tissue culture plates, the optimal incubation time was 2 days for influenza A viruses A/Beijing/2/2018 (pdmH1N1) and A/Switzerland/8060/2018 (H3N2), and 2.5 days for influenza B virus B/Beijing/1/2018 (B Yamagata). In 96-well plates, the optimal incubation time for A/Beijing/2/2018 (pdmH1N1) and A/Switzerland/8060/2018 (H3N2) and B/Beijing/1/2018 (B Yamagata) was 20 h and 24 h, respectively. 0.5log 10 was appropriate dilution for T-705. Both 12-well and 96-well plates could be used to detect the susceptibility of seasonal influenza virus to T-705. There was no significant difference between the two staining methods in 12-well plates, and 96-well plates could only be used for immuno-staining. The present study suggests that it is necessary to strictly control the incubation time of the virus and the concentration of the drug to detect the susceptibility of influenza viruses to polymerase inhibitors. Both 12-well and 96-well plates can be used to quantify the influenza virus and determine the susceptibility to polymerase inhibitors. Microplates have the advantages of high throughput and automatic reading compared with the traditional large-well plates. This study provides a reference for other laboratories to conduct similar assays.

Effect of a PI3K Inhibitor on NO Production and Inflammatory Response in the Lung Tissues of Mice with Viral Pneumonia Induced by Influenza A Virus FM1 Infection

YANG Yanlong;TU Mingli;XIE Mingshui

Chinese Journal of Virology,Vol 35,No. 05

【Abstract】 Influenza A virus (IAV) infection can trigger cytokine storms and increase the risk of acute respiratory distress syndrome (ARDS). Cascade amplification of inflammatory reactions in lung tissue plays a key role in this process. Phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signalling pathway participates in the regulation of cellular inflammatory response, stimulates the expression of endothelial nitric oxide synthase (eNOS), and increases the production of nitric oxide (NO). Through the activity of NO, the PI3K/AKT signalling pathway can increase vascular permeability, promote the infiltration of inflammatory cells, stimulate the activation of inflammatory cells, and secrete a large number of inflammatory factors. However, the role of PI3K/AKT signalling pathway in the virulent pneumonia caused by IAV infection has not been clarified. To study the effects of PI3K inhibitors on NO production and the inflammatory response in the lung tissues of mice with viral pneumonia induced by IAV FM1 infection, C57BL/6 mice were divided randomly into control group, H1N1 group and LY294002 group. The models of viral pneumonia induced by infection with the IAV were established by nasal drops in the latter two groups. The LY294002 group was given the PI3K inhibitor LY294002 (i. p.) for 7 days from the day of modeling. Differences of hematoxylin and eosin (H&E) staining, H1N1-virus copy number, expression of the PI3K/AKT/eNOS signalling pathway, NO and inflammatory factors in lung tissues of the three groups of mice were compared. H&E staining showed obvious pathologic damage in the lung tissues of the H1N1 group, and the H1N1-virus copy number, expression of p-PI3K, pAKT, eNOS and contents of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and intercellular adhesion molecule (ICAM)-1 were significantly higher than those of the control group ( P < 0.05). HE staining showed pathologic damage to be alleviated in the lung tissues of mice in the LY294002 group, and the expression of p-PI3K, p-AKT, eNOS and contents of IL-1β, IL-6, TNF-α, ICAM-1 were significantly lower than those of the H1N1 group ( P < 0.05). There was no significant difference in H1N1-virus copy number compared with that in the H1N1 group ( P>0.05). The present study suggests that a PI3K inhibitor can inhibit NO production and the inflammatory response in the lung tissues of mice with viral pneumonia induced by IAV FM1 infection.

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