Quantifying the rebound of influenza epidemics after relaxing nonpharmaceutical interventions during the coronavirus disease 2019 pandemic in China

The co-existence of coronavirus disease 2019 (COVID-19) and seasonal influenza epidemics has become a potential threat to human health, particularly in China in the oncoming season. However, with the relaxation of nonpharmaceutical interventions (NPIs) during the COVID-19 pandemic, the rebound extent of the influenza activities is still poorly understood. In this study, we constructed a susceptible-vaccinated-infectious-recovered-susceptible (SVIRS) model to simulate influenza transmission and calibrated it using influenza surveillance data from 2018 to 2022. We projected the influenza transmission over the next 3 years using the SVIRS model. We observed that, in epidemiological year 2021-2022, the reproduction numbers of influenza in southern and northern China were reduced by 38.6% and 30.2%, respectively, compared with those before the pandemic. The percentage of people susceptible to influenza virus increased by 138.6% and 57.3% in southern and northern China by October 1, 2022, respectively. After relaxing NPIs, the potential accumulation of susceptibility to influenza infection may lead to a large-scale and early influenza outbreak in the year 2022-2023, the scale of which may be affected by the intensity of the NPIs. And later relaxation of NPIs in the year 2023 would not lead to much larger rebound of influenza activities in the year 2023-2024. To control the influenza epidemic to the pre-pandemic level after relaxing NPIs, the influenza vaccination rates in southern and northern China should increase to 56.2% and 47.3%, respectively. Vaccination for influenza should be advocated to reduce the potential reemergence of the influenza epidemic in the next few years.

Meta-analysis reveals consistent immune response patterns in COVID-19 infected patients at single-cell resolution

A number of single-cell RNA studies looking at the human immune response to the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been recently published. However, the number of samples used in each individual study typically is small, moreover the technologies and protocols used in different studies vary, thus somewhat restricting the range of conclusions that can be made with high confidence. To better capture the cellular gene expression changes upon SARS-CoV-2 infection at different levels and stages of disease severity and to minimise the effect of technical artefacts, we performed meta-analysis of data from 9 previously published studies, together comprising 143 human samples, and a set of 16 healthy control samples (10X). In particular, we used generally accepted immune cell markers to discern specific cell subtypes and to look at the changes of the cell proportion over different disease stages and their consistency across the studies. While half of the observations reported in the individual studies can be confirmed across multiple studies, half of the results seem to be less conclusive. In particular, we show that the differentially expressed genes consistently point to upregulation of type I Interferon signal pathway and downregulation of the mitochondrial genes, alongside several other reproducibly consistent changes. We also confirm the presence of expanded B-cell clones in COVID-19 patients, however, no consistent trend in T-cell clonal expansion was observed.

Effects of pre-existing antibody on seroconversion rate after influenza vaccination / 中华微生物学和免疫学杂志

Objective:To investigate the effects of pre-existing antibody on seroconversion rate after influenza vaccination.Methods:This study recruited 1 900 healthy volunteers to receive influenza split vaccines in Xinjiang Uygur Autonomous region and Yunnan Province from September 2009 to October 2018. Hemagglutinin agglutination inhibition assay was used to detect the titers of specific antibodies in blood samples collected before vaccination and 28 d after vaccination and the effects of pre-existing antibody on the seroconversion to different influenza vaccine components were analyzed.Results:Trend analysis showed that with the increasing titer of pre-existing antibody, the seroconversion rates to A/H1N1, A/H3N2, B/Victoria and B/Yamagata vaccine components were gradually decreased (χ 2=121.76, P<0.001; χ 2=67.58, P<0.001; χ 2=45.25, P<0.001; χ 2=54.55, P<0.001). After adjusting for factors such as region, gender and age, multivariate logistic regression showed that pre-existing antibody titer equal to or higher than 40 was an independent factor that affected the seroconversion to A/H1N1, A/H3N2 and B/Victoria vaccine components, and the adjusted OR (95%CI) values were 2.50(2.00-3.13)、1.64(1.35-2.00) and 2.50(1.79-3.45), respectively. Conclusions:The seroconversion rate to each vaccine component was negatively correlated with the pre-existing antibody titer. The factor that pre-existing antibody titer equal to or higher than 40 was detrimental to the seroconversion to A/H1N1, A/H3N2 and B/Victoria vaccine components, but had no significant influence on B/Yamagata seroconversion.

Progress in the role of leptin in immune response / 中华微生物学和免疫学杂志

Leptin, a peptide hormone discovered in the 1990s, arouses interest as it can regulate the body′s metabolism. In recent years, many studies have shown that leptin can promote the proliferation, activation and cytokine synthesis of various immune cells, and participate in innate and adaptive immune responses. This article reviewed the role of leptin and involved signaling pathways in immune response and the potential of leptin as a vaccine adjuvant.

Characterization and analysis of VH1-2-encoded heterosubtypic antibodies isolated from an avian H5N1 patient / 中华实验和临床病毒学杂志

Objective@#To isolate the cross-reactive antibodies against hemagglutinin of influenza virus and identify its biological function.@*Methods@#The antibodies gene reservoir of cross-reactive and H5N1 pseudotype particles neutralizing B cell circulating in peripheral blood of a human H5N1 case was recovered by in vitro B cell culture, screening, RT-PCR and expression vector cloning techniques. The Ab gene pairing was screened by transient transfection of human kidney 293T cells and detected using ELISA and neutralization test. The heterosubtypic antibodies were prepared and characterized.@*Results@#We discovered the VH1-2-based heterosubtypic antibodies from two B cell lineages could neutralize GX-H5N1 pseudotype particles and have broader binding with Group 1 (including H1, H5, H6 and H9) and H7 subtype.@*Conclusions@#Cross-reactive antibodies can be induced by H5N1 infection.

Preparation and identification of influenza H1N1 subtype vaccine candidate strain in China / 中华实验和临床病毒学杂志

Objective@#Influenza H1N1 subtype vaccine candidate strains from a 2015—2016 year epidemic strain in China were prepared and identified by themethod of classical reassortment.@*Methods@#The influenza H1N1 epidemic strain and H3N2 high-yield reassortant parental strain (X-157) were mixed and inoculated into embryonated chicken eggs by the classical reassortmentmethod . The negative selection of mixed culture virus was carried out with the antiserum of H3 protein and the antiserum of X-157 strain. Real-time PCRmethod was used to test the HA and NA genes. Restriction enzyme digestionmethod was used to identify the internal genes. HA and NA genes of selected strains were sequenced. The strain which HA and NA genes possessed the same amino acid constitution with the wild type virus was selected and immunized to ferret. Two-way test was carried out.@*Results@#Five strains with expected HA and NA genes were selected by real-time PCR. Internal genes were identified, with 4 strains had 6+ 2 constitution, 1 strain had 5+ 3 constitution. Comparing with the wild type virus, HA and NA genes of the 5 strains had no mutation. HA titer of reassortant strains was above 1 024. HI titer of the selected NO.12 reassortment strain reached 5 120, and two-way test was passed. The yield of reassortant strain was 64 times that of the wild type strain.@*Conclusions@#A circulating influenza A (H1N1) strain of influenza A (2015—2016) was successfully prepared in China and laid the foundation for vaccine storage and disease prevention and control.

Generation and preliminary characterization of monoclonal antibodies against neuraminidase of H7N9 subtype influenza A virus / 中华实验和临床病毒学杂志

Objective@#To develop the monoclonal antibody (mAb) against neuraminidase of H7N9 subtype influenza A virus and identify its biological function.@*Methods@#Female 8 week-old BALB/c mice were immunized and the splenocytes of the mice were fused with Sp2/0 myeloma cells. Indirect ELISA was used to screen hybridoma and the positive clones were subject to be subcloned. Positive clones were identified and the monoclonal antibodies(mAbs) were obtained by purifying the ascetic fluid of mice injected with the hybridoma. The NA-binding as well as neuraminidase-inhibition activity of these mAbs were determined.@*Results@#Three mAbs against neuraminidase of H7N9 subtype influenza A virus, 1G8, 3C4 and 4E8, were obtained. They demonstrated different epitop-recognizing. 3C4 and 4E8 exhibited neuraminidase inhibitory activity, with a IC50 of 1.45 μg/ml and 8.65 μg/ml, respectively.@*Conclusions@#The results suggested that mAbs specific to neuraminidase of H7N9 subtype influenza A virus were developed, providing an useful tool in control and preventing the novel H7N9 influenza A virus.

Isolation and identification of human influenza virus from a stale respiratory tract specimen with human airway epithelial cells / 中华微生物学和免疫学杂志

Objective To investigate the possibility of using well-differentiated human airway epithelial cells (HAE) to isolate and identify human influenza A virus from a stale respiratory tract specimen.Methods The stale specimen used in this study was a nasopharyngeal swab specimen collected from a patient with unexplained pneumonia in Qinghai in 2010.It was positive for influenza A virus (H3N2) RNA, but negative for hemagglutination.Equal amount of the specimen was inoculated on HAE and on Madin-Darby canine kidney (MDCK) cells for virus isolation and passage.Cytopathic effects were observed daily after inoculation.Hemagglutination inhibition test was performed at every passage.Electron microscope was used to observe viral morphology.Viral genome was sequenced, followed by molecular evolutionary analysis.Results No progeny virus was isolated in MDCK cells, while a influenza A virus subtype H3N2 strain [A/Qinghai/178/2010(H3N2)] was isolated in HAE with a typical morphology and cytopathic effect of influenza A infection.The hemagglutination inhibition activity was 1∶16.Results of the molecular evolutionary analysis of viral genome showed that the influenza A virus (H3N2) strain was highly homologous to the A/Nanjing/1655/2010(H3N2) strain, which was isolated during the 2010 influenza pandemic in Nanjing.Conclusion HAE can be used for isolation and identification of virus from stale respiratory tract specimens.It is more sensitive than MDCK cells with regard to human influenza virus isolation.

Sudden increase in human infection with avian influenza A(H7N9) virus in China, September–December 2016

Since the first outbreak of avian influenza A(H7N9) virus in humans was identified in 2013, there have been five seasonal epidemics observed in China. An earlier start and a steep increase in the number of humans infected with H7N9 virus was observed between September and December 2016, raising great public concern in domestic and international societies. The epidemiological characteristics of the recently reported confirmed H7N9 cases were analysed. The results suggested that although more cases were reported recently, most cases in the fifth epidemic were still highly sporadically distributed without any epidemiology links; the main characteristics remained unchanged and the genetic characteristics of virus strains that were isolated in this epidemic remained similar to earlier epidemics. Interventions included live poultry market closures in several cities that reported more H7N9 cases recently.

Construction of a reassortant influenza B virus with reverse genetics system / 中华微生物学和免疫学杂志

Objective To construct a reverse genetic platform for influenza B virus and to rescue influenza B virus.Methods Eight plasmids carrying the gene segments of B/Florida/4/2006 virus were constructed by using the bidirectional promoter vector pHW2000.293T cells were co-cultured with MadinDarby canine kidney (MDCK) cells and then transfected with the eight plasmids.The supernatants of cell culture and cell debris were collected after transfection and then injected into embryonated chicken eggs and MDCK cells for rescuing the influenza B virus strains.Results This reverse genetic system could be used for the preparation of reassortant influenza B virus strains.The titers of hemagglutination units of the rescued virus achieved 128-256/50μl.Most of the reassortant virus particles were spherical under electron microscope.Conclusion The pHW2000 reverse genetic system could be used for the rescue of influenza B virus.Moreover,it could also be used for the construction of influenza B virus with specific mutations for further in vestigation on the characteristics of influenza B virus and the construction of vaccine strain.

Susceptibility of influenza B viruses to neuraminidase inhibitors during 2014 to 2015 in mainland China / 中华微生物学和免疫学杂志

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.

Quantitative assessment of the virucidal activities of three commercial disinfectants against human in-fected highly pathogenic avian influenza viruses subtype H5 / 中华微生物学和免疫学杂志

Objective To quantitatively assess the virucidal activities of three commercial disin-fectants against human infected highly pathogenic avian influenza viruses subtype H5. Methods The 50%tissue culture infective dose ( TCID50 ) of avian influenza viruses was calculated. Quantitative suspension test was performed to evaluate the efficacy of three disinfectants. In that test, 105 TCID50 of avian influenza viru-ses were exposed to different disinfectants at different concentrations for different times with or without the in-terference with fetal bovine serum ( FBS) simulating the contaminated condition. The residual infectivity was determined by endpoint titration in Madin-Darby canine kidney ( MDCK) cells. The detail steps were that the mixture of viruses and disinfectants was inoculated at 37℃ with 5% CO2 for 1 hour. Then, it was re-placed by virus dilution medium and further incubated for 18 to 20 hours. ELISA was performed for the cal-culation of TCID50 . The titers of residual viruses were calculated according to Reed and Muench method. The low pathogenic avian influenza virus H9N2 was chosen as the control in this study. Results The re-mained infectivities of three viruses after 1 minute exposure to 1% Virkon solution were below the limit of de-tection (1. 0 lgTCID50/100 μl). Exposing to 0. 5% Virkon solution decreased the viral titers of H5N1 and H9N2 viruses below the detection limit and reduced the titer of H5N6 virus to 1. 75 lgTCID50/100 μl. The virucidal efficacy of 0. 25% Virkon solution against some of the detected viruses was achieved by increasing the exposure time to 5 minutes. The 84 Disinfectant solutions at concentrations of 10%, 5% and 2. 5% low-ered the viral titers of three viruses below the detection limit of 1. 0 lgTCID50/100 μl, but the 1. 25% 84 Disinfectant solution only lowered the viral titers to 1. 25-2. 5 lgTCID50/100 μl. The similar results were ob-served in groups treated with SOLARSEPT solutions. 1% 84 Disinfectant solution didn′t show any virucidal activity against the three viruses after 1 minute of exposure even when the exposure time was extended to 5 minutes. Under the contaminated condition, 1% Virkon solution, 10% and 5% 84 Disinfectant solutions as well as 100% and 50% SOLARSEPT solutions lowered the viral titers below 1. 0 lgTCID50/100μl. Conclu-sion The three commercial disinfectants (1% Virkon solution, 10% 84 Disinfectant solution and SOLAR-SEPT solution) were efficient virucides for highly pathogenic avian influenza viruses subtype H5 even under the contaminated condition. Increasing the exposure time had no significant effects on the efficacy of three disinfectants after the virucidal activities were neutralized by enough viruses. No significant differences in vi-rucidal activities of three disinfectants against HPAI H5 viruses and LPAI H9 virus were observed.

Preparation and Identification of High Immunogenic A/PR/8/34 Maternal Strain HA Protein for Influenza Virus Classical Reassortment / 病毒学报

Preparation of maternal strain A/PR/8/34 HA antiserum for influenza virus classical reassortment. A/PR/8/34 virus was digested by bromelain after inactivation and purification. 5%-20% sucrose continuous density gradient centrifugation method was used to purify HA protein. SIRD method was used to select the target protein. SDS-PAGE method was used to identified HA protein. High Immunogenic A/PR/8/34 HA protein was successfully prepared and HI titer reached 10240. High purity HA antiserum was identified by SIRD method. The key reagent in the classical reassortment of influenza virus was prepared, and the complete set of technical methods were explored, which laid the foundation for the independent research and development of seasonal influenza vaccine strains of China.

Research Progress on Antiviral Activity of Interferon-induced Transmembrane Proteins / 病毒学报

Interferon-induced Transmembrane Proteins (IFITMs) were identified through small interference RNA (siRNA) screening method in 1980s. The antiviral properties of the IFITMs were firstly discovered in 1996. Recently, its antiviral effect and mechanism have become a research hotspot. Many studies have shown that IFITM can inhibit the replication of multiple pathogenic viruses, including influenza A virus (IAV), Human Immunodeficiency Virus (HIV-1), hepatitis C virus (HCV), Ebola virus (EBOV), West Nile virus and so on. IFITMs inhibit the replication of virus in the early stage of the viral life cycle, which occurred before the release of viral genomes into the cytosol. Recent studies indicate that IFITM proteins could block viral replication by mediate viral membrane fusion. However, the mechanism is still under investigation. Here we review the discovery and characterization of the IFITM proteins, elucidate their antiviral activities and the potential mechanisms.

Expression of Chimeric Influenza Hemagglutinin Antigen (cH7/3) using the Baculovirus Expression System and Identification of its Biological Activities / 病毒学报

Hemagglutinin (HA) contains a head domain with a high degree of variability and a relatively conserved stem region. HA is the major viral antigen on the surface of the influenza virus. To define the biologic activities of chimeric HA bearing different head domains and stem regions or their potential use, a HA chimeric gene containing the head domain of the H7 subtype virus and stem region of the H3 subtype virus was modified and expressed using a baculovirus expression vector. Then, the secreted protein was purified and its biologic activities characterized. Approximately 1.4 mg/mL cH7/3 HA could be obtained, and its molecular weight was ≈ 70 kD. The trimer form of cH7/3 protein had hemagglutination activity and could be recognized by specific antibodies. The method described here can be used for further studies on the screening of HA stem-reactive antibodies or the development of vaccines with conserved epitopes.

Detection of Avian Influenza Virus in Environmental Samples Collected from Live Poultry Markets in China during 2009-2013 / 病毒学报

Abstract: To investigate the distribution of avian influenza virus in environmental samples from live poultry markets (LPM) in China, samples were collected and tested by nucleic acid during 2009-2013 season. Each sample was tested by real-time RT PCR using flu A specific primers. If any real-time PCR was positive, the sample was inoculated into specific-pathogen-free (SPF) embryonated chicken eggs for viral isolation. The results indicated that the positive rate of nucleic acid in enviromental samples exhibited seasonality. The positive rate of nucleic acid was significantly higher in Winter and Spring. The positive rate of nucleic acid in LPM located in the south of China was higher than in northern China. Samples of Sewage for cleaning poultry and chopping board showed that higher positive rate of nucleic acid than other samples. The Subtype identification showed that H5 and H9 were main subtypes in the enviromental samples. Viral isolation indicated H5 subtypes was more than H9 subtypes between 2009 and 2013 while H9 subtypes increased in 2013. Our findings suggested the significance of public health based on LPM surveillance and provided the basis of prevention and early warning for avian flu infection human.

Google Flu Trends--the initial application of big data in public health / 中华预防医学杂志

Google Flu Trends (GFT) was the first application of big data in the public health field. GFT was open online in 2009 and attracted worldwide attention immediately. However, GFT failed catching the 2009 pandemic H1N1 and kept overestimating the intensity of influenza-like illness in the 2012-2014 season in the United States. GFT model has been updated for three times since 2009, making its prediction bias controlled. Here, we summarized the mechanism GFT worked, the strategy GFT used to update, and its influence on public health.

Susceptibility of human influenza A (H3N2) viruses to neuraminidase inhibitors isolated during 2011-2012 in China / 中华预防医学杂志

<p><b>OBJECTIVE</b>To analyze the susceptibility of influenza A (H3N2) viruses to neuraminidase inhibitors during 2011-2012 in Mainland China.</p><p><b>METHODS</b>All 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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>The influenza A(H3N2) viruses isolated during 2011-2012 in Mainland China were tested to be sensitive to oseltamivir and zanamivir.</p>

Virological characteristics of influenza A (H3N2) virus in mainland China during 2013-2014 / 病毒学报

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.