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@#Objective To construct encoding RNA that can be cyclized in vitro by using the permuted intron exon(PIE)strategy in the maturation process of eukaryotic mRNA,and transfect it into HEK-293T cells for expression.Methods The sequences of 5'and 3'cyclic arms with groupⅠcatalytic intron,the internal ribosome entry sites(IRES)of Coxsackievirus B3(CVB3)and the target gene were selected to construct the template plasmid. Linearization plasmid template obtained by PCR was used to synthesize linear RNA through in vitro transcription(IVT),which then started in vitro cyclization(IVC)by the addition of cyclization reagents to obtain circular RNA(circRNA). RNA cyclization was confirmed by agarose gel electrophoresis and ribonuclease R(RNase R)digestion. HEK-293T cells were transfected with circRNAs respectively carrying enhanced green fluorescent protein(EGFP),firefly luciferase(Fluc),and influenza virus hemagglutinin(HA)IVR-180 genes,to verify their expression with in vitro.Results With RNA cyclization,the main band of agarose gel electrophoresis became smaller and small fragments appeared. After RNase R digestion,only some circRNA bands remained.HEK-293T cells transfected with EGFP-circRNA showed significant green fluorescence under the fluorescence microscope.The Fluc expression values of HEK-293T cells transfected with Fluc-circRNA were on average 20 times higher than non cyclized RNA,and the relative light unit(RLU)scaled up with the increase of Fluc-circRNA transfection dose. Western blot analysis showed that HA protein was successfully expressed in HEK-293T cells transfected with HA-circRNA.Conclusion In this study,linear RNA was successfully cyclized in vitro and different proteins were expressed,which lays a foundation of the research of new influenza vaccines and mRNA vaccines.
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Hemagglutinin and neuraminidase, two important glycoproteins on the surface of influenza virus, play a considerable role in the entry and release stage of the viral life cycle, respectively. With in-depth investigation of influenza virus glycoproteins and the continuous innovation of drug discovery strategies, a new generation of glycoproteins inhibitors have been continuously discovered. From the point of view of medicinal chemistry, this review summarizes the current advances in seeking small-molecule inhibitors targeting influenza virus glycoproteins, hoping to provide valuable guidance for future development of novel antiviral drugs.
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@#At present,the most commonly used method for detecting hemagglutinin(HA)content in influenza vaccines is still single-radial immunodiffusion(SRID). However,the preparation of standards required by this method takes a long time,usually 2 ～ 3 months. Therefore,how to quantitatively analyze HA accurately has always been a difficult problem in the detection of HA content in the situation that reference products can not be obtained at the early stage of the pandemic influenza. High performance liquid chromatography(HPLC)has its own characteristics of rapidity,high sensitivity,good repeatability and high accuracy,which can rapidly determine HA content by using different separation principles and has been widely used in the detection of HA content in influenza vaccine. This paper reviewed the research progress of the application of HPLC in the determination of HA content in influenza vaccine.
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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 analyze the molecular characteristics of hemagglutinin-neuraminidase (HN) gene of human parainfluenza virus type 3 (HPIV3) among the cases with acute respiratory tract infection (ARI) in Henan Province.Methods:Nasal/throat swab samples collected from patients with severe acute respiratory tract infection (SARI) in Luohe and patients with influenza-like illness (ILI) in Zhengzhou were used in this study. HPIV nucleic acids in the samples were detected using real-time fluorescent PCR. HPIV3-positive samples were subjected to RT-PCR for the amplification of HN genes and the sequences were analyzed with Sanger method. CExpress and MEGA7.0 software were used for sequences editing, evolution tree construction and gene sequence analysis.Results:A total of 374 throat swab samples collected form ARI cases in Luohe and Zhengzhou were tested and 20 (5.3%) of them were positive for HPIV3. Eighteen HPIV3 HN gene sequences were successfully amplified and all belonged to C3 subgroups, including 16 sequences of C3f genotype and two sequences of C3a genotype. The 18 HN gene sequences shared the homology of 97.6%-100.0% in nucleotide and 99.3%-100.0% in amino acid, but the differences between them and the prototype strain Wash/47885/57 were significant. There were 12 amino acid mutations shared by them, including four function-related mutations (H295Y, I391V, D556N and I53T). There were no significant differences in the nucleotide or amino acid sequences as compared with the epidemic strain of China/BCH4210A/2014.Conclusions:The C3f and C3a branches of HPIV3 were the epidemic genotypes in Henan Province in recent years and a local circulating prevalence might be established. Continuous and in-depth monitoring of HPIV3 C3 subtype would be of great significance for the prevention and control of HPIV3-associated diseases.
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Objective:To prepare a recombinant hemagglutinin trimer (HA-Tri) vaccine against influenza viruses and to study its immunogenicity in a mouse model.Methods:A stable CHO cell line that could express HA-Tri was constructed. Western blot, single radial immunodiffusion, protein particle size detection and N-glycosylation site analysis were performed for qualitative and quantitative analysis of the recombinant protein. According to the different treatment conditions such as dosage and adjuvant, BALB/c mice were divided into 11 groups and subjected to consistent immunization procedures. Serum neutralizing antibody titers were measured on 56 d after the first immunization to evaluate the immunogenicity of HA-Tri.Results:The constructed CHO cells could secret and express HA-Tri proteins. The HA-Tri proteins were biologically active and capable of forming precipitation rings in the single radial immunodiffusion. The particle size of HA-Tri was approximately 18.79 nm and 10 N-glycosylation sites were detected, including high mannose, complex glycoforms and heterozygous glycoforms. After prime-boost immunization, there was no statistically significant difference in the titers of neutralizing antibodies induced in mice by 3.75 μg of HA-Tri in combination with RFH01 adjuvant and 15 μg of monovalent vaccine stock solution ( P=0.431 2, U=36). Serum antibody titers in the HA-Tri+ RFH01 groups were higher than those in the corresponding HA-Tri groups without RFH01 adjuvant, and the highest titer was induced in the 15 μg HA-Tri+ RFH01 group, which was 1 280. Conclusions:The recombinant HA-Tri protein was successfully prepared. HA-Tri in combination with RFH01 adjuvant could induce humoral immune responses against influenza viruses in BALB/c mice, which would provide reference for the development of influenza virus recombinant subunit vaccines.
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ObjectiveTo analyze the genetic characteristics of the hemagglutinin （H） gene of measles virus （MeV） in Shanghai， 2001‒2018. MethodsNasopharyngeal swab specimens were collected from suspected measles cases reported in Shanghai from 2001 to 2018， and the isolation of measles virus was conducted with Vero/hSLAM cell line. RT-PCR amplification and sequencing were conducted after RNA extraction to analyze the genetic characteristics of the complete H gene. ResultsIn total， 5 665 nasopharyngeal swab samples were collected by suspected measles case surveillance from 2001 to 2018， and 1 394 measles virus strains were isolated. The homology of nucleotide acid and amino acid among 349 representative measles virus isolates was 87.4%‒100.0% and 85.1%‒100.0%， respectively. The homology of nucleotide acid and amino acid between representative measles virus isolates and China vaccine strain （S191） was 85.7%‒100.0% and 84.1%‒100.0%， respectively. All the sub-genotype H1a MeV isolates had an amino acid substitution （Ser240Asn）， which removed a predicted N-linked glycosylation site. ConclusionMost of the MeV isolates are sub-genotype H1a analyzed based on H gene， which are identical to those of the N gene. The predicted amino acid sequences of the H protein are relatively conserved at most of the functionally significant amino acid positions.
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Objective:To express the head domain of influenza A virus hemagglutinin (HA) in a prokaryotic expression system and to evaluate its immunogenicity.Methods:The genes encoding the HA head domains of H1N1 and H3N2 influenza viruses were cloned into pET-22b(+ ) prokaryotic expression plasmid. After the induction with IPTG, the fusion proteins rH1N1-HA and rH3N2-HA containing HA head domain and His-tag were expressed and obtained from E. coli BL21. SDS-PAGE and Western blot was used to verify the expression of the recombinant proteins. Rabbits were immunized with multiple doses of the purified recombinant proteins to obtain polyclonal antibodies against the HA head domains of H1N1 and H3N2. The immunogenicity of the recombinant proteins was evaluated in BALB/c mice. Results:rH1N1-HA and rH3N2-HA induced protective antibodies (geometric mean titer ≥40) in mice and could be used as protective antigens. Polyclonal antibodies against rH1N1-HA and rH3N2-HA could be used as important materials for Western blot, ELISA and other immunological assays.Conclusions:The HA head domains prepared in this study could be used as protective antigens to induce protective antibodies in mice. Polyclonal antibodies against the HA head domains could be used for immunological and serological studies of influenza A viruses.
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Objective:To prepare and identify a broad-spectrum antibody FHA3 targeting influenza A virus hemagglutinin (HA).Methods:According to the single-chain antibody fragment (scFv) sequence, the heavy chain (VH) and light chain (VL) variable regions of FHA3 were amplified by PCR and a recombinant plasmid pFRT-IgG1κ-FHA3 was constructed by linking the expression vector pFRT-IgG1κ. FHA3 was expressed in the ExpiCHO system and purified by affinity purification. The binding activity of FHA3 to influenza A virus HA was detected by ELISA. The neutralizing activity of FHA3 was detected in vitro by infecting host cells with pseudovirus. Results:SDS-PAGE showed that high-purity FHA3 was obtained. FHA3 could bind to H1N1 HA, H2N2 HA, H3N2 HA, H5N1 HA, H7N9 HA and H9N2 HA in a concentration-dependent manner. FHA3 had good neutralizing activity in vitro that was it could effectively block the invasion of H5N1 and H7N9 pseudoviruses into target cells at a low concentration of 5 μg/ml and H1N1 pseudovirus at 0.012 5 μg/ml. Conclusions:A broad spectrum antibody targeting HA protein of influenza A virus with neutralizing activity in vitro was obtained.
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Objective:To study the epidemiological features of local influenza A(H1N1)pdm09 epidemic strains through analyzing the changes in lineages and to analyze how well the vaccine strains were matched to the circulating strains in Hangzhou.Methods:Of 1 112 clinical specimens from laboratory-confirmed A(H1N1)pdm09 infections in Hangzhou in consecutive seasons from 2009 to 2020, 208 (18.7%) with high viral load (Ct value <30) were randomly selected from 10 influenza epidemics for full-length hemagglutinin gene ( HA) gene sequencing. Genetic variation, evolution and lineage changes of these representative local strains were analyzed by comparison with vaccine strains and reference strains. Results:Since the 2009 pandemic, A(H1N1)pdm09 had become one of the predominant viruses causing seasonal influenza and been reported to co-circulate with influenza A(H3N2) and influenza B viruses in Hangzhou in the past decade. It caused 10 local influenza epidemics in the 12 consecutive seasons from 2009 to 2020. HA gene sequencing revealed complex sources and rapid variation of the local A(H1N1)pdm09 strains. The main epidemic strains often genetically drifted from the recommended northern hemisphere vaccine strains due to lineage changes. Conclusions:This study suggested that it was essential to update the recommended vaccine strains year by year. Besides, enhanced periodic monitoring of influenza A(H1N1)pdm09 strains circulating in the region was important for the prevention and control of influenza A(H1N1)pdm09 infection in the next epidemic season.
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@#Highly Pathogenic Avian Influenza (HPAI) is a highly contagious disease in poultry. The outbreaks can lead to flock mortality up to 100% in two to three days. In July 2018, high mortality in a commercial layer farm in Kauluan village, Sabah was reported. Samples were sent to Veterinary Research Institute Ipoh for diagnosis. Virus isolation and molecular detection is carried out simultaneously. The causative agent was then identified as AI H5N1 virus by real time reverse transcription-polymerase chain reaction (RT-PCR). The virus was then subjected for further nucleotide sequencing of full length hemagglutinin (HA) and neuraminidase (NA) gene. The PQRERRRKR/GLF motif at the HA cleavage site indicated that the isolate was of HPAI virus. Phylogenetic analysis of the HA gene showed that the isolate was belonged to the clade 2.3.2.1c virus. In the HA gene, besides the S133A substitution, the virus possesses conserved amino acid at most of the avian receptor binding sites including the glutamine (Q) and glycine (G) at position 222 and 224 respectively, indicating that the virus retains the avian-type receptor binding preference. As such, the zoonotic potential of the virus was relatively low. On the other hand, though the N154D and T156A substitution were detected in the same gene, the pandemic potential of this Sabah 2.3.2.1c virus is low in the absence of the Q222L, G224S, H103Y, N220K and T315I. A typical 20 amino acid deletion with loss of four corresponding glycosylation sites in the NA stalk region was visible. Though three NA resistance markers were detected, the virus was predicted to be sensitive to NA inhibitor. This is the first HPAI H5N1 outbreak in Sabah. The introduction of this virus into East Malaysia for the first time raised an alert alarm of the future epidemic potential. Strict farm biosecurity, continuous surveillance programme in poultry, wild birds, migratory birds; molecular epidemiology as well as risk assessment for the virus with pandemic potential are needed in dealing with emergence of new influenza virus in the country.
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Influenza B virus is one of the causes for seasonal influenza, which can account for serious illness or even death in some cases. We tested the expression of extracellular domain of hemagglutinin (HA-ecto) of influenza B viruses in mammalian cells, and then determined the immunogenicity of HA-ecto in mice. The gene sequence encoding influenza B virus HA-ecto, foldon sequence, and HIS tag was optimized and inserted into pCAGGS vector. The opening reading frame (ORF) of neuraminidase was also cloned into pCAGGS. The pCAGGS-HA-ecto and pCAGGS-NA were co-transfected into 293T cells using linear polyethylenimine. Cell supernatant after transfection was collected after 96 h, and the secreted trimmeric HA-ecto protein was purified by nickel ion affinity chromatography and size exclusion chromatography. Subsequently, the mice were immunized with HA-ecto protein, and the corresponding antibody titers were detected by ELISA and hemagglutination inhibition (HAI) assays. The results showed that soluble trimeric HA-ecto protein could be obtained using mammalian cell expression system. Moreover, trimeric HA-ecto protein, in combination with the adjuvant, induced high levels of ELISA and HAI antibodies against homogenous and heterologous antigens in mice. Thus, the soluble HA-ecto protein expressed in mammalian cells could be used as a recombinant subunit vaccine candidate for influenza B virus.
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Animals , Mice , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Hemagglutinins/genetics , Influenza B virus/metabolism , Influenza Vaccines/genetics , Mammals/metabolism , Mice, Inbred BALB CABSTRACT
The conserved hemagglutinin (HA) stem region of avian influenza virus (AIV) is an important target for designing broad-spectrum vaccines, therapeutic antibodies and diagnostic reagents. Previously, we obtained a monoclonal antibody (mAb) (5D3-1B5) which was reactive with the HA stem epitope (aa 428-452) of H7N9 subtype AIV. To systematically characterize the mAb, we determined the antibody titers, including the HA-binding IgG, hemagglutination-inhibition (HI) and virus neutralizing (VN) titers. In addition, the antigenic epitope recognized by the antibody as well as the sequence and structure of the antibody variable region (VR) were also determined. Moreover, we evaluated the cross-reactivity of the antibody with influenza virus strains of different subtypes. The results showed that the 5D3-1B5 antibody had undetectable HI and VN activities against H7N9 virus, whereas it exhibited strong reactivity with the HA protein. Using the peptide-based enzyme-linked immunosorbent assay and biopanning with a phage-displayed random peptide library, a motif with the core sequence (431W-433Y-437L) in the C-helix domain in the HA stem was identified as the epitope recognized by 5D3-1B5. Moreover, the mAb failed to react with the mutant H7N9 virus which contains mutations in the epitope. The VR of the antibody was sequenced and the complementarity determining regions in the VR of the light and heavy chains were determined. Structural modeling and molecular docking analysis of the VR verified specific binding between the antibody and the C-helix domain of the HA stem. Notably, 5D3-1B5 showed a broad cross-reactivity with influenza virus strains of different subtypes belonging to groups 1 and 2. In conclusion, 5D3-1B5 antibody is a promising candidate in terms of the development of broad-spectrum virus diagnostic reagents and therapeutic antibodies. Our findings also provided new information for understanding the epitope characteristics of the HA protein of H7N9 subtype AIV.
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Animals , Antibodies, Monoclonal , Antibodies, Viral , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Hemagglutinins , Influenza A Virus, H7N9 Subtype , Influenza in Birds , Molecular Docking SimulationABSTRACT
Coronaviruses cause animal and human respiratory and bowel infections. They have not been deemed highly pathogenic to humans until the outbreak of severe acute respiratory syndrome (SARS) in 2002 and 2003 in Guangdong province, China. Coronaviruses (CoVs) are large, enveloped, positive-sense, single-stranded RNA viruses that can infect both animals and humans. Coronaviruses didn't just appear recently. They are large family of viruses that have been around for a long time. Formerly, coronaviruses (CoVs) were seen as relatively harmless respiratory pathogens to humans. However, two outbreaks of severe respiratory tract infection, caused by the severe acute respiratory syndrome coronavirus (SARS-CoV) and the Middle East respiratory syndrome coronavirus (MERS-CoV) caused high pathogenicity and mortality rates among human populations as a result of zoonotic CoVs crossing the species barrier. Now the recent detection of the 2019 novel coronavirus (COVID-19), added a new member in corona virus family.The novel coronavirus (COVID 19) is one of the member of coronavirus family which infect human. Scientists have divided coronaviruses into four sub- groupings, called alpha, beta, gamma and delta. Seven of these viruses can infect people. The four common coronaviruses are-229E(alpha), NL63(alpha), OC43(beta), HKU1(beta). The three less-common coronaviruses are- MERS-CoV(beta), SARS-CoV(beta), SARS-CoV-2. Our main target is to describe the the structure, Pathogenecity, Transmissibility and Epidemiology of above mentioned subgroups of corona viruses in our review
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The avian influenza A (H7N9) virus is a zoonotic virus that is closely associated with live poultry markets. It has caused infections in humans in China since 2013. Five waves of the H7N9 influenza epidemic occurred in China between March 2013 and September 2017. H7N9 with low-pathogenicity dominated in the first four waves, whereas highly pathogenic H7N9 influenza emerged in poultry and spread to humans during the fifth wave, causing wide concern. Specialists and officials from China and other countries responded quickly, controlled the epidemic well thus far, and characterized the virus by using new technologies and surveillance tools that were made possible by their preparedness efforts. Here, we review the characteristics of the H7N9 viruses that were identified while controlling the spread of the disease. It was summarized and discussed from the perspectives of molecular epidemiology, clinical features, virulence and pathogenesis, receptor binding, T-cell responses, monoclonal antibody development, vaccine development, and disease burden. These data provide tools for minimizing the future threat of H7N9 and other emerging and re-emerging viruses, such as SARS-CoV-2.
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Animals , Humans , COVID-19 , China/epidemiology , Influenza A Virus, H7N9 Subtype , Influenza in Birds/epidemiology , Influenza, Human/prevention & control , Poultry , SARS-CoV-2ABSTRACT
Influenza A virus (H1N1) seriously affects the health of human and disrupts the development of global economic. The antimicrobial peptide urumin specifically binds to the conserved stem of the hemagglutinin (HA) protein of H1N1 virus, but its binding site and the mechanism of action are not clear. In this study, we investigated the possible binding sites and key amino acids for the interaction of urumin with HA protein by molecular docking and enzyme-linked immunosorbent assay (ELISA) experiments, suggesting that HA residues His32 (HA1), Asp19 (HA2), and Trp21 (HA2) are the key residues for the interaction of HA with urumin. Urumin's Arg4, Asn9, and Cys16 were associated with HA protein residues Asp19 (HA2), Trp21 (HA2), His32 (HA1), and Asn53 (HA2) form hydrogen bonding interactions, and Trp12 forms an aromatic π-stacking interaction with His32 (HA1) of HA, these interactions maintain the binding of urumin to HA protein. Wild-type HA and its alanine mutant [alanine substitutions His32 (HA1), Asp19 (HA2), and Trp21 (HA2)] were expressed in 293T cells. ELISA experiments showed that the affinity ability of urumin with HA wild-type was significantly higher than that of HA alanine mutant, suggesting that His32 (HA1), Asp19 (HA2), and Trp21 (HA2) may be the key residues for HA to interact with urumin. This study provides a theoretical and experimental basis for further modification and application of urumin.
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Animals , Humans , Amino Acid Sequence , Cell Culture Techniques , Cell Line , Chickens , Eggs , Erythrocytes , Guinea Pigs , Hand , Hemagglutination , Hemagglutinins , Influenza Vaccines , Influenza, Human , Neuraminidase , Orthomyxoviridae , Ovum , Sequence Analysis , Specific Pathogen-Free OrganismsABSTRACT
Objective To analyze the genetic characteristics of the hemagglutinin （HA) and neuraminidase （NA) genes of influenza B viruses isolated in Yancheng City from 2015 to 2017. Methods The throat swab specimens of influenza-like illness( ILI) from sentinel surveillance hospital and outbreak sites were collected and sent to Yancheng CDC for virus nucleic acids and virus isolation testing. After validation with serological tests, eighteen strains of influenza B virus isolates were selected to amplify their HA1 and NA genes through RT-PCR assay. Their molecular characteristics of the obtained viral HA1 and NA gene sequences were analyzed using bioinformation software from three aspects, including nucleic acid level, amino acid level and molecular evolution level. Results Basically, the clustering relationships and the branche patterns between HA1 and NA genes from the 18 Yancheng influenza B virus strains were similar. The Yamagata lineage strains in 2015 were distributed in the Yamagata Clade 3 branch, belonging to Phuket/3073 strains. The Victoria lineage strains in 2016-2017 were distributed in the Victoria Clade 1A branch, belonging to Brisbane/60 strains. D196N substitution was detected on HA1 protein in all of Yamagata lineage strains at 190-helix epitope; Amino acid substitutions of victoria lineage strains involved two antigenic epitopes, 117 and 129 sites of 120-loop epitope and 197 and 199 sites of 190-helix epitope. No Intra-lineage or inter-lineage rearrangements occurred in Yancheng strains. Eighteen influenza B strains had no mutations in catalytic residues and drug resistant sites of NA genes. Conclusion The Yamagata strains well matched with vaccine strain B/Phuket/3073/2013. The HA1 and NA genes of victoria lineage strains circulated in Yancheng City during 2016 to 2017 are changing gradually. The accumulation of these mutations will result in antigenic drift of victoria lineage strains and increase the mismatch of the IFV field stains with the available vaccine strains, which may reduce the protective effect of flu vaccine.
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Objective To understand the epidemiological characteristics and variation of H3N2 influenza virus hemagglutinin (HA) gene in Changzhou from 2017 to 2018. Methods Throat swab specimens of the influenza-like cases were collected from Changzhou Influenza Monitoring Sentinel Hospital from April 2017 to March 2018. RNA was extracted from the specimens for influenza diagnosing and genotyping using real-time RT-PCR．H3N2 positive samples were isolated, and extracted RNA was used for amplification, sequencing and phylogenetic analysis of HA gene. Results From April 2017 to March 2018, 28 strains of influenza A (H3N2) virus were isolated. After gene sequencing, a phylogenetic tree was constructed. It was found that all of the strains belonged to Group3C.2a, which was similar to the vaccine strain A/Hong Kong/4801/2014. The HA amino acid sequence difference was analyzed and compared between the H3N2 influenza virus strains isolated in Changzhou and the vaccine strain A/Hong Kong/4801/2014. It was found that the epidemic strain isolated in Changzhou was in the HA epitope (A-E) region. Ten amino acid site mutations in the HA epitope (A-E) region and two amino acid site mutations in the stem region of HA antigen were found. Conclusion From April 2017 to March 2018, the influenza virus H3N2 prevalent in Changzhou was distributed on the same evolutionary branch with the vaccine strain A/Hong Kong/4801/2014 (group 3C.2a), rendering the popular trend of one subgroup. However, some amino acid sites of the HA epitope had variations, suggesting that mutations may occur, which may affect the immune effect of the vaccine. Monitoring needs to be strengthened in the future work.
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@#Objective To analyze genetic characteristics of hemagglutinin( HA) gene of H9N2 avian influenza viruses( AIVs) circulating in Anhui Province from 2013 to 2018． Methods All H9N2 positive samples tested by real－time polymerase chain reaction( PCＲ) were inoculated into specific patho- gen free ( SPF) chicken eggs for isolation and purification． Viral ＲNA was reversely transcribed into cD- NA and then amplified with gene specific primers． PCＲ products were sequenced and the gene sequences were analyzed using molecular and bioinformatics software． The DATAMONKEY online server was conducted to analyze selection pressure，and protein structure homology modelling was computed by the SWISS－MODEL server． Ｒesults 33 H9N2 AIVs isolated from live poultry markets belonged to h9．4．2．5 in the phylogenetic tree． The receptor binding sites of HA gene at 183，226 and 227 position were mutated into N，L and M，respectively． Meanwhile 189 and 190 sites presented with genetic polymorphism． Since 2015，all H9N2 viruses in this study carried 6 potential N－linked glycosylation sites． It was found that po- sition 160 of HA gene was subjected greater positive selection pressure，presented 7 spatial conformations at least． Conclusions The H9N2 viruses isolated from live poultry markets in Anhui Province possess the molecular characteristics of infecting mammals and the ability of antigenic drift，so we need to pay more attention to the genetic characteristics of the viruses．