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.
Animals ; Antibodies, Monoclonal ; Antibodies, Viral ; Hemagglutinin Glycoproteins, Influenza Virus/genetics* ; Hemagglutinins ; Influenza A Virus, H7N9 Subtype ; Influenza in Birds ; Molecular Docking Simulation

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.
Animals ; Hemagglutinin Glycoproteins, Influenza Virus/genetics* ; Hemagglutinins/genetics* ; Influenza B virus/metabolism* ; Influenza Vaccines/genetics* ; Mammals/metabolism* ; Mice ; Mice, Inbred BALB C

To evaluate the immunogenicity of HA globular head domain of H5 subtype influenza virus (H5HA), the gene of H5HA was optimized and the recombinant pPICZaA-H5HA expressing vector was constructed and transfected into Pichia pastoris. The expression of the recombinant H5HA was confirmed by SDS-PAGE and Western blotting and the results demonstrated that the recombinant H5HA (37 kDa) was highly expressed in Pichia pastoris with concentration of 0.2 mg/mL in medium. The recombinant H5HA was concentrated and purified using Ni-NTA affinity chromatography. The immunogenicity of H5HA was evaluated by immunizing eight groups of chicken through intranasal or intramuscular injection with different doses of purified H5HA combined with different adjuvants, respectively. The results showed that the recombinant H5HA could induce high level IgG (HI titer was 1:64 and neutralizing antibody titer was 1:218) and the optimal dosage of the recombinant H5HA was 50 μg combined with oil. In addition, intramuscular injection was better than nasal immunization. This study provided a theoretical support for subunit vaccine development.
Animals ; Antibodies, Viral ; Birds ; Hemagglutinin Glycoproteins, Influenza Virus ; Influenza A Virus, H5N1 Subtype ; Influenza Vaccines ; Influenza in Birds ; Pichia ; Vaccination

Objective: To understand the molecular characteristics of hemagglutinin (HA) and neuraminidase (NA) as well as the disease risk of influenza virus A H7N9 in Guizhou province. Methods: RNAs were extracted and sequenced from HA and NA genes of H7N9 virus strains obtained from 18 cases of human infection with H7N9 virus and 6 environmental swabs in Guizhou province during 2014-2017. Then the variation and the genetic evolution of the virus were analyzed by using a series of bioinformatics software package. Results: Homology analysis of HA and NA genes revealed that 2 strains detected during 2014-2015 shared 98.8%-99.2% and 99.2% similarities with vaccine strains A/Shanghai/2/2013 and A/Anhui/1/2013 recommended by WHO, respectively. Two strains detected in 2016 and 14 strains detected in 2017 shared 98.2%-99.3% and 97.6%-98.8% similarities with vaccine strain A/Hunan/02650/2016, respectively. Other 6 stains detected in 2017 shared 99.1%-99.4% and 98.9%-99.3% similarities with strain A/Guangdong/17SF003/2016, respectively. Phylogenetic analysis showed that all the strains were directly evolved in the Yangtze River Delta evolution branch, but they were derived from different small branch. PEVPKRKRTAR↓GLF was found in 6 of 24 strains cleavage site sequences of HA protein, indicating the characteristic of highly pathogenic avian influenza virus. Mutations A134V, G186V and Q226L at the receptor binding sites were found in the HA. All the strains had a stalk deletion of 5 amino acid residue "QISNT" in NA protein, and drug resistance mutation R294K occurred in strain A/Guizhou-Danzhai/18980/2017. In addition, potential glycosylation motifs mutations NCS42NCT were found in the NA of 9 of 24 strains. Conclusions: HA and NA genes of avian influenza A (H7N9) virus showed genetic divergence in Guizhou province during 2014-2017. The mutations of key sites might enhance the virulence of the virus, human beings are more susceptible to it. Hence, the risk of infection is increasing.
Animals ; Base Sequence ; Birds ; China/epidemiology* ; Genome, Viral ; Hemagglutinin Glycoproteins, Influenza Virus/immunology* ; Hemagglutinins/genetics* ; Humans ; Influenza A Virus, H7N9 Subtype/isolation & purification* ; Influenza in Birds ; Influenza, Human/virology* ; Neuraminidase/genetics* ; Phylogeny ; RNA, Viral/genetics* ; Sequence Analysis, DNA

Objective To develop neutralizing monoclonal antibodies (MAbs) against H10N8 avian influenza virus hemagglutinin and to identify the binding sites. Methods MAbs against hemagglutinin of H10N8 avian influenza virus were developed by genetic engineering. Neutralizing MAbs were screened by microneutralization assay,and then tested by enzyme-linked immunosorbent assay and Western blot to identity the binding sites.The homology modeling process was performed using Discovery Studio 3.5 software,while the binding epitopes were analyzed by BioEdit software. Results One MAb that could neutralize the H10N8 pseudovirus was obtained and characterized. Analysis about epitopes suggested that the antibody could bind to the HA1 region of hemagglutinin,while the epitopes on antigen were conserved in H10 subtypes.Conclusions One neutralizing antibody was obtained by this research.The MAb may potentially be further developed as a pre-clinical candidate to treat avian influenza H10N8 virus infection.
Antibodies, Monoclonal ; immunology ; Antibodies, Neutralizing ; immunology ; Antibodies, Viral ; immunology ; Enzyme-Linked Immunosorbent Assay ; Epitopes ; immunology ; Hemagglutinin Glycoproteins, Influenza Virus ; immunology ; Influenza A Virus, H10N8 Subtype ; Neutralization Tests

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.
Animals ; Antibodies, Viral ; immunology ; Electrophoresis, Polyacrylamide Gel ; Female ; Hemagglutination Inhibition Tests ; Hemagglutinin Glycoproteins, Influenza Virus ; analysis ; immunology ; Humans ; Influenza A Virus, H1N1 Subtype ; genetics ; immunology ; Influenza, Human ; immunology ; virology ; Rabbits ; Reassortant Viruses ; genetics ; immunology

As part of our ongoing influenza surveillance program in South China, 19 field strains of H9N2 subtype avian influenza viruses (AIVs) were isolated from dead or diseased chicken flocks in Guangdong province, South China, between 2012 and 2013. Hemagglutinin (HA) genes of these strains were sequenced and analyzed and phylogenic analysis showed that 12 of the 19 isolates belonged to the lineage h9.4.2.5, while the other seven belonged to h9.4.2.6. Specifically, we found that all of the viruses isolated in 2013 belonged to lineage h9.4.2.5. The lineage h9.4.2.5 viruses contained a PSRSSRdownward arrowGLF motif at HA cleavage site, while the lineage h9.4.2.6 viruses contained a PARSSRdownward arrowGLF at the same position. Most of the isolates in lineage h9.4.2.5 lost one potential glycosylation site at residues 200-202, and had an additional one at residues 295-297 in HA1. Notably, 19 isolates had an amino acid exchange (Q226L) in the receptor binding site, which indicated that the viruses had potential affinity of binding to human like receptor. The present study shows the importance of continuing surveillance of new H9N2 strains to better prepare for the next epidemic or pandemic outbreak of H9N2 AIV infections in chicken flocks.
Animals ; *Chickens ; China ; Hemagglutinin Glycoproteins, Influenza Virus/chemistry/*genetics/metabolism ; Influenza A Virus, H9N2 Subtype/*genetics/metabolism ; Influenza in Birds/virology ; Phylogeny ; Poultry Diseases/*virology ; Sequence Analysis, RNA/veterinary

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

To analyze influenza pathogen spectrum in Yunnan province during 2009-2014 years, and analyze HA and NA genes of influenza A H1N1. Analysis was made on the monitoring date of influenza cases in Yunnan province in recent 6 years, 23 strains of influenza virus of HA and NA gene was sequenced and analyzed by MEGA 5 software to construct phylogenetic tree. 4 times of influenza AH1N1 epidemic peak were monitored from 2009-2014 years in Yunnan Province, as the nucleic acid detection results of influenza A H1N1 accounted for 28.8% of the total. The sequencing result showed that HA and NA gene were divided into 3 groups, one was detected with H275Y mutation strains. Influenza A H1N1 is one of the important subtypes in Yunnan province and their genes have divided into three branches during the period of 2009-2014 years, the vast majority of influenza a H1N1 are still sensitive to neuraminidase inhibitors.
China ; epidemiology ; Hemagglutinin Glycoproteins, Influenza Virus ; genetics ; metabolism ; Humans ; Influenza A Virus, H1N1 Subtype ; classification ; enzymology ; genetics ; isolation & purification ; Influenza, Human ; epidemiology ; virology ; Molecular Sequence Data ; Mutation ; Neuraminidase ; genetics ; metabolism ; Phylogeny ; Viral Proteins ; genetics ; metabolism

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.
Antibodies, Viral ; immunology ; Baculoviridae ; genetics ; metabolism ; Gene Expression ; Genetic Vectors ; genetics ; metabolism ; Hemagglutination ; Hemagglutinin Glycoproteins, Influenza Virus ; genetics ; immunology ; Humans ; Influenza Vaccines ; genetics ; immunology ; Influenza, Human ; prevention & control ; virology