scholarly journals Antigenic and genetic analysis of equine influenza viruses from tropical Africa in 1991

1996 ◽  
Vol 117 (2) ◽  
pp. 367-374 ◽  
Author(s):  
C. A. O. Adeyefa ◽  
M. L. James ◽  
J. W. McCauley
Keyword(s):  
Amino Acid ◽  
Nucleotide Sequence ◽  
Antigenic Site ◽  
Glycosylation Site ◽  
Influenza Viruses ◽  
Amino Acid Substitutions ◽  
Antigenic Analysis ◽  
Equine Influenza ◽  
Antigenic Sites ◽  
European Strain

SummaryA detailed analysis of equine (H3N8) influenza viruses isolated in Nigeria during early 1991 has been undertaken. Antigenic analysis and the complete nucleotide sequence of the HA gene of three Nigerian equine influenza viruses A/eq/Ibadan/4/91, A/eq/Ibadan/6/91 and A/eq/Ibadan/9/91 are presented and limited sequence analysis of each of the genes encoding the internal polypeptides of the virus has been carried out. These results establish that, despite the geographical location from which these viruses were isolated, two were similar to the viruses which were concurrently causing disease in Europe in 1989 and 1991 and were related to viruses that have been predominating in horses since 1985. The third was more closely related to viruses isolated from 1991 onward in Europe but also in other parts of the globe. A comparison of the nucleotide sequence of two of the viruses isolated in Nigeria (A/eq/Ibadan/4/91 and A/eq/Ibadan/6/91) with a European strain (A/eq/Suffolk/89) showed limited variation in the haemagglutinin gene which caused amino acid substitutions in one of the antigenic sites: this mutation resulted in the potential production of a new glycosylation site in antigenic site A. The other Nigerian virus (A/eq/Ibadan/9/91) showed only a single one amino acid change from another European strain (A/eq/Arundel/12369/91). The two distinct Nigerian viruses had several amino acid substitutions in the antigenic sites of the haemagglutinin glycoprotein.

scholarly journals Whole genomic analysis of two influenza H3N2 virus strains isolated from Qinghai, China

2019 ◽  
Author(s):  
Huaxiang Rao ◽  
Hong Li ◽  
Nannan Lu ◽  
Youju Lei ◽  
Shengcang Zhao ◽  
...  
Keyword(s):  
Hong Kong ◽  
Amino Acid ◽  
Vaccine Strain ◽  
Amino Acid Substitution ◽  
Antigenic Site ◽  
Influenza Viruses ◽  
H3n2 Virus ◽  
Amino Acid Substitutions ◽  
Qinghai Province ◽  
Influenza H3n2

Abstract Background Influenza H3N2 virus has a faster evolution rate than other types of influenza viruses. This study was performed to better understand the molecular evolution of influenza H3N2 in Qinghai Province, China in 2017.Methods Complete sequences of eight gene segments of two influenza H3N2 isolates in 2017 in Qinghai Province were sequenced and analyzed by MEGA 6.06 software.Results Phylogenetic analysis showed that two Qinghai H3N2 isolates were relatively close to the 2016–2017 vaccine strain, 3C.2a-A/Hong Kong/4801/2014. In HA protein, compared with the 2015-2016 WHO recommended vaccine strain A/Switzerland/971 5293/2013, six amino acid substitutions were observed in epitopes A and B in Qinghai isolates in 2017, however, only two amino acid substitutions were observed in epitopes A and B in Qinghai isolates compared with the A/Hong Kong/4801/2014, which indicated 2016-2017 vaccine strain might have a better protection against the strains circulating in Qinghai Province in 2017 . Besides, amino acid substitution of K160T at the glycosylation site of HA and H75P in PB1-F2 in the two Qinghai isolates might affect the antibodies binding ability and the virulence of influenza virus. And there was no key amino acid substitution in the key sites of segment NA, M, NP, NS, PA and PB2.Conclusions The presence of several antigenic site mutations in Qinghai H3N2 isolates confirms the evolution of circulating H3N2 strains. Enhancing the surveillance of influenza epidemic by whole genome sequencing is important to monitor whether the selected vaccine strains are protective against the circulating strains in Qinghai Province.

scholarly journals Genetic diversity of influenza A viruses circulating in Bulgaria during the 2018–2019 winter season

2020 ◽  
Vol 69 (7) ◽  
pp. 986-998
Author(s):  
Neli Korsun ◽  
Rodney Daniels ◽  
Svetla Angelova ◽  
Burcu Ermetal ◽  
Iliyana Grigorova ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Influenza A ◽  
Winter Season ◽  
Vaccine Virus ◽  
Influenza Viruses ◽  
Amino Acid Substitutions ◽  
Influenza A Viruses ◽  
Antigenic Sites

Introduction. Influenza viruses evolve rapidly and change their antigenic characteristics, necessitating biannual updates of flu vaccines. Aim. The aim of this study was to characterize influenza viruses circulating in Bulgaria during the 2018/2019 season and to identify amino acid substitutions in them that might impact vaccine effectiveness. Methodology. Typing/subtyping of influenza viruses were performed using real-time Reverse Transcription-PCR (RT-PCR) and results of phylogenetic and amino acid sequence analyses of influenza strains are presented. Results. A(H1N1)pdm09 (66 %) predominated over A(H3N2) (34 %) viruses, with undetected circulation of B viruses in the 2018/2019 season. All A(H1N1)pdm09 viruses studied fell into the recently designated 6B.1A subclade with over 50 % falling in four subgroups: 6B.1A2, 6B.1A5, 6B.1A6 and 6B.1A7. Analysed A(H3N2) viruses belonged to subclades 3C.2a1b and 3C.2a2. Amino acid sequence analysis of 36 A(H1N1)pdm09 isolates revealed the presence of six–ten substitutions in haemagglutinin (HA), compared to the A/Michigan/45/2015 vaccine virus, three of which occurred in antigenic sites Sa and Cb, together with four–nine changes at positions in neuraminidase (NA), and a number of substitutions in internal proteins. HA1 D222N substitution, associated with increased virulence, was identified in two A(H1N1)pdm09 viruses. Despite the presence of several amino acid substitutions, A(H1N1)pdm09 viruses remained antigenically similar to the vaccine virus. The 28 A(H3N2) viruses characterized carried substitutions in HA, including some in antigenic sites A, B, C and E, in NA and internal protein sequences. Conclusion. The results of this study showed the genetic diversity of circulating influenza viruses and the need for continuous antigenic and molecular surveillance.

scholarly journals Accumulation of Amino Acid Substitutions Promotes Irreversible Structural Changes in the Hemagglutinin of Human Influenza AH3 Virus during Evolution

2005 ◽  
Vol 79 (10) ◽  
pp. 6472-6477 ◽  
Author(s):  
Katsuhisa Nakajima ◽  
Eri Nobusawa ◽  
Alexander Nagy ◽  
Setsuko Nakajima
Keyword(s):  
Amino Acid ◽  
Structural Changes ◽  
Single Point ◽  
Influenza Viruses ◽  
Site Directed Mutagenesis ◽  
Amino Acid Substitutions ◽  
Human Influenza ◽  
Random Mutation ◽  
Antigenic Sites ◽  
Ha Protein

ABSTRACT In order to clarify the effect of an accumulation of amino acid substitutions on the hemadsorption character of the influenza AH3 virus hemagglutinin (HA) protein, we introduced single-point amino acid changes into the HA1 domain of the HA proteins of influenza viruses isolated in 1968 (A/Aichi/2/68) and 1997 (A/Sydney/5/97) by using PCR-based random mutation or site-directed mutagenesis. These substitutions were classified as positive or negative according to their effects on the hemadsorption activity. The rate of positive substitutions was about 50% for both strains. Of 44 amino acid changes that were identical in the two strains with regard to both the substituted amino acids and their positions in the HA1 domain, 22% of the changes that were positive in A/Aichi/2/68 were negative in A/Sydney/5/97 and 27% of the changes that were negative in A/Aichi/2/68 were positive in A/Sydney/5/97. A similar discordance rate was also seen for the antigenic sites. These results suggest that the accumulation of amino acid substitutions in the HA protein during evolution promoted irreversible structural changes and therefore that antigenic changes in the H3HA protein may not be limited.

scholarly journals Molecular Characterization of Seasonal Influenza A and B from Hospitalized Patients in Thailand in 2018–2019

Viruses ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 977
Author(s):  
Kobporn Boonnak ◽  
Chayasin Mansanguan ◽  
Dennis Schuerch ◽  
Usa Boonyuen ◽  
Hatairat Lerdsamran ◽  
...  
Keyword(s):  
Amino Acid ◽  
Influenza A ◽  
Seasonal Influenza ◽  
Influenza Viruses ◽  
Surface Proteins ◽  
Antigenic Drift ◽  
Influenza B ◽  
Receptor Binding Site ◽  
Antigenic Sites ◽  
Ha Protein

Influenza viruses continue to be a major public health threat due to the possible emergence of more virulent influenza virus strains resulting from dynamic changes in virus adaptability, consequent of functional mutations and antigenic drift in surface proteins, especially hemagglutinin (HA) and neuraminidase (NA). In this study, we describe the genetic and evolutionary characteristics of H1N1, H3N2, and influenza B strains detected in severe cases of seasonal influenza in Thailand from 2018 to 2019. We genetically characterized seven A/H1N1 isolates, seven A/H3N2 isolates, and six influenza B isolates. Five of the seven A/H1N1 viruses were found to belong to clade 6B.1 and were antigenically similar to A/Switzerland/3330/2017 (H1N1), whereas two isolates belonged to clade 6B.1A1 and clustered with A/Brisbane/02/2018 (H1N1). Interestingly, we observed additional mutations at antigenic sites (S91R, S181T, T202I) as well as a unique mutation at a receptor binding site (S200P). Three-dimensional (3D) protein structure analysis of hemagglutinin protein reveals that this unique mutation may lead to the altered binding of the HA protein to a sialic acid receptor. A/H3N2 isolates were found to belong to clade 3C.2a2 and 3C.2a1b, clustering with A/Switzerland/8060/2017 (H3N2) and A/South Australia/34/2019 (H3N2), respectively. Amino acid sequence analysis revealed 10 mutations at antigenic sites including T144A/I, T151K, Q213R, S214P, T176K, D69N, Q277R, N137K, N187K, and E78K/G. All influenza B isolates in this study belong to the Victoria lineage. Five out of six isolates belong to clade 1A3-DEL, which relate closely to B/Washington/02/2009, with one isolate lacking the three amino acid deletion on the HA segment at position K162, N163, and D164. In comparison to the B/Colorado/06/2017, which is the representative of influenza B Victoria lineage vaccine strain, these substitutions include G129D, G133R, K136E, and V180R for HA protein. Importantly, the susceptibility to oseltamivir of influenza B isolates, but not A/H1N1 and A/H3N2 isolates, were reduced as assessed by the phenotypic assay. This study demonstrates the importance of monitoring genetic variation in influenza viruses regarding how acquired mutations could be associated with an improved adaptability for efficient transmission.

scholarly journals Evolution and Adaptation of the Avian H7N9 Virus into the Human Host

2020 ◽  
Vol 8 (5) ◽  
pp. 778
Author(s):  
Andrew T. Bisset ◽  
Gerard F. Hoyne
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Influenza A ◽  
Amino Acid Sequences ◽  
Influenza Viruses ◽  
Amino Acid Substitutions ◽  
Upper Respiratory Tract ◽  
Viral Polymerase ◽  
Evolutionary Changes ◽  
Avian Origin

Influenza viruses arise from animal reservoirs, and have the potential to cause pandemics. In 2013, low pathogenic novel avian influenza A(H7N9) viruses emerged in China, resulting from the reassortment of avian-origin viruses. Following evolutionary changes, highly pathogenic strains of avian influenza A(H7N9) viruses emerged in late 2016. Changes in pathogenicity and virulence of H7N9 viruses have been linked to potential mutations in the viral glycoproteins hemagglutinin (HA) and neuraminidase (NA), as well as the viral polymerase basic protein 2 (PB2). Recognizing that effective viral transmission of the influenza A virus (IAV) between humans requires efficient attachment to the upper respiratory tract and replication through the viral polymerase complex, experimental evidence demonstrates the potential H7N9 has for increased binding affinity and replication, following specific amino acid substitutions in HA and PB2. Additionally, the deletion of extended amino acid sequences in the NA stalk length was shown to produce a significant increase in pathogenicity in mice. Research shows that significant changes in transmissibility, pathogenicity and virulence are possible after one or a few amino acid substitutions. This review aims to summarise key findings from that research. To date, all strains of H7N9 viruses remain restricted to avian reservoirs, with no evidence of sustained human-to-human transmission, although mutations in specific viral proteins reveal the efficacy with which these viruses could evolve into a highly virulent and infectious, human-to-human transmitted virus.

scholarly journals MOLECULAR AND GENETIC CHARACTERISTICS OF SURFACE AND NONSTRUCTURE PROTEINS OF PANDEMIC INFLUENZA VIRUSES A(H1N1)PDM09 IN 2015-2016 EPIDEMIC SEASON

2016 ◽  
Vol 72 (2) ◽  
pp. 44-48
Author(s):  
O. Smutko ◽  
L. Radchenko ◽  
A. Mironenko
Keyword(s):  
Amino Acid ◽  
Pandemic Influenza ◽  
Influenza A ◽  
Phylogenetic Trees ◽  
Influenza Viruses ◽  
Amino Acid Substitutions ◽  
Ns1 Protein ◽  
Genetic Characteristics ◽  
Epidemic Season ◽  
Influenza A H1n1

The aim of the present study was identifying of molecular and genetic changes in hemaglutinin (HA), neuraminidase (NA) and non-structure protein (NS1) genes of pandemic influenza A(H1N1)pdm09 strains, that circulated in Ukraine during 2015-2016 epidemic season. Samples (nasopharyngeal swabs from patients) were analyzed using real-time polymerase chain reaction (RTPCR). Phylogenetic trees were constructed using MEGA 7 software. 3D structures were constructed in Chimera 1.11.2rc software. Viruses were collected in 2015-2016 season fell into genetic group 6B and in two emerging subgroups, 6B.1 and 6B.2 by gene of HA and NA. Subgroups 6B.1 and 6B.2 are defined by the following amino acid substitutions. In the NS1 protein were identified new amino acid substitutions D2E, N48S, and E125D in 2015-2016 epidemic season. Specific changes were observed in HA protein antigenic sites, but viruses saved similarity to vaccine strain. NS1 protein acquired substitution associated with increased virulence of the influenza virus.

scholarly journals Amino Acid Residue 217 in the Hemagglutinin Glycoprotein Is a Key Mediator of Avian Influenza H7N9 Virus Antigenicity

2018 ◽  
Vol 93 (1) ◽  
Author(s):  
Pengxiang Chang ◽  
Joshua E. Sealy ◽  
Jean-Remy Sadeyen ◽  
Munir Iqbal
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Immune Escape ◽  
Influenza Viruses ◽  
Single Mutation ◽  
H7n9 Virus ◽  
Avian Influenza Viruses ◽  
Antigenic Analysis ◽  
Neutralizing Capacity ◽  
High Pathogenicity

ABSTRACTAvian influenza viruses continue to evolve and acquire mutations that facilitate antigenic drift and virulence change. In 2017, low-pathogenicity H7N9 avian influenza viruses evolved to a high-pathogenicity phenotype in China. Comparative antigenic analysis of the low- and high-pathogenicity virus strains showed marked variability. In order to identify residues that may be linked to the antigenic change among the H7N9 viruses, we serially passaged the viruses in the presence of homologous ferret antiserum. Progeny viruses able to overcome the neutralizing capacity of the antiserum were sequenced. The analysis showed that the emergent immune escape viruses contained mutations A125T, A151T, and L217Q in the hemagglutinin (HA) glycoprotein as early as passage 5 and that these mutations persisted until passage 10. The results revealed that a single mutation, L217Q, in the HA of H7N9 virus led to 23- and 8-fold reductions in hemagglutination inhibition (HI) titer with ferret and chicken antisera, respectively. Further analysis showed that this change also contributed to antigenic differences between the low- and high-pathogenicity H7N9 viruses, thus playing a major role in their antigenic diversification. Therefore, evolutionary changes at amino acid position 217 in the H7N9 viruses can serve as a genetic marker for virus antigenic diversity during vaccine seed matching and selection. Thein vitroimmune escape mutant selection method used in this study could also aid in the prediction of emerging antigenic variants in naturally infected or immunized animals.IMPORTANCEAvian influenza H7N9 viruses circulating in poultry and wild birds continue to evolve and acquire important phenotypic changes. Mutations to the virus hemagglutinin (HA) glycoprotein can modulate virus antigenicity and facilitate virus escape from natural or vaccine-induced immunity. The focus of this study was to identify evolutionary markers in the HA of H7N9 that drive escape from antibody-based immunity. To achieve this, we propagated low-pathogenicity H7N9 virus in the presence of polyclonal antiserum derived from ferrets infected with the same strain of virus (homologous antiserum). This selection process was repeated 10 times. The HA gene sequences of viruses recovered after the fifth passage showed that the viruses readily acquired mutations at three different amino acid positions (A125T, A151T, and L217Q). Further functional analysis of these mutations confirmed that the mutation at residue 217 in the HA was responsible for mediating changes to the immunological properties of the H7N9 virus.

scholarly journals Epitope Mapping of the Hemagglutinin Molecule of a Highly Pathogenic H5N1 Influenza Virus by Using Monoclonal Antibodies

2007 ◽  
Vol 81 (23) ◽  
pp. 12911-12917 ◽  
Author(s):  
Nikolai V. Kaverin ◽  
Irina A. Rudneva ◽  
Elena A. Govorkova ◽  
Tatyana A. Timofeeva ◽  
Aleksandr A. Shilov ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Amino Acid ◽  
H5n1 Virus ◽  
Antigenic Site ◽  
H5n1 Influenza Virus ◽  
Highly Pathogenic ◽  
H5n1 Influenza ◽  
Antigenic Sites ◽  
Escape Mutants ◽  
Pathogenic H5n1

ABSTRACT We mapped the hemagglutinin (HA) antigenic epitopes of a highly pathogenic H5N1 influenza virus on the three-dimensional HA structure by characterizing escape mutants of a recombinant virus containing A/Vietnam/1203/04 (H5N1) ΔHA and neuraminidase genes in the genetic background of A/Puerto Rico/8/34 (H1N1) virus. The mutants were selected with a panel of eight anti-HA monoclonal antibodies (MAbs), seven to A/Vietnam/1203/04 (H5N1) virus and one to A/Chicken/Pennsylvania/8125/83 (H5N2) virus, and the mutants’ HA genes were sequenced. The amino acid changes suggested three MAb groups: four MAbs reacted with the complex epitope comprising parts of the antigenic site B of H3 HA and site Sa of H1 HA, two MAbs reacted with the epitope corresponding to the antigenic site A in H3 HA, and two MAbs displayed unusual behavior: each recognized amino acid changes at two widely separate antigenic sites. Five changes were detected in amino acid residues not previously reported as changed in H5 escape mutants, and four others had substitutions not previously described. The HA antigenic structure differs substantially between A/Vietnam/1203/04 (H5N1) virus and the low-pathogenic A/Mallard/Pennsylvania/10218/84 (H5N2) virus we previously characterized (N. V. Kaverin et al., J. Gen. Virol. 83:2497-2505, 2002). The hemagglutination inhibition reactions of the MAbs with recent highly pathogenic H5N1 viruses were consistent with the antigenic-site amino acid changes but not with clades and subclades based on H5 phylogenetic analysis. These results provide information on the recognition sites of the MAbs widely used to study H5N1 viruses and demonstrate the involvement of the HA antigenic sites in the evolution of highly pathogenic H5N1 viruses, findings that can be critical for characterizing pathogenesis and vaccine design.

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