scholarly journals The R251K Substitution in Viral Protein PB2 Increases Viral Replication and Pathogenicity of Eurasian Avian-like H1N1 Swine Influenza Viruses

Viruses ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 52 ◽  
Author(s):  
Mengkai Cai ◽  
Ruting Zhong ◽  
Chenxiao Qin ◽  
Zhiqing Yu ◽  
Xiaoyan Wen ◽  
...  
Keyword(s):  
Amino Acid ◽  
Reverse Genetics ◽  
H1n1 Virus ◽  
Swine Influenza ◽  
Polymerase Activity ◽  
Human Infection ◽  
Influenza Viruses ◽  
Epidemiological Surveillance ◽  
Single Amino Acid ◽  
Swine Industry

The Eurasian avian-like swine (EA) H1N1 virus has affected the Chinese swine industry, and human infection cases have been reported occasionally. However, little is known about the pathogenic mechanism of EA H1N1 virus. In this study, we compared the mouse pathogenicity of A/swine/Guangdong/YJ4/2014 (YJ4) and A/swine/Guangdong/MS285/2017 (MS285) viruses, which had similar genotype to A/Hunan/42443/2015 (HuN-like). None of the mice inoculated with 106 TCID50 of YJ4 survived at 7 days post infection, while the survival rate of the MS285 group was 100%. Therefore, a series of single fragment reassortants in MS285 background and two rescued wild-type viruses were generated by using the reverse genetics method, and the pathogenicity analysis revealed that the PB2 gene contributed to the high virulence of YJ4 virus. Furthermore, there were 11 amino acid differences in PB2 between MS285 and YJ4 identified by sequence alignment, and 11 single amino acid mutant viruses were generated in the MS285 background. We found that the R251K mutation significantly increased the virulence of MS285 in mice, contributed to high polymerase activity and enhanced viral genome transcription and replication. These results indicate that PB2-R251K contributes to the virulence of the EA H1N1 virus and provide new insight into future molecular epidemiological surveillance strategies.

scholarly journals The substitution of T271A in PB2 protein could enhance the infectivity and pathogenicity of Eurasian avian-like H1N1 swine influenza viruses in mice

2020 ◽  
Author(s):  
Zhaomin Feng ◽  
Wenfei Zhu ◽  
Lijuan Zhou ◽  
Yongkun Chen ◽  
Xiyan Li ◽  
...  
Keyword(s):  
H1n1 Virus ◽  
Swine Influenza ◽  
Polymerase Activity ◽  
Influenza Viruses ◽  
Pandemic H1n1 ◽  
Recombinant Viruses ◽  
Avian Cell ◽  
Molecular Makers

Abstract BackgroundCurrently, Eurasian avian-like H1N1 (EA H1N1) swine influenza viruses (SIVs) are widely prevalent in pigs in China, with sporadic human cases reported as well. As one of the key molecular makers detected in avian H5N1 and H 7N9 viruses and pandemic H1N1 2009 virus, contributions of T271A in PB2 protein to the EA H1N1 viruses are still unknown. In this study, we investigated the effects of residue 271 in PB2 protein on the viral properties of EA H1N1 viruses.MethodsInfectivity, replication, virulence and pathogenicity of the recombinant viruses containing A or T in position 271 in PB2 protein were studied in cells and mice.ResultsThe results showed that the substitution PB2-T271A increased the viral replication in mammalian and avian cell lines. In addition, the mutation enhanced the viral infectivity, virulence and pathogenicity in mice. The viral titers of lung tissue in the rgHuN271A virus were higher than that of the rgHuN271T at 1, 4, and 7 dpi. The MID50 of the rgHuN271A and rgHuN271T virus were 101.1 TCID50 and 101.9 TCID50, respectively. Besides, the substitution of PB2-T271A enhanced the viral polymerase activity in mammalian cells.ConclusionsThe pathogenicity and replication of EA H1N1 virus containing 271A in PB2 protein were higher than the EA H1N1 virus containing 271T in PB2 protein in vivo and in vitro. Therefore, the PB2-T271A mutation should be continually monitored in influenza viruses circulating in pigs and humans.

scholarly journals Molecular Basis of Replication of Duck H5N1 Influenza Viruses in a Mammalian Mouse Model

2005 ◽  
Vol 79 (18) ◽  
pp. 12058-12064 ◽  
Author(s):  
Zejun Li ◽  
Hualan Chen ◽  
Peirong Jiao ◽  
Guohua Deng ◽  
Guobin Tian ◽  
...  
Keyword(s):  
Amino Acid ◽  
Host Range ◽  
Reverse Genetics ◽  
Southern China ◽  
Single Gene ◽  
Influenza Viruses ◽  
Single Amino Acid ◽  
Species Barrier ◽  
H5n1 Influenza ◽  
The One

ABSTRACT We recently analyzed a series of H5N1 viruses isolated from healthy ducks in southern China since 1999 and found that these viruses had progressively acquired the ability to replicate and cause disease in mice. In the present study, we explored the genetic basis of this change in host range by comparing two of the viruses that are genetically similar but differ in their ability to infect mice and have different pathogenicity in mice. A/duck/Guangxi/22/2001 (DKGX/22) is nonpathogenic in mice, whereas A/duck/Guangxi/35/2001 (DKGX/35) is highly pathogenic. We used reverse genetics to create a series of single-gene recombinants that contained one gene from DKGX/22 and the remaining seven gene segments from DKGX/35. We find that the PA, NA, and NS genes of DKGX/22 could attenuate DKGX/35 virus to some extent, but PB2 of DKGX/22 virus attenuated the DKGX/35 virus dramatically, and an Asn-to-Asp substitution at position 701 of PB2 plays a key role in this function. Conversely, of the recombinant viruses in the DKGX/22 background, only the one that contains the PB2 gene of DKGX/35 was able to replicate in mice. A single amino acid substitution (Asp to Asn) at position 701 of PB2 enabled DKGX/22 to infect and become lethal for mice. These results demonstrate that amino acid Asn 701 of PB2 is one of the important determinants for this avian influenza virus to cross the host species barrier and infect mice, though the replication and lethality of H5N1 influenza viruses involve multiple genes and may result from a constellation of genes. Our findings may help to explain the expansion of the host range and lethality of the H5N1 influenza viruses to humans.

scholarly journals Erratum for Xu et al., “A Single Amino Acid at Position 431 of the PB2 Protein Determines the Virulence of H1N1 Swine Influenza Viruses in Mice”

2020 ◽  
Vol 94 (13) ◽  
Author(s):  
Chengzhi Xu ◽  
Bangfeng Xu ◽  
Yunpu Wu ◽  
Shiman Yang ◽  
Yunhui Jia ◽  
...  
Keyword(s):  
Amino Acid ◽  
Swine Influenza ◽  
Influenza Viruses ◽  
Single Amino Acid

scholarly journals A Single Amino Acid at Position 431 of the PB2 Protein Determines the Virulence of H1N1 Swine Influenza Viruses in Mice

2020 ◽  
Vol 94 (8) ◽  
Author(s):  
Chengzhi Xu ◽  
Bangfeng Xu ◽  
Yunpu Wu ◽  
Shiman Yang ◽  
Yunhui Jia ◽  
...  
Keyword(s):  
Amino Acid ◽  
Genetic Basis ◽  
Critical Role ◽  
Swine Influenza ◽  
Influenza Viruses ◽  
Liaoning Province ◽  
Single Amino Acid ◽  
Genetic Determinants ◽  
Viral Virulence ◽  
Swine Population

The frequent reassortment among different influenza viruses in pigs adds complexity to the epidemiology of swine influenza. The diverse viral virulence phenotypes underline the need to investigate the possible genetic determinants for evaluating the pandemic potential to human public health. Here, we found that multiple genotypes of influenza viruses cocirculate in the swine population in Liaoning Province, China. Furthermore, we pinpointed a single amino acid at position 431 in the PB2 protein which plays a critical role in the virulence of H1N1 viruses in mice and found that the alteration of viral polymerase activities is the cause of the different virulence. Our study further indicated that the virulence of influenza virus is a polygenic trait, and the newly identified virulence-related residue in the PB2 provides important information for broadening knowledge on the genetic basis of viral virulence of influenza viruses.

scholarly journals A Single-Amino-Acid Substitution at Position 225 in Hemagglutinin Alters the Transmissibility of Eurasian Avian-Like H1N1 Swine Influenza Virus in Guinea Pigs

2017 ◽  
Vol 91 (21) ◽  
Author(s):  
Zeng Wang ◽  
Huanliang Yang ◽  
Yan Chen ◽  
Shiyu Tao ◽  
Liling Liu ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Amino Acid ◽  
Glutamic Acid ◽  
Guinea Pigs ◽  
Swine Influenza Virus ◽  
Virus Transmission ◽  
Swine Influenza ◽  
Influenza Viruses ◽  
Single Amino Acid ◽  
Efficient Transmission

ABSTRACT Efficient transmission from human to human is the prerequisite for an influenza virus to cause a pandemic; however, the molecular determinants of influenza virus transmission are still largely unknown. In this study, we explored the molecular basis for transmission of Eurasian avian-like H1N1 (EAH1N1) swine influenza viruses by comparing two viruses that are genetically similar but differ in their transmissibility in guinea pigs: the A/swine/Guangxi/18/2011 virus (GX/18) is highly transmissible by respiratory droplet in guinea pigs, whereas the A/swine/Heilongjiang/27/2012 virus (HLJ/27) does not transmit in this animal model. We used reverse genetics to generate a series of reassortants and mutants in the GX/18 background and tested their transmissibility in guinea pigs. We found that a single-amino-acid substitution of glycine (G) for glutamic acid (E) at position 225 (E225G) in the HA1 protein completely abolished the respiratory droplet transmission of GX/18, whereas the substitution of E for G at the same position (G225E) in HA1 enabled HLJ/27 to transmit in guinea pigs. We investigated the underlying mechanism and found that viruses bearing 225E in HA1 replicated more rapidly than viruses bearing 225G due to differences in assembly and budding efficiencies. Our study indicates that the amino acid 225E in HA1 plays a key role in EAH1N1 swine influenza virus transmission and provides important information for evaluating the pandemic potential of field influenza virus strains. IMPORTANCE Efficient transmission among humans is a prerequisite for a novel influenza virus to cause a human pandemic. Transmissibility of influenza viruses is a polygenic trait, and understanding the genetic determinants for transmissibility will provide useful insights for evaluating the pandemic potential of influenza viruses in the field. Several amino acids in the hemagglutinin (HA) protein of influenza viruses have been shown to be important for transmissibility, usually by increasing virus affinity for human-type receptors. In this study, we explored the genetic basis of the transmissibility difference between two Eurasian avian-like H1N1 (EAH1N1) swine influenza viruses in guinea pigs and found that the amino acid glutamic acid at position 225 in the HA1 protein plays a critical role in the transmission of EAH1N1 virus by increasing the efficiency of viral assembly and budding.

Variation in the HA antigenicity of A(H1N1)pdm09-related swine influenza viruses

2021 ◽  
Author(s):  
Ahmed Magdy Khalil ◽  
Reiko Yoshida ◽  
Tatsunori Masatani ◽  
Ayato Takada ◽  
Makoto Ozawa
Keyword(s):  
Genetic Diversity ◽  
Amino Acid ◽  
Influenza A ◽  
Influenza Pandemic ◽  
Gene Segment ◽  
Swine Influenza ◽  
Influenza Viruses ◽  
Single Amino Acid ◽  
Ha Gene ◽  
The Impact

Since the influenza pandemic in 2009, the causative agent ‘A(H1N1)pdm09 virus’, has been circulating in both human and swine populations. Although phylogenetic analyses of the haemagglutinin (HA) gene segment have revealed broader genetic diversity of A(H1N1)pdm09-related swine influenza A viruses (swIAVs) compared with human A(H1N1)pdm09 viruses, it remains unclear whether the genetic diversity reflects the antigenic differences in HA. To assess the impact of the diversity of the HA gene of A(H1N1)pdm09-related swIAVs on HA antigenicity, we characterized 12 swIAVs isolated in Japan from 2013 to 2018. We used a ferret antiserum and a panel of anti-HA mouse monoclonal antibodies (mAbs) raised against an early A(H1N1)pdm09 isolate. The neutralization assay with the ferret antiserum revealed that five of the 12 swIAVs were significantly different in their HA antigenicity from the early A(H1N1)pdm09 isolate. The mAbs also showed differential neutralization patterns depending on the swIAV strains. In addition, the single amino acid substitution at position 190 of HA, which was found in one of the five antigenically different swIAVs but not in human isolates, was shown to be one of the critical determinants for the antigenic difference of swIAV HAs. Two potential N-glycosylation sites at amino acid positions 185 and 276 of the HA molecule were identified in two antigenically different swIAVs. These results indicated that the genetic diversity of HA in the A(H1N1)pdm09-related swIAVs is associated with their HA antigenic variation. Our findings highlighted the need for surveillance to monitor the emergence of swIAV antigenic variants with public health importance.

scholarly journals Prevalent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection

2020 ◽  
Vol 117 (29) ◽  
pp. 17204-17210 ◽  
Author(s):  
Honglei Sun ◽  
Yihong Xiao ◽  
Jiyu Liu ◽  
Dayan Wang ◽  
Fangtao Li ◽  
...  
Keyword(s):  
Influenza Virus ◽  
H1n1 Virus ◽  
Swine Influenza Virus ◽  
Swine Influenza ◽  
Airway Epithelial Cells ◽  
Cross Reactivity ◽  
Human Infection ◽  
Influenza Viruses ◽  
Progeny Virus ◽  
Genotype 4

Pigs are considered as important hosts or “mixing vessels” for the generation of pandemic influenza viruses. Systematic surveillance of influenza viruses in pigs is essential for early warning and preparedness for the next potential pandemic. Here, we report on an influenza virus surveillance of pigs from 2011 to 2018 in China, and identify a recently emerged genotype 4 (G4) reassortant Eurasian avian-like (EA) H1N1 virus, which bears 2009 pandemic (pdm/09) and triple-reassortant (TR)-derived internal genes and has been predominant in swine populations since 2016. Similar to pdm/09 virus, G4 viruses bind to human-type receptors, produce much higher progeny virus in human airway epithelial cells, and show efficient infectivity and aerosol transmission in ferrets. Moreover, low antigenic cross-reactivity of human influenza vaccine strains with G4 reassortant EA H1N1 virus indicates that preexisting population immunity does not provide protection against G4 viruses. Further serological surveillance among occupational exposure population showed that 10.4% (35/338) of swine workers were positive for G4 EA H1N1 virus, especially for participants 18 y to 35 y old, who had 20.5% (9/44) seropositive rates, indicating that the predominant G4 EA H1N1 virus has acquired increased human infectivity. Such infectivity greatly enhances the opportunity for virus adaptation in humans and raises concerns for the possible generation of pandemic viruses.

scholarly journals A Single Amino Acid at Position 158 in Hemagglutinin Affects the Antigenic Property of Eurasian Avian-like H1N1 Swine Influenza Viruses

2021 ◽  
Author(s):  
Zeng Wang ◽  
Yan Chen ◽  
Huayuan Chen ◽  
Fei Meng ◽  
Shiyu Tao ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Amino Acid ◽  
Antigenic Variation ◽  
Swine Influenza ◽  
Antigenic Property ◽  
Cross Reactivity ◽  
Influenza Viruses ◽  
Antigenic Drift ◽  
Single Amino Acid ◽  
Ha Protein

Influenza viruses have been posing a great threat to public health and animal industry. The developed vaccines have been widely used to reduce the risk of potential pandemic; however, the ongoing antigenic drift makes influenza virus escape from host immune response and hampers vaccine efficacy. Until now, the genetic basis of antigenic variation remains largely unknown. In this study, we used A/swine/Guangxi/18/2011 (GX/18) and A/swine/Guangdong/104/2013 (GD/104) as models to explore the molecular determinant for antigenic variation of Eurasian avian-like H1N1 (EA H1N1) swine influenza viruses (SIVs), and found that the GD/104 virus exhibited 32~64-fold lower antigenic cross-reactivity with antibodies against GX/18 virus. Therefore, we generated polyclonal antibodies against GX/18 or GD/104 virus and a monoclonal antibody (mAb), named mAb102-95, targeted to the hemagglutinin (HA) protein of GX/18 virus, and found that a single amino acid substitution at position 158 in HA protein substantially altered the antigenicity of virus. The reactivity of GX/18 virus containing G158E mutation with the mAb102-95 decreased 8-fold than that of the parental strain. Contrarily, the reactivity of GD/104 virus bearing E158G mutation with the mAb102-95 increased by 32 times as compared with that of the parental virus. Structural analysis showed that the amino acid mutation from G to E was accompanied with the R group changing from -H to -(CH ) -COOH. The induced steric effect and increased hydrophilicity of HA protein surface jointly contributed to the antigenic drift of EA H1N1 SIVs. Our study provides experimental evidence that G158E mutation in HA protein affects the antigenic property of EA H1N1 SIVs, and widens our horizon on the antigenic drift of influenza virus.

scholarly journals A Single Point Mutation, Asn16→Lys, Dictates the Temperature-Sensitivity of the Reovirus tsG453 Mutant

Viruses ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 289
Author(s):  
Kathleen K. M. Glover ◽  
Danica M. Sutherland ◽  
Terence S. Dermody ◽  
Kevin M. Coombs
Keyword(s):  
Amino Acid ◽  
Temperature Sensitivity ◽  
Reverse Genetics ◽  
Core Protein ◽  
Single Point ◽  
Single Amino Acid ◽  
Single Point Mutation ◽  
Temperature Sensitive ◽  
Amino Acid Substitutions ◽  
Gene Encoding

Studies of conditionally lethal mutants can help delineate the structure-function relationships of biomolecules. Temperature-sensitive (ts) mammalian reovirus (MRV) mutants were isolated and characterized many years ago. Two of the most well-defined MRV ts mutants are tsC447, which contains mutations in the S2 gene encoding viral core protein σ2, and tsG453, which contains mutations in the S4 gene encoding major outer-capsid protein σ3. Because many MRV ts mutants, including both tsC447 and tsG453, encode multiple amino acid substitutions, the specific amino acid substitutions responsible for the ts phenotype are unknown. We used reverse genetics to recover recombinant reoviruses containing the single amino acid polymorphisms present in ts mutants tsC447 and tsG453 and assessed the recombinant viruses for temperature-sensitivity by efficiency-of-plating assays. Of the three amino acid substitutions in the tsG453 S4 gene, Asn16-Lys was solely responsible for the tsG453ts phenotype. Additionally, the mutant tsC447 Ala188-Val mutation did not induce a temperature-sensitive phenotype. This study is the first to employ reverse genetics to identify the dominant amino acid substitutions responsible for the tsC447 and tsG453 mutations and relate these substitutions to respective phenotypes. Further studies of other MRV ts mutants are warranted to define the sequence polymorphisms responsible for temperature sensitivity.

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