Mammalian-adaptive mutation NP-Q357K in Eurasian H1N1 Swine Influenza viruses determines the virulence phenotype in mice.
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ABSTRACT:
SUBMITTER: Zhu W
PROVIDER: S-EPMC6609330 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The continuous antigenic variation of influenza A viruses remains a major hurdle for vaccine selection; however, the molecular determinants and mechanisms of antigenic change remain largely unknown. In this study, two escape mutants were generated by serial passages of the Eurasian avian-like H1N1 swine influenza virus (EA H1N1 SIV) A/swine/Henan/11/2005 (HeN11) in the presence of two neutralizing monoclonal antibodies (mAbs) against the hemagglutinin (HA) protein, which were designated HeN11-2B6-P5 and HeN11-4C7-P8, respectively. The HeN11-2B6-P5 mutant simultaneously harbored the N190D and I230M substitutions in HA, whereas HeN11-4C7-P8 harbored the M269R substitution in HA (H3 numbering). The effects of each of these substitutions on viral antigenicity were determined by measuring the neutralization and hemagglutination inhibition (HI) titers with mAbs and polyclonal sera raised against the representative viruses. The results indicate that residues 190 and 269 are key determinants of viral antigenic variation. In particular, the N190D mutation had the greatest antigenic impact, as determined by the HI assay. Further studies showed that both HeN11-2B6-P5 and HeN11-4C7-P8 maintained the receptor-binding specificity of the parent virus, although the single mutation N190D decreased the binding affinity for the human-type receptor. The replicative ability in vitro of HeN11-2B6-P5 was increased, whereas that of HeN11-4C7-P8 was decreased. These findings extend our understanding of the antigenic evolution of influenza viruses under immune pressure and provide insights into the functional effects of amino acid substitutions near the receptor-binding site and the interplay among receptor binding, viral replication, and antigenic drift. IMPORTANCE The antigenic changes that occur continually in the evolution of influenza A viruses remain a great challenge for the effective control of disease outbreaks. Here, we identified three amino acid substitutions (at positions 190, 230, and 269) in the HA of EA H1N1 SIVs that determine viral antigenicity and result in escape from neutralizing monoclonal antibodies. All three of these substitutions have emerged in nature. Of note, residues 190 and 230 have synergistic effects on receptor binding and antigenicity. Our findings provide a better understanding of the functional effects of amino acid substitutions in HA and their consequences for the antigenic drift of influenza viruses.
| S-EPMC9400474 | biostudies-literature
Project description:Eurasian avian-like H1N1 (EA H1N1) swine influenza virus (SIV) outside European countries was first detected in Hong Kong Special Administrative Region (Hong Kong, SAR) of China in 2001. Afterwards, EA H1N1 SIVs have become predominant in pig population in this country. However, the epidemiology and genotypic diversity of EA H1N1 SIVs in China are still unknown. Here, we collected the EA H1N1 SIVs sequences from China between 2001 and 2018 and analyzed the epidemic and phylogenic features, and key molecular markers of these EA H1N1 SIVs. Our results showed that EA H1N1 SIVs distributed in nineteen provinces/municipalities of China. After a long-time evolution and transmission, EA H1N1 SIVs were continuously reassorted with other co-circulated influenza viruses, including 2009 pandemic H1N1 (A(H1N1)pdm09), and triple reassortment H1N2 (TR H1N2) influenza viruses, generated 11 genotypes. Genotype 3 and 5, both of which were the reassortments among EA H1N1, A(H1N1)pdm09 and TR H1N2 viruses with different origins of M genes, have become predominant in pig population. Furthermore, key molecular signatures were identified in EA H1N1 SIVs. Our study has drawn a genotypic diversity image of EA H1N1 viruses, and could help to evaluate the potential risk of EA H1N1 for pandemic preparedness and response.
| S-EPMC7973347 | biostudies-literature
Project description:Pigs are important intermediate hosts for generating novel influenza viruses. The Eurasian avian-like H1N1 (EAH1N1) swine influenza viruses (SIVs) have circulated in pigs since 1979, and human cases associated with EAH1N1 SIVs have been reported in several countries. However, the biologic properties of EAH1N1 SIVs are largely unknown. Here, we performed extensive influenza surveillance in pigs in China and isolated 228 influenza viruses from 36,417 pigs. We found that 139 of the 228 strains from pigs in 10 provinces in China belong to the EAH1N1 lineage. These viruses formed five genotypes, with two distinct antigenic groups, represented by A/swine/Guangxi/18/2011 and A/swine/Guangdong/104/2013, both of which are antigenically and genetically distinct from the current human H1N1 viruses. Importantly, the EAH1N1 SIVs preferentially bound to human-type receptors, and 9 of the 10 tested viruses transmitted in ferrets by respiratory droplet. We found that 3.6% of children (≤10 y old), 0% of adults, and 13.4% of elderly adults (≥60 y old) had neutralization antibodies (titers ≥40 in children and ≥80 in adults) against the EAH1N1 A/swine/Guangxi/18/2011 virus, but none of them had such neutralization antibodies against the EAH1N1 A/swine/Guangdong/104/2013 virus. Our study shows the potential of EAH1N1 SIVs to transmit efficiently in humans and suggests that immediate action is needed to prevent the efficient transmission of EAH1N1 SIVs to humans.
| S-EPMC4720320 | biostudies-literature
Project description:Genetic reassortments occurred continuously among multiple subtypes or genotypes of influenza viruses prevalent in pigs. Of note, some reassortant viruses bearing the internal genes of the 2009 pandemic H1N1 (2009/H1N1) virus sporadically caused human infection, which highlights their potential threats to human public health. In this study, we performed phylogenetic analysis on swine influenza viruses (SIVs) circulating in Liaoning Province, China. A total of 22 viruses, including 18 H1N1 and 4 H1N2 viruses, were isolated from 5,750 nasal swabs collected from pigs in slaughterhouses from 2014 to 2016. H1N1 viruses formed four genotypes, which included Eurasian avian-like H1N1 (EA H1N1) and double/triple reassortant H1N1 derived from EA H1N1, 2009/H1N1, and triple reassortant H1N2 (TR H1N2) viruses. H1N1 SIVs with different genotypes and even those within the same genotypes represented different pathogenicities in mice. We further characterized two naturally isolated H1N1 SIVs that had similar viral genomes but differed substantially in their virulence in mice and found that a single amino acid at position 431 in the basic polymerase 2 (PB2) protein significantly affected the viral replication capacity and virulence of these two viruses. Taken together, our findings revealed the diverse genomic origins and virulence of the SIVs prevalent in Liaoning Province during 2014 to 2016, which highlights that continuous surveillance is essential to monitor the evolution of SIVs. We identified a naturally occurring amino acid mutation in the PB2 protein of H1N1 SIVs that impacts the viral replication and virulence in mice by altering the viral polymerase activity.IMPORTANCE 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.
| S-EPMC7108842 | biostudies-literature
Project description:Several zoonotic influenza A viruses detected in humans contain genes derived from avian H9N2 subtypes. We uncovered a Eurasian avian-like H1N1 swine influenza virus with polymerase basic 1 and matrix gene segments derived from the H9N2 subtype, suggesting that H9N2 viruses are infecting pigs and reassorting with swine influenza viruses in China.
| S-EPMC9239857 | biostudies-literature
Project description:The 2009 pandemic H1N1 virus (pH1N1) was derived through reassortment of North American triple reassortant and Eurasian avian-like swine influenza viruses (SIVs). To date, when, how and where the pH1N1 arose is not understood. To investigate viral reassortment, we coinfected cell cultures and a group of pigs with or without preexisting immunity with a Eurasian H1N1 virus, A/Swine/Spain/53207/2004 (SP04), and a North American triple reassortant H1N1 virus, A/Swine/Kansas/77778/2007 (KS07). The infected pigs were cohoused with one or two groups of contact animals to investigate viral transmission. In coinfected MDCK or PK15 continuous cell lines with KS07 and SP04 viruses, more than 20 different reassortant viruses were found. In pigs without or with preexisting immunity (immunized with commercial inactivated swine influenza vaccines) and coinfected with both viruses, six or seven reassortant viruses, as well as the parental viruses, were identified in bronchoalveolar lavage fluid samples from the lungs. Interestingly, only one or two viruses transmitted to and were detected in contact animals. No reassortant containing a gene constellation similar to that of pH1N1 virus was found in either coinfected cells or pigs, indicating that the reassortment event that resulted in the generation of this virus is a rare event that likely involved specific viral strains and/or a favorable, not-yet-understood environment. IMPORTANCE The 2009 pandemic-like H1N1 virus could not be reproduced either in cell cultures or in pigs coinfected with North American triple reassortant H1N1 and Eurasian H1N1 swine influenza viruses. This finding suggests that the generation of the 2009 pandemic H1N1 virus by reassortment was a rare event that likely involved specific viral strains and unknown factors. Different reassortant viruses were detected in coinfected pigs with and without preexisting immunity, indicating that host immunity plays a relevant role in driving viral reassortment of influenza A virus.
| S-EPMC3952159 | biostudies-literature
Project description:ObjectivesTo examine cross-reactivity between hemagglutinin (HA) derived from A/California/7/09 (CA/09) virus and that derived from representative Eurasian "avian-like" (EA) H1N1 swine viruses isolated in Italy between 1999 and 2008 during virological surveillance in pigs.DesignModified vaccinia virus Ankara (MVA) expressing the HA gene of CA/09 virus (MVA-HA-CA/09) was used as a vaccine to investigate cross-protective immunity against H1N1 swine viruses in mice.SampleTwo classical swine H1N1 (CS) viruses and four representative EA-like H1N1 swine viruses previously isolated during outbreaks of respiratory disease in pigs on farms in Northern Italy were used in this study.SettingFemale C57BL/6 mice were vaccinated with MVA/HA/CA/09 and then challenged intranasally with H1N1 swine viruses.Main outcome measuresCross-reactive antibody responses were determined by hemagglutination- inhibition (HI) and virus microneutralizing (MN) assays of sera from MVA-vaccinated mice. The extent of protective immunity against infection with H1N1 swine viruses was determined by measuring lung viral load on days 2 and 4 post-challenge.Results and conclusionsSystemic immunization of mice with CA/09-derived HA, vectored by MVA, elicited cross-protective immunity against recent EA-like swine viruses. This immune protection was related to the levels of cross-reactive HI antibodies in the sera of the immunized mice and was dependent on the similarity of the antigenic site Sa of H1 HAs. Our findings suggest that the herd immunity elicited in humans by the pandemic (H1N1) 2009 virus could limit the transmission of recent EA-like swine HA genes into the influenza A virus gene pool in humans.
| S-EPMC4181486 | biostudies-literature
Project description: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.
| S-EPMC7019279 | biostudies-literature
Project description:Swine have often been considered as a mixing vessel for different influenza strains. In order to assess their role in more detail, we undertook a retrospective sequencing study to detect and characterize the reassortants present in European swine and to estimate the rate of reassortment between H1N1, H1N2 and H3N2 subtypes with Eurasian (avian-like) internal protein-coding segments. We analysed 69 newly obtained whole genome sequences of subtypes H1N1-H3N2 from swine influenza viruses sampled between 1982 and 2008, using Illumina and 454 platforms. Analyses of these genomes, together with previously published genomes, revealed a large monophyletic clade of Eurasian swine-lineage polymerase segments containing H1N1, H1N2 and H3N2 subtypes. We subsequently examined reassortments between the haemagglutinin and neuraminidase segments and estimated the reassortment rates between lineages using a recently developed evolutionary analysis method. High rates of reassortment between H1N2 and H1N1 Eurasian swine lineages were detected in European strains, with an average of one reassortment every 2-3 years. This rapid reassortment results from co-circulating lineages in swine, and in consequence we should expect further reassortments between currently circulating swine strains and the recent swine-origin H1N1v pandemic strain.
| S-EPMC3542128 | biostudies-literature
Project description:Host switch events of influenza A viruses (IAVs) continuously pose a zoonotic threat to humans. In 2013, swine-origin H1N1 IAVs emerged in dogs soon after they were detected in swine in the Guangxi province of China. This host switch was followed by multiple reassortment events between these H1N1 and previously circulating H3N2 canine IAVs (IAVs-C) in dogs. To evaluate the phenotype of these newly identified viruses, we characterized three swine-origin H1N1 IAVs-C and one reassortant H1N1 IAV-C. We found that H1N1 IAVs-C predominantly bound to human-type receptors, efficiently transmitted via direct contact in guinea pigs and replicated in human lung cells. Moreover, the swine-origin H1N1 IAVs-C were lethal in mice and were transmissible by respiratory droplets in guinea pigs. Importantly, sporadic human infections with these viruses have been detected, and preexisting immunity in humans might not be sufficient to prevent infections with these new viruses. Our results show the potential of H1N1 IAVs-C to infect and transmit in humans, suggesting that these viruses should be closely monitored in the future.
| S-EPMC7011970 | biostudies-literature