Characterization of a newly emerged genetic cluster of H1N1 and H1N2 swine influenza virus in the United States

Virus and Prion Diseases of Livestock Research Unit, National Animal Disease Center, USDA-ARS, 2300 Dayton Road, Ames, IA 50010, USA.
Virus Genes (Impact Factor: 1.58). 08/2009; 39(2):176-85. DOI: 10.1007/s11262-009-0386-6
Source: PubMed


H1 influenza A viruses that were distinct from the classical swine H1 lineage were identified in pigs in Canada in 2003–2004; antigenic and genetic characterization identified the hemagglutinin (HA) as human H1 lineage. The viruses identified in Canadian pigs were human lineage in entirety or double (human–swine) reassortants. Here, we report the whole genome sequence analysis of four human-like H1 viruses isolated from U.S. swine in 2005 and 2007. All four isolates were characterized as triple reassortants with an internal gene constellation similar to contemporary U.S. swine influenza virus (SIV), with HA and neuraminidase (NA) most similar to human influenza virus lineages. A 2007 human-like H1N1 was evaluated in a pathogenesis and transmission model and compared to a 2004 reassortant H1N1 SIV isolate with swine lineage HA and NA. The 2007 isolate induced disease typical of influenza virus and was transmitted to contact pigs; however, the kinetics and magnitude differed from the 2004 H1N1 SIV. This study indicates that the human-like H1 SIV can efficiently replicate and transmit in the swine host and now co-circulates with contemporary SIVs as a distinct genetic cluster of H1 SIV.

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Available from: Wenjun ma, Jul 08, 2014
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    • "Influenza A virus (FLUAV) infection is an acute highly contagious respiratory disease which affects swine and other species, including human (Vincent et al., 2014). In pigs, the disease is caused by viral subtypes H1N1, H3N2, H1N2 (Van Reeth et al., 2008; Vincent et al., 2009) and by pandemic H1N1 (H1N1pdm), that circulates in pig herds since 2009 (Howden et al., 2009). Although Brazil's pork exports and production are 4th in the world, very few and scattered information about FLUAV infection (Cunha et al., 1978; Rajao et al., 2013) before H1N1pdm (Schaefer et al., 2011) is available. "
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    ABSTRACT: Influenza A virus (FLUAV) infections are endemic in pork producing countries worldwide but in Brazil it was not considered an important pathogen in pigs. Since the emergence of 2009 pandemic H1N1 (H1N1pdm) FLUAV, many outbreaks of respiratory disease were observed in pig herds. The aim of this study was to evaluate FLUAV infection in swine in 48 pig farms located in seven Brazilian states with previous reports of influenza-like signs by clinical, serological and virological cross-sectional studies. Serological results showed that pigs from all farms had anti-influenza antibodies by NP-ELISA. Antibodies to H3N2, H1N2 and H1N1pdm were detected by HI in pigs from 24 farms. Co-infection with two or more FLUAV subtypes was detected in pigs in seven of those 24 farms. Detection of FLUAV in nasal swabs and oral fluids by RT-qPCR indicated a global concordance >81% for the two biological samples. Moreover, our results show that H1N1pdm, H1N2 and H3N2 viruses are widespread in Brazilian pig herds. The monitoring of FLUAV emergence and evolution in pigs is urgent, as well the study of the pathogenesis of Brazilian isolates, aiming to control influenza in pigs.
    Full-text · Article · Sep 2015 · Veterinary Microbiology
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    • "The starting tree was generated under parsimony methods, with the best-scoring tree and statistical support values obtained with the rapid bootstrap algorithm (1000 replications). Using the H1 phylogeny, H1N1 and H1N2 isolates were assigned to one of six previously described H1 clusters: H1␣, H1␤, H1␥, H1␦1, H1␦2, H1pdm09 (Vincent et al., 2009a, 2009b; Lorusso et al., 2011). Similarly, H3N2 isolates were assigned to one of four main clusters based upon the H3 phylogeny, and H3 Cluster IV isolates to one of 6 putative clades (Kitikoon et al., 2013). "
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    ABSTRACT: Multiple genetically and antigenically distinct hemagglutinin genes of the H1 and H3 influenza A virus (IAV) subtypes co-circulate in North American swine. This diversity has evolved by repeated transmission of IAVs from humans to swine and subsequent antigenic drift in swine. To understand the evolutionary dynamics of these diverse HA lineages in North American swine, we undertook a phylogenetic analysis of 1576 H1 and 607 H3 HA gene segments, as well as 834 N1 and 1293 N2 NA gene segments, and 2126 M gene segments. These data revealed yearly co-circulation of H1N1, H1N2, and H3N2 viruses, with three HA clades representing the majority of the HA sequences: of the H1 viruses, 42% were classified as H1δ1 and 40.6% were classified as H1γ; and of the H3 viruses 53% were classified as cluster IV-A H3N2. We detected a genetically distinct minor clade consisting of 37 H1 viruses isolated between 2003 and 2013, which we classified as H1γ-2. We estimated that this clade circulated in swine since approximately 1995, but it was not detected in swine until 2003. Though this clade only represents 1.07% of swine H1 sequences reported over the past 10 years, hemagglutination inhibition (HI) assays demonstrated that representatives of this clade of viruses are antigenically distinct, and, when measured using antigenic cartography, were as many as 7 antigenic units from other H1γ viruses and therefore vaccines against the contemporary H1γ viruses are not likely to cross-protect against γ-2 viruses. The long-term circulation of these γ-2 viruses suggests that minor populations of viruses may be underreported in the national dataset given the long branch lengths and gaps in detections. The identification of these γ-2 viruses demonstrates the need for robust surveillance to capture the full diversity IAVs in swine in the USA and the importance of antigenic drift in the diversification and emergence of new antigenic variants in swine, which complicates vaccine design.
    Full-text · Article · Feb 2015 · Virus Research
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    • "To represent the evolution of the currently circulating North American H1 viruses, a cluster classification was established. Viruses with the HA gene of the classical H1N1 viruses that have circulated in swine since 1918 evolved into the contemporary a-, b-and c-clusters, whereas H1 subtype isolates with HA genes most similar to those of human seasonal H1 viruses circulating in the early 2000s evolved into the d-cluster (Vincent et al., 2009b). All four HA gene cluster types (a, b, c, and d) can be found with NA genes of either the N1 or N2 subtype. "
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    ABSTRACT: Pigs and humans have shared influenza A viruses (IAV) since at least 1918, and many interspecies transmission events have been documented since that time. However, despite this interplay, relatively little is known regarding IAV circulating in swine around the world compared with the avian and human knowledge base. This gap in knowledge impedes our understanding of how viruses adapted to swine or man impacts the ecology and evolution of IAV as a whole and the true impact of swine IAV on human health. The pandemic H1N1 that emerged in 2009 underscored the need for greater surveillance and sharing of data on IAV in swine. In this paper, we review the current state of IAV in swine around the world, highlight the collaboration between international organizations and a network of laboratories engaged in human and animal IAV surveillance and research, and emphasize the need to increase information in high-priority regions. The need for global integration and rapid sharing of data and resources to fight IAV in swine and other animal species is apparent, but this effort requires grassroots support from governments, practicing veterinarians and the swine industry and, ultimately, requires significant increases in funding and infrastructure.
    Full-text · Article · Apr 2013 · Zoonoses and Public Health
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