Novel Swine Influenza Virus Subtype H3N1, United States

Lekcharoensuk, Porntippa; Lager, Kelly M.; Vemulapalli, Ramesh; Woodruff, Mary; Vincent, Amy L.; Richt, Jürgen A.

doi:10.3201/eid1205.051060

Cited by 77 publications

(56 citation statements)

References 40 publications

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“…Nevertheless, H3N1 viruses resulting from the reassortment between swine viruses (14,35,36) or from interspecies transmission and reassortment (2,37,38) have been detected previously. The HAs of the newly emerging H3N2 and H3N1 viruses that we describe are most genetically similar to those of recent human seasonal H3N2 strains from the 2010-2011 season, suggesting that these viruses evolved from a relatively recent spillover event of a human virus into pigs.…”

Section: Discussionmentioning

confidence: 99%

“…Even though H3N1 viruses have previously been detected in U.S. swine, they are rare (2,14). The novel H3N1 viruses reported here have a unique combination of surface genes from contemporary human seasonal H3N2 hemagglutinin (HA) and classical swine H1N1 (cH1N1) neuraminidase (NA) and internal genes derived from H1N1pdm09 and hence are distinct from current swine H3 viruses circulating in the United States as well as the human seasonal H3 viruses circulating globally.…”

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confidence: 84%

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Novel Reassortant Human-Like H3N2 and H3N1 Influenza A Viruses Detected in Pigs Are Virulent and Antigenically Distinct from Swine Viruses Endemic to the United States

Rajão

Gauger

Anderson

et al. 2015

J Virol

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Human-like swine H3 influenza A viruses (IAV) were detected by the USDA surveillance system. We characterized two novel swine human-like H3N2 and H3N1 viruses with hemagglutinin (HA) genes similar to those in human seasonal H3 strains and internal genes closely related to those of 2009 H1N1 pandemic viruses. The H3N2 neuraminidase (NA) was of the contemporary human N2 lineage, while the H3N1 NA was of the classical swine N1 lineage. Both viruses were antigenically distant from swine H3 viruses that circulate in the United States and from swine vaccine strains and also showed antigenic drift from human seasonal H3N2 viruses. Their pathogenicity and transmission in pigs were compared to those of a human H3N2 virus with a common HA ancestry. Both swine human-like H3 viruses efficiently infected pigs and were transmitted to indirect contacts, whereas the human H3N2 virus did so much less efficiently. To evaluate the role of genes from the swine isolates in their pathogenesis, reverse genetics-generated reassortants between the swine human-like H3N1 virus and the seasonal human H3N2 virus were tested in pigs. The contribution of the gene segments to virulence was complex, with the swine HA and internal genes showing effects in vivo. The experimental infections indicate that these novel H3 viruses are virulent and can sustain onward transmission in pigs, and the naturally occurring mutations in the HA were associated with antigenic divergence from H3 IAV from humans and swine. Consequently, these viruses could have a significant impact on the swine industry if they were to cause more widespread outbreaks, and the potential risk of these emerging swine IAV to humans should be considered. IMPORTANCE Pigs are important hosts in the evolution of influenza A viruses (IAV). Human-to-swine transmissions of IAV have resulted in the circulation of reassortant viruses containing human-origin genes in pigs, greatly contributing to the diversity of IAV in swine worldwide. New human-like H3N2 and H3N1 viruses that contain a mix of human and swine gene segments were recently detected by the USDA surveillance system. The human-like viruses efficiently infected pigs and resulted in onward airborne transmission, likely due to the multiple changes identified between human and swine H3 viruses. The human-like swine viruses are distinct from contemporary U.S. H3 swine viruses and from the strains used in swine vaccines, which could have a significant impact on the swine industry due to a lack of population immunity. Additionally, public health experts should consider an appropriate assessment of the risk of these emerging swine H3 viruses for the human population.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 84%

Novel Reassortant Human-Like H3N2 and H3N1 Influenza A Viruses Detected in Pigs Are Virulent and Antigenically Distinct from Swine Viruses Endemic to the United States

Rajão

Gauger

Anderson

et al. 2015

J Virol

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“…Therefore, we have developed a new generation of LAIV for SIV. For this purpose, we chose an H3N2 virus, belonging to cluster III, which along with cluster IV, has been one of the most prevalent influenza viruses in American swine herds (19,20). By means of reverse genetics, this SIV was modified in the PB2 and PB1 genes, making it temperature sensitive.…”

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confidence: 99%

Alternative Live-Attenuated Influenza Vaccines Based on Modifications in the Polymerase Genes Protect against Epidemic and Pandemic Flu

Solórzano

Pérez

2010

J Virol

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Human influenza is a seasonal disease associated with significant morbidity and mortality. Influenza vaccination is the most effective means for disease prevention. We have previously shown that mutations in the PB1 and PB2 genes of the live-attenuated influenza vaccine (LAIV) from the cold-adapted (ca) influenza virus A/Ann Arbor/6/60 (H2N2) could be transferred to avian influenza viruses and produce partially attenuated viruses. We also demonstrated that avian influenza viruses carrying the PB1 and PB2 mutations could be further attenuated by stably introducing a hemagglutinin (HA) epitope tag in the PB1 gene. In this work, we wanted to determine whether these modifications would also result in attenuation of a so-called triple reassortant (TR) swine influenza virus (SIV). Thus, the TR influenza A/swine/Wisconsin/14094/99 (H3N2) virus was generated by reverse genetics and subsequently mutated in the PB1 and PB2 genes. Here we show that a combination of mutations in this TR backbone results in an attenuated virus in vitro and in vivo. Furthermore, we show the potential of our TR backbone as a vaccine that provides protection against the 2009 swine-origin pandemic influenza H1N1 virus (S-OIV) when carrying the surface of a classical swine strain. We propose that the availability of alternative backbones to the conventional ca A/Ann Arbor/6/60 LAIV strain could also be useful in epidemic and pandemic influenza and should be considered for influenza vaccine development. In addition, our data provide evidence that the use of these alternative backbones could potentially circumvent the effects of original antigenic sin (OAS) in certain circumstances.

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“…Three major lineages of SIV, including a classical swine H1N1 virus, an H3N2 subtype of human epidemic strain origin and an avian-like H1N1 swine influenza virus, have dominated in the pig population [1]. Genetic reassortments among those subtypes have resulted in generation of SIVs with several different genetic constellations [10,14,18]. It has been demonstrated that receptors for both human and avian influenza virus exist on the epithelial cells of the pig trachea [2].…”

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confidence: 99%

Molecular Characterization of an H1N2 Swine Influenza Virus Isolated in Miyazaki, Japan, in 2006

Saito

Suzuki

Maeda

et al. 2008

The Journal of Veterinary Medical Science

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ABSTRACT. Swine influenza virus (SIV) was isolated from a farm in Miyazaki Prefecture in Japan in July 2006. An isolate was genetically subtyped as H1N2 and was designated A/swine/Miyazaki/1/2006 (H1N2). The nucleotide sequences of all eight viral RNA segments were determined, and then phylogenetic analysis was performed using the neighbor-joining method. All segments were shown to be closely related to those of Japanese SIV H1N2 isolates, which have been circulating since the 1980s. The results indicate the persistence of the SIV H1N2 subtype in the Japanese pig population for more than two decades and emphasize the importance of continuous surveillance for SIV.

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Novel Swine Influenza Virus Subtype H3N1, United States

Abstract: A new subtype H3N1 may have arisen from reassortment of a H3N2 turkey isolate, a human H1N1 isolate, and currently circulating swine viruses.

Cited by 77 publications

References 40 publications

Novel Reassortant Human-Like H3N2 and H3N1 Influenza A Viruses Detected in Pigs Are Virulent and Antigenically Distinct from Swine Viruses Endemic to the United States

Novel Reassortant Human-Like H3N2 and H3N1 Influenza A Viruses Detected in Pigs Are Virulent and Antigenically Distinct from Swine Viruses Endemic to the United States

Alternative Live-Attenuated Influenza Vaccines Based on Modifications in the Polymerase Genes Protect against Epidemic and Pandemic Flu

Molecular Characterization of an H1N2 Swine Influenza Virus Isolated in Miyazaki, Japan, in 2006

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