Evolution of an Eurasian Avian-like Influenza Virus in Naïve and Vaccinated Pigs

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Author(s)
Murcia, Pablo R.
Hughes, Joseph
Battista, Patrizia
Lloyd, Lucy
Baillie, Gregory J.
Ramirez-Gonzalez, Ricardo H.
Ormond, Doug
Oliver, Karen
Elton, Debra
Mumford, Jennifer A.
Caccamo, Mario
Kellam, Paul
Grenfell, Bryan T.
Holmes, Edward C.
Wood, James L. N.
Griffith University Author(s)
Year published
2012
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Show full item recordAbstract
Influenza viruses are characterized by an ability to cross species boundaries and evade host immunity, sometimes with
devastating consequences. The 2009 pandemic of H1N1 influenza A virus highlights the importance of pigs in influenza
emergence, particularly as intermediate hosts by which avian viruses adapt to mammals before emerging in humans.
Although segment reassortment has commonly been associated with influenza emergence, an expanded host-range is also
likely to be associated with the accumulation of specific beneficial point mutations. To better understand the mechanisms
that shape the genetic diversity of avian-like ...
View more >Influenza viruses are characterized by an ability to cross species boundaries and evade host immunity, sometimes with devastating consequences. The 2009 pandemic of H1N1 influenza A virus highlights the importance of pigs in influenza emergence, particularly as intermediate hosts by which avian viruses adapt to mammals before emerging in humans. Although segment reassortment has commonly been associated with influenza emergence, an expanded host-range is also likely to be associated with the accumulation of specific beneficial point mutations. To better understand the mechanisms that shape the genetic diversity of avian-like viruses in pigs, we studied the evolutionary dynamics of an Eurasian Avian-like swine influenza virus (EA-SIV) in naı¨ve and vaccinated pigs linked by natural transmission. We analyzed multiple clones of the hemagglutinin 1 (HA1) gene derived from consecutive daily viral populations. Strikingly, we observed both transient and fixed changes in the consensus sequence along the transmission chain. Hence, the mutational spectrum of intra-host EA-SIV populations is highly dynamic and allele fixation can occur with extreme rapidity. In addition, mutations that could potentially alter host-range and antigenicity were transmitted between animals and mixed infections were commonplace, even in vaccinated pigs. Finally, we repeatedly detected distinct stop codons in virus samples from co-housed pigs, suggesting that they persisted within hosts and were transmitted among them. This implies that mutations that reduce viral fitness in one host, but which could lead to fitness benefits in a novel host, can circulate at low frequencies.
View less >
View more >Influenza viruses are characterized by an ability to cross species boundaries and evade host immunity, sometimes with devastating consequences. The 2009 pandemic of H1N1 influenza A virus highlights the importance of pigs in influenza emergence, particularly as intermediate hosts by which avian viruses adapt to mammals before emerging in humans. Although segment reassortment has commonly been associated with influenza emergence, an expanded host-range is also likely to be associated with the accumulation of specific beneficial point mutations. To better understand the mechanisms that shape the genetic diversity of avian-like viruses in pigs, we studied the evolutionary dynamics of an Eurasian Avian-like swine influenza virus (EA-SIV) in naı¨ve and vaccinated pigs linked by natural transmission. We analyzed multiple clones of the hemagglutinin 1 (HA1) gene derived from consecutive daily viral populations. Strikingly, we observed both transient and fixed changes in the consensus sequence along the transmission chain. Hence, the mutational spectrum of intra-host EA-SIV populations is highly dynamic and allele fixation can occur with extreme rapidity. In addition, mutations that could potentially alter host-range and antigenicity were transmitted between animals and mixed infections were commonplace, even in vaccinated pigs. Finally, we repeatedly detected distinct stop codons in virus samples from co-housed pigs, suggesting that they persisted within hosts and were transmitted among them. This implies that mutations that reduce viral fitness in one host, but which could lead to fitness benefits in a novel host, can circulate at low frequencies.
View less >
Journal Title
PLoS Pathogens
Volume
8
Issue
5
Copyright Statement
©
2012 Murcia et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Subject
Medical Microbiology not elsewhere classified
Microbiology
Immunology
Medical Microbiology