tetano
Editor, Senior Moderator
Published ahead of print 9 July 2014, doi: 10.1128/JVI.01440-14 JVI.01440-14
Influenza A and B intertypic reassortment through compatible viral packaging signals
Steven F. Baker1,
Aitor Nogales1,
Courtney Finch4,
Kevin M. Tuffy1,
William Domm1,
Daniel R. Perez4,
David J. Topham1,2,3 and
Luis Mart?nez-Sobrido1*
Department of Microbiology and Immunology1
New York Influenza Center of Excellence2
David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences3, University of Rochester, Rochester, New York
Department of Veterinary Medicine4, University of Maryland College Park and Virginia-Maryland Regional College of Veterinary Medicine, College Park, Maryland, USA.
ABSTRACT
Influenza A and B viruses co-circulate in humans, and together cause disease and seasonal epidemics. These two types of influenza virus are evolutionarily divergent, and exchange of genetic segments inside co-infected cells occurs frequently within types, but never between influenza A and B viruses. Possible mechanisms inhibiting the intertypic reassortment of genetic segments could be due to incompatible protein functions of segment homologs, a lack of processing of heterotypic segments by influenza RNA-dependent RNA polymerase, an inhibitory effect of viral proteins on heterotypic virus function, or an inability to specifically incorporate heterotypic segments into budding virions. Here, we demonstrate that full-length influenza hemagglutinin (HA) of prototype B viruses can complement the function of multiple influenza A viruses. We show that viral non-coding regions were sufficient to drive gene expression for either type A or B influenza virus with its cognate or heterotypic polymerase. The native influenza B HA segment can not be incorporated into influenza A virions. However, by adding the influenza A packaging signals to full length influenza B glycoproteins, we rescued influenza A viruses that possessed HA, NA or both HA and NA of influenza B virus. Furthermore, we show that, similar to single-cycle infectious influenza A virus, influenza B virus cannot incorporate heterotypic transgenes due to packaging signal incompatibilities. Altogether, these results demonstrate that the lack of influenza A and B virus reassortants can be at least in part attributed to incompatibilities in the viral-specific packaging signals required for effective segment incorporation into nascent virions.
IMPORTANCE Reassortment of influenza A or B viruses provides an evolutionary strategy leading to unique genotypes, which can spawn influenza A viruses with pandemic potential. However, the mechanism preventing intertypic reassortment, or gene exchange between influenza A and B viruses, is not well understood. Nucleotides comprising the coding termini of each influenza A gene segment are required for specific segment incorporation during budding. Whether influenza B shares a similar selective packaging strategy, or if packaging signals prevent intertypic reassortment, remain unknown. Here, we provide evidence suggesting a similar mechanism of influenza B genome packaging. Furthermore, by appending influenza A packaging signals onto influenza B segments, we rescued recombinant A/B viruses that can reassort in vitro with another influenza A virus. These findings suggest that divergent evolution of packaging signals aid in the speciation of influenza A and B virus and are in part responsible for the lack of intertypic viral reassortment.
http://jvi.asm.org/content/early/2014/07/03/JVI.01440-14.abstract
Influenza A and B intertypic reassortment through compatible viral packaging signals
Steven F. Baker1,
Aitor Nogales1,
Courtney Finch4,
Kevin M. Tuffy1,
William Domm1,
Daniel R. Perez4,
David J. Topham1,2,3 and
Luis Mart?nez-Sobrido1*
Department of Microbiology and Immunology1
New York Influenza Center of Excellence2
David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences3, University of Rochester, Rochester, New York
Department of Veterinary Medicine4, University of Maryland College Park and Virginia-Maryland Regional College of Veterinary Medicine, College Park, Maryland, USA.
ABSTRACT
Influenza A and B viruses co-circulate in humans, and together cause disease and seasonal epidemics. These two types of influenza virus are evolutionarily divergent, and exchange of genetic segments inside co-infected cells occurs frequently within types, but never between influenza A and B viruses. Possible mechanisms inhibiting the intertypic reassortment of genetic segments could be due to incompatible protein functions of segment homologs, a lack of processing of heterotypic segments by influenza RNA-dependent RNA polymerase, an inhibitory effect of viral proteins on heterotypic virus function, or an inability to specifically incorporate heterotypic segments into budding virions. Here, we demonstrate that full-length influenza hemagglutinin (HA) of prototype B viruses can complement the function of multiple influenza A viruses. We show that viral non-coding regions were sufficient to drive gene expression for either type A or B influenza virus with its cognate or heterotypic polymerase. The native influenza B HA segment can not be incorporated into influenza A virions. However, by adding the influenza A packaging signals to full length influenza B glycoproteins, we rescued influenza A viruses that possessed HA, NA or both HA and NA of influenza B virus. Furthermore, we show that, similar to single-cycle infectious influenza A virus, influenza B virus cannot incorporate heterotypic transgenes due to packaging signal incompatibilities. Altogether, these results demonstrate that the lack of influenza A and B virus reassortants can be at least in part attributed to incompatibilities in the viral-specific packaging signals required for effective segment incorporation into nascent virions.
IMPORTANCE Reassortment of influenza A or B viruses provides an evolutionary strategy leading to unique genotypes, which can spawn influenza A viruses with pandemic potential. However, the mechanism preventing intertypic reassortment, or gene exchange between influenza A and B viruses, is not well understood. Nucleotides comprising the coding termini of each influenza A gene segment are required for specific segment incorporation during budding. Whether influenza B shares a similar selective packaging strategy, or if packaging signals prevent intertypic reassortment, remain unknown. Here, we provide evidence suggesting a similar mechanism of influenza B genome packaging. Furthermore, by appending influenza A packaging signals onto influenza B segments, we rescued recombinant A/B viruses that can reassort in vitro with another influenza A virus. These findings suggest that divergent evolution of packaging signals aid in the speciation of influenza A and B virus and are in part responsible for the lack of intertypic viral reassortment.
http://jvi.asm.org/content/early/2014/07/03/JVI.01440-14.abstract