Influenza A Virus PB1-F2 Protein Contributes to Viral Pathogenesis in Mice

ABSTRACT The influenza virus PB1-F2 protein is a novel protein previously shown to be involved in induction of cell death. Here we characterize the expression and the function of the protein within the context of influenza viral infection in tissue culture and a mouse model. We show that the C-terminal region of the protein can be expressed from a downstream initiation codon and is capable of interaction with the full-length protein. Using this knowledge, we generated influenza viruses knocked out for the expression of PB1-F2 protein and its downstream truncation products. Knocking out the PB1-F2 protein had no effect on viral replication in tissue culture but diminished virus pathogenicity and mortality in mice. The viruses replicated to similar levels in mouse lungs by day 3 postinfection, suggesting that the knockout did not impair viral replication. However, while the PB1-F2 knockout viruses were cleared after day 5, the wild-type viruses were detectable in mouse lungs until day 7, implying that expression of PB1-F2 resulted in delayed clearance of the viruses by the host immune system. Based on our findings and on the fact that the PB1 genomic segment was always newly introduced into some pandemic influenza viruses of the last century, we speculate that the PB1-F2 protein plays an important role in pathogenesis of influenza virus infection and may be an important contributor to pathogenicity of pandemic influenza viruses.

[1]  T. Tumpey,et al.  Depletion of Lymphocytes and Diminished Cytokine Production in Mice Infected with a Highly Virulent Influenza A (H5N1) Virus Isolated from Humans , 2000, Journal of Virology.

[2]  Jonathan W. Yewdell,et al.  The Influenza A Virus PB1-F2 Protein Targets the Inner Mitochondrial Membrane via a Predicted Basic Amphipathic Helix That Disrupts Mitochondrial Function , 2003, Journal of Virology.

[3]  A. García-Sastre,et al.  Rescue of influenza A virus from recombinant DNA. , 2007, Journal of virology.

[4]  C. Naeve,et al.  Large-Scale Sequence Analysis of Avian Influenza Isolates , 2006, Science.

[5]  Yamamura Ken-ichi,et al.  Efficient selection for high-expression transfectants with a novel eukaryotic vector , 1991 .

[6]  Shannon C Miller,et al.  Identification of protective and non-protective T cell epitopes in influenza. , 2006, Vaccine.

[7]  Qingmin Wu,et al.  H9N2 influenza viruses prevalent in poultry in China are phylogenetically distinct from A/quail/Hong Kongl/G1/97 presumed to be the donor of the internal protein genes of the H5N1 Hong Kong/97 virus , 2003, Avian pathology : journal of the W.V.P.A.

[8]  H. Niwa,et al.  Efficient selection for high-expression transfectants with a novel eukaryotic vector. , 1991, Gene.

[9]  B. Murphy,et al.  The avian influenza virus nucleoprotein gene and a specific constellation of avian and human virus polymerase genes each specify attenuation of avian-human influenza A/Pintail/79 reassortant viruses for monkeys , 1987, Journal of virology.

[10]  Rong Wang,et al.  Influenza Virus PB1-F2 Protein Induces Cell Death through Mitochondrial ANT3 and VDAC1 , 2005, PLoS pathogens.

[11]  A. Osterhaus,et al.  Human influenza virus A/HongKong/156/97 (H5N1) infection. , 1998, Vaccine.

[12]  R. Webster,et al.  Genetic Reassortment of Avian, Swine, and Human Influenza A Viruses in American Pigs , 1999, Journal of Virology.

[13]  P. Borrow,et al.  Virus-induced immunosuppression: immune system-mediated destruction of virus-infected dendritic cells results in generalized immune suppression , 1995, Journal of virology.

[14]  P. Henklein,et al.  Influenza A virus protein PB1‐F2: synthesis and characterization of the biologically active full length protein and related peptides , 2005, Journal of peptide science : an official publication of the European Peptide Society.

[15]  Jonathan W. Yewdell,et al.  A novel influenza A virus mitochondrial protein that induces cell death , 2001, Nature Medicine.

[16]  Y. Guan,et al.  Molecular characterization of H9N2 influenza viruses: were they the donors of the "internal" genes of H5N1 viruses in Hong Kong? , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[17]  R. Webster,et al.  Avian-to-human transmission of the PB1 gene of influenza A viruses in the 1957 and 1968 pandemics , 1989, Journal of virology.

[18]  J. Yewdell,et al.  PB1-F2, an Influenza A Virus-Encoded Proapoptotic Mitochondrial Protein, Creates Variably Sized Pores in Planar Lipid Membranes , 2004, Journal of Virology.

[19]  Robert M Krug Clues to the Virulence of H5N1 Viruses in Humans , 2006, Science.

[20]  David E. Swayne,et al.  Characterization of the Reconstructed 1918 Spanish Influenza Pandemic Virus , 2005, Science.

[21]  R. Webster,et al.  Lethal H5N1 influenza viruses escape host anti-viral cytokine responses , 2002, Nature Medicine.

[22]  R. Lamb,et al.  Death by influenza virus protein , 2001, Nature Medicine.

[23]  A. García-Sastre,et al.  Attenuation of Equine Influenza Viruses through Truncations of the NS1 Protein , 2005, Journal of Virology.

[24]  A. García-Sastre,et al.  Influenza A and B viruses expressing altered NS1 proteins: A vaccine approach. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[25]  R. Webster,et al.  Pathogenic and Antigenic Properties of Phylogenetically Distinct Reassortant H3N2 Swine Influenza Viruses Cocirculating in the United States , 2003, Journal of Clinical Microbiology.

[26]  F. Ennis,et al.  Recovery from a viral respiratory infection. I. Influenza pneumonia in normal and T-deficient mice. , 1981, Journal of immunology.

[27]  Youichirou Higashi,et al.  Mitochondrial targeting sequence of the influenza A virus PB1‐F2 protein and its function in mitochondria , 2004, FEBS letters.

[28]  J. Yewdell,et al.  Systematic search fails to detect immunogenic MHC class-I-restricted determinants encoded by influenza A virus noncoding sequences. , 2003, Virology.