Date Full Report Received


Date Abstract Report Received



Primary Investigator:

The objectives of this study were to initiate an investigation into the impact of a newly identified influenza virus protein, PB1-F2, in swine lineage influenza virus (SIV) pathogenicity. PB1-F2 was first identified in human and avian lineage influenza virus strains, and was shown to play a crucial role in the pathogenicity of these virus strains by initiating the induction of a host cell pathway, termed apoptosis, that results in cell death via localization to cellular mitochondria. While most swine lineage influenza viruses encode the capacity to express PB1-F2, the proteins are substantially different at the primary amino-acid sequence level from PB1-F2 proteins that have been studied. In this work, we utilized an SIV strain isolated from clinically ill pigs and humans at a 2007 Ohio state fair that is representative of a group of currently circulating strains to investigate the role of swine lineage PB1-F2 in induction of cell death of swine and human cells. An antibody specific for swine lineage PB1-F2 was created and utilized to examine PB1-F2 in SIV infected cells. Multiple untagged and tagged plasmid clones were additionally created to further investigate the PB1-F2 protein from SIV. Additionally, clones were created in reverse genetics plasmids in which the PB1-F2 ORF was mutated such that recombinant viruses can be created that do not express PB1-F2 to identify the function of PB1-F2 in SIV replication and pathogenicity. Unlike the previously described mitochondrial localization of human lineage influenza PB1-F2, swine lineage PB1-F2 was found not to substantially localize to this cellular organelle, suggesting it may play an alternative role in SIV infection. SIV PB1-F2 was instead found to localize to the nucleus of infected cells. Localization of PB1-F2 to the nucleus likely impacts its function. PB1-F2 expression in infected cells was also differentially regulated in a strain specific manner at the level of protein synthesis. This regulation involves two sequence-dependent elements located in the PB1-F2 open reading frame (ORF) and downstream of the PB1-F2 ORF in the PB1 gene. Understanding the mechanisms involved in PB1-F2 sub-cellular localization and translational regulation will give insight into predicting PB1-F2 expression and virulence potential in swine influenza viruses.

Cathy L. Miller
Iowa State University College of Veterinary Medicine
1802 University Blvd. VMRI Building 3, Ames, IA 50011
Phone: 515-294-4797, email: clm@iastate.edu