The role of Bik in the replication and severity of influenza A virus

Influenza A virus (IAV) is responsible for seasonal epidemics that results in severe respiratory illness and deaths worldwide, costing billions of dollars annually in the U.S. alone. Cancer patients are at increased risk of developing a secondary pneumonia after influenza, which can lead to significant complications. Influenza infections pose serious challenges due to the lack of effective therapeutic interventions, frequent appearances of new strains of the virus, and rapid development of drug resistance. New approaches to control infection may stem from cellular factors or pathways that directly or indirectly interact with viral proteins to enhance or inhibit virus replication. One of the emerging concepts in the field of IAV is that host cellular factors and pathways are required for maintaining IAV genome integrity, which is essential for viral replication. Our preliminary data show that a deficiency of a host cellular protein, Bik, is associated with significant reduction in IAV replication. Our major findings found that Bik deficiency reduces viral protein levels and viral replication in infected airway epithelial cells. Furthermore, bik-/- compared to bik+/+ mice exhibit less severe lung inflammation, reduced lung viral load, and a significant increase in survival rate after infection with IAV. Similarly, a single nucleotide polymorphism (SNP) in the BIK gene (G→A) that increases Bik expression levels significantly increases viral NP level and replication in primary normal human bronchial epithelial cells (NHBEs). Furthermore, data from an IAV- infected human cohort showed that the AA variant of BIK SNP is a risk allele associated with influenza disease severity. Bik disrupts the interaction of Bcl-2 with IAV-encoded nucleoprotein (NP) and form a Bik/NP complex that may help assemble viral proteins. The goals of this proposal are to define the role of a host cell protein Bik in promoting viral replication. Our central hypothesis is that IAV increases host cell Bik protein expression, which interacts with and disrupts Bcl-2/NP interaction to allow NP to assemble components of viral ribonucleoprotein (vRNP) and facilitate efficient viral replication. To test this hypothesis, we propose two Specific Aims. Aim 1 identifies the Bik-binding domain of viral NP required for IAV replication. Aim 2 determines whether a BIK SNP associated with increased Bik expression is a risk factor for influenza disease severity in humans. Studies are designed to identify the sites of Bik/NP interaction that may serve as potential drug targets in the future. This study may identify underlying host genetic risk factors contributing to influenza susceptibility and severity and may have potential implications in regard to targeted prevention and treatment based on susceptibility factors. The proposed studies will have significant impacts on the field by dissecting key mechanisms that promote IAV replication. In the long term, developing peptides or small molecules that disrupt Bik/NP interactions may improve therapy by reducing IAV replication. Further, this study will identify genetic factors contributing to IAV disease severity, which can have a broad public health significance.