Megan VanderWal, University of Victoria

Megan VanderWal, Rachel Witt, Mariya Goncheva

Expressing & Multiplying

Influenza A virus (IAV) infections are often complicated by bacterial co-infections, most frequently with Staphylococcus aureus. Our lab has found that S. aureus secreted lipases are pro-viral in primary fibroblast cells, enhancing viral replication up to 10-fold in chicken embryonic fibroblast (CEF) cells and 6-fold in normal human lung fibroblast (NHLF) cells. Upon performing untargeted lipidomics on CEF cells infected with IAV and treated with lipase after inoculation, we found 57 lipids that were significantly modified with wild type lipases, including an increase in amounts of phosphatidylinositol (PI) 36:2. It has been well characterized that IAV uses Ras-associated binding (Rab) proteins like Rab11 to transport viral ribonucleoproteins (vRNPs) from the nucleus to the plasma membrane (PM), where viral budding occurs. PI is phosphorylated by PI 4-kinase to generate PI 4-phosphate (PI4P), a known regulator of Rab11 transport. To examine this, we assessed the distribution of vRNPs and Rab11 in the presence of lipases using immunofluorescence microscopy. Our data indicate that higher levels of Rab11 are seen closer to the PM in the presence of lipases. Additional experiments utilizing specific chemical inhibition of PI4P, as well as an established PI4P sensor, are aiming to decipher the precise mechanism of this interaction. IAV – S. aureus co-infections represent a great clinical challenge, as little is known about how S. aureus's secreted lipases increase IAV infectivity. Through uncovering this mechanism, we will better understand IAV- S. aureus co-infections and develop novel therapeutics to benefit patients.