Pulmonary microvascular endothelial cell tau contributes to H1N1 Influenza A Virus replication kinetics and cellular injury during infection

Influenza A virus (IAV) remains a significant public health challenge, with seasonal influenza accounting for approximately 43 million cases of illness in the U.S. during the 2024-2025 season. While IAV primarily manifests as an upper respiratory tract infection, its most severe complications and associated mortality arise from lower respiratory tract involvement. During lower respiratory tract infection, IAV replicates in alveolar epithelium. Virions are symmetrically released from apical and basolateral aspects of epithelial cells and consequently presented to capillary endothelial cells where additional viral replication cycles can occur. The objective of this study was to determine the extent to which pulmonary microvascular endothelial cells (PMVECs) support IAV infection and to test whether the microtubule-associated protein tau is required for efficient viral replication in these cells. We hypothesized that tau stabilizes peripheral microtubules to support early endosomal trafficking of the IAV genome to the nucleus for replication, and further, that loss of tau limits viral replication and endothelial injury. To test this idea, wild-type PMVECs were infected with the A/WSN/1933 (H1N1) strain of IAV and viral particle accumulation was measured by reverse transcription quantitative polymerase chain reaction across a 48-hour time course. Tau phosphorylation was also assessed over this time course by Western blot. IAV particle numbers began to increase in as little as 3-hours post infection of PMVECs; whereas 12-hours was required for particle numbers to increase in A549 cells, a Gold-standard cell line for IAV infection. By 48-hours, widespread gap formation and cell death were evident in both A549 cells and PMVECs. To determine whether tau contributes to viral replication in PMVECs, IAV infection was tested in both tau knockout cells and tau knockout cells in which tau expression was rescued (i.e., tau-rescue). Tau-knockout PMVECs produced approximately 2.5 log fewer viral particles than the wild-type controls, and remarkably, endothelial barrier integrity was preserved over the entire 48-hour time course. In stark contrast, tau-rescue cells supported IAV infection at a rate that was equivalent to wild type cells, and widespread gap formation and death were also evident. In tau-expressing cells, IAV infection promoted tau phosphorylation at serine-214 within 30 minutes of exposure to IAV, indicating rapid modification of tau during the period of viral entry and trafficking. Together, these results demonstrate that PMVECs support IAV infection and provide evidence that endothelial tau plays a role in IAV replication kinetics and endothelial cell injury. Studies are ongoing to determine the extent to which tau represents a critical host factor that regulates endothelial infection with IAV; however, our preliminary results suggest that tau phosphorylation during IAV infection may represent a previously unrecognized endothelial mechanism contributing to the progression of IAV-induced pneumonia. Supported by HL140182, HL167997, and HL148069. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.