Turner, A. H. | Search bioRxiv

bioRxiv2025

Primary bovine embryonic fibroblasts support seasonal influenza A virus infection and demonstrate variable fitness of HPAI H5N1

The emergence of highly pathogenic avian influenza (HPAI) H5N1 (clade 2.3.4.4b, genotype B3.13) in dairy cattle presents substantial challenges to the agricultural sector and public health. Mechanistic studies of infection and transmission in cattle have proven difficult due to animal handling restrictions as well as limited availability of established cell culture models. Primary Bovine Embryonic Fibroblasts (BeEFs) were collected from a Montana cow and are investigated here as a model to study influenza A virus (IAV) infection dynamics. We compared sialylation profiles, infectious virus production, viral replication, and plaque morphology in both BeEFs and chicken DF-1 cells following infection with the bovine HPAI H5N1 and an earlier 2.3.4.4b genotype (B1.1) isolated in 2022. The data presented here show increased viral fitness of the bovine origin HPAI H5N1 strains across multiple species and bovine susceptibility to human seasonal IAV. This study highlights the ability of BeEFs to serve as a model for studying IAV infections in bovine hosts.

microbiology↗

bioRxiv2025

Rab11B is required for binding and entry of recent H3N2, but not H1N1, influenza A isolates

As an obligate intracellular parasite, influenza A virus (IAV) depends on host proteins to complete several important functions, including trafficking viral proteins throughout the cell. Previous work has established a critical role for the cellular vesicular trafficking protein, Rab11A, in transporting the viral genome segments to the site of budding at the plasma membrane. While the role of Rab11A in IAV assembly is relatively well understood, very little is known about the function of a closely related isoform (Rab11B) during influenza virus infection. We have shown that both Rab11A and Rab11B are required for successful IAV infection by current H1N1 or H3N2 isolates. Cells in which either Rab11A or Rab11B were depleted failed to efficiently produce virus, with significant reductions in infectious titer. Surprisingly, our data revealed that recent (2022) H3N2, but not H1N1, isolates failed to efficiently produce viral proteins in single-cycle infections when Rab11B (but not Rab11A) was depleted. Flow cytometry analysis suggests that the defect in protein production is driven by a reduction in the total number of infected cells, rather than a decrease in viral protein production at the single cell level. Using reverse genetics and 7+1 reassortant viruses we mapped this Rab11B-dependent early defect in recent H3N2 isolates to the HA gene. RT-qPCR analysis of H3N2 virions bound to the cell surface showed a [~]50% decrease in virus binding the surface of cells depleted of Rab11B, but not Rab11A. This data suggests a novel role for Rab11B during viral entry, likely at the stage of viral binding, that is specific to H3N2 isolates.

microbiology↗