Molecular Characterization of PB1-F2-Mediated Pathology in Influenza Mouse Model of Infection

PB1-F2 is a virulence factor of influenza A virus (IAV) known to increase viral pathogenicity in mammalian host. PB1-F2 is an intrinsically disordered protein displaying a propensity to form amyloid-like fibers in IAV-infected cells. Using synchrotron Fourier-transform infrared (FTIR) spectroscopy, we previously evidenced the presence of PB1-F2 fibers in IAV-infected cells and assigned an IR β-aggregated signature at the single-cell level. Using DUV (Deep Ultraviolet) microscopy and taking advantage of the high content of tryptophan residues in the sequence of PB1-F2 (5/90 aa), we showed that the increase of the autofluorescent signal recorded in IAV-infected cells can be correlated with the IR detection of β-aggregates. Here, we used FT-IR and DUV microscopies to prove the presence of PB1-F2 fibers in IAVinfected mice. Mice were infected with a wild-type IAV and its PB1-F2 knockout mutant and monitored at different time post-infection. DUV microscopy was used to map the presence of PB1-F2 β-aggregates within slices of lung tissues of IAV-infected mice. IR spectra were recorded in the regions of interest and subjected to multivariate analysis revealing the presence of β-aggregated structures in mice infected with PB1-F2-expressing IAV. In order to study the correlation between PB1-F2 structure and inflammatory response, NF-KB luciferase transgenic mice were intranasally instilled with monomeric, fibrillated or Cand Nterminal domains of recombinant PB1-F2. Our results clearly show the pro-inflammatory effect of fibrillated PB1-F2 compared to monomeric and non-fibrillated forms. It is noteworthy that only the N-terminal part of PB1-F2, unable to fibrillate, does not provoke any inflammation. Thus, the PB1-F2-induced inflammation is tightly correlated with sequence and oligomerization status of the protein. Toward Structural Study of HCV Core Protein at SOLEIL T. Disparti, Y. Gohon, M. Froissard Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris Saclay, 78026 Versailles, France