With more than 80 members worldwide, the Orthobunyavirus genus in the Peribunyaviridae family is a large genus of enveloped RNA viruses, many of which are emerging pathogens in humans and livestock. How orthobunyaviruses (OBVs) penetrate and infect mammalian host cells remains poorly characterized. Here, we investigated the entry mechanisms of the OBV Germiston (GERV). Viral particles were visualized by cryo-electron microscopy and appeared roughly spherical with an average diameter of 98 nm. Labeling of the virus with fluorescent dyes did not adversely affect its infectivity and allowed the monitoring of single particles in fixed and live cells. Using this approach, we found that endocytic internalization of bound viruses was asynchronous and occurred within 30-40 min. The virus entered Rab5a+ early endosomes and, subsequently, late endosomal vacuoles containing Rab7a but not LAMP-1. Infectious entry did not require proteolytic cleavage, and endosomal acidification was sufficient and necessary for viral fusion. Acid-activated penetration began 15-25 min after initiation of virus internalization and relied on maturation of early endosomes to late endosomes. The optimal pH for viral membrane fusion was slightly below 6.0, and penetration was hampered when the potassium influx was abolished. Overall, our study provides real-time visualization of GERV entry into host cells and demonstrates the importance of late endosomal maturation in facilitating OBV penetration.
Journal of Virology
This work was supported by INRAE starter funds, Project IDEXLYON (University of Lyon) within the Programme Investissements d’Avenir (ANR-16-IDEX-0005), and FINOVIAO14 (Fondation pour l’Université de Lyon), all to P.Y.L. This work was also supported by CellNetworks Research Group funds and Deutsche Forschungsgemeinschaft (DFG) funding (grant numbers LO-2338/1-1 and LO-2338/3-1) awarded to P.Y.L., Austrian Science Fund (FWF) grant P31445 to F.K.M.S., a Chinese Scholarship Council (CSC;no. 201904910701) fellowship to Q.X., and a ministére de l’enseignement supérieur, de la recherche et de l’innovation (MESRI) doctoral thesis grant to M.D.
Windhaber S, Xin Q, Uckeley ZM, et al. The Orthobunyavirus Germiston enters host cells from late endosomes. Journal of Virology. 2022;96(5). doi:10.1128/jvi.02146-21
Windhaber, S., Xin, Q., Uckeley, Z. M., Koch, J., Obr, M., Garnier, C., … Lozach, P.-Y. (2022). The Orthobunyavirus Germiston enters host cells from late endosomes. Journal of Virology. American Society for Microbiology. https://doi.org/10.1128/jvi.02146-21
Windhaber, Stefan, Qilin Xin, Zina M. Uckeley, Jana Koch, Martin Obr, Céline Garnier, Catherine Luengo-Guyonnot, Maëva Duboeuf, Florian KM Schur, and Pierre-Yves Lozach. “The Orthobunyavirus Germiston Enters Host Cells from Late Endosomes.” Journal of Virology. American Society for Microbiology, 2022. https://doi.org/10.1128/jvi.02146-21.
S. Windhaber et al., “The Orthobunyavirus Germiston enters host cells from late endosomes,” Journal of Virology, vol. 96, no. 5. American Society for Microbiology, 2022.
Windhaber S, Xin Q, Uckeley ZM, Koch J, Obr M, Garnier C, Luengo-Guyonnot C, Duboeuf M, Schur FK, Lozach P-Y. 2022. The Orthobunyavirus Germiston enters host cells from late endosomes. Journal of Virology. 96(5), e02146-21.
Windhaber, Stefan, et al. “The Orthobunyavirus Germiston Enters Host Cells from Late Endosomes.” Journal of Virology, vol. 96, no. 5, e02146-21, American Society for Microbiology, 2022, doi:10.1128/jvi.02146-21.