Cell–cell fusion induced by reovirus FAST proteins enhances replication and pathogenicity of non-enveloped dsRNA viruses

• Published in: PLoS pathogens Vol. 15; no. 4; p. e1007675
• Main Authors: Kanai, Yuta, Kawagishi, Takahiro, Sakai, Yusuke, Nouda, Ryotaro, Shimojima, Masayuki, Saijo, Masayuki, Matsuura, Yoshiharu, Kobayashi, Takeshi
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 25.04.2019; Public Library of Science (PLoS)
• Subjects: Animals; Arthritis; Biology and Life Sciences; Cell Fusion; Double-stranded RNA; Encephalitis; FAST protein; Funding; Fusion protein; Fusion proteins; Glycoproteins; Homology; Infection; Infections; Infectious diseases; Male; Medicine and Health Sciences; Mice; Mice, Inbred C3H; Mutation; Pathogenicity; Pathogens; Physiological aspects; Plasmids; Pneumonia; Proteins; Reoviridae - genetics; Reoviridae - pathogenicity; Reoviridae Infections - genetics; Reoviridae Infections - metabolism; Reoviridae Infections - virology; Replication; Research and Analysis Methods; Risk factors; Rotavirus infections; Veterinary medicine; Viral Fusion Proteins - genetics; Viral Fusion Proteins - metabolism; Virology; Virulence; Virus Replication; Viruses; Japan
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1007675

Fusogenic reoviruses encode fusion-associated small transmembrane (FAST) protein, which induces cell-cell fusion. FAST protein is the only known fusogenic protein in non-enveloped viruses, and its role in virus replication is not yet known. We generated replication-competent, FAST protein-deficient pteropine orthoreovirus and demonstrated that FAST protein was not essential for viral replication, but enhanced viral replication in the early phase of infection. Addition of recombinant FAST protein enhanced replication of FAST-deficient virus and other non-fusogenic viruses in a fusion-dependent and FAST-species-independent manner. In a mouse model, replication and pathogenicity of FAST-deficient virus were severely impaired relative to wild-type virus, indicating that FAST protein is a major determinant of the high pathogenicity of fusogenic reovirus. FAST-deficient virus also conferred effective protection against challenge with lethal homologous virus strains in mice. Our results demonstrate a novel role of a viral fusogenic protein and the existence of a cell-cell fusion-dependent replication system in non-enveloped viruses.