Viral syncytia evolve to resist interferon
- Tiansheng Li
- Insung Kang
- Juan Ye
- Zhe Hu
- James Gibbs
- Chengjin Ye
- Kazuyo Takeda
- Ivan Kosik
- Guoli Shi
- Jaroslav Holly
- Martina Kosikova
- Zhiping Ye
- Alex A. Compton
- Luis Martinez-Sobrido
- Reed F. Johnson
- Hang Xie
- Jonathan W. Yewdell
2026-07-20
SARS-CoV-2, like many viruses, generates syncytia but the role of syncytia formation in viral evolution remains unknown. Using SARS-CoV-2 and SARS-CoV-2 Spike (S) replacement vesicular stomatitis (VSV), we show that S-mediated syncytia impair the antiviral effects of interferons in cultured cells, human lung cell cultures, and hACE2 transgenic mice. Amino acid substitutions that modulate syncytia formation in Delta- and Omicron-encoded S have parallel effects on viral interferon resistance. S-mediated syncytia compromise antibody-mediated virus neutralization in cultured cells. We recapitulate interferon and neutralizing antibody resistance in syncytia generated by the orthoreovirus p14 fusion-associated small transmembrane (FAST) protein in VSV, influenza virus, and seasonal coronavirus OC43 infections. These findings explain selection of SARS-CoV-2 fusogenic variants in humans and, more generally, the evolution of fusogenic viruses driven by adaptive and innate immunity.