Nonstructural Protein NSs Activates Inflammasome and Pyroptosis through Interaction with NLRP3 in Human Microglial Cells Infected with Severe Fever with Thrombocytopenia Syndrome Bandavirus

Chengfeng Gao, Yufeng Yu, Chunxia Wen, Zhifeng Li, Haida Ding, Xian Qi, Carol J. Cardona, Zheng Xing

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne febrile disease caused by SFTS virus (SFTSV), or Dabie bandavirus, in the Phenuiviridae family. Clinically neurological disorders in SFTS have been commonly reported, but their neuropathogenesis has rarely been studied. Microglia are a type of neuroglia accounting for 10 to 12% of all cells in the brain. As resident immune cells, microglial cells are the first line of immune defense present in the central nervous system (CNS). Here, we report that SFTSV was able to infect microglial cells and stimulate interleukin 1β (IL-1β) secretion in the brains of infected neonatal BALB/c mice. We characterized the cell death induced in infected human microglial HMC3 cells, also susceptible to SFTSV, and found that the NOD-like receptor protein 3 (NLRP3) inflammasome was activated, leading to secretion of IL-1β and pyroptosis. Knockdown of NLRP3 or inhibition of the NLRP3 inflammasome activation suppressed the viral replication, suggesting that the activation of the NLRP3 inflammasome may support SFTSV replication in microglial cells. Viral nonstructural protein NSs, a known modulator of immune responses, interacted and colocalized with NLRP3 for the inflammasome activation. It appeared that the N-terminal fragment, amino acids 1 to 66, of NSs was critical to promote the assembly of the inflammasome complex by interacting with NLRP3 for its activation in microglial cells. Our findings provide evidence that SFTSV may cause neurological disorders through infecting microglia and activating the inflammasome through its nonstructural protein NSs for neural cell death and inflammation. This study may have revealed a novel mechanism of SFTSV NSs in dysregulating host response. IMPORTANCE Encephalitis or encephalopathy during severe fever with thrombocytopenia syndrome (SFTS) is considered a critical risk factor leading to high mortality, but there have been no studies to date on the pathogenesis of encephalitis or encephalopathy caused by SFTS virus. Here, we report that SFTSV infection can active the NLRP3 inflammasome and induce IL-1β secretion in the brains of infected newborn mice. In infected human HMC3 microglia, SFTSV activated the NLRP3 inflammasome via the viral nonstructural protein NSs through interaction with its N-terminal fragment. Notably, our findings suggest that the activation of the NLRP3 inflammasome may promote SFTSV replication in infected microglial cells. This study may reveal a novel mechanism by SFTSV to dysregulate host responses through its nonstructural protein, which could help us understand viral neuropathogenesis in SFTS patients.

Original languageEnglish (US)
JournalJournal of virology
Volume96
Issue number13
DOIs
StatePublished - Jul 2022

Bibliographical note

Funding Information:
This study was supported by National Natural Science Foundation of China (no. 81971923 to Z.X. and 82102388 to Y.Y.). Z.X. was also supported by funding from the Minnesota Department of Agriculture. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We declare that no competing interests exist.

Publisher Copyright:
Copyright © 2022 American Society for Microbiology. All Rights Reserved.

Keywords

  • NLRP3
  • SFTSV
  • inflammasome
  • microglia
  • severe fever with thrombocytopenia syndrome virus
  • Encephalitis
  • Microglia/metabolism
  • Pyroptosis
  • NLR Family, Pyrin Domain-Containing 3 Protein/genetics
  • Humans
  • Severe Fever with Thrombocytopenia Syndrome/immunology
  • Cells, Cultured
  • Viral Nonstructural Proteins/metabolism
  • Phlebovirus/metabolism
  • Animals
  • Inflammasomes/metabolism
  • Mice

PubMed: MeSH publication types

  • Research Support, Non-U.S. Gov't
  • Journal Article

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