A yellow fever virus NS4B inhibitor not only suppresses viral replication, but also enhances the virus activation of RIG-I-like receptor-mediated innate immune response

• Published in: PLoS pathogens Vol. 18; no. 1; p. e1010271
• Main Authors: Gao, Zhao, Zhang, Xuexiang, Zhang, Lin, Wu, Shuo, Ma, Julia, Wang, Fuxuan, Zhou, Yan, Dai, Xinghong, Bullitt, Esther, Du, Yanming, Guo, Ju-Tao, Chang, Jinhong
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01-01-2022; Public Library of Science (PLoS)
• Subjects: Animal models; Antiviral activity; Antiviral agents; Antiviral Agents - pharmacology; Benzodiazepines; Benzodiazepines - pharmacology; Biology and Life Sciences; Cell Line; Cytokines; DEAD Box Protein 58 - immunology; Dengue fever; Disease prevention; Double-stranded RNA; Drug dosages; Endoplasmic reticulum; Epidemics; Fatalities; Fever; Gene expression; Genetic aspects; GTP-binding protein; Hamsters; Humans; Immune response; Immune system; Immunity, Innate - immunology; Infections; Inflammation; Innate immunity; Intermediates; Medicine and Health Sciences; Membrane proteins; Membranes; Mutation; NS4B protein; Organelles; Prevention; Proteins; Replication; Research and analysis methods; RNA viruses; Transmembrane domains; Vaccines; Vector-borne diseases; Viral Nonstructural Proteins - antagonists & inhibitors; Viral Nonstructural Proteins - drug effects; Virus Replication - drug effects; Viruses; Yellow fever; Yellow Fever - immunology; Yellow fever virus - drug effects; Yellow fever virus - immunology; United States; Brazil
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1010271

Flavivirus infection of cells induces massive rearrangements of the endoplasmic reticulum (ER) membrane to form viral replication organelles (ROs) which segregates viral RNA replication intermediates from the cytoplasmic RNA sensors. Among other viral nonstructural (NS) proteins, available evidence suggests for a prominent role of NS4B, an ER membrane protein with multiple transmembrane domains, in the formation of ROs and the evasion of the innate immune response. We previously reported a benzodiazepine compound, BDAA, which specifically inhibited yellow fever virus (YFV) replication in cultured cells and in vivo in hamsters, with resistant mutation mapped to P219 of NS4B protein. In the following mechanistic studies, we found that BDAA specifically enhances YFV induced inflammatory cytokine response in association with the induction of dramatic structural alteration of ROs and exposure of double-stranded RNA (dsRNA) in virus-infected cells. Interestingly, the BDAA-enhanced cytokine response in YFV-infected cells is attenuated in RIG-I or MAD5 knockout cells and completely abolished in MAVS knockout cells. However, BDAA inhibited YFV replication at a similar extent in the parent cells and cells deficient of RIG-I, MDA5 or MAVS. These results thus provided multiple lines of biological evidence to support a model that BDAA interaction with NS4B may impair the integrity of YFV ROs, which not only inhibits viral RNA replication, but also promotes the release of viral RNA from ROs, which consequentially activates RIG-I and MDA5. Although the innate immune enhancement activity of BDAA is not required for its antiviral activity in cultured cells, its dual antiviral mechanism is unique among all the reported antiviral agents thus far and warrants further investigation in animal models in future.