Bunyaviruses pose a significant threat to human health, prosperity, and food security. In response to viral infections, interferons (IFNs) upregulate the expression of hundreds of interferon-stimulated genes (ISGs), whose cumulative action can potently inhibit the replication of bunyaviruses. We used a flow cytometry-based method to screen the ability of ~500 unique ISGs from humans and rhesus macaques to inhibit the replication of Bunyamwera orthobunyavirus (BUNV), the prototype of both the Peribunyaviridae family and the Bunyavirales order. Candidates possessing antibunyaviral activity were further examined using a panel of divergent bunyaviruses. Interestingly, one candidate, ISG20, exhibited potent antibunyaviral activity against most viruses examined from the Peribunyaviridae, Hantaviridae, and Nairoviridae families, whereas phleboviruses (Phenuiviridae) largely escaped inhibition. Similar to the case against other viruses known to be targeted by ISG20, the antibunyaviral activity of ISG20 is dependent upon its functional RNase activity. Through use of an infectious virus-like particle (VLP) assay (based on the BUNV minigenome system), we confirmed that gene expression from all 3 viral segments is strongly inhibited by ISG20. Using in vitro evolution, we generated a substantially ISG20-resistant BUNV and mapped the determinants of ISG20 sensitivity/resistance. Taking all the data together, we report that ISG20 is a broad and potent antibunyaviral factor but that some bunyaviruses are remarkably ISG20 resistant. Thus, ISG20 sensitivity/resistance may influence the pathogenesis of bunyaviruses, many of which are emerging viruses of clinical or veterinary significance.
Bibliographical noteFunding Information:
J.F. dedicates this paper to the memory of his late supervisor Richard M. Elliott, who passed away on 5 June 2015 and will forever be missed as a friend and mentor. We thank Jeroen Kortekaas for sharing the nonspreading RVFV system as well as Alain Kohl, Sophie Jegouic, Idoia Busnadiego, Ingeborg van Knippenberg, Ping Li, Angela Elliott, and Edward Dornan for their helpful discussions, technical advice, and support. This study was funded by Wellcome Trust grant 099220/Z/12/Z (to R.M.E.), NIH NIAID grant R01-AI091707 (to C.M.R.), and Medical Research Council (MRC) grants MR/ K024752/1 and MC_UU_12014/10 (to S.J.W.). J.F. was supported by the China Scholarship Council (CSC) and the University of Glasgow.
This study was funded by Wellcome Trust grant 099220/Z/12/Z (to R.M.E.), NIH NIAID grant R01-AI091707 (to C.M.R.), and Medical Research Council (MRC) grants MR/ K024752/1 and MC_UU_12014/10 (to S.J.W.). J.F. was supported by the China Scholarship Council (CSC) and the University of Glasgow.
© 2018 American Society for Microbiology.
- Innate immunity
- Restriction factor