Capsid protein mediated evasion of IRAK1-dependent signalling is essential to Sindbis virus neuroinvasion and virulence in mice

ABSTRACT

Alphaviruses are arthropod-borne, single-stranded positive-sense RNA viruses that are recognized as rapidly emerging pathogens. Despite being exquisitely sensitive to the effects of the innate immune response alphaviruses can readily replicate, disseminate, and induce pathogenesis in immunologically competent hosts. Nonetheless, how alphaviruses evade the induction of an innate immune response prior to viral gene expression, or in non-permissive infections, is unknown. Previously we reported the identification of a novel host/pathogen interaction between the viral Capsid (CP) protein and the host IRAK1 protein. The CP/IRAK1 interaction was determined to negatively impact IRAK1-dependent PAMP detection in vitro, however, the precise importance of the CP/IRAK1 interaction to alphaviral infection remained unknown. Here we detail the identification of the CP/IRAK1 interaction determinants of the Sindbis virus (SINV) CP protein and examine the importance of the interaction to alphaviral infection and pathogenesis in vivo using an interaction deficient mutant of the model neurotropic strain of SINV. Importantly, these interaction determinants are highly conserved across multiple Old-World alphaviruses, including Ross River virus (RRV), Mayaro virus (MAYV), Chikungunya virus (CHIKV), and Semliki Forest virus (SFV). In the absence of a functional CP/IRAK1 interaction, SINV replication is significantly restricted and fails to disseminate from the primary site of inoculation due to the induction of a robust type-I Interferon response. Altogether these data indicate that the evasion of IRAK1-dependent signalling is critical to overcoming the host innate immune response and the in vivo data presented here demonstrate the importance of the CP/IRAK1 interaction to neurovirulence and pathogenesis.

KEYWORDS:

• Alphavirus
• Sindbis virus
• capsid
• IRAK1
• neurovirulence
• pathogenesis
• innate immunity

Acknowledgements

We thank the members of the laboratories of K.J. Sokoloski, D. Chung, I.S. Lukashevich, T.C. Mitchell, and J. Bagaitkar for their invaluable input during the development and execution of this project, and the preparation/editing of this manuscript. We also thank Jenna Olson for assistance with the analysis of flow cytometry data.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by grants from the National Institute of Allergy and Infectious Diseases (NIH-NIAID), specifically R01 AI153275 to K.J.S.; and by a COBRE programme grant from the National Institute of General Medical Sciences (NIGMS), P20 GM125504 to K.J.S. and R. Lamont. Sequencing and bioinformatics support for this work provided by National Institutes of Health (NIH) grants P20GM103436 (Martha Bickford, PI) and P20GM106396 (Donald Miller, PI). V.D.L was supported by an NIH-NIAID funded predoctoral fellowship, T32 AI132146. Additional support was received from the Integrated Programs in Biomedical Sciences (IPIBS) to C.M.I, and a generous startup package from the University of Louisville to K.J.S. This work was supported in part by a grant from the Jewish Heritage Fund for Excellence in Research Enhancement Grant Program at the University of Louisville School of Medicine.