Defining the Role of the RSV Small Hydrophobic Protein in Viral Pathogenesis 2255472

Abstract

Abstract Introduction Respiratory Syncytial Virus (RSV) accounts for 33 million infections worldwide each year and is the leading cause of lower respiratory tract infections in infants. Severe RSV-induced disease is associated with the host response to the infection including the increased production of the inflammatory cytokines IL-1β and IL-6. The RSV small hydrophobic (SH) protein has been previously implicated in regulating the secretion of IL-1β following infection. The SH protein is classified as a viroporin, a class of transmembrane proteins that oligomerize to form pores in membranes and can facilitate ion flux to modulate multiple signaling pathways. It is currently unknown what role SH may play in modulating RSV disease severity beyond the modulation of IL-1β production; however, in 2017 there was an outbreak of RSV-B cases containing a mutation in the SH protein that resulted in high hospitalization rates. This outbreak occurred in the summer, an unusual season for RSV cases prior to the COVID-19 pandemic, with the virus expressing a single nucleotide polymorphism within the SH protein that changed an asparagine into an aspartic acid at amino acid 64 (SH N64D). Methods To study the impact of the N64 mutation, we generated a recombinant A2 laboratory strain virus encoded with an aspartic acid at amino acid 63 which is termed A2 SH N63D. We utilized plaque assays, ELISAs, qPCR for cytosolic mtDNA, and human monocyte THP-1 cell lines with a dual reporter for NF-κB and type I IFN response. Results The A2 SH N63D mutant elicited decreased viral titers and early disease compared to the wildtype A2 (WT A2) in mice. We have also observed increased inflammatory cytokines and a type I IFN response following A2 SH N63D infection. We have observed mtDNA release after A2 SH N63D infection within THP-1 cells as well as a STING-dependent type I IFN response Conclusion These results suggest that the aspartic acid within the C-terminus of the SH protein may contribute to RSV pathogenesis and the type I IFN response. Funding Source NIAID R01 AI167249 Topic Categories Viral Immunology (VIR)