Investigation of Respiratory Syncytial Virus Structural Determinants and Exploitation of the Host Ubiquitin System

Respiratory syncytial virus (RSV) is a globally circulating, non-segmented, negative sense (NNS) RNA virus that causes severe lower respiratory infections. This study explored several avenues to ultimately expand upon our understanding of RSV pathogenesis at the protein level. Evaluation of RSV intrinsic protein disorder increased the relatively limited description of the RSV structure-function relationship. Global proteomics analysis provided direction for further hypothesis-driven investigation of host pathways altered by RSV infection, specifically the interaction between the RSV NS2 protein and the host ubiquitin system. NS2 primarily acts to antagonize the innate immune system by targeting STAT2 for proteasomal degradation. The goal was to identify NS2 residues important for interaction with the host ubiquitin system, as well as describe the mechanism by which NS2 induces host protein ubiquitination. Bioinformatics analysis provided a platform for development of loss-of-ubiquitin-function NS2 mutants. Combining critical mutations as double or triple NS2 ubiquitin mutants displayed an additive effect on reducing NS2-induced ubiquitination. Recombinant RSV (rRSV) containing NS2 ubiquitin mutations maintained their effect on ubiquitin expression during infection in addition to limiting STAT2 degradation activity. NS2 ubiquitin mutants decreased rRSV growth and increased levels of innate immune responses, indicating a correlation between NS2’s ubiquitin function and antagonism of type I IFN to enhance viral replication. Finally, several proteomics strategies were employed to identify specific cellular proteins ubiquitinated by NS2 to further define host-pathogen interactions during RSV infection. This study demonstrates an effective approach for limiting viral protein function to enhance immune responses during infection