UC Davis

Amongst the Poxviridae family one viral species: Cowpox virus (CPXV) has exhibited the broadest known host range and is becoming increasingly of concern due to lethal outbreaks in various zoo animals, pets, and humans across 12 Eurasian countries. Modern phylogenetics has revealed CPXV to include at least 5 major clades, with species-level genetic differences that remain functionally uncharacterized, highlighting the dire need for more research to reclassify cowpox viruses (CPXVs) and understand what was once thought of as a monophyletic species. In this dissertation, we cover the history of CPXV naming with a comprehensive review regarding multiple facets of CPXVs, including phylogenetics, animal and molecular research, pathology, geographic and host range, modern outbreaks, and the potential threat of these viruses. Next, we explore this viral diversity by examining CPXV orthologs of the host range gene K3L which antagonizes the antiviral innate immune protein PKR, with orthologs found throughout the class Mammalia, mapping out how K3L sequence diversity is associated with different orthopoxviruses. We then functionally test 15 of 18 unique CPXV K3L in luciferase-based assays of PKR inhibition, identifying unique species-specific and K3L-specific patterns of PKR inhibition. We characterize CPXV K3Ls in vitro, generating congenic cell lines and CPXV K3L-containing vaccinia viruses and screening the effects on viral replication via viral EGFP expression and titrations on HeLa cells. Finally, we explore the interactions between E3L (another poxvirus PKR inhibitor) and K3L with PKRs of opposite susceptibility and resistance to E3L and K3L, using a split dual luciferase tag system to better understand the mechanism of inhibition of these important host range genes.