Doctor of Philosophy (PhD)


Department of Pathobiological Sciences

Document Type



Several members of the Family Herpesviridae are clinically significant pathogens, affecting humans and a wide range of animals. Alphaherpesviruses infect epithelial cells at the primary site of infection and subsequently invade adjacent sensory neurons. Infectious bovine rhinotracheitis (IBR) is an economically important disease caused by bovine herpesvirus 1 (BoHV-1), which belongs to the subfamily Alphaherpesvirinae, genus Varicellovirus. To date, vaccination is the only preventive measure against IBR. Understanding determinants of herpesvirus replication and innate immune regulation is important to help further develop vaccines that are efficacious and incapable of establishing latency in the host nervous system. The alphaherpesvirus tegument protein UL37 is a multi-functional, well-conserved protein that serves functional roles in virion morphogenesis and innate immune regulation, which makes it a potential target for virus attenuation. In this study, key structural characteristics of herpes simplex virus type 1 (HSV-1) tegument protein UL37 were predicted and analyzed using multiple computational software; comparatively, the importance of BoHV-1 UL37 in virion morphogenesis was determined; and the ability of BoHV-1 UL37 to regulate the innate immune response via targeting cyclic GMP-AMP synthase (cGAS) was demonstrated. Using AlphaFold, the predicted structure of the entire HSV-1 UL37 was determined, especially the previously undetermined structure of the C-terminal half of UL37, containing alpha-helical regions and an unstructured, disordered tail end. In Vero and SH-Sy5Y cells, an HSV-1 Δ480N mutant virus was used to show that the HSV-1 UL37 C-terminal half is sufficient to effectively transport the virus towards the nucleus of infected cells. To compare functional differences of UL37 in BoHV-1, a BoHV-1 UL37 knockout mutant virus (BoHV-1 ΔUL37) was constructed and analyzed in Madin-Darby bovine kidney (MDBK) cells. Viral replication kinetics, plaque morphology analysis and immunofluorescence assay (IFA) of BoHV-1 ΔUL37, compared to BoHV-1 wild-type (WT), showed a slight delay in viral growth, a decrease in plaque size and delayed viral capsid transport in BoHV-1 ΔUL37. Therefore, BoHV-1 UL37 plays a key role in facilitating intracellular transport, and viral spread, but is dispensable for virus replication and transport to the nucleus in MDBK cells. Lastly, the role of BoHV-1 UL37 in innate immune regulation was examined. To analyze the interaction of BoHV-1 UL37 and bovine cGAS, a FLAG-tagged BoHV-1 UL37 was co-expressed with eGFP-tagged bovine cGAS (GFP-boCGAS) in 293 cells. Western blot analysis showed co-immunoprecipitation of BoHV-1 UL37 and bocGAS. In addition, IFA imaging using confocal microscopy showed that bocGAS is sequestered to perinuclear zones in the presence of BoHV-1 UL37. Relative mRNA expression levels of interferon alpha (IFNα) and interferon beta (IFNβ) were significantly increased in BoHV-1 ΔUL37 as compared to BoHV-1 WT. Analysis of 2’3’-cGAMP levels in MDBK infected cells suggest that BoHV-1 UL37 regulates type 1 interferon response by targeting cGAS function. These results suggest that BoHV-1 UL37 may be a desirable target for attenuation of the virus and its deletion may potentially induce an adjuvant effect in vaccine candidates. Further studies are necessary to analyze the potential of a BoHV-1 ΔUL37 mutant virus as a candidate for vaccine development against BoHV-1.



Committee Chair

Kousoulas, Konstantin G.

Available for download on Friday, July 10, 2026