OROPOUCHE VIRUS DISRUPTION OF HOST CELL FUNCTIONS: PYROPTOSIS INDUCTION AND TRANSCRIPTIONAL SUPPRESSION

Oropouche virus (OROV) is an arthropod-borne virus that infects several species of animals and humans, primarily in Central and South America. Despite being described as a human pathogen more than 60 years ago and of its public health significance, little progress has been made towards describing molecular host-cell interactions of this pathogen. While typically self-limiting, severe complications such as aseptic meningoencephalitis, miscarriage, and neonatal malformations can occur. This dissertation contributes to the better understanding of OROV and its host-pathogen interactions by exploring its effects in macrophages as well as the effects of the non-structural protein from the small (S) segment of OROV (OROV NSs protein) in virus-infected culture cells. Macrophages are critical in host defense, but their response to OROV infection remains poorly understood. IL-1β, a key pro-inflammatory cytokine, plays a central role in the febrile response and is regulated by inflammasomes, such as NLRP3. This dissertation demonstrates that macrophages, but not monocytes, are permissive to OROV infection and undergo pyroptosis through the activation of caspases-1, -3, and -8, leading to the cleavage of Gasdermin D (GSDMD) and Gasdermin E (GSDME), and the release of IL-1β. Furthermore, NLRP3-deficient macrophages fail to activate caspases, cleave Gasdermins, or produce IL-1β upon infection. These results indicate that OROV infection triggers NLRP3-mediated IL-1β maturation and release via pyroptosis in macrophages, underscoring their potential role in OROV pathogenesis, which requires further validation using animal models. In other members of the Bunyaviricetes, the NSs protein serves as a major virulence factor. The results from this research reveal that OROV NSs protein targets nucleoli and suppresses host transcription by reducing the levels of the C-terminal domain of the RPB1 subunit of RNA Polymerase II (RNAPII), primarily the hyperphosphorylated llo form. Wild-type (wt) OROV infection decreases RPB1 independently of proteasomal degradation, suggesting an impairment in RPB1 synthesis. Additionally, the translocation of nucleolar protein NPM1 to the nucleoplasm occurs upon the expression of OROV NSs protein from a recombinant Rift Valley Fever Virus MP-12 strain (rMP12-ORONSs) or wt OROV, indicating potential disruption of nucleolar functions alongside transcriptional suppression. These findings suggest that OROV NSs protein facilitates RNAPII RPB1 degradation and host transcriptional suppression, highlighting its role as a major virulence factor in OROV infection. Altogether, the work presented in this dissertation sheds light on molecular virology and host-pathogen interactions, contributing to the fundamental knowledge required for the development of viral countermeasures.

Name thesis:degree_name

Microbiology and Immunology (Doctoral)

Discipline thesis:degree_discipline

Virology/Innate immunity/Molecular Biology

Grantor

The University of Texas Medical Branch at Galveston

Year dc:date.issued

2025

Author dc:creator

• Jurado-Cobena, Eduardo Tarquino 1976-

Advisor dc:contributor.advisor

• Ikegami, Tetsuro, PhD (teikegam@utmb.edu)

Committee members dc:contributor.committeemember

• Alan Barrett, PhD (abarrett@utmb.edu)
• Alexander Freiberg, PhD (anfreibe@utmb.edu)
• Parimal Samir, PhD (fnparima@utmb.edu)
• Michael Holbrook, PhD (michael.holbrook@nih.gov)

Language dc:language.iso

English

Handle dc:identifier.uri

https://hdl.handle.net/2152.3/12837

OAI identifier oai:identifier

oai:utmb-ir.tdl.org:2152.3/12837