Date of Award

6-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Biomedical Sciences

Track

Microbiology, Immunology, and Biochemistry

Research Advisor

Stacey Schultz-Cherry, PhD

Committee

Carolyn B. Coyne, PhD; Radhakrishna Rao, PhD; Jason W. Rosch, PhD; Michael A. Whitt, PhD

Abstract

While human astroviruses (HAstV) were discovered nearly 45 years ago, these small positive-sense RNA viruses remain critically understudied. These studies provide fundamental new research on astrovirus pathogenesis and disruption of the gut epithelium by induction of epithelial-mesenchymal transition (EMT) following astrovirus infection. Here we characterize HAstV-induced EMT as an upregulation of SNAI1 and VIM with a down regulation of CDH1 and OCLN, loss of cell-cell junctions most notably at 18 hours post-infection (hpi), and loss of cellular polarity by 24 hpi. While active transforming growth factor- (TGF-) increases during HAstV infection, inhibition of TGF- signaling does not hinder EMT induction. However, HAstV-induced EMT does require active viral replication. These are among the first studies describing the induction of EMT by a non-oncogenic virus and provides an exciting opportunity to understand EMT induction independent of cancer. Our findings likely extend beyond astrovirus to other viruses and may shed light on novel ways pathogens can circumvent the barriers meant to protect against them. Crossing these barriers can lead to systemic and even fatal infections. Astroviruses can be especially problematic in immunocompromised individuals and infants where the virus has been associated with necrotizing enterocolitis, severe and persistent diarrhea, and even encephalitis and meningitis. Using our novel tools and models, we demonstrate that the FDA-approved broad-spectrum anti-infective drug nitazoxanide (NTZ) blocks astrovirus replication in vitro with a 50% effective concentration (EC50) of approximately 1.47μM. It can be administered up to 8 hours post-infection and is effective against multiple human astrovirus serotypes including clinical isolates. Most importantly, NTZ reduces viral shed in vivo, exhibiting its potential as a future clinical therapeutic. Overall, these studies will further our understanding of astrovirus pathogenesis leading to the development of therapeutic options for vulnerable populations.

Declaration of Authorship

Declaration of Authorship is included in the supplemental files.

ORCID

0000-0003-3883-1232

DOI

10.21007/etd.cghs.2020.0507

2020-016-Hargest-DOA.pdf (392 kB)
Declaration of Authorship

Available for download on Friday, June 25, 2021

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