Canine Coronavirus Infection Alters the Cell Derived-Extracellular Vesicles Biogenesis and Pharmacological-Mediated Cellular Activity

Date of Award

Spring 2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

Qiana L. Matthews

Second Advisor

Vida A. Dennis

Third Advisor

Daniel Abugri

Abstract

The recent outbreak of novel severe acute respiratory syndrome coronavirus (SARS-CoV)-2 and its ongoing Coronavirus Disease 2019 (COVID-19) pandemic has become a major global health concern. SARS-CoV-2 is the third highly pathogenic coronavirus emerging in the span of the last two decades after SARS-CoV and the Middle East respiratory syndrome (MERS)-CoV, and unfortunately, coronaviruses have the potential to become a long-lasting global health crisis. Coronaviruses can cause acute to severe respiratory, gastrointestinal, neurological, and other systematic diseases in various animal hosts, including birds, humans, and companion animals. Enormous efforts are ongoing to find effective therapeutic strategies for the prevention and management of coronavirus infection; however, this has been limited due to a limited understanding of virus-mediated host responses and pathogenesis. Herein, we propose using naturally secreted extracellular vesicles (EVs), specifically exosomes, to study host-pathogen responses after coronavirus infection. Exosomes utilize similar endosomal sorting pathways and mechanisms as viruses and play a pivotal role in the cell-to-cell progression of viral disease owing to their ability to deliver the exosomal cargo to neighboring or distant target cells while avoiding host immune recognition. Exosomes can manipulate different cellular processes such as inflammation, coagulation, and immunomodulation during viral infection. Hence, we hypothesize that coronavirus could hijack the host exosomal pathway and alter the biogenesis and composition of the EVs in the different host cell lines. Human carcinoma alveolar basal (A549) epithelial cells, Crandell–Rees feline kidney (CRFK) cells, Madin-Darby canine kidney (MDCK) cells, and canine fibroblast tumor cells (A-72) were infected with canine coronavirus (CCoV) in an exosome-free medium at different multiplicity of infection (MOI) at various time points to study susceptibility, exosome biology and pharmacological activity. The cell viability of CRFK, MDCK, and A-72 cells decreased over time, as determined by the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Post-infection EVs were isolated, and transmission electron microscopy (TEM) showed the presence of small EVs (sEVs) after CCoV infection in CRFK and MDCK cells. NanoSight particle tracking analysis (NTA) revealed that EV sizes averaged between 100 and 200 nm at both 48 h and 72 h post-infection. EV particle size and concentration were higher in the CCoV-infected MDCK-derived EVs; however, particle size was reduced at 48 h in CCoV-infected CRFK-derived EVs. Total DNA and total protein were elevated in infection-EV from CRFK and MDCK after CCoV infection. Quantitative analysis of protein levels showed that the expression levels of ACE-2, annexin-V, flotillin-1, TLR-7, LAMP, TNF-α, caspase-1, caspase-8, and others were altered in EVs after infection. In addition, the antiviral potential of pharmacological agents, ketoconazole (1 µM and 5 µM) and climbazole (5 µM and 10 µM), were tested, and the cell viability after CCoV infection was decreased relative to control CRFK cells. However, the cell viability was restored in the co-treatment of CCoV with 5 µM ketoconazole relative to CCoV alone. Although climbazole has shown inhibitory effect on CRFK cells at 10 µM concentration, the cell death was limited when co-treated with CCoV and climbazole at both concentrations relative to CCoV alone. Our findings suggested that coronavirus infection modulates EV biogenesis and composition, which could impact viral progression and disease development. The pharmacological study suggested that the 5 µM of both ketoconazole and climbazole is safe for antiviral activity against CCoV in CRFK cells. Further experimentation is needed to investigate their effectiveness in biogenesis and release. Future experiments with different animal CoVs will also provide a detailed understanding of host EV biology in infection pathogenesis and progression. Hence, EVs could offer a diagnostic and therapeutic tool to study virus-mediated host responses that could be extended to study the interspecies jump of animal CoVs to cause infection in humans.

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