Identifying novel antiviral defences against VSV and HIV-1

Aziz, Muhamad Afiq (2019) Identifying novel antiviral defences against VSV and HIV-1. PhD thesis, University of Glasgow.

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Mammalian cells encode an arsenal of antiviral defences, which can be deployed following sensing of an invading pathogen. These cell autonomous defences are stimulated by interferon (IFN) signalling which activates the expression of interferon-stimulated genes (ISGs) that encode numerous antiviral proteins and can alter the thermal landscape of the host. These ISGs can constrain virus replication, transmission and pathogenesis. However, the function of many ISGs in limiting Vesicular Stomatitis Virus (VSV) and Human Immunodeficiency Virus 1 (HIV-1) infection is incompletely understood. In this study, the role of ISGs and fever responses in restricting VSV and HIV-1 replication were investigated.
The IFN system and fever are two interconnected components of the intricate host response to viral infections. In experiments where the incubation temperature was raised to fever-like temperatures, reduced single cycle infection of VSV but not HIV-1 was observed, indicating the possible involvement of host factors that specifically target VSV in these conditions. To further understand how ISGs limit infection, an arrayed ISG expression screen was performed against VSV. This gain-of-function screen revealed TRIM69 as a potent IFN-inducible inhibitor of VSV. Further work identified this inhibition to be highly specific for the VSV Indiana serotype, as VSV New Jersey, DENV-2 and HIV-1 were not inhibited. Using an in vitro evolution approach, a single amino acid substitution in the VSV phosphoprotein, D70Y, conferred complete resistance to the potent inhibitory effect of TRIM69.
In addition to screening for VSV restriction factors, HIV-1 antiviral ISGs were investigated. Analysing several candidate ISGs against a lab-adapted HIV-1 identified EHD4 as a host factor that could block the late stages of HIV-1 replication. However, EHD4 was minimally induced by type I IFN in T-lymphocyte cell lines and primary PBMCs, and deletion of endogenous EHD4 in T-lymphocyte cells did not enhance HIV-1 propagation. An in vitro evolution experiment with lab strain HIV-1 revealed that a single amino acid V35I substitution was sufficient to confer near complete resistance to EHD4. Intriguingly, this V35I mutation was also observed in a virus derived from a chronically infected patient which was propagated in the presence of type I IFN. Further analysis indicated that this V35I substitution was not solely responsible for type I IFN resistance in transmitted HIV-1. Finally, an ISG expression screen against paired transmitted founder (TF) and chronic control (CC) HIV-1 viruses identified several ISGs that could specifically target CC virus but not TF virus. Collectively, this work highlights the complexity of the host defences to not only different viruses but also different strains of virus and at different times after infection which may impact viral transmission and pathogenesis.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: IFN, TF, CC, ISG, VSV, HIV-1.
Subjects: Q Science > QR Microbiology
Q Science > QR Microbiology > QR355 Virology
Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Supervisor's Name: Wilson, Dr. Sam
Date of Award: 2019
Embargo Date: 14 December 2021
Depositing User: Mr Muhamad Afiq Aziz
Unique ID: glathesis:2019-76771
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 20 Dec 2019 15:43
Last Modified: 05 Mar 2020 22:41
Thesis DOI: 10.5525/gla.thesis.76771
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