An investigation into BK Polyomavirus and host-virus interactions
Caller, Laura Grace
University of Cambridge
Department of Pathology
Doctor of Philosophy (PhD)
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Caller, L. G. (2018). An investigation into BK Polyomavirus and host-virus interactions (Doctoral thesis). https://doi.org/10.17863/CAM.35391
The potentially oncogenic human pathogen BK Polyomavirus (BKPyV) was first identified in 1971 and has since been associated with a number of diseases primarily in immunosuppressed patients. Infection is established in early life and by adulthood up to 90% of populations show seroconversion for the major capsid protein VP1. Despite this infections are rarely cleared, maintaining a silent asymptomatic persistence punctuated with periods of viral shedding in the urine. The virus is non-enveloped and comprises a simple ~5.2 Kb dsDNA genome which expresses just seven known proteins, necessitating a heavy reliance on, and interactions with, host mechanisms in order to efficiently replicate and disseminate within a population. The poorly understood lifelong persistence and failure to clear infection highlights our lack of understanding of the viral life cycle and viral interactions with host processes and responses to infection. Indeed, non-enveloped viruses are thought to spread solely through infected cell lysis but such large-scale lysis should trigger an acute inflammatory response, which is rarely seen in healthy immunocompetent individuals. The research conducted for this thesis first investigates the egress of BKPyV in a non-lytic manner, presenting evidence for an active non-lytic method of viral egress that is dependent on cellular anion homeostasis. Moreover, data generated for this thesis suggests that virions egress via an unconventional secretion pathway which traffics directly from the endoplasmic reticulum (ER) to the plasma membrane in single-membraned vesicles. Further research undertook a whole cell quantitative temporal viromic (QTV) approach, post-experimentally tagging whole cell lysate peptides with isobaric labels (Tandem Mass Tagging, TMT) to provide a greater understanding of host cell proteomic changes throughout BKPyV infection in two primary human cell types over 72 hours of infection. Such an approach identified ~9000 cellular proteins, of which a surprisingly small number changed significantly in abundance in response to BKPyV infection. Of those that were changed in abundance a large proportion were related to cell cycle, revealing that BKPyV infection induces a pseudo-G2 arrest, similar to the G2/M checkpoint. Validation of TMT results in both cell types provided confidence in this robust data set, and further studies highlighted the importance of not only cell cycle status, but the activity of CDK1 for efficient viral infection and replication. Additionally, TMT generated data emphasised the lack of innate immune induction in response to BKPyV infection, suggesting BKPyV exhibits a sophisticated evasion of pathogen recognition.
Virology, Polyomavirus, dsDNA virus, Proteomics, Tandem Mass Tagging, Cell cycle, Immune response
Medical Research Council, Department of Pathology funding.
This record's DOI: https://doi.org/10.17863/CAM.35391
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