Chronic HCV infection (CHC) is a significant cause of both liver related and non-liver related morbidity and mortality worldwide. Disease progression through to cirrhosis and hepatocellular carcinoma is highly variable, and once chronicity of infection has been established, the likelihood of spontaneous clearance without antiviral treatment is extremely low. Safe and highly effective oral antiviral therapy is now available for the treatment of CHC, however price and accessibility may limit the global use of these agents. Furthermore, concerns have been raised regarding the incidence of hepatocellular carcinoma in HCV-infected individuals receiving oral antiviral regimens, and there appears to be a ‘point of no return’ beyond which cirrhotic HCV-infected individuals fail to benefit from antiviral treatment. Thus, there remain a number of unanswered questions on the natural history of HCV infection. Ageing of the immune system, or immunosenescence, appears to contribute to poorer clinical and treatment outcomes, however robust, non-invasive, clinically relevant biomarkers are lacking. MicroRNAs (miRNAs) are short, endogenous non-coding RNAs responsible for post-transcriptional control of host gene expression. Specific patterns of miRNA deregulation have been described in the serum, liver tissue and peripheral immune cells of HCV-infected subjects, and it is hypothesised that they may be suitable as both diagnostic and prognostic biomarkers. We interrogated 3 patient cohorts (providing access to local and national clinical data) to identify patient factors associated with disease progression and both spontaneous and treatment-associated clearance of CHC. We found that chronological age and elevated BMI had the strongest association with hepatic cirrhosis. Co-morbid type 2 diabetes mellitus was associated with poor clinical outcomes during antiviral therapy. Spontaneous clearance of CHC occurred rarely (0.36 per 100 person-years follow up), and was associated with female gender, earlier age at infection, low HCV viral load and co-infection with HBV. Current injecting drug use was negatively associated with spontaneous clearance. We also explored the use of miRNAs as biomarkers in these cohorts. We correlated miRNA expression with cellular markers of immunosenescence to identify novel prognostic biomarkers for disease outcomes in CHC. Our findings demonstrated that CHC was associated with a distinct miRNA signature in the serum and peripheral immune cells. Serum miR-21-5p, miR-122-5p and miR-885-5p levels correlated with the expression of previously described biomarkers of ageing, however these miRNAs performed poorly as biomarkers of cirrhosis in CHC. Elevated serum miR-21-5p expression was an independent predictor of virologic relapse following antiviral therapy, together with HCV genotype. MiR-21-5p also appeared to predict the likelihood of an adverse clinical event during treatment. We identified a further microRNA, miR-345-5p, elevated baseline expression of which correlated with negative clinical outcome during treatment, and was associated with the presence of both hepatic and extra-hepatic malignancy. We explored the regulation of miRNA expression in an in vitro model, and found that interferon-stimulated gene expression is necessary for IFN-induced miR-21-5p expression. Finally, we performed pathway analysis for target genes regulated by miRNAs deregulated during CHC, and found that pathways in cancer were highly enriched. Pathway enrichment was similar between HCV-infected cirrhotic subjects and non-cirrhotic, immunosenescent subjects, suggesting that non-cirrhotic individuals with elevated biomarkers of immunosenescence may be at an increased risk of hepatocellular carcinoma and may benefit from enhanced surveillance and prioritisation for antiviral treatment. Overall, the wealth of clinical and molecular data provided the opportunity to explore possibilities for integrating novel biomarkers into clinical decision-making for monitoring liver-related disease in HCV-infected subjects.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:744142 |
| Date | January 2018 |
| Creators | Bulteel, Naomi Sarah |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/9079/ |
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