Protection from hepatitis C : a study of potential immune mechanisms

Hepatitis C virus (HCV) infection is common with more than 180 million people infected worldwide. The majority of individuals who acquire the virus develop chronic infection leading to chronic hepatitis, and are at risk of developing cirrhosis and hepatocellular carcinoma. In the minority who clear infection acutely, an effective adaptive immune response against the virus is paramount. There is presently no available preventative vaccine against HCV infection. In the developed world, injection drug use (IOU) of illicit substances is the dominant source of new infections with high rates of HCV transmission. Rates of HCV infection are particularly high in long term I DU who frequently share drug injecting equipment such as needles and syringes. Despite this there is a cohort of long term I DU with high risk injecting practises who remain negative for any markers of HCV infection when tested for by commercial assays. It is possible they are being exposed to HCV yet remain uninfected, and have been termed exposed uninfected (or EU). It is possible that they possess immune mechanisms of protection. Understanding these mechanisms could be important in developing preventative strategies against HCV infection. This thesis has set out work to identify the potential immune mechanisms that may underlie this resistance to HCV infection in this unique cohort of IOU. Earlier studies had demonstrated HCV specific T cell reactivity in up to 50% of this cohort. These responses were of low amplitude and thus did not entirely explain this apparent resistance. To further study these T cell responses, HCV specific T cell reactivity against recombinant HCV proteins and overlapping peptides spanning the entire HCV polyprotein were studied in EU subjects using the ELlSPOT assay. Multispecific T cell responses were confirmed in up to 50% EU subjects, however were still of comparatively lower amplitude when compared to those seen in spontaneous resolvers of HCV. A large panel of serum cytokines were analysed in 22 EU subjects and levels compared to those found in cases with spontaneous clearance of HCV and chronically infected patients. This demonstrated a distinct cytokine profile in EU with raised levels of innate immune cytokines and proinflammatory chemokines, particularly Interleukin-6 and interleukin-8. These findings suggested an upregulation of the innate immune system in these individuals. To investigate host innate immunogenetic factors possibly related to protection from HCV in this cohort, a functional single nucleotide polymorphism (SNP) in the promoter region of the IL-6 gene as well as the recently discovered IL-28B related SNPs, rs12979860 and rs8099917, were studied. No over-expression or association was demonstrated betvveen these variants and this cohort. As studies had demonstrated an association with EU and a NK cell receptor:HLA compound genotype that favours viral clearance, immunophenotyping of NK cells and dendritic cells was performed in EU cases. The predominantly cytotoxic NK cell subset, CD56dim NK cells, was found to be expanded in EU, suggesting a possible phenotypic alteration in NK cell subsets in this cohort. Further studies on NK cell cytotoxicity against NK-sensitive K562 cell line demonstrated enhanced I L-2 induced cytotoxicity in EU compared to chronic viraemics. Overall, the studies performed in this thesis demonstrated a distinct immune phenotype in EU SUbjects with low amplitude HCV specific T cell reactivity, upregulated innate immune cytokines and cytotoxic NK cell subsets with enhanced cytotoxicity, thus pointing to the initial innate immune responses as the predominant factor in preventing HCV infection in this cohort.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Multicentre comparison of the Glasgow Blatchford and Rockall scores in the prediction of clinical end-points after upper gastrointestinal haemorrhage

Background: The Glasgow Blatchford Score (GBS) is increasingly being used to predict intervention and outcome following upper gastrointestinal haemorrhage (UGIH). Aim: To compare the GBS with both the admission and full Rockall scores in predicting specific clinical end‐points following UGIH. Patients and methods: Data on consecutive patients presenting to four UK hospitals were collected. Admission history, clinical and laboratory data, endoscopic findings, treatment and clinical follow‐up were recorded. Using ROC curves, we compared the three scores in the prediction of death, endoscopic or surgical intervention and transfusion. Results: A total of 1555 patients (mean age 56.7 years) presented with UGIH during the study period. Seventy‐four (4.8%) died, 223 (14.3%) had endoscopic or surgical intervention and 363 (23.3%) required transfusion. The GBS was similar at predicting death compared with both the admission Rockall (area under ROC curve 0.804 vs. 0.801) and full Rockall score (AUROC 0.741 vs. 0.790). In predicting endo‐surgical intervention, the GBS was superior to the admission Rockall (AUROC 0.858 vs. 0.705; P < 0.00005) and similar to the full Rockall score (AUROC 0.822 vs. 0.797). The GBS was superior to both admission Rockall (AUROC 0.944 vs. 0.756; P < 0.00005) and full Rockall scores (AUROC 0.935 vs. 0.792; P < 0.00005) in predicting need for transfusion. Conclusions: Despite not incorporating age, the GBS is as effective as the admission and full Rockall scores in predicting death after UGIH. It is superior to both the admission and full Rockall scores in predicting need for transfusion, and superior to the admission Rockall score in predicting endoscopic or surgical intervention

A national survey of the provision of ultrasound surveillance for the detection of hepatocellular carcinoma

Objective Hepatocellular carcinoma (HCC), the sixth most common cancer worldwide and third most common cause of cancer related death, is closely associated with the presence of cirrhosis. Survival is determined by the stage of the cancer, with asymptomatic small tumours being more amenable to treatment. Early diagnosis is dependent on regular surveillance and the primary objective of this survey was to gain a better understanding of the baseline attitudes towards and provision of ultrasound surveillance (USS) HCC surveillance in the UK. In addition, information was obtained on the stages of cancer of the patients being referred to and discussed at regional multidisciplinary team meetings.Design UK hepatologists, gastroenterologists and nurse specialists were sent a questionnaire survey regarding the provision of USS for detection of HCC in their respective hospitals.Results Provision of surveillance was poor overall, with many hospitals lacking the necessary mechanisms to make abnormal results, if detected, known to referring clinicians. There was also a lack of standard data collection and in many hospitals basic information on the number of patients with cirrhosis and how many were developing HCC was not known. For the majority of new HCC cases was currently being made only at an incurable late stage (60%).Conclusions In the UK, the current provision of USS based HCC surveillance is poor and needs to be upgraded urgently

Detection of HCV-specific IFN-gamma responses in HCV antibody and HCV RNA negative injecting drug users

Background: Detectable HCV-specific cellular immune responses in HCV antibody and RNA negative people who inject drugs (PWID) raise the question of whether some are resistant to HCV infection. Immune responses from people who have been exposed to hepatitis C virus (HCV) and remain anti-HCV negative are of interest for HCV vaccine development; however, limited research addresses this area. Objectives: In a cohort of HCV antibody and RNA negative PWID, we assessed whether the presence of HCV-specific IFN-γ responses or genetic associations provide any evidence of protection from HCV infection. Patients and Methods: One hundred and ninety-eight participants were examined longitudinally for clinical, behavioral, social, environmental and genetic characteristics (IFNL3 genotype [formally IL-28B] and HLA type). Sixty-one of the 198 participants were HCV antibody and RNA negative, with 53 able to be examined longitudinally for HCV-specific IFN-γ ELISpot T cell responses.Results: Ten of the 53 HCV antibody and RNA negative participants had detectable HCV-specific IFN-γ responses at baseline (18%). The magnitude of IFN-γ responses averaged 131 +/- 96 SFC/106 PBMC and the breadth was mean 1 +/- 1 pool positive. The specificity of responses were mainly directed to E2, NS4b and NS5b. Participants with (10) and without (43) HCV-specific IFN-γ responses did not differ in behavioral, clinical or genetic characteristics (P > 0.05). There was a larger proportion sharing needles (with 70%, without 49%, P = 0.320) and a higher incidence of HCV (with 35.1 per 100 py, 95% CI 14.6, 84.4, without 16.0 per 100 py, 95% CI 7.2, 35.6, P = 0.212) in those with IFN-γ responses, although not statistically significant. Half the participants with baseline IFN-γ responses became HCV RNA positive (5/10), with one of these participants spontaneously clearing HCV. The spontaneous clearer had high magnitude and broad Th1 responses, favorable IFNL3 genotype and favorable HLA types. Conclusions: This study demonstrated the detection of HCV-specific IFN-γ responses in HCV antibody and RNA negative individuals, with a tendency for HCV-specific IFN-γ responses to be associated with HCV exposure. The potential role of HCV-specific IFN-γ responses in those who remained HCV RNA negative is of value for the development of novel HCV therapeutics