Dendritic cells (DCs) constitute a large family of immune cells with a dendritic morphology and a critical role in all aspects of an immune response and immune regulation, from immunogenicity to tolerance. One of the important characteristic of DCs is maturation, during which DCs undergo significant changes in their phenotypic and functional properties and change from phagocytic cells to highly efficient antigen presenting cells (APCs). Dendritic cells have recently been at the centre of attention as a promising tool in treatment or control of cancer and infectious diseases. Accordingly, DCs have been generated, matured, and loaded with tumor-associated or microbial antigens ex vivo, to be subsequently used as therapeutic tools or vaccine carriers.<p> Hepatitis C virus (HCV) is a hepatotropic virus, which infects the liver in humans and results in a chronic infection in most cases. The persistent infection of the liver eventually results in cirrhosis and/or hepatocellular carcinoma in 15-20 years. Chronic hepatitis C (CHC) has recently become a serious health concern and the leading cause of liver transplantation. The mechanism of persistence of the virus is not clear yet, but as a Th1-type immune response is strongly correlated with elimination of HCV in vivo, it is evident that insufficient cellular immunity is a contributing factor. Non-cytopathic viruses such as HCV may infect immune cells to modify and evade a protective immune response. Dendritic cells, which are the most potent APCs, and uniquely capable of initiating a primary immune response, have been considered as a target for HCV. Inhibition of DC maturation by HCV has been suggested as a potential contributing factor in immune evasion; however, this issue remains controversial as many contradictory results have been reported.<p> To investigate this contention, we initially planned to evaluate the effects of HCV on DCs of CHC patients; however, due to limited access to patients blood, we instead elected to examine the effects of HCV genes products on in vitro generated DCs from healthy volunteers. Specific attention was paid to the generation, maturation, and transfection of DCs in vitro, as variability in procedures might have been responsible for the controversial reports. Viral vectors have generally been used to transfect DCs; however, a vector and HCV genes might have synergistic effects on DC maturation. Thus, our first objective was to develop an efficient non-viral transfection method while retaining high viability of the DCs, as previous efforts in this regard resulted either in low efficiency or in low viability of DCs after transfection. In order to improve the viability of DCs after transfection, we established a new method for fast generation of monocyte-derived DCs (Mo-DCs) in two to three days. By performing a comprehensive study on transfection reagents, electroporation, and nucleofection with DNA or in vitro transcribed (IVT) RNA, we successfully established a new, highly efficient non-viral method for transfection of DCs with long-term viability. This method is based on the use of the X1 program of a nucleofection device with IVT RNA and results in high transfection efficiency of 93%, with 75% viability of DCs 72 h after transfection.<p> Subsequently, we performed a comprehensive study on the effects of different maturation methods on the phenotype, function and gene expression profile of DCs. Three commonly used treatments, TNF-á, LPS and a maturation cocktail (MC) consisting of IL-1â, IL-6, TNF-á, and prostaglandin E2 (PGE2) were compared. Our results showed that there is a significant difference in the level of maturity between these treatments, and MC generated more functionally competent mDCs than TNF-á or LPS. In addition, MC induced Th1-promoting changes in the transcriptional profile of mDCs. This observation was important, as the presence of PGE2 in MC was previously challenged based on the potential induction of Th2-biased immune responses. However, our results suggest retaining PGE2 in the cocktail because of the fact that MC generated highly competent and functional mDCs with a Th1-promoting transcriptional profile. Finally, Mo-DCs were transfected with IVT HCV RNAs, individually or in combination. While HCV genes had no inhibitory effect on DC maturation, transfection of DCs with IVT core RNA appeared to result in changes compatible with maturation. To investigate this in more detail, the transcriptional profiles of DCs transfected with IVT core, NS3 or green fluorescent protein (GFP) RNA were examined using a DC-specific membrane array. Of the 288 genes on the array, 46 genes were distinctively up- or down-regulated by transfection with IVT core RNA in comparison to NS3 or GFP RNA treatments, 42 of which are involved in DC maturation. The effects of core on maturation of DCs were further confirmed by a significant increase in surface expression of CD83 and HLA-DR, a reduction of phagocytosis, as well as an increase in proliferation and IFN-ã secretion by T cells in a mixed lymphocyte reaction assay. These results show that HCV core does not have an inhibitory effect on human DC maturation, but could be a target for the immune system.<p> The use of a non-viral method of transfection combined with confirmed transcriptional profiles of DCs in this study may make these results conclusive for in vitro generated DCs from healthy volunteers. However, further investigations are required to confirm the effects on DCs from CHC patients.

Dendritic cells (DCs) constitute a large family of immune cells with a dendritic morphology and a critical role in all aspects of an immune response and immune regulation, from immunogenicity to tolerance. One of the important characteristic of DCs is maturation, during which DCs undergo significant changes in their phenotypic and functional properties and change from phagocytic cells to highly efficient antigen presenting cells (APCs). Dendritic cells have recently been at the centre of attention as a promising tool in treatment or control of cancer and infectious diseases. Accordingly, DCs have been generated, matured, and loaded with tumor-associated or microbial antigens ex vivo, to be subsequently used as therapeutic tools or vaccine carriers.<p> Hepatitis C virus (HCV) is a hepatotropic virus, which infects the liver in humans and results in a chronic infection in most cases. The persistent infection of the liver eventually results in cirrhosis and/or hepatocellular carcinoma in 15-20 years. Chronic hepatitis C (CHC) has recently become a serious health concern and the leading cause of liver transplantation. The mechanism of persistence of the virus is not clear yet, but as a Th1-type immune response is strongly correlated with elimination of HCV in vivo, it is evident that insufficient cellular immunity is a contributing factor. Non-cytopathic viruses such as HCV may infect immune cells to modify and evade a protective immune response. Dendritic cells, which are the most potent APCs, and uniquely capable of initiating a primary immune response, have been considered as a target for HCV. Inhibition of DC maturation by HCV has been suggested as a potential contributing factor in immune evasion; however, this issue remains controversial as many contradictory results have been reported.<p> To investigate this contention, we initially planned to evaluate the effects of HCV on DCs of CHC patients; however, due to limited access to patients blood, we instead elected to examine the effects of HCV genes products on in vitro generated DCs from healthy volunteers. Specific attention was paid to the generation, maturation, and transfection of DCs in vitro, as variability in procedures might have been responsible for the controversial reports. Viral vectors have generally been used to transfect DCs; however, a vector and HCV genes might have synergistic effects on DC maturation. Thus, our first objective was to develop an efficient non-viral transfection method while retaining high viability of the DCs, as previous efforts in this regard resulted either in low efficiency or in low viability of DCs after transfection. In order to improve the viability of DCs after transfection, we established a new method for fast generation of monocyte-derived DCs (Mo-DCs) in two to three days. By performing a comprehensive study on transfection reagents, electroporation, and nucleofection with DNA or in vitro transcribed (IVT) RNA, we successfully established a new, highly efficient non-viral method for transfection of DCs with long-term viability. This method is based on the use of the X1 program of a nucleofection device with IVT RNA and results in high transfection efficiency of 93%, with 75% viability of DCs 72 h after transfection.<p> Subsequently, we performed a comprehensive study on the effects of different maturation methods on the phenotype, function and gene expression profile of DCs. Three commonly used treatments, TNF-á, LPS and a maturation cocktail (MC) consisting of IL-1â, IL-6, TNF-á, and prostaglandin E2 (PGE2) were compared. Our results showed that there is a significant difference in the level of maturity between these treatments, and MC generated more functionally competent mDCs than TNF-á or LPS. In addition, MC induced Th1-promoting changes in the transcriptional profile of mDCs. This observation was important, as the presence of PGE2 in MC was previously challenged based on the potential induction of Th2-biased immune responses. However, our results suggest retaining PGE2 in the cocktail because of the fact that MC generated highly competent and functional mDCs with a Th1-promoting transcriptional profile. Finally, Mo-DCs were transfected with IVT HCV RNAs, individually or in combination. While HCV genes had no inhibitory effect on DC maturation, transfection of DCs with IVT core RNA appeared to result in changes compatible with maturation. To investigate this in more detail, the transcriptional profiles of DCs transfected with IVT core, NS3 or green fluorescent protein (GFP) RNA were examined using a DC-specific membrane array. Of the 288 genes on the array, 46 genes were distinctively up- or down-regulated by transfection with IVT core RNA in comparison to NS3 or GFP RNA treatments, 42 of which are involved in DC maturation. The effects of core on maturation of DCs were further confirmed by a significant increase in surface expression of CD83 and HLA-DR, a reduction of phagocytosis, as well as an increase in proliferation and IFN-ã secretion by T cells in a mixed lymphocyte reaction assay. These results show that HCV core does not have an inhibitory effect on human DC maturation, but could be a target for the immune system.<p> The use of a non-viral method of transfection combined with confirmed transcriptional profiles of DCs in this study may make these results conclusive for in vitro generated DCs from healthy volunteers. However, further investigations are required to confirm the effects on DCs from CHC patients.

This thesis investigated how virologic and serologic kinetics of the hepatitis B virus (HBV) could influence the natural history and treatment of chronic hepatitis B (CHB). Virologic kinetics were described in the first five studies, with serologic kinetics being described in the next five. The first study delineated the HBV DNA profiles of 1,400 treatment-naive Asian CHB patients. Increasing viremia was noted with increasing age, highlighting the large therapeutic demand in Asian patients with hepatitis B e antigen (HBeAg)-negative CHB. The second study analyzed the association between viral load and liver histology in 319 patients, showing HBV DNA levels to have strong association with HBeAg-negative disease severity. The next three studies investigated the efficacy of baseline and on-treatment HBV DNA levels in predicting clinical outcomes in 117, 165 and 222 patients on telbivudine, lamivudine plus adefovir and entecavir respectively. Absolute on-treatment HBV DNA levels at week 12 or 24 predicted favorable outcome with telbivudine and lamivudine / adefovir therapy, while excellent viremic suppression with very low rate of resistance development was shown in the entecavir study. The following three studies examined the role of serum HBsAg measurements in different disease phases of CHB. First, histology specimens of 140 HBeAg-positive patients were analyzed together with HBsAg levels. High HBsAg titers (>25,000 IU/mL) were found to be predictive of insignificant fibrosis. In the next study involving 300 treatment-naive HBeAg-negative patients stratified by their viral loads, combination of low HBsAg and HBV DNA levels predicted significant HBsAg decline. This is followed by a study comparing HBsAg levels of 203 CHB patients achieving HBsAg seroclearance with 203 age- and sex-matched controls over a 3-year period. Serum HBsAg <200 IU/mL and a significant annual HBsAg reduction were found to be predictive of HBsAg seroclearance. The penultimate study investigated the usage of two novel HBV serologic markers, linearized HBsAg and hepatitis B core-related antigen, in 329 CHB patients achieving HBsAg seroclearance with a conventional HBsAg assay. More than 40% of patients had seropositivity to one or both serologic tests. Finally, the last study of this thesis investigated and compared the changes in serum HBsAg, intrahepatic HBV DNA and covalently closed circular DNA (cccDNA) after 1 year of nucleoside analogue therapy. Minimal changes in both serum HBsAg and intrahepatic cccDNA were noted after 1 year of therapy, but in patients with a significant decline in serum HBsAg levels, there was a corresponding significant reduction in cccDNA. This series of studies illustrated how the monitoring of serum HBV DNA and HBsAg levels could assist in optimizing management strategies for CHB. / published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Medicine / Master / Doctor of Medicine

Infection with hepatitis C virus (HCV) causes significant morbidity and mortality. An understanding of the factors associated with both acquisition and clearance of HCV infection is critical to prevention strategies including vaccine development. Although research in the prison environment is logistically challenging, inmates are a premier risk group. Accordingly, a prospective cohort study of prisoners with monthly sampling for HCV viraemia was undertaken to assess the incidence of, and risk factors for, infection; and to assess the natural history of infection when detected by viraemia. The incidence of infection was 8 per 100 person years, with the incidence of "high risk" and "possible" HCV transmission risk events being 61 and 210 per 100 person years respectively. The first case of HCV infection in prison with tattooing as the probable route of acquisition was reported. A novel phenotype of HCV infection with HCV viraemia and subsequent clearance without the development of symptoms, biochemical hepatitis or seroconversion on HCV specific enzyme immunoassay (EIA), despite more than one year of follow-up, was reported. HCV-specific cell mediated immune responses were detected in the subjects analysed. These subjects also had indeterminate HCV serological responses directed against non-structural proteins detected on a recombinant immunob10t assay (RIBA) that were stable over time and typically predated HCV viraemia. The prevalence of such responses ranged from 29-79% in other relevant cohorts, including injecting drug users (IDUs) and multiply-transfused patients with thalassaemia. The antibody response against the non-structural protein, NS5 was the most reproducible. This reactivity was blocked in 57% of subjects when sera were pre-incubated with recombinant HCV proteins, suggesting HCV-specificity. A case-control study was undertaken to examine whether such responses predicted protection from "classical" HCV infection with EIA seroconversion. Cases that developed HCV viraemia and EIA seroconversion were more likely to have these responses at baseline (when aviraemic) than controls, demonstrating that they do not protect against acute infection. However, the rate of viral clearance in subjects with indeterminate RIBA responses that subsequently developed acute infection and were followed for viral clearance was high (88%), suggesting that such subjects have immune responses that are associated with viral clearance.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (M. Med. Sc.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 51-58).

Mainz, Univ., Diss., 2001.

Mainz, Univ., Diss., 2001.

Mainz, Univ., Diss., 2001.