Browsing by Subject "Hepatocytes"
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Item Histological and Immunohistochemical Findings in Two Subtypes of Hepatitis B Related Acute Liver Failure(2017-01-17) Choo, Vincent; Peng, Lan; Dao, Doan Y.; Hameed, Bilal; Lee, William M.; Acute Liver Failure Study Group (ALFSG)BACKGROUND: Acute liver failure (ALF) occurs when rapid-onset, severe liver cell damage results in coagulopathy and encephalopathy. Multiple etiologies yield a remarkably similar syndrome including acetaminophen overdose, drug-induced liver injury, and Hepatitis B Virus (HBV) infection. ALF in the setting of HBV occurs in 1% of primary acute HBV infections (AHBV-ALF), but can also evolve during chronic HBV infection (CHBV-ALF), particularly in reactivation, when patients receive immunosuppressive or cancer chemotherapy. OBJECTIVE: To determine whether differences between the two varieties of HBV-ALF, primary acute HBV infection and reactivation of HBV, are reflected in differences in HBV immunohistochemical bio-markers in liver: HBV core antigen (HBcAg) & HBV surface antigen (HBsAg). METHODS: A total of 21 patients from the Acute Liver Failure Study Group (ALFSG) were identified as having sufficient liver tissue for the staining panel required. Samples were immunostained using dye-labeled antibodies for HBV core antigen (HBcAg) and HBV surface antigen (HBsAg). We performed routine hematoxylin & eosin (H&E) staining for overall morphology (degree of necrosis, presence of plasma cells) and reviewed clinical history to stratify each case as either AHBV-ALF (primary infection, N=11) or CHBV-ALF (reactivation, N=10). For H&E, we assessed number of plasma cells, percent tissue necrosis, and degree of collapse. Eleven biopsies had <25% viable hepatocytes, making further analysis of staining patterns unsuccessful. The remaining acute HBV cases had very little, if any, HBsAg staining and variable levels of nuclear HBcAg staining. In contrast, one CHBV-ALF case had intense staining for both HBsAg and HBcAg, probably related to the presence of immunosuppression. SUMMARY/CONCLUSION: Immunohistochemical staining of liver biopsies/explants revealed scant viable hepatocytes in more than half, limiting assessment of location of viral products within cells. In general, when assessment was possible, AHBV-ALF demonstrated little to no HBsAg and variable amounts of HBcAg staining. Immunosuppression leads to much higher levels of HBV proteins within hepatocytes, and perhaps suggests that the virus is directly cytotoxic in this setting. By the time of liver transplantation, virtually all HBsAg had disappeared from hepatocytes in AHBV-ALF, but high quantities of HBsAg and HBcAg were found in immunosuppressed patients with reactivation. These two forms of acute liver failure due to hepatitis B have remarkably different pathogenetic phenotypes.Item Identification of Host Factors Required for Hepatitis C Virus Infection(2009-01-14) Huang, Hua; Ye, JinHepatitis C virus (HCV), a positive-strand RNA virus, infects more than 170 million people and is the leading cause of liver failure worldwide. A protective vaccine is not yet available. Current interferon-based therapies are only effective in a fraction of patients. Thus, there is an urgent need to develop better therapeutic strategies. However, the intrinsic low fidelity of HCV replication makes it more difficult to develop drugs targeting viral proteins since HCV could quickly generate drug-resistant strains. In this context, drugs targeting host factors that control HCV infection may be more effective therapies in that the potency of drugs is not affected by viral mutations. For this purpose, more knowledge regarding host factors involved in HCV infection is needed. HCV is known to replicate on intracellular membrane vesicles. In searching for host proteins localized in membrane vesicles containing HCV replication complex, a magnetic immuno-isolation procedure was employed. This study identified that Apolipoprotein B, Microsomal Triglyceride Transfer Protein, and Apolipoprotein E, three proteins participated in the assembly of very low-density lipoprotein (VLDL) were enriched in membrane vesicles. It was demonstrated that agents inhibiting VLDL assembly also inhibit the secretion of HCV. These studies raise the possibility for treating HCV infection with agents blocking VLDL secretion. HCV infection is also known to produce reactive oxygen species (ROS), which initiate lipid peroxidation. We found that when HCV-infected cells were exposed to polyunsaturated fatty acids (PUFAs) in the absence of lipid-soluble antioxidants, a dramatic increase in lipid peroxidation caused a reduction in HCV RNA. Because peroxidation of PUFAs only occurs in HCV-infected cells that produce ROS, PUFAs could be used to suppress HCV replication in patients without intolerable toxicity. Different in vitro model systems have been used to study the HCV lifecycle. However, the genotype1 HCV, which is the most difficult strain to treat in clinic, still can not be grown in cultured cells. We found a cell line named HCV Replication Permissive 1 (HRP1) that supports the replication of genotype 1 HCV. Interestingly, HRP1 cells appear to have normal interferon response, suggesting a novel innate antiviral pathway may be disrupted in these cells.Item The Role of Interferon Stimlated Genes in Resistance and Immunity to Hepatitis C Virus Infection(2009-01-15) Erickson, Andrea Kaup; Gale, Michael, Jr.Hepatitis C Virus (HCV) is a global public health issue with 170 million people chronically infected. The only approved treatment for HCV infection is interferon-alpha based therapy, resulting in viral clearance in approximately fifty percent of patients treated. Interferon therapy mimics endogenous type I interferon signaling, which plays a crucial role in the innate antiviral response through the regulation of interferon stimulated genes (ISGs). ISGs encode antiviral effector proteins that limit viral replication and spread. Hundreds of ISGs have been identified in the liver of HCV patients who respond to IFN therapy; however the functions of most these genes are not known. In order to better understand the molecular mechanisms of the IFN antiviral response, studies were initiated to identify and characterize the functions of novel ISGs involved in controlling HCV infection. To determine the most effective IFN for these studies, the antiviral activity and functional effects of three distinct type I IFN subtypes were evaluated. Consensus interferon demonstrated maximal suppression of HCV replication, correlating with enhanced IFN signaling and ISG induction. A functional genomics analysis of IFN treated primary hepatocytes resulted in the identification of eighty-six ISGs differentially induced by consensus interferon. Future evaluations of the role of these genes in HCV outcome, using integrated approaches as described here, will be invaluable in further defining the molecular mechanisms of the innate IFN antiviral response. Although a number of ISGs have recently been reported to function as antiviral proteins in vitro, these studies did not validate the involvement of these genes in innate immunity or disease outcome. In order to evaluate the biological relevance of a genetic variant of the oligoadenylate synthetase 1 (OAS1) gene in resistance to HCV infection, an integrated approach of epidemiology, molecular genetics, and functional biology was used. Genetic and epidemiologic analyses identified a single-base mutation in OAS1 that associates with HCV resistance in individuals with a high-risk for HCV infection. Functional studies of the resulting OAS1 variant demonstrated altered biological activities of the protein, resulting in enhanced suppression of HCV genotype 1a and 2a infectious clones. Furthermore, a recombinant drug form of the OAS1 variant demonstrated broad antiviral activity, suggesting great promise for this protein as a therapeutic for HCV infection.