Exploring the role of IKKε during hepatitis C virus infection with focus on lipid accumulation
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Hepatitis C virus (HCV) targets the hepatocytes in the liver. HCV develops a chronic infection in 85% of infected patients which develops over decades and have different outcomes, for example hepatic steatosis (accumulation of fat in the hepatocytes). The lipid droplet is an important organelle for HCV replication, and HCV is associated with very-low-density lipoproteins (VLDLs) and low-density lipoproteins (LDLs) which take a part in virus entry and assembly by making a hybrid with the virus particle, called a lipoviroparticle (LVP). The pattern recognition receptors (PRRs), e.g. retinoic acid-inducible gene-I-like receptor (RIG-I) and toll-like receptor 3 (TLR3), of the innate immune system detect HCV and activate downstream signals in the cell to activate the immune system. IKKε function to phosphorylate the transcription factors, IRF3 and NF-κB, involved to activate interferons (IFN- β) and proinflammatory cytokines. IKKα has been proven to be a critical host factor for HCV. It is shown that HCV interacts with the PRR DDX3X for its own benefit, resulting in production of lipid droplets for viral assembly. The aim of this master’s thesis was to explore the function of IKKε during HCV infection with focus on lipid accumulation and its role in HCV infection in Huh7.25CD81 cells. The hypothesis was to study if IKKε may have a similar role as IKKα for HCV in the host cell based on the facts that Amlexanox (which inhibits IKKε and TBK1) reverses hepatic steatosis in diet-induced obese mice. IKKε was found to be expressed similar in non-infected and HCV-infected cells. siIKKε was found to have an effective knockdown effect on IKKε in the cells and was used to knockdown IKKε in HCV-infected cells. The absent of IKKε did not benefit HCV at an early stage (day 3 post infection) where HCV-core and HCV RNA expression were weaker compared to cells not treated with siIKKε. The absent of IKKε did benefit HCV at a later stage (day 6 post infection) where HCV-core and HCV RNA expression were stronger compared to cells not treated with siIKKε. This may imply that IKKε plays an inhibitory role on HCV-infection at a later stage as a component involved in the immune system of the host cell. Accumulation of lipid droplets were significant difference in HCV-infected cells compared to non-infected cells. There was a significant difference of lipid droplets accumulation in HCV-infected cells treated with and without siIKKε. This imply how IKKε has an inhibitory effect on HCV-induced lipid droplets accumulation.