bHepatitis C virus (HCV) genome replication is thought to occur in a membranous cellular compartment derived from the endoplasmic reticulum (ER). The molecular mechanisms by which these membrane-associated replication complexes are formed during HCV infection are only starting to be unraveled, and both viral and cellular factors contribute to their formation. In this study, we describe the discovery of nonopioid sigma-1 receptor (S1R) as a cellular factor that mediates the early steps of viral RNA replication. S1R is a cholesterol-binding protein that resides in lipid-rich areas of the ER and in mitochondrion-associated ER membranes (MAMs). Several functions have been ascribed to this ER-resident chaperone, many of which are related to Ca 2؉ signaling at the MAMs and lipid storage and trafficking. Downregulation of S1R expression by RNA interference (RNAi) in Huh-7 cells leads to a proportional decrease in susceptibility to HCV infection, as shown by reduced HCV RNA accumulation and intra-and extracellular infectivity in single-cycle infection experiments. Similar RNAi studies in persistently infected cells indicate that S1R expression is not rate limiting for persistent HCV RNA replication, as marked reduction in S1R in these cells does not lead to any decrease in HCV RNA or viral protein expression. However, subgenomic replicon transfection experiments indicate that S1R expression is rate limiting for HCV RNA replication without impairing primary translation. Overall, our data indicate that the initial steps of HCV infection are regulated by S1R, a key component of MAMs, suggesting that these structures could serve as platforms for initial RNA replication during HCV infection. It is estimated that 170 million humans are chronically infected with hepatitis C virus (HCV). Chronic HCV infection is associated with persistent liver inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma (1). Recently, combination therapy, including pegylated alpha 2a interferon (IFN-␣2a), ribavirin, and specific HCV protease inhibitors, has been approved for the treatment of HCV-infected patients, with high cure rates compared with pegylated IFN-␣2a and ribavirin alone, the previous standard of care (2, 3). However, adverse effects and cost considerations limit the implementation of these new treatment regimens.HCV is an enveloped RNA virus with a single 9.6-kb positivestrand RNA genome that encodes a single open reading frame of approximately 3,000 amino acids flanked by 5= and 3= untranslated regions (UTR) that regulate translation and replication of the viral genome. The 5= UTR contains an internal ribosomal entry site (4) that cooperates with the 3= UTR regions for efficient viral polyprotein translation and RNA replication. Individual viral proteins are produced as a result of the sequential proteolysis of the HCV polyprotein by cellular and viral proteases, which produce structural proteins (core, E1, and E2) that are major components of the viral particles and p7 and NS2, which mediate infectious-particle assembly in...

A major goal in the control of hepatitis C infection is the development of a vaccine. Here, we have developed a novel HCV vaccine candidate based on the highly attenuated poxvirus vector MVA (referred to as MVA-HCV) expressing the nearly full-length (7.9-kbp) HCV sequence, with the aim to target almost all of the T and B cell determinants described for HCV. In infected cells, MVA-HCV produces a polyprotein that is subsequently processed into the structural and nonstructural HCV proteins, triggering the cytoplasmic accumulation of dense membrane aggregates. In both C57BL/6 and transgenic HLA-A2-vaccinated mice, MVA-HCV induced high, broad, polyfunctional, and long-lasting HCV-specific T cell immune responses. The vaccine-induced T cell response was mainly mediated by CD8 T cells; however, although lower in magnitude, the CD4 ؉ T cells were highly polyfunctional. In homologous protocol (MVA-HCV/MVA-HCV) the main CD8 ؉ T cell target was p7؉NS2, whereas in heterologous combination (DNA-HCV/MVA-HCV) the main target was NS3. Antigenic responses were also detected against other HCV proteins (Core, E1-E2, and NS4), but the magnitude of the responses was dependent on the protocol used. The majority of the HCVinduced CD8؉ T cells were triple or quadruple cytokine producers. The MVA-HCV vaccine induced memory CD8 ؉ T cell responses with an effector memory phenotype. Overall, our data showed that MVA-HCV induced broad, highly polyfunctional, and durable T cell responses of a magnitude and quality that might be associated with protective immunity and open the path for future considerations of MVA-HCV as a prophylactic and/or therapeutic vaccine candidate against HCV. More than 170 million people are infected with hepatitis C virus (HCV) worldwide, and each year 3 million people are newly infected (1). Twenty percent of infected people eliminate the virus over the weeks or months following an acute infection and are frequently asymptomatic. The remaining 80% will develop chronic disease and, of these, nearly 20% of the chronic patients ultimately develop liver cirrhosis and 1 to 5% will develop liver cancer (2, 3).The standard-of-care treatment for patients infected with HCV is a combination of pegylated interferon-␣ and ribavirin. This treatment is long, displays a broad side effect profile, commonly fails, and is prohibitively expensive in developing countries (4). A major effort has been directed to the development of new antiviral agents. Direct-acting antivirals in clinical development include NS3-4A protease inhibitors, two of which, telaprevir and boceprevir, have recently been approved for the treatment of HCV genotype 1 infection in combination with pegylated interferon-␣ and ribavirin, nucleoside/nucleotide analogue, and non-nucleoside inhibitors of HCV RNA-dependent RNA polymerase and NS5A inhibitors, as well as host target agents (5). Due to the cost, side effects, and complex treatments, as well as the development of HCV-resistant mutants and viral heterogeneity, antiviral therapy is not the solution to eradicate...

Hepatitis C virus (HCV) infection constitutes a significant health burden worldwide, because it is a major etiologic agent of chronic liver disease, cirrhosis and hepatocellular carcinoma. HCV replication cycle is closely tied to lipid metabolism and infection by this virus causes profound changes in host lipid homeostasis. We focused our attention on a phosphatidate phosphate (PAP) enzyme family (the lipin family), which mediate the conversion of phosphatidate to diacylglycerol in the cytoplasm, playing a key role in triglyceride biosynthesis and in phospholipid homeostasis. Lipins may also translocate to the nucleus to act as transcriptional regulators of genes involved in lipid metabolism. The best-characterized member of this family is lipin1, which cooperates with lipin2 to maintain glycerophospholipid homeostasis in the liver. Lipin1-deficient cell lines were generated by RNAi to study the role of this protein in different steps of HCV replication cycle. Using surrogate models that recapitulate different aspects of HCV infection, we concluded that lipin1 is rate limiting for the generation of functional replicase complexes, in a step downstream primary translation that leads to early HCV RNA replication. Infection studies in lipin1-deficient cells overexpressing wild type or phosphatase-defective lipin1 proteins suggest that lipin1 phosphatase activity is required to support HCV infection. Finally, ultrastructural and biochemical analyses in replication-independent models suggest that lipin1 may facilitate the generation of the membranous compartment that contains functional HCV replicase complexes.