INTERFERON GAMMA AND CONTROL OF HCV REPLICATION

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 黑猩猩是唯一可用的丙型肝炎病毒（HCV）感染的动物模型。HCV在大约70%的感染者中终生存在。 这种病毒的慢性感染是严重的长期健康问题的原因，包括肝病和癌症。事实上，美国的大多数肝移植都是由HCV引起的慢性肝病的直接结果。约2%的世界人口感染HCV，因此它被认为是一个重大的全球健康问题。目前，还没有针对这种病毒的疫苗，可用的治疗方法在许多情况下是有毒和无效的。 HCV复制的控制机制，并最终终止那些能够解决感染的人仍然不清楚，然而，生产这种病原体的有效疫苗，并有效的治疗方法的未来发展是至关重要的。在转基因小鼠模型和黑猩猩中的实验中，已经证明可以通过免疫细胞分泌细胞因子IFN-γ来控制B型肝炎病毒复制（Guidotti和Chisari. Ann Rev Immunol 2001; 19：65-89），而不是需要通过免疫系统杀死感染细胞的病毒控制。使用体外系统的实验表明，IFN-γ可有助于控制HCV复制（Frese等Hepatology 2002; 35：694703; Lanford等人J Virol 2003; 77：1092-1104）。然而，该体外数据不一定反映体内事件。已经进行了一项研究，检查IFN-γ的补充是否改变慢性HCV感染中的病毒复制（Shin等J Virol 2005; 79：13412-30）;然而，很可能感染病毒已经从HCV特异性应答中逃逸，并且持续的HCV特异性免疫应答在该感染阶段是有缺陷的（Bowen和步行者。Nature 2005; 436：946-52）。因此，该数据不太可能反映IFN-γ在解决感染的个体中自然控制感染中所起的作用。 本研究将通过仔细定义IFN-γ的生物学效应被阻断时病毒复制的动力学和免疫应答来解决这个问题。为了建立比较的基线，将用同源病毒再次感染先前已解决HCV感染的黑猩猩，并监测病毒学和免疫学参数。这些动物应快速控制和解决感染（Shoukry等人，J Exp. 2003; 197：1645-1655; Grakoui等人Science. 2003; 302：659-662）。 此后，研究动物将再次感染，同时IFN-γ的生物学效应被中和，并再次评估病毒复制和免疫应答的动力学。这两种感染的比较将允许评估这种细胞因子在控制HCV复制中所起的作用。IFN-γ作用的中和通过施用先前已用于灵长类动物的抗IFN-γ的人源化单克隆抗体来实现。通过这个实验，我们希望确定病毒复制的控制是否依赖于IFN-γ。 这将为开发预防性HCV疫苗和修复导致慢性感染的免疫应答缺陷的可能疗法提供重要信息。 关于HCV清除机制的线索很少，因此控制HCV感染结果的因素（即病毒的持续、终身复制与暴露于病毒后几周的急性消退）仍然未知。 了解主要抗病毒细胞因子IFN-γ所起的作用对于设计疫苗以抑制HCV在肝脏中的复制并希望在对器官造成永久性损伤之前消除它至关重要。这一点至关重要，因为选择何种疫苗技术来引发抗病毒反应可能决定免疫接种的成败。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The chimpanzee is the only available animal model for hepatitis C virus (HCV) infection. HCV persistents life-long in humans in approximately 70% of individuals infected. Chronic infection with this virus is the cause of serious long-term health problems that include liver disease and cancer. Indeed, most liver transplantations in the United States are the direct result of chronic liver disease caused by HCV. Approximately 2% of the world's population is infected with HCV, and it is therefore considered a significant global health problem. Currently, there are no vaccines available for this virus, and available therapy is toxic and ineffective in many. The mechanisms by which replication of HCV is controlled and eventually terminated by those individuals that are able to resolve infection remain unclear, however are of paramount importance both to the production of an effective vaccine for this pathogen, and to future development of effective therapies. In experiments in transgenic mouse models and the chimpanzee, it has been demonstrated that control of hepatitis B virus replication can be controlled by secretion of the cytokine IFN-gamma by immune cells (Guidotti and Chisari. Ann Rev Immunol 2001; 19: 65-89), rather than viral control requiring killing of infected cells by the immune system. Experiments using in vitro systems suggest that IFN-gamma could contribute to control of HCV replication (Frese et al Hepatology 2002; 35:694703; Lanford et al J Virol 2003; 77: 1092-1104). However this in vitro data does not necessarily reflect in vivo events. A single study has been carried out examining whether supplementation of IFN-gamma alters viral replication in chronic HCV infection (Shin et al. J Virol 2005; 79: 13412-30); however it is likely that both the infecting virus has escaped from HCV-specific responses and that persisting HCV-specific immune responses are defective by this stage of infection (Bowen and Walker. Nature 2005; 436: 946-52). This data is thus unlikely to reflect the role played by IFN-gamma in natural control of infection in individuals that resolve infection. This study will address this issue by carefully defining the kinetic of viral replication and the immune response when the biological effects of IFN-gamma are blocked. In order to establish a baseline for comparison, chimpanzees that have previously resolved HCV infection will be reinfected with homologous virus and virological and immunological parameters monitored. These animals should rapidly control and resolve infection (Shoukry et al. J Exp. Med. 2003; 197:1645-1655; Grakoui et al Science. 2003; 302: 659-662). Following this, study animals will be reinfected while the biological effects of IFN-gamma are simultaneously neutralized, and the kinetics of viral replication and the immune response again assessed. Comparison of these two infections will allow assessment of the role played by this cytokine in control of HCV replication. Neutralization of the effects of IFN-gamma is achieved by administration of a humanized monoclonal antibody against IFN-gamma that has been previously used in primates. Through this experiment we hope to define whether control of viral replication is dependent upon IFN-gamma. This will provide important information for development of preventive HCV vaccines and possibly therapies for repairing defects in the immune response that lead to chronic infection. There are few clues to the mechanisms by which clearance of HCV is achieved, and hence the factors governing the outcome of HCV infection (i.e. persistent, life-long replication of the virus versus acute resolution a few weeks after exposure to the virus) remain unknown. An understanding of the role played by the major anti-viral cytokine IFN-gamma will be critical for the design of vaccines to blunt replication of HCV in the liver and hopefully eliminate it before permanent damage to the organ can occur. This is critically important, as the choice of vaccine technologies to prime antiviral responses may make the difference between success and failure of immunization.