Immunoglobulin Allotypes in Hepatitis C Virus Infection

描述(申请人提供)：丙型肝炎病毒(丙型肝炎病毒)是一个主要的健康问题，影响着全球超过1.7亿人。在急性感染丙型肝炎病毒的人中，约15%的人会自发清除病毒。由于实验模型的局限性和对自然急性感染的认识不多，病毒清除的机制还知之甚少。有临床和流行病学线索表明宿主因素是关键因素。在影响丙型肝炎病毒感染结局的因素中，宿主遗传因素被认为起主导作用。免疫球蛋白(Ig)GM和KM同种异型分别是Ig G重链和K型轻链的遗传性抗原决定簇，与病毒免疫学特性有关，因此是研究丙型肝炎病毒致病危险因素的理想候选遗传系统。我们推测GM和KM同种异型可能通过影响对病毒抗原的同型限制性抗体反应而导致丙型肝炎病毒感染的结局。此外，它们可能通过与FcGamma受体(FcGammaR)的不同相互作用而影响抗体依赖性T细胞对丙型肝炎病毒的杀伤作用。Gm和Km同种异型也可以调节这种病毒逃避宿主免疫监视的策略--Ig分子模仿和FcGammaR样活性。为了验证我们的假设，设计了一项病例对照研究，目的如下：(1)进一步确定非裔美国人中丙型肝炎病毒感染结局与免疫球蛋白GM和Km同型之间的关联程度；(2)确定高加索人中GM和Km等位基因是否与丙型肝炎病毒感染的结局相关；(3)测量针对丙型肝炎病毒抗原(核心、E1、E2、NS3、NS4、NS5)的体液免疫应答的特异性和滴度，并确定这些抗体的产生是否受到Gm和Km同种异型的影响；(4)确定丙型肝炎病毒编码的FcGammaR是否与携带不同GM同种异型的免疫球蛋白分子有不同的结合。Gm和Km基因分型将通过血凝抑制、DNA直接测序和PCR-RFLP方法进行。丙型肝炎病毒免疫球蛋白抗体将通过酶联免疫吸附试验检测。不同GM同种异型的免疫球蛋白分子与丙型肝炎病毒FcGammaR的结合和比较亲和力将通过表面等离子共振检测进行监测。这项研究的结果将加深我们对宿主遗传因素在丙型肝炎病毒感染清除和持续中的作用的理解。

DESCRIPTION (provided by applicant): Hepatitis C virus (HCV) is a major health problem, affecting over 170 million people worldwide. Of persons acutely infected with HCV, about 15% spontaneously clear the virus. Because of limitations in experimental models and the infrequent recognition of natural acute infection, the mechanisms of viral clearance are poorly understood. There are clinical and epidemiologic clues that suggest host factors are critical. Among the factors influencing the outcome of HCV infection, the host genetic factors are thought to play a predominant role. Immunoglobulin (Ig) GM and KM allotypes-hereditary antigenic determinants of IgG heavy chains and k-type light chains, respectively-are associated with viral immunological properties, and thus are ideal candidate genetic systems for investigations to identify risk-conferring factors in HCV pathogenesis. We hypothesized that GM and KM allotypes may contribute to the outcome of HCV infection through their possible influence on allotype-restricted antibody responses to the viral antigens. Additionally, they may influence antibody dependent T cell cytotoxicity to HCV by their differential interaction with Fcgamma receptors (FcgammaR). GM and KM allotypes could also modulate the strategies-Ig molecular mimicry and FcgammaR-like activity-employed by this virus to evade host immune surveillance. To test our hypothesis, a case control study has been designed with the following specific aims: (1) to further establish the magnitude of association between the outcome of HCV infection and Ig GM and KM allotypes in African Americans; (2) to determine if GM and KM allotypes are associated with the outcome of HCV infection in Caucasians; (3) to measure the specificity and titer of the humoral immune responses to HCV antigens (core, E1,E2,NS3,NS4,NS5) and determine if the production of these antibodies is influenced by GM and KM allotypes; (4) to determine if HCV-encoded FcgammaR binds differentially with IgG molecules carrying different GM allotypes. GM and KM allotyping will be done by hemagglutination-inhibition, direct DNA sequencing, and PCR-RFLP methods. IgG antibodies to HCV antigens will be measured by an ELISA. Binding and comparative affinities of IgG molecules of different GM allotypes to HCV-FcgammaR will be monitored by surface plasmon resonance detection. Results of this investigation will advance our understanding of the role of host genetic factors in clearance and persistence of hepatitis C virus infection.