Physiological and immunological responses to measles vaccine

总结 麻疹仍然是全世界儿童发病和死亡的最重要原因之一。研究 在儿童和特征良好的恒河猴模型中， (WT)麻疹病毒（MeV）RNA在感染性病毒清除后持续数月 在外周血单核细胞和淋巴组织中。RNA持续存在伴随着持续的 持续产生MeV特异性浆母细胞的免疫刺激，抗体（Ab）成熟， 多波功能不同的T细胞。这些免疫反应导致对麻疹的终身免疫， 但活的减毒MeV疫苗没有可比较的数据。MeV疫苗是在 根据经验，通过在鸡细胞中传代使WT MeV分离物减毒。所得减毒活疫苗 疫苗于1963年获得许可，尽管是通过注射给药， 对持续的高覆盖率造成了障碍，这可能通过呼吸输送来缓解。它的安全记录， 结合反向遗传学对负链病毒的研究进展， 重组形式作为针对其它感染的免疫的载体和作为用于多种疾病的溶瘤剂， 肿瘤。然而，对MeV疫苗病毒在体内生物学的基本方面的有限理解阻碍了 发展例如，对疫苗病毒在哪里复制、疫苗的机制和疫苗的免疫机制知之甚少。 毒力减弱或诱导的免疫应答与WT感染诱导的免疫应答有何不同 除了注意到抗体滴度较低并且保护较不持久。我们假设， 疫苗株和WT株感染之间的差异是在淋巴细胞中复制和持续的能力， 组织中该提案将通过以下方式解决这一知识缺口：1）确定疫苗病毒在其中的靶细胞 复制不如WT病毒好。我们假设减弱的复制是细胞类型特异性的， MeV疫苗株在骨髓、内皮和上皮细胞中复制良好，但在淋巴样细胞中复制较差。（二） 鉴定低效MeV疫苗病毒复制的病毒决定因素。我们假设 血凝素（H）和基质（M）蛋白是淋巴细胞中无效复制的主要决定因素 通过对TLR2信号传导、病毒组装和释放的影响，并将通过构建 将在淋巴细胞中进行复制试验的EZ疫苗重组菌株。3)确定体内部位 恒河猴中疫苗病毒复制和病毒RNA清除的动力学。我们假设 MeV疫苗株不能有效地从淋巴感染部位传播， 病毒RNA被迅速清除。4)识别CD4 + T细胞和Ab对感染反应的差异 疫苗和WT MeV。我们假设疫苗株诱导较少的MeV特异性抗体分泌细胞 与WT相比，持续较短的时间，与较不稳健和较不多功能的CD4 + T细胞应答相关 菌株

Summary Measles remains one of the most important causes of child morbidity and mortality worldwide. Studies of measles in children and in a well-characterized rhesus macaque model have shown that clearance of wild type (WT) measles virus (MeV) RNA is ongoing for many months after clearance of infectious virus with persistence in peripheral blood mononuclear cells and lymphoid tissues. RNA persistence is accompanied by ongoing immune stimulation with continued production of MeV-specific plasmablasts, antibody (Ab) maturation and multiple waves of functionally distinct T cells. These immune responses result in lifelong immunity to measles, but comparable data are not available for the live attenuated MeV vaccine. The MeV vaccine was developed empirically by attenuation of a WT MeV isolate by passage in chicken cells. The resultant live attenuated vaccine was licensed in 1963 and has been remarkably safe and successful although delivery by injection creates hurdles to sustained high coverage that might be alleviated with respiratory delivery. Its safety record, combined with advances in reverse genetics for negative strand viruses, have led to development of recombinant versions as vectors for immunization against other infections and as oncolytic agents for a variety of tumors. However, limited understanding of fundamental aspects of MeV vaccine virus in vivo biology hinders development. For instance, there is little knowledge of where the vaccine virus replicates, the mechanism(s) of attenuation of virulence or how the immune responses induced differ from those induced by WT infection except to note that antibody titers are lower and protection is less durable. We hypothesize that a central difference between infection with vaccine and WT strains is the ability to replicate and persist in lymphoid tissues. This proposal will address this knowledge gap by: 1) Identifying the target cell(s) in which vaccine virus replicates less well than WT virus. We hypothesize that attenuated replication is cell type-specific and that vaccine strains of MeV replicate well in myeloid, endothelial and epithelial cells, but poorly in lymphoid cells. 2) Identifying the viral determinants of inefficient MeV vaccine virus replication. We hypothesize that the hemagglutinin (H) and matrix (M) proteins are the primary determinants of inefficient replication in lymphocytes through effects on TLR2 signaling, virus assembly and release and will test the hypothesis by constructing recombinant strains of EZ vaccine that will tested for replication in lymphocytes. 3) Determining the in vivo sites of vaccine virus replication and dynamics of viral RNA clearance in rhesus macaques. We hypothesize that vaccine strains of MeV do not spread efficiently from lymphoid sites of infection and that both infectious virus and viral RNA are cleared quickly. 4) Identifying differences in the CD4+ T cell and Ab responses to infection with vaccine and WT MeV. We hypothesize that vaccine strains induce fewer MeV-specific Ab-secreting cells for a shorter period of time associated with a less robust and less polyfunctional CD4+ T cell response than WT strains.