Pathophysiologic and Transcriptomic Analyses of Viscerotropic Yellow Fever in a Rhesus Macaque Model

Infection with yellow fever virus (YFV), an explosively replicating flavivirus, results in viral hemorrhagic disease characterized by cardiovascular shock and multi-organ failure. Unvaccinated populations experience 20 to 50% fatality. Few studies have examined the pathophysiological changes that occur in humans during YFV infection due to the sporadic nature and remote locations of outbreaks. Rhesus macaques are highly susceptible to YFV infection, providing a robust animal model to investigate host-pathogen interactions. In this study, we characterized disease progression as well as alterations in immune system homeostasis, cytokine production and gene expression in rhesus macaques infected with the virulent YFV strain DakH1279 (YFV-DakH1279). Following infection, YFV-DakH1279 replicated to high titers resulting in viscerotropic disease with ∼72% mortality. Data presented in this manuscript demonstrate for the first time that lethal YFV infection results in profound lymphopenia that precedes the hallmark changes in liver enzymes and that although tissue damage was noted in liver, kidneys, and lymphoid tissues, viral antigen was only detected in the liver. These observations suggest that additional tissue damage could be due to indirect effects of viral replication. Indeed, circulating levels of several cytokines peaked shortly before euthanasia. Our study also includes the first description of YFV-DakH1279-induced changes in gene expression within peripheral blood mononuclear cells 3 days post-infection prior to any clinical signs. These data show that infection with wild type YFV-DakH1279 or live-attenuated vaccine strain YFV-17D, resulted in 765 and 46 differentially expressed genes (DEGs), respectively. DEGs detected after YFV-17D infection were mostly associated with innate immunity, whereas YFV-DakH1279 infection resulted in dysregulation of genes associated with the development of immune response, ion metabolism, and apoptosis. Therefore, WT-YFV infection is associated with significant changes in gene expression that are detectable before the onset of clinical symptoms and may influence disease progression and outcome of infection.黄热病毒（Yellow Fever Virus, YFV）是一种复制能力极强的黄病毒（Flavivirus），感染该病毒可引发以心血管休克和多器官衰竭为特征的病毒性出血性疾病。未接种疫苗的人群病死率可达20%至50%。由于黄热疫情具有散发性且暴发地点偏远，目前针对黄热病毒感染后人体病理生理变化的研究为数不多。恒河猴（Rhesus Macaque）对黄热病毒高度易感，是探究宿主-病原体相互作用的理想动物模型。本研究针对感染强毒株YFV-DakH1279（YFV-DakH1279）的恒河猴，对其疾病进程、免疫系统稳态变化、细胞因子产生及基因表达特征进行了系统表征。感染后，YFV-DakH1279可增殖至高滴度，引发内脏型疾病，病死率约为72%。本研究数据首次证实，致死性黄热病毒感染会引发严重的淋巴细胞减少症，且该症状早于肝脏酶学标志性变化出现；尽管在肝脏、肾脏及淋巴组织中均观察到组织损伤，但病毒抗原仅能在肝脏中被检测到。上述结果提示，额外的组织损伤可能源于病毒复制的间接效应。确实，多种细胞因子的循环水平在安乐死前不久达到峰值。本研究还首次描述了感染后3天、即在出现任何临床症状前，外周血单个核细胞（Peripheral Blood Mononuclear Cells, PBMCs）中YFV-DakH1279诱导的基因表达变化。数据显示，感染野生型YFV-DakH1279与减毒活疫苗株YFV-17D（YFV-17D）后，分别会导致765个和46个差异表达基因（Differentially Expressed Genes, DEGs）的产生。YFV-17D感染后检测到的差异表达基因主要与先天免疫相关，而YFV-DakH1279感染则会引发与免疫应答发育、离子代谢及细胞凋亡相关基因的表达失调。因此，野生型黄热病毒感染会引发显著的基因表达变化，这些变化可在临床症状出现前被检测到，并可能影响疾病进程与感染结局。