Biliary Secretion of Quasi-Enveloped Human Hepatitis A Virus.
Biliary Secretion of Quasi-Enveloped Human Hepatitis A Virus.
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DOI：
10.1128/mbio.01998-16
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发表时间：
2016-12-06
期刊：
影响因子：
6.4
通讯作者：
Lemon SM
中科院分区：
文献类型：
--
作者：
Hirai-Yuki A;Hensley L;Whitmire JK;Lemon SM
甲型肝炎病毒 (HAV) 是一种不寻常的小核糖核酸病毒，从宿主细胞膜中释放出来。这些准包膜病毒粒子 (eHAV) 是感染期间在血液中循环的唯一颗粒类型，而只有无包膜病毒粒子会在粪便中脱落。其原因尚不确定。肝细胞是已知支持 HAV 体内复制的唯一细胞类型，是高度极化的上皮细胞，其基底外侧膜面向肝（血）窦，顶膜邻接胆小管，胆汁从胆小管分泌到肠道。为了评估 eHAV 和无包膜病毒是否通过载体上不同的途径从细胞中流出，我们研究了受感染的 Caco-2 和 HepG2-N6 细胞的极化培养物。大多数 (>99%) 子代病毒体从 Caco-2 细胞顶部释放，而 HepG2-N6 细胞的基底外侧 (64%) 与顶部 (36%) 释放更为平衡。顶部和底部释放的病毒粒子均主要被包膜，没有迹象表明 eHAV 与裸病毒粒子的载体释放存在差异。在 HepG2-N6 细胞中，两种颗粒类型的基底外侧到顶端转胞吞作用都很小（<0.02%/h），反对将此作为血清与粪便病毒膜包封差异的机制。高浓度的人胆汁酸将 eHAV 转化为无包膜病毒体，而感染 HAV 的 Ifnar1−/− Ifngr1−/− 和 Mavs−/− 小鼠的胆汁中存在的病毒，其密度范围从 eHAV 延伸到无包膜病毒体。我们得出的结论是，排泄在粪便中的无包膜病毒粒子源自跨小管膜释放的 eHAV，并通过近端胆小管内胆汁酸的去污作用剥离膜。 HAV 是一种嗜肝性、粪便/口腔传播的小核糖核酸病毒，可导致人类严重肝炎。最近的研究表明它有一个不寻常的生命周期。在细胞培养物上清液中发现的病毒有两种成熟的感染性形式：一种被膜包裹（准包膜），另一种则为非包膜。急性感染期间，膜包裹的病毒粒子在血液中循环，并且对中和抗体具有抵抗力，可能促进 HAV 在肝脏内传播。另一方面，粪便中排出的病毒是无包膜的且高度稳定，有利于流行病的传播和向幼稚宿主的传播。控制这两种不同形式的病毒在感染人类中生物发生的因素尚不清楚。在这里，我们描述了极化上皮细胞培养物中准包膜病毒粒子的矢量释放，并提供了胆汁酸在 eHAV 分泌到胆道后剥离膜的证据。这些结果增强了我们对这种不寻常的小核糖核酸病毒生命周期的理解。
Hepatitis A virus (HAV) is an unusual picornavirus that is released from cells cloaked in host-derived membranes. These quasi-enveloped virions (eHAV) are the only particle type circulating in blood during infection, whereas only nonenveloped virions are shed in feces. The reason for this is uncertain. Hepatocytes, the only cell type known to support HAV replication in vivo, are highly polarized epithelial cells with basolateral membranes facing onto hepatic (blood) sinusoids and apical membranes abutting biliary canaliculi from which bile is secreted to the gut. To assess whether eHAV and nonenveloped virus egress from cells via vectorially distinct pathways, we studied infected polarized cultures of Caco-2 and HepG2-N6 cells. Most (>99%) progeny virions were released apically from Caco-2 cells, whereas basolateral (64%) versus apical (36%) release was more balanced with HepG2-N6 cells. Both apically and basolaterally released virions were predominantly enveloped, with no suggestion of differential vectorial release of eHAV versus naked virions. Basolateral to apical transcytosis of either particle type was minimal (<0.02%/h) in HepG2-N6 cells, arguing against this as a mechanism for differences in membrane envelopment of serum versus fecal virus. High concentrations of human bile acids converted eHAV to nonenveloped virions, whereas virus present in bile from HAV-infected Ifnar1−/− Ifngr1−/− and Mavs−/− mice banded over a range of densities extending from that of eHAV to that of nonenveloped virions. We conclude that nonenveloped virions shed in feces are derived from eHAV released across the canalicular membrane and stripped of membranes by the detergent action of bile acids within the proximal biliary canaliculus. HAV is a hepatotropic, fecally/orally transmitted picornavirus that can cause severe hepatitis in humans. Recent work reveals that it has an unusual life cycle. Virus is found in cell culture supernatant fluids in two mature, infectious forms: one wrapped in membranes (quasi-enveloped) and another that is nonenveloped. Membrane-wrapped virions circulate in blood during acute infection and are resistant to neutralizing antibodies, likely facilitating HAV dissemination within the liver. On the other hand, virus shed in feces is nonenveloped and highly stable, facilitating epidemic spread and transmission to naive hosts. Factors controlling the biogenesis of these two distinct forms of the virus in infected humans are not understood. Here we characterize vectorial release of quasi-enveloped virions from polarized epithelial cell cultures and provide evidence that bile acids strip membranes from eHAV following its secretion into the biliary tract. These results enhance our understanding of the life cycle of this unusual picornavirus.