Department of Microbiology, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104-6076, USA.
J Virol. 2011 Oct;85(19):10058-68. doi: 10.1128/JVI.05075-11. Epub 2011 Jul 13.
Previous studies have demonstrated that mouse hepatitis virus (MHV) hepatotropism is determined largely by postentry events rather than by availability of the viral receptor. In addition, mutation of MHV nonstructural protein 2 (ns2) abrogates the ability of the virus to replicate in the liver and induce hepatitis but does not affect replication in the central nervous system (CNS). Here we show that replication of ns2 mutant viruses is attenuated in bone marrow-derived macrophages (BMM) generated from wild-type (wt) mice but not in L2 fibroblasts, primary astrocytes, or BMM generated from type I interferon receptor-deficient (IFNAR(-/-)) mice. In addition, ns2 mutants are more sensitive than wt virus to pretreatment of BMM, but not L2 fibroblasts or primary astrocytes, with alpha/beta interferon (IFN-α/β). The ns2 mutants induced similar levels of IFN-α/β in wt and IFNAR(-/-) BMM, indicating that ns2 expression has no effect on the induction of IFN but rather that it antagonizes a later step in IFN signaling. Consistent with these in vitro data, the virulence of ns2 mutants increased to near that of wt virus after depletion of macrophages in vivo. These data imply that the ability of MHV to replicate in macrophages is a prerequisite for replication in the liver and induction of hepatitis but not for replication or disease in the CNS, underscoring the importance of IFN signaling in macrophages in vivo for protection of the host from hepatitis. Our results further support the notion that viral tissue tropism is determined in part by postentry events, including the early type I interferon response.
先前的研究表明，小鼠肝炎病毒（MHV）的嗜肝性主要取决于进入后事件，而不是病毒受体的可用性。此外，MHV 非结构蛋白 2（ns2）的突变会破坏病毒在肝脏中复制并引发肝炎的能力，但不会影响其在中枢神经系统（CNS）中的复制。在这里，我们表明，来自野生型（wt）小鼠的骨髓来源的巨噬细胞（BMM）中 ns2 突变病毒的复制被减弱，但在 L2 成纤维细胞、原代星形胶质细胞或来自 I 型干扰素受体缺陷（IFNAR（-/-））小鼠的 BMM 中不受影响。此外，ns2 突变体比 wt 病毒对 BMM 的预处理更敏感，但对 L2 成纤维细胞或原代星形胶质细胞不敏感。预处理 BMM 用 α/β干扰素（IFN-α/β）。ns2 突变体在 wt 和 IFNAR（-/-）BMM 中诱导相似水平的 IFN-α/β，表明 ns2 表达对 IFN 的诱导没有影响，而是拮抗 IFN 信号传递的后期步骤。与这些体外数据一致，在体内耗尽巨噬细胞后，ns2 突变体的毒力增加到接近 wt 病毒的水平。这些数据表明，MHV 在巨噬细胞中复制的能力是在肝脏中复制和诱导肝炎的前提，但不是在 CNS 中复制或疾病的前提，强调了 IFN 信号在体内巨噬细胞中对宿主保护免受肝炎的重要性。我们的结果进一步支持了这样的观点，即病毒的组织嗜性部分取决于进入后事件，包括早期的 I 型干扰素反应。
