Department of Biomedicine, Aarhus Universitygrid.7048.b, Aarhus, Denmark.
J Virol. 2022 Mar 9;96(5):e0155721. doi: 10.1128/JVI.01557-21. Epub 2022 Jan 12.
CD46 is a receptor for human herpesvirus 6A (HHV-6A) and is in some cells also important for infection with HHV-6B. CD46 has several isoforms of which the most commonly expressed can be distinguished by expression of a BC domain or a C domain in a serine-threonine-proline-rich (STP) extracellular region. Using a SupT1 CD46 CRISPR-Cas9 knockout model system reconstituted with specific CD46 isoforms, we demonstrated that HHV-6A infection was more efficient when BC isoforms were expressed as opposed to C isoforms, measured by higher levels of intracellular viral transcripts and recovery of more progeny virus. Although the B domain contains several -glycosylations, mutations of Ser and Thr residues did not prevent infection with HHV-6A. The HHV-6A infection was blocked by inhibitors of clathrin-mediated endocytosis. In contrast, infection with HHV-6B was preferentially promoted by C isoforms mediating fusion-from-without, and this infection was less affected by inhibitors of clathrin-mediated endocytosis. Taken together, HHV-6A preferred BC isoforms, mediating endocytosis, whereas HHV-6B preferred C isoforms, mediating fusion-from-without. This demonstrates that the STP region of CD46 is important for regulating the mode of infection in SupT1 cells and suggests an epigenetic regulation of the host susceptibility to HHV-6A and HHV-6B infection. CD46 is the receptor used by human herpesvirus 6A (HHV-6A) during infection of T cells, but it is also involved in infection of certain T cells by HHV-6B. The gene for CD46 allows expression of several variants of CD46, known as isoforms, but whether the isoforms matter for infection of T cells is unknown. We used a genetic approach to delete CD46 from T cells and reconstituted them with separate isoforms to study them individually. We expressed the isoforms known as BC and C, which are distinguished by the potential inclusion of a B domain in the CD46 molecule. We demonstrate that HHV-6A prefers the BC isoform to infect T cells, and this occurs predominantly by clathrin-mediated endocytosis. In contrast, HHV-6B prefers the C isoform and infects predominantly by fusion-from-without. Thus, CD46 isoforms may affect susceptibility of T cells to infection with HHV-6A and HHV-6B.
CD46 是人类疱疹病毒 6A（HHV-6A）的受体，在某些细胞中对于感染 HHV-6B 也很重要。CD46 有几种同工型，其中最常见的同工型可以通过在丝氨酸-苏氨酸-脯氨酸丰富（STP）细胞外区域表达 BC 结构域或 C 结构域来区分。使用具有特定 CD46 同工型的 SupT1 CD46 CRISPR-Cas9 敲除模型系统，我们证明与表达 C 同工型相比，表达 BC 同工型时 HHV-6A 感染效率更高，这可以通过更高水平的细胞内病毒转录本和更多的子代病毒回收来衡量。尽管 B 结构域包含几个糖基化位点，但丝氨酸和苏氨酸残基的突变并不能阻止 HHV-6A 的感染。HHV-6A 感染被网格蛋白介导的内吞作用抑制剂阻断。相比之下，HHV-6B 感染则被介导融合的 C 同工型优先促进，并且这种感染受网格蛋白介导的内吞作用抑制剂的影响较小。总之，HHV-6A 偏爱介导内吞作用的 BC 同工型，而 HHV-6B 偏爱介导融合的 C 同工型。这表明 CD46 的 STP 区域对于调节 SupT1 细胞中的感染方式很重要，并提示 CD46 对 HHV-6A 和 HHV-6B 感染的宿主易感性存在表观遗传调控。
CD46 是人类疱疹病毒 6A（HHV-6A）在感染 T 细胞时使用的受体，但它也参与 HHV-6B 感染某些 T 细胞。CD46 基因允许表达几种 CD46 变体，称为同工型，但同工型是否对 T 细胞感染很重要尚不清楚。我们使用基因敲除的方法从 T 细胞中删除 CD46，并使用单独的同工型重建它们以单独研究它们。我们表达了称为 BC 和 C 的同工型，它们通过 CD46 分子中 B 结构域的潜在包含来区分。我们证明 HHV-6A 更喜欢 BC 同工型来感染 T 细胞，并且这种感染主要通过网格蛋白介导的内吞作用发生。相比之下，HHV-6B 更喜欢 C 同工型，并且主要通过融合发生感染。因此，CD46 同工型可能会影响 T 细胞对 HHV-6A 和 HHV-6B 感染的易感性。
