Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029.
Laboratory of Medical Virology, Institute for Frontier Life and Medical Sciences, Kyoto University, 606-8507 Kyoto, Japan.
Proc Natl Acad Sci U S A. 2021 May 4;118(18). doi: 10.1073/pnas.2026027118.
Measles virus (MeV) is resurgent and caused >200,000 deaths in 2019. MeV infection can establish a chronic latent infection of the brain that can recrudesce months to years after recovery from the primary infection. Recrudescent MeV leads to fatal subacute sclerosing panencephalitis (SSPE) or measles inclusion body encephalitis (MIBE) as the virus spreads across multiple brain regions. Most clinical isolates of SSPE/MIBE strains show mutations in the fusion (F) gene that result in a hyperfusogenic phenotype in vitro and allow for efficient spread in primary human neurons. Wild-type MeV receptor-binding protein is indispensable for manifesting these mutant F phenotypes, even though neurons lack canonical MeV receptors (CD150/SLAMF1 or nectin-4). How such hyperfusogenic F mutants are selected and whether they confer a fitness advantage for efficient neuronal spread is unresolved. To better understand the fitness landscape that allows for the selection of such hyperfusogenic F mutants, we conducted a screen of ≥3.1 × 10 MeV-F point mutants in their genomic context. We rescued and amplified our genomic MeV-F mutant libraries in BSR-T7 cells under conditions in which MeV-F-T461I (a known SSPE mutant), but not wild-type MeV, can spread. We recovered known SSPE mutants but also characterized at least 15 hyperfusogenic F mutations with an SSPE phenotype. Structural mapping of these mutants onto the prefusion MeV-F trimer confirm and extend our understanding of the F regulatory domains in MeV-F. Our list of hyperfusogenic F mutants is a valuable resource for future studies into MeV neuropathogenesis and the regulation of paramyxovirus F.
麻疹病毒（MeV）卷土重来，2019 年导致超过 20 万人死亡。MeV 感染可导致大脑慢性潜伏感染，在原发感染恢复数月至数年后可重新发作。重新发作的 MeV 导致致命的亚急性硬化性全脑炎（SSPE）或麻疹包涵体脑炎（MIBE），因为病毒在多个大脑区域传播。大多数 SSPE/MIBE 株的临床分离株在融合（F）基因中显示突变，导致体外超融合表型，并允许在原代人神经元中有效传播。野生型 MeV 受体结合蛋白对于表现出这些突变 F 表型是必不可少的，即使神经元缺乏典型的 MeV 受体（CD150/SLAMF1 或 nectin-4）。这些超融合 F 突变体如何被选择，以及它们是否为有效神经元传播提供适应性优势，仍未解决。为了更好地理解允许选择这种超融合 F 突变体的适应性景观，我们在其基因组背景下对≥3.1×10 的 MeV-F 点突变体进行了筛选。我们在 BSR-T7 细胞中，在允许 MeV-F-T461I（一种已知的 SSPE 突变体）但不是野生型 MeV 传播的条件下，拯救和扩增我们的基因组 MeV-F 突变体文库。我们回收了已知的 SSPE 突变体，但也表征了至少 15 种具有 SSPE 表型的超融合 F 突变体。这些突变体在预融合 MeV-F 三聚体上的结构映射证实并扩展了我们对 MeV-F 调节结构域的理解。我们的超融合 F 突变体列表是未来研究 MeV 神经发病机制和副粘病毒 F 调节的宝贵资源。
