Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America.
PLoS One. 2013;8(1):e52306. doi: 10.1371/journal.pone.0052306. Epub 2013 Jan 3.
The measles virus (MV) is serologically monotypic. Life-long immunity is conferred by a single attack of measles or following vaccination with the MV vaccine. This is contrary to viruses such as influenza, which readily develop resistance to the immune system and recur. A better understanding of factors that restrain MV to one serotype may allow us to predict if MV will remain monotypic in the future and influence the design of novel MV vaccines and therapeutics. MV hemagglutinin (H) glycoprotein, binds to cellular receptors and subsequently triggers the fusion (F) glycoprotein to fuse the virus into the cell. H is also the major target for neutralizing antibodies. To explore if MV remains monotypic due to a lack of plasticity of the H glycoprotein, we used the technology of Immune Dampening to generate viruses with rationally designed N-linked glycosylation sites and mutations in different epitopes and screened for viruses that escaped monoclonal antibodies (mAbs). We then combined rationally designed mutations with naturally selected mutations to generate a virus resistant to a cocktail of neutralizing mAbs targeting four different epitopes simultaneously. Two epitopes were protected by engineered N-linked glycosylations and two epitopes acquired escape mutations via two consecutive rounds of artificial selection in the presence of mAbs. Three of these epitopes were targeted by mAbs known to interfere with receptor binding. Results demonstrate that, within the epitopes analyzed, H can tolerate mutations in different residues and additional N-linked glycosylations to escape mAbs. Understanding the degree of change that H can tolerate is important as we follow its evolution in a host whose immunity is vaccine induced by genotype A strains instead of multiple genetically distinct wild-type MVs.
麻疹病毒（MV）在血清学上是单型的。麻疹或接种麻疹疫苗后，单一攻击即可产生终身免疫力。这与流感等病毒相反，流感病毒很容易对免疫系统产生抵抗力并复发。更好地了解限制 MV 为单一血清型的因素，可能使我们能够预测 MV 在未来是否仍将保持单型，并影响新型 MV 疫苗和治疗方法的设计。MV 血凝素（H）糖蛋白与细胞受体结合，随后触发融合（F）糖蛋白将病毒融合到细胞中。H 也是中和抗体的主要靶标。为了探索 MV 是否由于 H 糖蛋白缺乏可塑性而保持单型，我们使用免疫抑制技术生成具有合理设计的 N-连接糖基化位点和不同表位突变的病毒，并筛选逃避单克隆抗体（mAbs）的病毒。然后，我们将合理设计的突变与自然选择的突变相结合，生成一种能够抵抗针对四个不同表位的中和 mAb 鸡尾酒的病毒。两个表位由工程化的 N-连接糖基化保护，两个表位通过在 mAbs 存在下进行两轮连续人工选择获得逃逸突变。这三个表位都被已知干扰受体结合的 mAb 靶向。结果表明，在所分析的表位内，H 可以耐受不同残基和额外的 N-连接糖基化突变以逃避 mAb。了解 H 可以耐受的变化程度很重要，因为我们在宿主中跟踪其进化，宿主的免疫是由基因型 A 株诱导的，而不是多种遗传上不同的野生型 MV。
