Human respiratory syncytial virus (hRSV) is the primary cause of severe respiratory tract disease in children and infants as well as in elderly and immunocompromised adults. The fusion protein (F) of hRSV is the major antigen eliciting a neutralizing antibody response and protective immunity in the host, especially those recognizing the prefusion F protein (pre-F). In this study, we made genetic constructs for expression of a recombinant prefusion F protein in Pichia pastoris GS115, called RGF. Using Escherichia coli BL21, we expressed the pre-F and postfusion F protein (Post-F), called RBF and Post-RBF, respectively. RGF and RBF showed high affinity for 5C4, a highly potent monoclonal antibody specific for pre-F. We studied the immunogenicity of RGF and RBF in mice. Compared to mice immunized with formalin-inactivated RSV (FI-RSV), mice immunized with RGF or RBF exhibited superior protective immunity, which was confirmed by serum neutralizing activity and viral clearance after challenge. As judged from the IgG1/IgG2a ratios and numbers of IFN-γ- and IL-4-secreting cells, RGF or RBF with alum adjuvant induced a balanced Th1-biased immune response and produced no signs of enhanced respiratory disease (ERD) upon hRSV challenge. In addition, the immunogenicity and protective efficacy of RGF were superior to those of RBF in mice. Therefore, RGF represents a potential vaccine candidate for the prevention of human infection with hRSV.

中文翻译：

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在巴斯德毕赤酵母或大肠杆菌中表达的人呼吸道合胞病毒F蛋白诱导保护性免疫，而不会引起小鼠呼吸道疾病的增强。

人类呼吸道合胞病毒（hRSV）是儿童和婴儿以及老年人和免疫力低下的成年人中严重呼吸道疾病的主要原因。hRSV的融合蛋白（F）是在宿主中引起中和抗体反应和保护性免疫的主要抗原，尤其是那些识别融合前F蛋白（pre-F）的抗原。在这项研究中，我们制备了用于在巴斯德毕赤酵母GS115中表达重组前融合F蛋白的基因构建体，称为RGF。使用大肠杆菌BL21，我们表达了前F和融合后F蛋白（Post-F），分别称为RBF和Post-RBF。RGF和RBF对5C4具有高度亲和力，5C4是对pre-F特异的高效单克隆抗体。我们研究了小鼠中RGF和RBF的免疫原性。与用福尔马林灭活的RSV（FI-RSV）免疫的小鼠相比，用RGF或RBF免疫的小鼠表现出优异的保护性免疫，激发后的血清中和活性和病毒清除率证实了这一点。从IgG1 / IgG2a比率以及分泌IFN-γ和IL-4的细胞数量判断，具有明矾佐剂的RGF或RBF诱导了平衡的Th1偏向免疫反应，并且在hRSV时未产生增强的呼吸道疾病（ERD）的迹象挑战。另外，RGF在小鼠中的免疫原性和保护功效优于RBF。因此，RGF代表了预防人类感染hRSV的潜在疫苗候选物。带有明矾佐剂的RGF或RBF诱导了平衡的Th1偏向的免疫反应，并且在hRSV攻击后未产生增强的呼吸道疾病（ERD）迹象。另外，RGF在小鼠中的免疫原性和保护功效优于RBF。因此，RGF代表了预防人类感染hRSV的潜在候选疫苗。带有明矾佐剂的RGF或RBF诱导了平衡的Th1偏向的免疫反应，并且在hRSV攻击后未产生增强的呼吸道疾病（ERD）迹象。另外，RGF在小鼠中的免疫原性和保护功效优于RBF。因此，RGF代表了预防人类感染hRSV的潜在候选疫苗。