Center of Excellence in Plant-produced Pharmaceuticals, Chulalongkorn University, Bangkok, Thailand.
Department of Pharmacognosy and Pharmaceutical Botany, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok, Thailand.
J Med Virol. 2022 Sep;94(9):4265-4276. doi: 10.1002/jmv.27881. Epub 2022 Jun 1.
The constantly emerging severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) variants of concerns (VOCs) with mutations in the receptor-binding domain (RBD) spread rapidly and has become a severe public health problem worldwide. Effective vaccines and optimized booster vaccination strategies are thus highly required. Here, the gene encoding six different RBD (Alpha, Beta, Gamma, Kappa, Delta, and Epsilon variants) along with the Fc fragment of human IgG1 (RBD-Fc) was cloned into plant expression vector and produced in Nicotiana benthamiana by transient expression. Further, the immunogenicity of plant-produced variant RBD-Fc fusion proteins were tested in cynomolgus monkeys. Each group of cynomolgus monkeys was immunized three times intramuscularly with variant RBD-Fc vaccines at Day 0, 21, 42, and neutralizing antibody responses were evaluated against ancestral (Wuhan), Alpha, Beta, Gamma, and Delta variants. The results showed that three doses of the RBD-Fc vaccine significantly enhanced the immune response against all tested SARS-CoV-2 variants. In particular, the vaccines based on Delta and Epsilon mutant RBD elicit broadly neutralizing antibodies against ancestral (Wuhan), Alpha, and Delta SARS-CoV-2 variants whereas Beta and Gamma RBD-Fc vaccines elicit neutralizing antibodies against their respective SARS-CoV-2 strains. The Delta and Epsilon RBD-Fc based vaccines displayed cross-reactive immunogenicity and might be applied as a booster vaccine to induce broadly neutralizing antibodies. These proof-of-concept results will be helpful for the development of plant-derived RBD-Fc-based vaccines against SARS-CoV-2 and its variants.
不断出现的具有受体结合域（RBD）突变的严重急性呼吸综合征冠状病毒 2 （SARS-CoV-2）变异株（VOC）迅速传播，已成为全球严重的公共卫生问题。因此，迫切需要有效的疫苗和优化的加强针接种策略。在这里，编码六个不同 RBD（Alpha、Beta、Gamma、Kappa、Delta 和 Epsilon 变体）以及人 IgG1 的 Fc 片段（RBD-Fc）的基因被克隆到植物表达载体中，并通过瞬时表达在烟草中产生。此外，还在食蟹猴中测试了植物生产的变体 RBD-Fc 融合蛋白的免疫原性。每组食蟹猴在第 0、21、42 天通过肌肉内免疫三次接种变体 RBD-Fc 疫苗，并评估针对原始（武汉）、Alpha、Beta、Gamma 和 Delta 变体的中和抗体反应。结果表明，三剂 RBD-Fc 疫苗显著增强了对所有测试 SARS-CoV-2 变体的免疫反应。特别是，基于 Delta 和 Epsilon 突变 RBD 的疫苗可引发针对原始（武汉）、Alpha 和 Delta SARS-CoV-2 变体的广谱中和抗体，而 Beta 和 Gamma RBD-Fc 疫苗可引发针对其各自 SARS-CoV-2 株的中和抗体。基于 Delta 和 Epsilon RBD 的疫苗显示出交叉反应性免疫原性，可能作为加强针疫苗应用，以诱导广谱中和抗体。这些概念验证结果将有助于开发针对 SARS-CoV-2 及其变体的基于植物 RBD-Fc 的疫苗。
