Gaikwad Hanmant, Li Yue, Wang Guankui, Li Ronghui, Dai Shaodong, Rester Cody, Kedl Ross, Saba Laura, Banda Nirmal K, Scheinman Robert I, Patrick Casey, Mallela Krishna M G, Moghimi S Moein, Simberg Dmitri
Colorado Center for Nanomedicine and Nanosafety, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States.
Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States.
ACS Nano. 2022 May 4. doi: 10.1021/acsnano.2c02794.
Many aspects of innate immune responses to SARS viruses remain unclear. Of particular interest is the role of emerging neutralizing antibodies against the receptor-binding domain (RBD) of SARS-CoV-2 in complement activation and opsonization. To overcome challenges with purified virions, here we introduce "pseudovirus-like" nanoparticles with ∼70 copies of functional recombinant RBD to map complement responses. Nanoparticles fix complement in an RBD-dependent manner in sera of all vaccinated, convalescent, and naı̈ve donors, but vaccinated and convalescent donors with the highest levels of anti-RBD antibodies show significantly higher IgG binding and higher deposition of the third complement protein (C3). The opsonization anti-RBD antibodies is not an efficient process: on average, each bound antibody promotes binding of less than one C3 molecule. C3 deposition is exclusively through the alternative pathway. C3 molecules bind to protein deposits, but not IgG, on the nanoparticle surface. Lastly, "pseudovirus-like" nanoparticles promote complement-dependent uptake by granulocytes and monocytes in the blood of vaccinated donors with high anti-RBD titers. Using nanoparticles displaying SARS-CoV-2 proteins, we demonstrate subject-dependent differences in complement opsonization and immune recognition.
对SARS病毒的先天性免疫反应的许多方面仍不清楚。特别令人感兴趣的是，针对严重急性呼吸综合征冠状病毒2（SARS-CoV-2）受体结合域（RBD）的新型中和抗体在补体激活和调理作用中的作用。为了克服纯化病毒粒子带来的挑战，我们在此引入具有约70个功能性重组RBD拷贝的“类假病毒”纳米颗粒，以描绘补体反应。纳米颗粒在所有接种疫苗者、康复者和未接触过病毒者的血清中以RBD依赖的方式固定补体，但抗RBD抗体水平最高的接种疫苗者和康复者显示出显著更高的IgG结合以及第三补体蛋白（C3）的更高沉积。抗RBD抗体的调理作用并非一个有效的过程：平均而言，每个结合的抗体促进结合的C3分子少于一个。C3沉积仅通过替代途径进行。C3分子与纳米颗粒表面的蛋白质沉积物而非IgG结合。最后，“类假病毒”纳米颗粒促进具有高抗RBD滴度的接种疫苗者血液中的粒细胞和单核细胞进行补体依赖性摄取。通过展示SARS-CoV-2蛋白的纳米颗粒，我们证明了补体调理作用和免疫识别存在个体差异。
