Abstract
Three clinically relevant ebolaviruses – Ebola (EBOV), Bundibugyo (BDBV), and Sudan (SUDV) viruses, are responsible for severe disease and occasional deadly outbreaks in Africa. The largest Ebola virus disease (EVD) epidemic to date in 2013-2016 in West Africa highlighted the urgent need for countermeasures, leading to the development and FDA approval of the Ebola virus vaccine rVSV-ZEBOV (Ervebo®) in 2020 and two monoclonal antibody (mAb)-based therapeutics (Inmazeb® [atoltivimab, maftivimab, and odesivimab-ebgn] and Ebanga® (ansuvimab-zykl) in 2020. The humoral response plays an indispensable role in ebolavirus immunity, based on studies of mAbs isolated from the antibody genes in peripheral blood circulating ebolavirus-specific human memory B cells. However, antibodies in the body are not secreted by circulating memory B cells in the blood but rather principally by plasma cells in the bone marrow. Little is known about the protective polyclonal antibody responses in convalescent plasma. Here we exploited both single-cell antibody gene sequencing and proteomic sequencing approaches to assess the composition of the ebolavirus glycoprotein (GP)-reactive antibody repertoire in the plasma of an EVD survivor. We first identified 1,512 GP-specific mAb variable gene sequences from single cells in the memory B cell compartment. Using mass spectrometric analysis of the corresponding GP-specific plasma IgG, we found that only a portion of the large B cell antibody repertoire was represented in the plasma. Molecular and functional analysis of proteomics-identified mAbs revealed recognition of epitopes in three major antigenic sites - the GP head domain, the glycan cap, and the base region, with a high prevalence of neutralizing and protective mAb specificities that targeted the base and glycan cap regions on the GP. Polyclonal plasma antibodies from the survivor reacted broadly to EBOV, BDBV, and SUDV GP, while reactivity of the potently neutralizing mAbs we identified was limited mostly to the homologous EBOV GP. Together these results reveal a restricted diversity of neutralizing humoral response in which mAbs targeting two antigenic sites on GP – glycan cap and base – play a principal role in plasma-antibody-mediated protective immunity against EVD.
Highlights
Ebolaviruses are responsible for severe disease and occasional deadly outbreaks in Africa posing a significant health threat
Cells were pre-incubated with Ebola virus (EBOV)-GP-reactive monoclonal antibodies (mAb) for which the epitope specificity is known, including antibodies that recognize glycan cap (13C6) [33], base region (4G7, EBOV-515, and EBOV-520) [19, 33], receptor binding site (MR78 that is specific to Marburg virus [MARV] GP and recognize EBOV GPCL) [35, 36], stalk (BDBV317), or mAb DENV 2D22 specific to dengue virus [37]
This study revealed that polyclonal antibody responses in this survivor targeted glycan cap and base region epitopes on intact GP and the GP base and RBS regions on GPCL, with a high prevalence of base- and RBS-specific antibodies directed against GPCL (Figure 2C)
Summary
Ebolaviruses are responsible for severe disease and occasional deadly outbreaks in Africa posing a significant health threat. The unpredictable nature of EVD outbreaks and public health challenges stemming from the severity of the disease underscores the need for development of medical countermeasures and systematic studies to elucidate correlates of immune response-mediated protection against EVD. A landmark achievement was the development and FDA approval of a recombinant viral vector-based vaccine (Ervebo®) for prevention of EVD [12, 13], vaccination with which has been shown to induce long-lasting antibody responses in clinical trials [14]. EBOV GP-reactive CD19+ B cells were identified after labeling with biotinylated recombinant soluble EBOV GP protein followed by detection with allophycocyanin-conjugated streptavidin. From108 PBMCs we sorted ∼20,000 EBOV GP-reactive B cells and identified 1,512 paired antibody heavy and light chain variable region sequences (Table S1)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
