Structural and energetic profiling of SARS-CoV-2 receptor binding domain antibody recognition and the impact of circulating variants

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Abstract

The SARS-CoV-2 pandemic highlights the need for a detailed molecular understanding of protective antibody responses. This is underscored by the emergence and spread of SARS-CoV-2 variants, including Alpha (B.1.1.7) and Delta (B.1.617.2), some of which appear to be less effectively targeted by current monoclonal antibodies and vaccines. Here we report a high resolution and comprehensive map of antibody recognition of the SARS-CoV-2 spike receptor binding domain (RBD), which is the target of most neutralizing antibodies, using computational structural analysis. With a dataset of nonredundant experimentally determined antibody-RBD structures, we classified antibodies by RBD residue binding determinants using unsupervised clustering. We also identified the energetic and conservation features of epitope residues and assessed the capacity of viral variant mutations to disrupt antibody recognition, revealing sets of antibodies predicted to effectively target recently described viral variants. This detailed structure-based reference of antibody RBD recognition signatures can inform therapeutic and vaccine design strategies.

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  1. SciScore for 10.1101/2021.03.21.436311: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Antibodies
    SentencesResources
    To permit consistency among antibody-RBD complex structures, and to facilitate calculations, antibodies were truncated to include variable domains, and full spike glycoproteins were truncated to include only RBD residues (residues 330-530) of the sole or major target of the antibody.
    antibody-RBD
    suggested: None
    Antibodies with > 20 atomic clashes with ACE2 were classified as likely to block ACE2 binding.
    ACE2
    suggested: None
    Four antibodies that engaged the closed spike and exhibited cross-protomer binding, as confirmed by inspection of antibody-spike complex structures (S2M11, C144, mNb6,
    C144
    suggested: None
    An in-house Perl script was used to analyze SARS-CoV-2 antibody- antigen interfaces and calculate epitope conservation.
    antibody-
    suggested: None
    Software and Algorithms
    SentencesResources
    Hierarchical clustering of antibody RMSDs was performed in R version 4.0.3 (www.r-project.org) with the distance matrix of RMSDs as input, and Ward’s minimum variance method (“ward.D2” method in hclust).
    hclust
    suggested: (HCLUST, RRID:SCR_009154)
    Principal component analysis of antibody-RBD contact profile data was performed with the scikit-learn Python module.
    Python
    suggested: (IPython, RRID:SCR_001658)
    Buried surface areas (BSAs) were calculated using the naccess program (v. 2.1.1) (Hubbard and Thornton, 1993), subtracting the solvent accessible surface area of the antibody-RBD complex structure from the total solvent accessible surface area of the separate antibody and RBD structures, dividing by two to avoid double-counting interface area and to make BSA values commensurate with those from other tools including PISA (http://www.ebi.ac.uk/pdbe/prot_int/pistart.html).
    PISA
    suggested: (PISA, RRID:SCR_015749)
    Pearson correlation coefficients (PCC) between measured and predicted ΔΔG values, and receiver operating characteristic area under the curve (AUC) values for prediction of hotspot residues (measured ΔΔG for alanine residue substitution > 1 kcal/mol), were calculated using scipy and scikit-learn (sklearn
    scipy
    suggested: (SciPy, RRID:SCR_008058)
    scikit-learn
    suggested: (scikit-learn, RRID:SCR_002577)
    An example command line used for flex ddG calculations in this study is: rosetta_scripts.linuxgccrelease -s input.pdb -parser:protocol flexddg.xml -parser:script_vars chainstomove=1,2 mutate_resfile_relpath=input.resfile number_backrub_trials=35000 max_minimization_iter=5000 abs_score_convergence_thresh=1.0 backrub_trajectory_stride=7000 -restore_talaris_behavior -in:file:fullatom - ignore_unrecognized_res -ignore_zero_occupancy false -ex1 -ex2 For ΔΔG calculations in FoldX (Schymkowitz et al., 2005), complex structures were pre- processed using the FoldX RepairPDB protocol, and ΔΔG values were calculated using the FoldX PSSM protocol.
    FoldX
    suggested: (FoldX, RRID:SCR_008522)
    Sequence conservation: Assessment of sequence conservation of SARS-CoV-2 RBD positions in the SARS-CoV-1 sequence was performed using SARS-CoV-2 (GenBank: QHD43416) and SARS-CoV-1 (GenBank: AAP13441) spike reference sequences aligned with BLAST (Altschul et al., 1990).
    BLAST
    suggested: (BLASTX, RRID:SCR_001653)
    Figures: Figures of structures were generated using PyMOL version 1.8 (Schrodinger, Inc.).
    PyMOL
    suggested: (PyMOL, RRID:SCR_000305)
    Boxplots and dendrograms were generated using the ggplot2 (Wickham, 2016) and factoextra (Kassambara and Mundt, 2020) packages in R, and heatmaps were generated using the ComplexHeatmap package (Gu et al., 2016) in R.
    ggplot2
    suggested: (ggplot2, RRID:SCR_014601)
    ComplexHeatmap
    suggested: (ComplexHeatmap, RRID:SCR_017270)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).


    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.


    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.


    Results from JetFighter: We did not find any issues relating to colormaps.


    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

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