(a) SUDV NP610 with sdAb interfaces colored yellow for the apical approach and moss green for the cavern approach as would occur when 2 sdAbs bind each of 2 NP domains in the tetramer. (b) As for (a), except the interface residue locations predicted by PDBSum to be used by Fab MJ120 are colored orange. (c) The entire Fab (orange) is shown with the NP positioned as in (a) and (b), while (d) represents our typical “top-down” view of the NP V-shelf and entire Fab. SUDV, Sudan ebolavirus; NP, nucleoprotein; sdAb, single-domain antibody.