%0 Journal Article
%T A Collection of Single-Domain Antibodies that Crowd Ricin Toxin¡¯s Active Site
%A C. Russell Middaugh
%A Chi My Thi Nguyen
%A David D. Weis
%A David J. Vance
%A David Volkin
%A Michael J. Rudolph
%A Nicholas J. Mantis
%A Siva Krishna Angalakurthi
%A Yinghui Rong
%J -
%D 2018
%R https://doi.org/10.3390/antib7040045
%X Abstract In this report, we used hydrogen exchange-mass spectrometry (HX-MS) to identify the epitopes recognized by 21 single-domain camelid antibodies (V HHs) directed against the ribosome-inactivating subunit (RTA) of ricin toxin, a biothreat agent of concern to military and public health authorities. The V HHs, which derive from 11 different B-cell lineages, were binned together based on competition ELISAs with IB2, a monoclonal antibody that defines a toxin-neutralizing hotspot (¡°cluster 3¡±) located in close proximity to RTA¡¯s active site. HX-MS analysis revealed that the 21 V HHs recognized four distinct epitope subclusters (3.1¨C3.4). Sixteen of the 21 V HHs grouped within subcluster 3.1 and engage RTA ¦Á-helices C and G. Three V HHs grouped within subcluster 3.2, encompassing ¦Á-helices C and G, plus ¦Á-helix B. The single V HH in subcluster 3.3 engaged RTA ¦Á-helices B and G, while the epitope of the sole V HH defining subcluster 3.4 encompassed ¦Á-helices C and E, and ¦Â-strand h. Modeling these epitopes on the surface of RTA predicts that the 20 V HHs within subclusters 3.1¨C3.3 physically occlude RTA¡¯s active site cleft, while the single antibody in subcluster 3.4 associates on the active site¡¯s upper rim. View Full-Tex
%K toxin
%K antibody
%K camelid
%K vaccine
%K biodefense
%K hydrogen exchange-mass spectrometry
%U https://www.mdpi.com/2073-4468/7/4/45