Structural basis for selective cross-reactivity in a bactericidal antibody against inner core lipooligosaccharide from Neisseria meningitidis†,‡

Abstract

The structure of a antigen-binding fragment (Fab) from the bactericidal monoclonal antibody LPT3-1 specific to lipooligosaccharide (LOS) inner cores from Neisseria meningitidis has been solved in complex with an eight-sugar inner core fragment NmL3 galE lpt3 KOH to 2.69 Å resolution. The epitope is centered about an inner core N-acetylglucosamine residue unique to N. meningitidis and does not include the lipid A moiety, which is disordered in the structure, but is positioned to allow the binding of free and membrane-anchored full-length LOS. All the amino acid residues that contact antigen are of germline origin but, remarkably, two consecutive somatic mutations of serine to glycine in the heavy chain at residues 52 and 52a are positioned to deprive the antibody of advantageous interactions and so weaken binding. However, these mutations are key to allowing selective cross-reactivity with the HepII-3-PEtn inner core variant expressed by 70% of strains. Neisseria meningitidis is a leading cause of disease in the developed world and is especially dangerous to children, who lack the necessary protective antibodies. The structure of Fab LPT3-1 in complex with LOS provides insight into the antibody's selective ability to recognize multiple clinically relevant variations of the LOS inner core from N. meningitidis.

Antibody Binding to the O-Specific Antigen of Pseudomonas aeruginosa O6 Inhibits Cell Growth

“…N1F10 scFv was expressed and purified as described for the S20 scFv. MF23-1 MAb was digested to release the Fab fragment using a protocol similar to that described by Parker et al (44). The optimal digestion conditions were 0.02 mg ml Ϫ1 papain, 2 mg ml Ϫ1 MF23-1, and 4 h at 37°C.…”

Structural basis for antibody targeting of the broadly expressed microbial polysaccharide poly-N-acetylglucosamine

“…Of the bacterial carbohydrate-binding antibodies being investigated for clinical use, F598 is unique in its ability to target PNAG, a carbohydrate found on the surface of a wide range of pathogens (17). While there are currently no carbohydratebinding antibodies approved for the therapy of bacterial infections (12,15), several crystal structures of bacterial saccharides as complexes with antibody fragments have been determined (31)(32)(33)(34)(35)(36)(37)(38)(39). To compare the mode of carbohydrate recognition displayed by F598 to other antibodycarbohydrate complexes, a simple 4 Å distance cut-off was used to define carbohydrate atoms contacting the antibodies ( Figure 6 and Figure S4).…”

Synthesis of Chlamydia Lipopolysaccharide Haptens through the use of α‐Specific 3‐Iodo‐Kdo Fluoride Glycosyl Donors

“…[8] Recently it has been shown, that these Kdo residues are involved in important binding interactions with proteins, and insight into the recognition of Kdo saccharides by monoclonal antibodies and Toll-like receptor-4 (TLR-4) has been achieved at the molecular level. [9] Thus, the chemical synthesis of Kdo glycosides is an attractive goal in the field of (bio)organic chemistry in order to provide immunoreagents and antigens for the development of synthetic carbohydrate-based vaccines and diagnostics. [10]…”