Structure of the meningococcal vaccine antigen NadA and epitope mapping of a bactericidal antibody

Abstract

Serogroup B Neisseria meningitidis (MenB) is a major cause of severe sepsis and invasive meningococcal disease, which is associated with 5-15% mortality and devastating long-term sequelae. Neisserial adhesin A (NadA), a trimeric autotransporter adhesin (TAA) that acts in adhesion to and invasion of host epithelial cells, is one of the three antigens discovered by genome mining that are part of the MenB vaccine that recently was approved by the European Medicines Agency. Here we present the crystal structure of NadA variant 5 at 2 Å resolution and transmission electron microscopy data for NadA variant 3 that is present in the vaccine. The two variants show similar overall topology with a novel TAA fold predominantly composed of trimeric coiled-coils with three protruding wing-like structures that create an unusual N-terminal head domain. Detailed mapping of the binding site of a bactericidal antibody by hydrogen/deuterium exchange MS shows that a protective conformational epitope is located in the head of NadA. These results provide information that is important for elucidating the biological function and vaccine efficacy of NadA.meningitis | coiled coil | thermostability | hydrogen-deuterium exchange | trimeric autotransporter adhesin

Phage display revisited: Epitope mapping of a monoclonal antibody directed againstNeisseria meningitidisadhesin A using the PROFILER technology

“…(B) in-silico model of NadA3 built from the X-ray structure of the recently solved variant 5. 17 Dashes show regions of unknown secondary structure. The red and orange bar indicates the A250-H312 sequence that was found to be sufficient, in the present study, to fully recapitulate the reactivity of NadA against the mAb.…”

“…17 In Fig. 5A, the HDX-MS results have been simplified reporting the extent of deuterium uptake for only 19 sequential peptide fragments covering the entire peptide map.…”

“…14,17 Procedures involving mice were conductedin accordance to the guidelines of the European Unionfor the handling of laboratory animals. The mAb was purified 355from culture supernatants by Protein G affinity columns (GEHealthcare, cat.…”

“…17 Briefly, early-log phase cultures of bacteria were diluted in Dulbecco's PBS containing 1% BSA and 0.1% glucose (assay buffer) at a working dilution of 10 4 -10 5 CFU/ml. Bacteria were incubated with serial 2-fold dilutions of mAb 9F11 (from 0.37 mg/ml to 0.023 mg/ml), and 25% baby rabbit complement.…”

“…17 Briefly, the HDX experiments, with and without the mAb, were performed in the same experimental session. The antigen/mAb complex was formed by adding 250 pmols of NadA antigen to the mAb, using a molar ratio of 1:1 and incubated for 30 min at RT.…”