Discovery and characterization of an anti-Neisseria gonorrhoeae NGO_1985 monoclonal antibody and cognate antigen.

Gonorrhea, caused by the Gram-negative bacterium Neisseria gonorrhoeae (Ng), affects millions of people globally. The absence of a vaccine and the rising antibiotic resistance complicate infection control, highlighting the urgent need for new prophylactic and therapeutic strategies. Since partial protection against gonorrhea has reportedly been linked to vaccination with the anti-meningococcal 4CMenB vaccine, we utilized Reverse Vaccinology 2.0 to identify gonococcal antigens through characterization of monoclonal antibodies (mAbs) produced by memory B cells (MBCs) following vaccination of volunteers with 4CMenB. A mAb, named mAb_4, with cross-reactivity among Ng strains was selected for deeper investigation. Genetic and biochemical approaches revealed that the cognate antigen was NGO_1985, a protein involved in outer membrane biogenesis and stability. Notably, NGO_1985 is the ortholog of the N. meningitidis (Nm) GNA_2091 protein, which is included as a fusion protein in the 4CMenB vaccine and contributes to stability and immunogenicity. The NGO_1985 epitope recognized by mAb_4 was predicted in silico and experimentally confirmed by Hydrogen Deuterium Exchange Mass Spectrometry. This study enhances our understanding of the molecular basis for the cross-reaction/protection conferred by 4CMenB and might guide future developments of antibody cocktail therapeutics, protein-based vaccines, and in vivo research.