Characterization of an Antibody Recognizing the Conserved Inner Core of Pseudomonas aeruginosa Lipopolysaccharides

Bacterial infections are a growing public health threat with carbapenem-resistant Pseudomonas aeruginosa being classified as a Priority 1 critical threat by the World Health Organization. Antibody-based therapeutics can serve as an alternative and in some cases supplement antibiotics for the treatment of bacterial infections. The glycans covering the bacterial cell surface have been proposed as intriguing targets for binding by antibodies; however, antibodies that can engage with high affinity and specificity with glycans are much less common compared to antibodies that engage with protein antigens. In this study, we sought to characterize an antibody that targets a conserved glycan epitope on the surface of Pseudomonas. First, we characterized the breadth of binding of VSX, demonstrating that the VSX is specific to Pseudomonas but can bind across multiple serotypes of the organism. Next, we provide insight into how VSX engages with its target epitope, using a combination of biolayer interferometry and nuclear magnetic resonance, and verify our results using site-directed mutagenesis experiments. We demonstrate that the antibody, with limited somatic hypermutation of the complementarity-determining regions (CDRs) and with a characteristic set of arginines within the CDRs, specifically targets the conserved inner core of Pseudomonas lipopolysaccharides. Our results provide important additional context to antibody-glycan contacts and provide insight useful for the construction of vaccines and therapeutics against Pseudomonas aeruginosa, an important human pathogen.