Specificity and function of murine monoclonal antibodies and immunization- induced human polyclonal antibodies to lipopolysaccharide subtypes of Pseudomonas aeruginosa serogroup 06

Abstract

Structural and antigenic heterogeneity has been noted among lipopolysaccharides (LPS) produced by Pseudomonas aeruginosa within serogroups previously considered to be serologically homogeneous. We characterized murine monoclonal antibodies (MAbs) and immunization-induced human polyclonal antibodies reactive with one or more of five structurally variant LPS subtypes belonging to serogroup 06 of the International Antigenic Typing System. Analyses of five different MAbs employing purified LPS or whole bacteria in enzyme-linked immunosorbent assays and Western blot (immunoblot) assays revealed five distinct patterns of subtype specificity, ranging from recognition of a single subtype to reactivity with all five. MAb-mediated opsonophagocytic killing and in vivo protection against live challenge in mice correlated, in general, with differential binding to various LPS subtypes. In comparison, sera from human vaccinees immunized with LPS-derived high-molecular-weight polysaccharide from P. aeruginosa Fisher immunotype 1, one of five serogroup 06 subtypes, exhibited LPS binding and opsonic activity against all five subtypes. Antibodies in the human sera effectively inhibited binding to all five LPS subtype antigens of the cross- reactive MAb, LC3-2H2, suggesting the existence of a common serogroup- related epitope. These findings emphasize the importance of defining subtype- associated variations in LPS antigenicity and corresponding differences in antibody specificity and function as a basis for designing immunoprophylactic or therapeutic strategies which target P. aeruginosa LPS.