Lectin mediated adhesion of Streptococcus pneumoniae and its specific inhibition in vitro and in vivo

Immunological Outcomes of Antibody Binding to Glycans Shared between Microorganisms and Mammals

Glycans constitute basic cellular components of living organisms across biological kingdoms, and glycan-binding Abs participate in many cellular interactions during immune defense against pathogenic organisms. Glycan epitopes are expressed as carbohydrate-only entities or as oligomers or polymers on proteins and lipids. Such epitopes on glycoproteins may be formed by posttranslational modifications or neoepitopes resulting from metabolic-catabolic processes and can be altered during inflammation. Pathogenic organisms can display host-like glycans to evade the host immune response. However, Abs to glycans, shared between microorganisms and the host, exist naturally. These Abs are able to not only protect against infectious disease, but also are involved in host housekeeping functions and can suppress allergic disease. Despite the reactivity of these Abs to glycans shared between microorganisms and host, diverse tolerance-inducing mechanisms permit the B cell precursors of these Ab-secreting cells to exist within the normal B cell repertoire.

Lectin-mediated bacterial adhesion to human tissue

In vitro experiments with frozen sections of human lung and kidney demonstrated that adhesion of Streptococcus pneumoniae Pn 629 Type 14 and Pseudomonas aeruginosa ATCC 27853 to human cells was mediated by bacterial lectins (adhesins) with N-acetyl-D-glucosamine/D-galactose or N-acetyl-neuraminic acid specificity. Blocking of the lectin binding sites on bacterial surfaces with competitive carbohydrates completely prevented the bacterial adherence, whereas non-specific carbohydrates (D-mannose, D-xylose) did not inhibit adherence.