Binding studies of a monoclonal antibody specific for 3-deoxy-D-manno-octulosonic acid with a panel of Klebsiella pneumoniae lipopolysaccharides representing all of the O serotypes.

A monoclonal antibody (MAb) raised against Salmonella minnesota R595 and specific for alpha-3-deoxy-D-manno-octulosonic acid (alpha-Kdo) of the inner core was tested for binding to lipopolysaccharides (LPS) of Klebsiella pneumoniae. The MAb was tested in several assay systems (enzyme-linked immunosorbent assay, passive hemolysis, and inhibition of passive hemolysis) with a large panel (n = 23) of K. pneumoniae LPS representing all nine currently known O serotypes. MAb 20 showed reactivity with almost all O serotypes of K. pneumoniae LPS, and this reactivity could be inhibited by synthetic Kdo. This suggests an epitope in the cores of these Klebsiella LPS much like that in the inner core of LPS of S. minnesota. Large differences in reactivity between LPS of different strains belonging to the same O serotype were observed. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis of LPS followed by immunoblotting, reactivity of MAb 20 was observed only with the fast-moving fraction possibly representing the nonsubstituted core. No binding was seen with the high-molecular-weight fraction that contained core material substituted with several units of O-antigen building blocks. The chemical basis for these differences in reactivity remains to be established. As far as we know, this is the first report containing comprehensive immunochemical data on the LPS core of K. pneumoniae.