Human anti-scrub typhus rickettsia and rabbit anti-Proteus antibodies recognize similar epitope in the O-polysaccharide part of Proteus mirabilis OXKlipopolysaccharide

In the Weil-Felix test, sera from patients infected with Orientia tsutsugam ushi reacted with lipopolysaccharide (LPS) from Proteus mirabilis OXK strai ns. The O-polysaccharide of P. mirabilis OXK LPS consisted of pentasacchari de repeating units, with amidically-linked lysine residues. The lysine, lin ked to galacturonic residues, which plays an important role in the reaction with rabbit anti-OXK antibodies, was revealed with the aid of synthetic an tigens. Using ELISA, immunoglobulin M antibodies from scrub typhus patients reacted with the O-specific polysaccharide of strain OXK LPS only. This re action was inhibited by rabbit antibodies specific to the O-antigen of stra in OXK LPS. Both human and rabbit antibodies may bind to similar epitopes o n the O-polysaccharide part of P. mirabilis OXK LPS.