Structure of the Acid-Labile Galactosyl Phosphate-Containing O-Antigen of the Bacterium Proteus vulgaris OX19 (Serogroup O1) Used in the Weil--Felix Test

S. N. Senchenkova,¹ A. S. Shashkov,¹ F. V. Toukach,¹ A. Ziolkowski,² A. S. Swierzko,² K.-I. Amano,³ W. Kaca,² Yu. A. Knirel,^1,4 and N. K. Kochetkov¹

¹Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Leninskii pr. 47, Moscow, 117913 Russia; fax: (7-095) 135-53-28; E-mail: knirel@ioc.ac.ru

²Center of Microbiology and Virology, Polish Academy of Sciences, ul. Lodowa 106, 93-232 Lodz, Poland; fax: (48-42) 49-16-33.

³Central Research Laboratory, Akita University, School of Medicine, 1-1-1, Hondo, Akita 010, Japan.

⁴To whom correspondence should be addressed.

Submitted January 30, 1997.

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The structure of the O-specific polysaccharide chain of Proteus vulgaris OX19 lipopolysaccharide which determines the O1 specificity of Proteus and is used in the Weil--Felix test for diagnostics of rickettsiosis was established. On the basis of ¹H- and ¹³C-NMR spectroscopy, including two-dimensional correlation spectroscopy (COSY), H-detected ¹H,¹³C heteronuclear multiple-quantum coherence (HMQC), and rotating-frame nuclear Overhauser effect spectroscopy (ROESY), it was found that the polysaccharide consists of branched pentasaccharide repeating units containing D-galactose, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, and 2-acetamido-2,6-dideoxy-D-glucose (QuiNAc, two residues), which are connected to each other via a phosphate group (P) (see full article for figure). The polysaccharide is acid-labile, the glycosyl phosphate linkage being cleaved at pH 4.5 (70°C) to give a phosphorylated pentasaccharide with a galactose residue at the reducing end. Structural analysis of the oligosaccharide and a product of its dephosphorylation with 48% hydrofluoric acid using ¹H- and ¹³C-NMR spectroscopy and electrospray ionization mass spectrometry confirmed the structure of the polysaccharide.

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KEY WORDS: lipopolysaccharide, O-antigen, bacterial polysaccharide, structure, serological cross-reactivity, rickettsiosis, Weil--Felix test, Proteus vulgaris, Rickettsia.

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