Structures of the O-specific polysaccharide chains of lipopolysaccharides from Proteus group OX strains (serogroups O1-O3) used as antigens in Weil-Felix test for diagnosis of rickettsiosis, were established, From them, the acid-labile polysaccharide of Proteus vulgaris OX19 (O1) is built up of the following branched pentasaccharide repeating units connected via a phosphate group: →4)-α-L-QuipNac-(1→3)-α-D-GlcpNac-(1→4)-α-D-GalpNac[3→1]α-L-QuipNac -(1→4)-α-D-Galp-1-P-(O→ where QuiNAc stands for 2-acetamido-2,6-dideoxyglucose (N-acetylquinovosamine). The basis of serospecificity of the Proteus group OX antigens and their cross-reactivity with human anti-rickettsial antibodies is discussed.
Ziolkowski, A., Shashkov, A. S., Swierzko, A. S., Senchenkova, S. N., Toukach, F. V., Cedzynski, M., … Knirel, Y. A. (1997). Structures of the O-antigens of Proteus bacilli belonging to OX group (serogroups O1-O3) used in Weil-Felix test. FEBS Letters, 411(2–3), 221–224. https://doi.org/10.1016/S0014-5793(97)00694-7