Structural properties of lipopolysaccharides from Rickettsia typhi and Rickettsia prowazekii and their chemical similarity to the lipopolysaccharide from Proteus vulgaris OX19 used in the Weil-Felix test

Abstract

The lipopolysaccharides (LPSs) isolated from typhus group (TG) rickettsiae Rickettsia typhi and Rickettsia prowazekii were characterized by chemical analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by silver staining. LPSs from two species of TG rickettsiae contained glucose, 3-deoxy-D-manno-octulosonic acid, glucosamine, quinovosamine, phosphate, and fatty acids (beta-hydroxylmyristic acid and heneicosanoic acid) but not heptose. The O-polysaccharides of these LPSs were composed of glucose, glucosamine, quinovosamine, and phosphorylated hexosamine. Resolution of these LPSs by their apparent molecular masses by SDS-PAGE showed that they have a common ladder-like pattern. Based on the results of chemical composition and SDS-PAGE pattern, we suggest that these LPSs act as group-specific antigens. Furthermore, glucosamine, quinovosamine, and phosphorylated hexosamine were also found in the O-polysaccharide of the LPS from Proteus vulgaris OX19 used in the Weil-Felix test, suggesting that they may represent the antigens common to LPSs from TG rickettsiae and P. vulgaris OX19.

FIG. 1

Comparison of LPSs from TG rickettsiae and S. typhimurium by SDS-PAGE with a 12.5% acrylamide gel concentration. After electrophoresis, the gels were stained with silver. Lanes: 1, LPS from S. typhimurium wild-type strain LT2; 2, LPS from S. typhimurium Re mutant G30/C21; 3, R. typhi LPS; 4, R. prowazekii LPS. Molecular mass markers: 97.4 kDa, phosphorylase b; 68 kDa, bovine serum albumin; 43 kDa, ovalbumin; 25.7 kDa, α-chymotrypsin; 18.4 kDa, β-lactoglobulin; 14.3 kDa, lysozyme.