Structural and Genetic Characterization of the Shigella boydii Type 10 and Type 6 O Antigens

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Abstract
Comparison of the O antigens of Shigella boydii types 10 and 6 by chemical analysis and nuclear magnetic resonance spectroscopy showed that their structures are similar, with the only difference being the presence or absence of d -ribofuranose, which is the immunodominant sugar in S. boydii type 10. In S. boydii type 6, a residue previously reported as α- d -Glc p A, was shown to be β- d -Glc p A as in S. boydii type 10. S. boydii types 10 and 6 are reported not to cross-react serologically, and the role of d -ribofuranose in the specificity of S. boydii was confirmed by making a mutant of type 10 that lacked d -ribofuranose. However, S. boydii type 11, which has a d -ribofuranose but with different linkage does show cross-reaction with type 10. The O-antigen gene loci of S. boydii types 10 and 6 were shown to be virtually identical except that orf8 ( wbaM ), which was confirmed as the ribofuranosyltransferase gene, is interrupted by IS 629 in type 6. Therefore, it is proposed that the O-antigen gene cluster of S. boydii type 6 was derived from type 10 by an IS element insertion.