Structural Study of Lipopolysaccharides from Shigella flexneri

A.C. CASABUONO,; C. A.VAN DER PLOEG; A. D. ROGÉ; A.S. COUTO

Madryn- Chubut

Congreso; XLVI Reunión Anual de la SAIB; 2010

SAIB

STRUCTURAL STUDY OF LIPOPOLYSACHARIDES FROM SHIGELLA FLEXNERI A.C. Casabuono1, C. A.van der Ploeg2 , A. D. Rogé and A.S. Couto1 1CIHIDECAR-Depto. Q. Orgánica, FCEyN, UBA., 2INPB - ANLIS “Dr. Carlos G. Malbrán”, Argentina   adrcas@qo.fcen.uba.ar Shigella flexneri, a Gram-negative bacterium which causes dysentery, is classified into several serotypes on the basis of antigenic determinants on the lipopolysaccharide (LPS). Antisera produced by immunization of rabbits are used for the serotyping of different strains; however, these reagents may not able to cover all possible epitopes of the O antigen of S. flexneri. Therefore, the knowledge of the structure of the LPSs obtained from each serotype is essential. In this work we have performed a structural characterization of the LPSs obtained from S. flexneri 67X by mass spectrometry in order to compare its structure with strains with atypical serology. Dried cells were extracted by the hot phenol-water method rendering a water phase LPS, named S-LPS and a phenol soluble R-LPS. Each of the LPSs was subjected to weak acid hydrolysis to split Lipids A from the oligosaccharide. Mass spectrometry analysis of the purified Lipids A revealed different degree of acylation and phosphorylation. The oligosaccharides obtained were hydrolyzed and the sugar components analyzed by HPAEC-PAD. Differences in the sugar relationship between both samples indicated the absence of the O-antigen in the R-LPS. When both LPSs were analyzed by mass spectrometry, ions showing a common Lipid A + core region were detected. In addition, signals corresponding to the O-antigen were characterized in the S-LPS.