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Infection and Immunity, September 2003, p. 5005-5011, Vol. 71, No. 9
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.9.5005-5011.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Actinobacillus actinomycetemcomitans Serotype d-Specific Antigen Contains the O Antigen of Lipopolysaccharide

Institute of Dentistry, University of Helsinki, and Department of Oral and Maxillofacial Diseases, Helsinki University Central Hospital,¹ Department of Health and Functional Ability,² Department of Molecular Medicine, National Public Health Institute, Helsinki, Finland,³ Adhesion Center/Oral Microbiology, Department of Medicine and Odontology, Umeå University, Umeå, Sweden⁴

Received 17 March 2003/ Returned for modification 15 April 2003/ Accepted 11 June 2003

Actinobacillus actinomycetemcomitans is a gram-negative, facultatively anaerobic bacterium which is associated especially with aggressive forms of periodontitis. Contradictory results on the localization of the A. actinomycetemcomitans serotype-specific antigen have been reported. The aim of the present study was to characterize the A. actinomycetemcomitans serotype d-specific antigen. The antigen was isolated by affinity chromatography. The affinity column was prepared from immunoglobulin G isolated from rabbit antiserum raised against A. actinomycetemcomitans serotype d. The isolated antigen was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting, and silver staining, all of which revealed a ladder-like structure typical for the O antigen of lipopolysaccharide (LPS). In a displacement enzyme-linked immunosorbent assay (ELISA), the isolated antigen displaced in a concentration-dependent manner the binding of the polyclonal rabbit antiserum raised against A. actinomycetemcomitans serotype d to the competing whole-cell serotype d antigen. The isolated antigen contained LPS, and an equal concentration of LPS isolated from A. actinomycetemcomitans serotype d gave a similar displacement curve in the ELISA. In order to test the immunogenic properties of the isolated antigen, it was used to immunize a rabbit. The antiserum raised against the isolated antigen displayed specificity in Western blotting and ELISA similar to that of antibody raised against LPS isolated from A. actinomycetemcomitans serotype d. In conclusion, our results show that the A. actinomycetemcomitans serotype d-specific antigen contains the O-antigenic structure of LPS.

Editor: J. D. Clements

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• Lakio, L., Lehto, M., Tuomainen, A. M., Jauhiainen, M., Malle, E., Asikainen, S., Pussinen, P. J. (2006). Pro-atherogenic properties of lipopolysaccharide from the periodontal pathogen Actinobacillus actinomycetemcomitans. Innate Immunity 12: 57-64 [Abstract]