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bioRxiv · 10.64898/2026.05.05.723094

Capsular K-antigen Coats Outer Membrane Vesicles of Porphyromonas gingivalis

Kim, H. Y.·Ko, Y. K.·Hasturk, H.·Gibson, F. C.·Yu, M.·Davey, M. E.
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Abstract

Periodontal disease is an inflammatory disorder that arises from dysbiosis of the subgingival microbiota, with Porphyromonas gingivalis acting as a keystone pathogen in the shift from health to disease. P. gingivalis employs multiple strategies to subvert host immune defenses, and its capsular K-antigen serves as a key virulence determinant. Here, a pre-adsorbed antiserum (pAds106) was generated by removing nonspecific antibodies using cells from a K-antigen-null mutant (W83{Delta}PG0106), resulting in exceptional specificity for the P. gingivalis K1-antigen. Immunofluorescence analysis revealed that the K-antigen preferentially coats outer membrane vesicles (OMVs), rather than attaching to the bacterial cell surface. This localization was further confirmed by ELISAs of density gradient ultracentrifuge-purified OMVs, with background signal detected in OMVs derived from K-antigen-deficient strains, non-K1-strains, and other oral Bacteroidetes. K-antigen-coated OMVs exhibited higher hydrophilicity and elicited weaker inflammatory responses compared to K-antigen-deficient OMVs, consistent with previously reported properties of encapsulated strains. Importantly, the antiserum detected K-antigen-coated OMVs in subgingival plaque from periodontal patients, suggesting that K-antigen is actively produced at diseased sites. These findings revise the prevailing view that K-antigen solely encapsulates the bacterial cell body and suggest that K-antigen-coated OMVs produced by P. gingivalis play distinct roles in immune evasion during periodontal disease.

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Kim, H. Y., Ko, Y. K., Hasturk, H., Gibson, F. C., Yu, M., Davey, M. E.. 2026-05-06. Capsular K-antigen Coats Outer Membrane Vesicles of Porphyromonas gingivalis. https://doi.org/10.64898/2026.05.05.723094

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