The O-antigen is both a major structural outer-membrane component and the dominant epitope of most Gram-negative bacteria. Pseudomonas aeruginosa 1244 produces a Type IV pilus and covalently links an O-antigen repeating unit to each pilin monomer. Here we show that immunization of mice with pure pilin from strain 1244, using either the mouse respiratory or the thermal injury model, resulted in protection from challenge with a pilus-null O-antigen-producing 1244 mutant. These results provide evidence that the pilin glycan stimulates a protective response that targets the O-antigen, suggesting that this system could be utilized as the basis for develping a variety of protective anti-Gram-negative bioconjugate vaccines.

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