The present application relates to glycoengineered outer membrane vesicles obtained from recombinant, gram-negative bacteria comprising hetereologous DNA encoding an enzyme or enzymes that produce a heterologous glycan that replaces all or a portion of the naturally-occurring O antigen in the lipopolysaccharides of the bacteria. Also provided by the present application are immunogenic compositions and vaccines prepared from the glycoengineered outer membrane vesicles expressing the heterologous glycans at their surface.
