Outer membrane vesicles displaying engineered glycotopes elicit protective antibodies

Proc Natl Acad Sci U S A. 2016 Jun 28;113(26):E3609-18. doi: 10.1073/pnas.1518311113. Epub 2016 Jun 6.


The O-antigen polysaccharide (O-PS) component of lipopolysaccharides on the surface of gram-negative bacteria is both a virulence factor and a B-cell antigen. Antibodies elicited by O-PS often confer protection against infection; therefore, O-PS glycoconjugate vaccines have proven useful against a number of different pathogenic bacteria. However, conventional methods for natural extraction or chemical synthesis of O-PS are technically demanding, inefficient, and expensive. Here, we describe an alternative methodology for producing glycoconjugate vaccines whereby recombinant O-PS biosynthesis is coordinated with vesiculation in laboratory strains of Escherichia coli to yield glycosylated outer membrane vesicles (glycOMVs) decorated with pathogen-mimetic glycotopes. Using this approach, glycOMVs corresponding to eight different pathogenic bacteria were generated. For example, expression of a 17-kb O-PS gene cluster from the highly virulent Francisella tularensis subsp. tularensis (type A) strain Schu S4 in hypervesiculating E. coli cells yielded glycOMVs that displayed F. tularensis O-PS. Immunization of BALB/c mice with glycOMVs elicited significant titers of O-PS-specific serum IgG antibodies as well as vaginal and bronchoalveolar IgA antibodies. Importantly, glycOMVs significantly prolonged survival upon subsequent challenge with F. tularensis Schu S4 and provided complete protection against challenge with two different F. tularensis subsp. holarctica (type B) live vaccine strains, thereby demonstrating the vaccine potential of glycOMVs. Given the ease with which recombinant glycotopes can be expressed on OMVs, the strategy described here could be readily adapted for developing vaccines against many other bacterial pathogens.

Keywords: O-antigen polysaccharide; anti-glycan antibodies; glycan; glycoconjugate vaccine; humoral immune response.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Bacterial / immunology*
  • Bacterial Vaccines / genetics
  • Bacterial Vaccines / immunology*
  • Bacterial Vaccines / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Female
  • Francisella tularensis / genetics
  • Francisella tularensis / immunology*
  • Francisella tularensis / metabolism
  • Glycosylation
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • O Antigens / immunology
  • Transport Vesicles / genetics
  • Transport Vesicles / metabolism*
  • Tularemia / immunology*
  • Tularemia / microbiology
  • Tularemia / prevention & control
  • Vaccination


  • Antibodies, Bacterial
  • Bacterial Vaccines
  • O Antigens