Chemical synthesis of the outer core oligosaccharide of Escherichia coli R3 and immunological evaluation.

Lipopolysaccharides (LPS), major virulence determinants in Gram-negative bacteria, are responsible for many pathophysiological responses and can elicit strong immune responses. In order to better understand the role of LPS in host-pathogen interactions and elucidate the immunogenic properties of LPS outer core oligosaccharides, an all α-linked Escherichia coli R3 outer core pentasaccharide was first synthesized with a propyl amino linker at the reducing end. This oligosaccharide was also covalently conjugated to a carrier protein (CRM197) via the reducing end propyl amino linker. Immunological analysis demonstrated that this glycoconjugate can elicit specific anti-pentasaccharide antibodies with in vitro bactericidal activity. These findings will contribute to the further exploration of this pentasaccharide antigen as a vaccine candidate.