Inspired by the specificity of α-(2,9)-sialyl epitopes
in
bacterial capsular polysaccharides (CPS), a doubly fluorinated disaccharide
has been validated as a vaccine lead against Neisseria
meningitidis serogroups C and/or B. Emulating the
importance of fluorine in drug discovery, this molecular editing approach
serves a multitude of purposes, which range from controlling α-selective
chemical sialylation to mitigating competing elimination. Conjugation
of the disialoside with two carrier proteins (CRM197 and PorA) enabled
a semisynthetic vaccine to be generated; this was then investigated
in six groups of six mice. The individual levels of antibodies formed
were compared and classified as highly glycan-specific and protective.
All glycoconjugates induced a stable and long-term IgG response and
binding to the native CPS epitope was achieved. The generated antibodies
were protective against MenC and/or MenB; this was validated in vitro by SBA and OPKA assays. By merging the fluorinated
glycan epitope of MenC with an outer cell membrane protein of MenB,
a bivalent vaccine against both serogroups was created. It is envisaged
that validation of this synthetic, fluorinated disialoside bioisostere
as a potent antigen will open new therapeutic avenues.