Synthesis and immunodetection of 6-O-methyl-phosphoramidyl-α-D-galactose: a Campylobacter jejuni antigenic determinant.

Campylobacter jejuni is a leading cause of traveler's diarrhea. Previously, we have shown that a C. jejuni capsule polysaccharide (CPS) conjugate vaccine can fully prevent C.jejuni diarrhea in non-human primates. C.jejuni CPSs are decorated with non-stoichiometric amounts of O-methyl phosphoramidate (MeOPN) units that are key serospecific markers. In the case of C.jejuni serotype complex HS23/36, the MeOPN are at positions 2 and 6 of the CPS galactose (Gal). We describe here the synthesis of the p-methoxyphenyl glycoside of MeOPN→6-α-D-Galp, and its immunodetection by antisera raised by C.jejuni CPS conjugates with MeOPN at primary positions. The synthetic approach in this work served as the foundation for a similar MeOPN→6-Gal construct used in a conjugate vaccine, whose synthesis, immunogenicity and efficacy will be described elsewhere.