Constructing a Novel Conjugate Vaccine for Cholera: Conjugation of a Protective Vibrio cholerae Virulence Factor to Dextran by Squaric Acid Chemistry

Cholera, a devastating acute diarrheal disease caused by the bacteria Vibrio cholerae serogroups O1 and O139, remains to be a global health problem without suitable vaccines for endemic control or outbreak relief. While licensed vaccines do exist, among other disadvantages, they have low efficacy in young children and infants, indicating a need for better vaccines. V. cholerae O-specific polysaccharide (OPS), a component of the lipopolysaccharide (LPS), is the major protective antigen of pathogenic V. cholera. Because of this, promising vaccine development efforts have gone towards developing a glycoconjugate vaccine containing V. cholerae OPS. However, vaccine development efforts thus far have employed medically acceptable, non-Vibrio proteins as polysaccharide carriers rather than antigenically relevant proteins. Some have hypothesized that an antigenic carrier protein could increase protection conferred by a conjugate vaccine. N-acetylglucosamine (GlcNAc) binding protein A (GbpA) is a virulence factor of Vibrio cholerae and has been found to be essential for effective colonization of the intestines, a key characteristic of cholera disease. Previous studies have shown that serum antibodies against GbpA are protective, thus indicating GbpA as a potential vaccine target for cholera and a potential antigenic carrier for pathogenic V. cholera OPS. Here, I report that GbpA can be efficiently conjugated via squaric acid chemistry to 6kDa monoamino dextran, carrying ~1-11 dextrans per GbpA, validating GbpA as a potential novel, antigenic carrier protein for a V. cholerae OPS conjugate vaccine