Investigating the candidacy of a capsular polysaccharide-based glycoconjugate as a vaccine to combat Haemophilus influenzae type a disease: A solution for an unmet public health need

After the introduction of the glycoconjugate vaccine based upon the capsular polysaccharide of Haemophilus influenzae type b in the mid 1980s there was a remarkable decrease in the number of invasive cases reported for this organism. Since the 1990s several groups have observed the emergence of Haemophilus influenzae type a (Hia), especially in indigenous communities in the northern regions of Canada and Alaska, to a stage where a solution is warranted to prevent further unnecessary deaths due to this pathogen. A glycoconjugate vaccine solution based upon the type a capsular polysaccharide (CPS) was investigated pre-clinically in an effort to illustrate the proof of concept for this approach. In this study we describe the growth of Hia and the isolation, purification and conjugation of the CPS to several carrier proteins. The resulting glycoconjugates were immunised in mice and rabbits provoking sera that facilitated bactericidal killing against all type a strains that we tested. This study has illustrated the pre-clinical proof of concept of a glycoconjugate vaccine based on the CPS of Hia as a solution to this emerging disease.