Successful Induction of Protective Antibody Responses against Haemophilus influenzae Type b and Diphtheria after Transcutaneous Immunization with the Glycoconjugate Polyribosyl Ribitol Phosphate-Cross-Reacting Material sub(197) Vaccine

We examined the antibody responses elicited in rats after transcutaneous immunization (TCI) with the Haemophilus influenzae type b (Hib)-cross-reacting material (CRM sub(197)) glycoconjugate vaccine coadministered with cholera toxin or mutants of heat-labile enterotoxin of Escherichia coli (LTK63 and LTR72) as adjuvants. The glycoconjugate vaccine was immunogenic, eliciting high antibody responses to the capsular polysaccharide of Hib and to diphtheria toxin. Passively transferred immune serum protected infant rats against challenge with the Hib Eagan strain and exhibited strong neutralizing activity against diphtheria toxin both in vitro and in vivo. The finding that TCI of rats can elicit antibody responses surpassing the minimum levels required for protective immunity against Hib and diphtheria suggests that this immunization strategy holds a lot of promise for future pediatric use. However, further studies are required to confirm the potential of TCI with glycoconjugate vaccines in humans.