Pharmaceutical and Immunological Evaluation of Cholera Toxin A1 Subunit as an Adjuvant of Hepatitis B Vaccine Microneedles

Purpose For successful delivery of a solid vaccine formulation into the skin using microneedles, the solubility of an adjuvant should be considered because the decrease in the dissolution rate by the addition of adjuvant decreases the delivery efficiency of the vaccine. Methods In this study, cholera toxin A subunit 1 (CTA1) was examined as an adjuvant to Hepatitis B vaccine (HBV) microneedles because of its good water solubility, improved safety, and positive effect as shown in intramuscular administration of a liquid vaccine. Results All solid formulations with CTA 1 dissolved in in vivo mouse skin within 30 min, and they were successfully delivered into the skin. In experiments with mice, the addition of CTA1 led to improved IgG immune response compared to the use of an aluminum hydroxide–based formulation and intramuscular administration of HBV. In addition, CTA1 induced CD8 + T cell response as much as in which the aluminum hydroxide–based formulation induced. Conclusions CTA1 is an adjuvant that satisfies both the delivery efficiency and the immunological characteristics required for vaccine microneedles. CTA1 will be used as a potential adjuvant through vaccine microneedles.