Oral delivery of gastro-resistant microencapsulated typhoid vaccine.

Oral vaccination has long been regarded as the best alternative to conventional parenteral vaccination considering practical, economical, and immunological aspects. The purpose of this study was to develop albumin-chitosan mixed matrix microsphere-filled coated capsule formulations of Typhoid Vi antigen and to determine whether it can induce antigen-specific mucosal and systemic immune responses on oral administration. Formulations with Typhoid Vi antigen were prepared and filled into hard gelatin capsules (size # 9) and enteric coated. Formulations were characterized and administered to Sprague-Dawley rats to evaluate the induction of immune response to the antigen. The results indicated that the particle size, zeta potential, swelling, and disintegration rates were optimal for the oral delivery of microencapsulated vaccines. In vivo studies displayed multifold increase of antigen-specific IgG and IgA levels 8 weeks after oral immunization. No statistically significant difference in the antigen-specific IgG and IgA levels were found between oral and parenteral injection groups 8 weeks after vaccination. On the basis of the results of the study, it can be concluded that the oral administration of Typhoid Vi antigen microspheres was successful in inducing antigen-specific systemic and mucosal immune response.