The present disclosure relates to a thiolated hydroxypropyl methylcellulose phthalate (T-HPMCP) drug delivery vehicle which is pH responsive and is loaded with either a protein drug or an antigen, to T-HPMCP microparticles, and to a production method for an ileum-specific, pH responsive, T-HPMCP drug delivery vehicle, the method including a step of loading a protein drug or an antigen onto the T-HPMCP microparticles. The T-HPMCP microparticles of the present disclosure are soluble in chlorinated methane because of the introduction of the thiol group, while a T-HPMCP drug delivery vehicle produced from the particles can efficiently effect in vivo delivery of the protein drug or antigen which is loaded thereon, since said vehicle is pH responsive such that the in vivo residence time is extended and the vehicle can act specifically on the ileum.