A fusion protein for use as an immunogen enhancer for enhancing antigen-specific T cell responses is disclosed. The fusion protein comprises: (a) an antigen-presenting cell (APC)-binding domain or a CD91 receptor-binding domain; (b) a protein transduction domain; and (c) an antigen of a pathogen, wherein the APC-binding domain or the CD91 receptor-binding domain is located at the N-terminus of the fusion protein, and the antigen of the pathogen is located at the C-terniinus of the protein transduction domain. The protein transduction domain is selected from the group consisting of: (i) a fusion polypeptide, comprising a T cell sensitizing signal-transducing peptide, a linker, and a translocation peptide; (it) a T cell-sensitizing signal-transducing peptide; and (iii) a translocation peptide of 34-112 amino acid residues in length.