A chimeric fusion protein useful as an immunogen for inducing HIV antigen-specific immune responses contains a first polypeptidyl region and a second polypeptidyl region. The first polypeptidyl region includes a Pseudomonas Exotoxin A (PE) binding domain and a PE translocation domain. The second polypeptidyl region includes (i) a first peptidyl segment containing a fragment of gp120 C1 domain, located at the N-terminus of the second peptidyl region； (ii) a second peptidyl segment containing a fragment of gp120 C5 domain, located at the C-terminus of the first peptidyl segment； and (iii) a third peptidyl segment containing a fragment of gp41, located at the C-terminus of the second peptidyl segment. The second polypeptidyl region contains an antigenic determinant specific to one subtype of HIV. An intermediate polypeptide containing a non-Env, HIV antigenic determinant selected from Gag24, Nef, Tat and Rev may be included.
