The insertion of two lysine residues (cleavage sites of cathepsin B) at the boundary of a peptide recognized by B cells (BD) and a class-II- presentable sequence (TDh) enhanced the anti-BD antibody induction capacity of this type of peptide construct, as well as production of IL2. It is postulated that these lysines generate a neoprocessable site which helps in release of the TDh moiety from the construct, enabling its presentation to class II molecules, an essential step in clonal expansion of the antibody-producing B cell after internalization of the construct via the BD moiety.