GP2 and neoplasm: Interestingly, only the gpD::GP2 chimera in which the GP2 peptide was directly linked to gpD by an in-frame short linker contains GG and GS (T-S-G-S-G-S-G-S-G-S-G-S-G-S-G) flexible space was successfully processed and cross-presented and induced effective anti-tumor CTL responses.