Vectors used to engineer AAPC^A2 AAPC^A2P495 and AAPC^A2pp65. Monocistronic retroviral vectors were used to express human β₂ microglobulin (hβ2m) and the costimulatory molecules CD80 (B7.1), CD54 (LFA-3), and CD58 (ICAM-1). (A) Bicistronic vectors were used to express HLA A2.1 (B), the CMV protein pp65 (C), and the CMV peptide P495 (D) using an internal ribosomal entry site (IRES) linked to either neomycin phosphotransferase (neoR), or puromycin-N-acetyltransferase (puroR). SD indicates splicing donor; SA, splicing acceptor; and ψ⁺, extended packaging signal.