Figure 1.

Schematic diagram of the retroviral replicating vector (RRV) configurations encoding different transgenes. RRV configurations with either an internal ribosomal entry site (IRES) or 2A peptide for transgene expression. The approximate size of the IRES-transgene and 2A-transgene cassette is shown in parentheses. The amino acid sequence of the 2A peptides from the equine rhinitis A virus (E2A), foot-and-mouth disease virus (F2A), porcine teschovirus-1 (P2A), and Thosea asigna virus (T2A) are shown. For each 2A peptide sequence, a glycine–serine–glycine peptide linker (GSG linker) was also included or excluded on the N-terminus. The conserved amino acid residues of the 2A peptides are shown in bold. The arrow indicates the site where the viral envelope protein at the N-terminus of the polyprotein is released from the ribosome in the 2A sequence.