Tricistronic and tetracistronic retroviral vectors for gene transfer

We have combined the picornavirus foot-and-mouth disease virus (FMDV) 2A se quence and the internal ribosome entry sites (IRESes) from encephalomyocard itis virus (ECMV) and avian reticuloendotheliosis virus type A (REV-A) to c onstruct tricistronic and tetracistronic vectors. All the polycistronic con structs show high titers and expression of the genes inserted. Clones have been obtained in which cells simultaneously express the three or four genes carried by the polycistronic vectors.