Construction and characterization of pentacistronic retrovirus vectors

The picornavirus foot-and-mouth disease virus 2A sequence was combined with three different internal ribosome entry segments to construct and characterize three independent pentacistronic retroviruses of different sizes. Efficient co-expression of the five proteins was successful and titres obtained for these pentacistronic virus vectors (final genome size approximately 7.9 kb) were comparable to those of vector systems with shorter genomes. Other vectors constructed that exceeded the genome length of the wild-type virus suffered frequent deletions.