Influence of the nature of the reporter gene and selection pressure on stability of avian retrovirus vectors.

We have compared the long-term stability of 2 avian non-replicative retroviral vectors in an infected permanent cell line from quail fibroblasts (QT6). Vectors NL53 and NPL, expressing both the neo and LacZ genes under control of cis-acting elements originated from avian erythroblastosis virus (AEV), are similar to each other except for the presence of the phleomycin-resistance SHble gene fused upstream the reporter LacZ gene, in NPL vector. The use of such vectors, with an uniform backbone, to infect QT6 cells, allowed us to demonstrate that stability of the beta-galactosidase activity encoded by the SHble-LacZ fusion gene remains higher than that encoded by the native LacZ gene, as determined in the same conditions of culture. Moreover, stability of the provirus was dependent on the selection pressure. Here we show that stability of beta-galactosidase activity in infected QT6 cells was obtained with high dose selection for the selectable SHble-LacZ fusion gene.