A murine leukemia virus with Cre-LoxP excisible coding sequences allowing superinfection, transgene delivery, and generation of host genomic deletions.

BACKGROUND: To generate a replication-competent retrovirus that could be conditionally inactivated, we flanked the viral genes of the Akv murine leukemia virus with LoxP sites. This provirus can delete its envelope gene by LoxP/Cre mediated recombination and thereby allow superinfection of Cre recombinase expressing cells. RESULTS: In our studies, the virus repeatedly infected the cell and delivered multiple copies of the viral genome to the host genome; the superinfected cells expressed a viral transgene on average twenty times more than non-superinfected cells. The insertion of multiple LoxP sites into the cellular genome also led to genomic deletions, as demonstrated by comparative genome hybridization. CONCLUSION: We envision that this technology may be particularly valuable for delivering transgenes and/or causing deletions.