Retroviruses have a number of features that make them unique as gene delivery vehicles.Their life cycle includes an integrated state in the DNA of the host chromosome. Depending upon local chromatin context(s), often influenced by cell type-specific promoter events, the retroviral promoter can direct high-level, efficient expression of genes encoded within the confines of its genome.As evidenced by the discovery of oncogenes within certain strains of leukemia and sarcoma-inducing murine retroviruses, the retroviral genome can accomodate changes to its configuration.

For these and other reasons retroviruses offer gene transfer specialists and gene therapy researchers probably the best utility for delivering genes to target cells at high efficiency in a manner that allows for long-term, stable expression of introduced genetic elements