Collapsing retroviruses for efficient delivery of viro-toxic cargoes

Retroviruses are excellent tools for delivering and expressing transgenic cargoes with broad utility in research and therapy. However, many cargoes including virus restriction factors can dramatically limit virus production and/or infectivity. An extreme viro-toxic cargo is the DNA cytosine deaminase APOBEC3B, which potently restricts retrovirus infectivity by a direct cDNA deamination-dependent mechanism. To overcome viro-toxicity, an APOBEC3B minigene cargo is disrupted by a translation stop cassette flanked by a direct repeat of its own sequence. The integrity of the minigene is reconstituted naturally by retroviral recombination during transduction. Efficiency can be improved from 90% to nearly 100% by coupling the minigene to the translation of a downstream selectable marker. Collapsing retrovirus (CRV) technology enables the functional delivery of APOBEC3B to a target cell population and may have broad utility for delivering viro-toxic cargoes.