CMV FLuc Reporter Lentivirus

The skin is an easily accessible organ, and transferring therapeutic genes to the skin remains an attractive alternative approach for the treatment of skin diseases. Although efficient lentiviral gene delivery to human skin has been documented previously, adeno-associated virus (AAV)-based vectors are one of the most promising gene delivery tools for in vivo purposes. Here, researchers compared recombinant AAV vectors of various serotypes and lentiviral vectors for potential use in gene transfer to human skin in a xenograft mouse model. Vector constructs encoding firefly luciferase were packaged in AAV capsids of serotypes 1, 2, 5, 6, 8, and 9 and administered individually in human skin grafts by intradermal injection. For all serotypes, live bioimaging revealed low levels of transgene expression in human skin grafts, and firefly luciferase expression was primarily observed in adjacent tissues outside the graft. In contrast, gene delivery efficiency was high with intradermal injection of lentiviral vectors and resulted in widespread and persistent expression of firefly luciferase exclusively within human skin grafts. This study demonstrates that single-stranded AAV vectors of six commonly used serotypes have limited ability to deliver genes to human skin in vivo.

Here, researchers show that lentiviral vectors are able to transduce human skin cells within the injected graft, whereas rAAV vectors (whose potency varies by serotype) primarily transduce cells outside the graft. To confirm this finding, experiments comparing the efficacy of LV/CMV-FLuc and rAAV2/6-CMV-FLuc were repeated in a larger group of mice (n=5). Importantly, a strong bioluminescent signal was observed in all mice treated with rAAV2/6-CMV-Fluc in this experiment, while the signal intensity in LV/CMV-FLuc-injected mice was lower but clearly restricted to the graft (Figure 1a). Next, grafts were isolated from all 10 mice and the expression topology within the graft was analyzed (Figure 1b). For grafts from all five mice injected with LV/CMV-FLuc, the researchers confirmed strong gene expression centered inside the graft, whereas the remaining expression for rAAV2/6-CMV-FLuc-injected grafts was detected only in the periphery of the graft and most likely in neighboring connective tissue attached to the isolated graft.

Figure 1. rAAV2/6 transduction of neighboring tissues but not of the skin graft after intradermal vector injection. (Jakobsen M, et al., 2015)