A Vector-Host System to Fingerprint Virus Tropism.

Publication Type:

Journal Article


Human gene therapy (2012)


Reporter genes are important tools for assessing vector pharmacology in vivo. While useful, current systems are limited by 1) the need to generate a new vector for each different reporter, 2) the inability to package reporter genes in small vectors, and 3) variations in reporter gene feedback due to variations in cell to cell vector copy number. To circumvent these problems, we have utilized Cre recombinase as a "cat's paw" to activate reporter genes embedded in transgenic mice. The small Cre gene was introduced into self-complementary adeno-associated virus (scAAV) vectors with limited packaging capacity. Injection of scAAV-Cre vectors into mice with loxP-inactivated luciferase enabled in vivo imaging distributions comparable to the signal observed after AAV-luciferase injection. When injected into mT/mG mice, AAV-Cre converted ubiquitous expression of red fluorescent protein (RFP) to green fluorescent protein (GFP) expression only where the vectors transduced cells. Injection into F1 hybrid luciferase and mT/mG mice enabled simultaneous three reporter tracking. This system was able to discriminate cell-specific transduction in all organs tested, with particular utility for detecting AAV serotype-specific transduction in the liver, kidney, and muscle. Given that F1 mice bear exactly one copy of luciferase and one copy of RFP-GFP, each reporter gene is either "on" or "off" in a cell. The Cre system there provides a unique quantum method to quantify vector delivery that can be applied when vector capacity is limited.