Effective transduction by self-complementary adeno-associated viruses of human dendritic cells with no alteration of their natural characteristics.

Background: Effective gene delivery techniques are required to genetically manipulate dendritic cells (DCs). We therefore investigated the feasibility of using various self-complementary recombinant adeno-associated virus (scAAV) serotypes to deliver genes to human DCs.

Methods: Monocytes isolated from healthy volunteers were differentiated to immature DCs (iDC) by incubation with interleukin (IL)-4 and granulocyte macrophage colony-stimulating factor. The iDCs were transduced with scAAV1, 2, 3, 4, 5, 6 or 8 at various multiplicities of infection (MOIs). Transduction efficiency (TE), cell viability and functional characteristics of the transduced DCs were evaluated.

Results: TE of scAAV was three-fold greater than TE of conventional recombinant adeno-associated virus with a single-stranded genome. The TEs of scAAV2, 5, and 6 were much higher than those of the other scAAVs; at 1000 MOI, the TEs were 22.2% +/- 9.5%, 27.0% +/- 8.8% and 28.4% +/- 6.0%, respectively. Exposure of iDCs to 5000 MOI of these viruses increased their TEs, leading to the transduction of nearly the entire DC population. In addition, gene transfer by scAAV did not cause any cytotoxicity. Flow cytometric analysis of scAAV-transduced DCs showed no changes in surface marker profiles. Moreover, transduced cells maintained their functional properties, as represented by active antigen uptake. These cells could efficiently differentiate into mature DCs, as shown by their release of IL-12, the substantial loss of antigen-uptake activity, and the ability of T-cell stimulation.

Conclusions: These findings strongly indicate that scAAVs, especially subtypes 2, 5 and 6, hold a promising potential as gene delivery tools in human DCs.