AbstractBackgroundThe high affinity Fcγ receptor I (FcγRI; aka CD64) is expressed by dendritic cells (DC) and antigens targeted to this receptor elicit enhanced immune responses. This study was designed to test the hypothesis that targeting an adenoviral (Ad) vector to FcγRI would lead to enhanced transduction of DC and an improved immune response to vector‐encoded antigens.MethodsA bispecific adaptor molecule consisting of a trimeric adenovirus fiber‐binding moiety fused to a single‐chain antibody specific for human FcγRI was generated. Transduction of cultured cells, including human DC, by the FcγRI‐targeted Ad was then evaluated using reporter genes (GFP, luciferase). Immunophenotypic and functional characteristics of vector‐transduced DC were also measured by flow cytometry, cytokine ELISA and mixed lymphocyte reaction (MLR); antigen‐specific stimulation of autologous CD8+ T cells was evaluated using vectors encoding cytomegalovirus (CMV) pp65.ResultsFcγRI‐targeted Ad transduced primary DC with 10–15‐fold greater efficiency than unmodified Ad or Ad vectors complexed to an adaptor protein that targeted an irrelevant receptor. However, FcγRI‐targeting had no effect of Ad‐induced activation of DC, as measured by cytokine release or expression of cell surface activation markers. Finally, FcγRI‐targeting of vectors encoding CMV pp65 resulted in an increase in the activation of antigen‐specific autologous human CD8+ T cells.ConclusionsFcγRI‐targeting significantly enhances the efficiency of Ad vector‐mediated gene transfer in primary human DC, and results in an improved immune response to a vector‐encoded antigen. Copyright © 2007 John Wiley & Sons, Ltd.