Abstract
In situ delivery of tumor-associated antigen (TAA) genes into dendritic cells (DC) has great potential as a generally applicable tumor vaccination approach. Although adenoviruses (Ad) are an attractive vaccine vehicle in this regard, Ad-mediated transduction of DCs is hampered by the lack of expression of the Ad receptor CAR on the DC surface. DC activation also requires interaction of CD40 with its ligand CD40L to generate protective T-cell-mediated tumor immunity. Therefore, to create a strategy to target Ads to DCs in vivo, we constructed a bispecific adaptor molecule with the CAR ectodomain linked to the CD40L extracellular domain via a trimerization motif (CFm40L). By targeting Ad to CD40 with the use of CFm40L, we enhanced both transduction and maturation of cultured bone marrow-derived DCs. Moreover, we improved transduction efficiency of DCs in lymph node and splenic cell suspensions in vitro and in skin and vaccination site-draining lymph nodes in vivo. Furthermore, CD40 targeting improved the induction of specific CD8(+) T cells along with therapeutic efficacy in a mouse model of melanoma. Taken together, our findings support the use of CD40-targeted Ad vectors encoding full-length TAA for in vivo targeting of DCs and high-efficacy induction of antitumor immunity.
Highlights
Melanoma vaccines based on ex vivo prepared autologous dendritic cells (DC) have been reported to induce specific T-cell responses which in some cases were associated with improved survival [1,2,3]
Bone marrow–derived DCs (BMDC) were more efficiently transduced by CD40-Ad than by untargeted-Ad as determined by GFP transgene expression (Fig. 1A) and simultaneously underwent maturation as determined by expression levels of the DC maturation markers MHC-II and CD86 (Fig. 1B)
Mice were vaccinated with syngeneic BMDCs transduced in vitro by CD40-targeted- or untargeted-Ad-GFP-TRP2aa180–188
Summary
Melanoma vaccines based on ex vivo prepared autologous dendritic cells (DC) have been reported to induce specific T-cell responses which in some cases were associated with improved survival [1,2,3]. In spite of its first clinical successes, serious drawbacks are inherent to this approach. The ex vivo culture and antigen loading of DCs according to cGMP guidelines and on a per-patient basis are laborious, time consuming, and introduce interdonor variability that may complicate the interpretation of clinical outcome. Ex vivo modified DC migrate poorly in vivo, affecting the efficacy of the vaccine [4]. In vivo targeting of tumor-associated antigens (TAA) and/or activating agents to DC presents an attractive.
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