Chemokine gene modification of human dendritic cell-based tumor vaccines using a recombinant adenoviral vector

Previous animal studies conducted in our laboratory have shown that tumor antigen-pulsed dendritic cells (TP-DC) can mediate antitumor effects in vivo. However, durable and complete regression of established tumors has been difficult to achieve through the administration of TP-DC alone. To better augment immune priming to tumors in vivo, we have hypothesized that it is necessary to achieve an increased number of host-derived, naïve T cells at the site of TP-DC vaccine injections. To accomplish this goal, we have embarked on a series of studies that utilize defined chemokines. One of these molecules, secondary lymphoid tissue chemokine (SLC), has been shown to be uniquely chemoattractant for naïve T cells and dendritic cells. We propose that gene modification of DC-based tumor vaccines to produce human SLC will enhance T-cell recruitment and immune priming to tumor-associated antigens, and thereby translate into improved antitumor vaccine efficacy in vivo. Utilizing an E1-, E3-deleted adenoviral vector containing the gene for human SLC, we have been able to transduce human DC to produce biologically active human SLC that chemoattracts human T cells in vitro. SLC production by transduced DC was markedly enhanced upon DC maturation. Additionally, these SLC-secreting DC were found to be viable to a large extent despite the cytopathic effect inherent in adenoviral gene transfer and, most importantly, functional as determined by their ability to prime autologous T cells to a known melanoma-associated antigen, MART-1. Based on these encouraging results, we plan to initiate Phase I clinical studies utilizing DC-SLC to treat patients with advanced solid tumors.