Dendritic Cells Transduced with Protein Antigens Induce Cytotoxic Lymphocytes and Elicit Antitumor Immunity

Abstract

Dendritic cell (DC)-based vaccines are being developed for treatment of patients with cancer, in part because DC are potent inducers of CD8+ CTL. DC MHC class I:antigenic peptide complexes that are required for CTL elicitation are most often generated by incubating DC with peptides or by transfecting (or transducing) DC with cDNAs (or viral vectors) that encode protein Ags. The former approach is feasible when MHC class I Ags and relevant peptides are known. The latter approach may be hampered by inefficient DC transfection (transduction) and/or difficulties associated with preparation and use of viral vectors. Herein we demonstrate that a bacterial recombinant model tumor-associated Ag (OVA) that contains the HIV TAT protein transduction domain (PTD) was readily engineered and purified, efficiently transduced murine lymphocytes and DC, and was processed by proteasomes for MHC class I-restricted presentation to CTL. In addition, PTD-containing rOVA was processed and presented by DC to CD4 T cells as efficiently as native OVA or rOVA lacking the PTD. PTD-OVA-transduced DC induced CTL in vivo in a Th cell-independent fashion and vaccinated against OVA-expressing tumors. In contrast, rOVA lacking the PTD did not enter the DC MHC class I presentation pathway and DC treated with this protein did not prime OVA-specific CTL in vivo. Treatment of mice harboring clinically apparent OVA-expressing tumors with PTD-OVA-transduced DC resulted in tumor regression in some animals. This straightforward vaccination strategy may translate into DC-based treatments for patients with cancer and other serious diseases.

Comparison of recombinant adenovirus and synthetic peptide for DC-based melanoma vaccination

“…The same technique was also successfully employed using recombinant TRP2 protein and cultured DC. 33 Our results provide one possible explanation for the lack of efficacy in human clinical studies using peptide-pulsed DC and suggest that antigenloading strategies for DC-based melanoma vaccines need to be optimized. As a clinically more attractive alternative, we also demonstrated that direct injection of recombinant Adenovirus can be as effective as administration with cultured DC provided that the TRP2 aa180-188 peptide epitope is attached to an immunogenic helper protein such as EGFP.…”

“…Diverse antigen-loading strategies including synthetic or mixed tumor-derived MHC class I-binding peptides, recombinant or crude tumor cell-derived protein, plasmid DNA, recombinant virus, synthetic or whole tumor-derived RNA, as well as whole tumor cells or tumor cell-derived apoptotic bodies have been evaluated. 10,11,33,34 Currently, the optimal culture protocol and the optimal antigen-loading strategy for DC-based melanoma vaccines are both a matter of intense debate.…”

Enhanced antigen presentation and CTL activity by transduction of mature rather than immature dendritic cells with octaarginine-modified liposomes

“…This pathway is currently called "cross-presentation" pathway [4,21]. In an attempt to enhance the cellular uptake and promote the cross-presentation pathway in DCs, many investigators perused the recombinant fusion protein or synthetic peptides which contain CPPs tandemly linked to the Ag [7][8][9][10][11][12][13][14]. However the construction of such a recombinant proteins/ peptides are specific for a single Ag, limiting the usefulness of this technology.…”

“…Because the Ag uptake by DCs decreases as the cells mature from iDCs to mDCs, most groups have used iDCs to promote Ag capture and uptake [6]. To facilitate the Ag uptake by DCs, arginine-rich cell-penetrating peptides (CPPs) including HIV-TAT, poly-arginine and penetratin (Int) derived from Antennapedia has been applied recently [7][8][9][10]. Kim et al were the first to demonstrate that Ag-specific cytotoxic T lymphocytes (CTLs) are generated in vivo by immunizing mice with DCs that had been exposed to protein-TAT conjugates [7].…”

“…Since then various research groups, including our own, have applied CPP transduction to DCs as a method of stimulating Ag-specific T cells. Many studies reported that mice immunized with DCs transduced with recombinant CPP-Ag protein suppressed the tumor growth significantly [8][9][10][11][12][13][14][15]. Apart from the recombinant fusion protein, synthetic polypeptide containing CPP tandemly linked to peptide epitopes is another striking approach [14].…”