Intradermal injections of polyarginine-containing immunogenic antigens preferentially elicit Tc1 and Th1 activation and antitumour immunity

Pro-inflammatory responses after peptide-based cancer immunotherapy

Therapeutic vaccinations are designed to prevent cancer by inducing immune responses against tumor antigens. in cancer cells, tumor-associated antigens (TAA) or tumor-specific (mutated) derived peptides are presented within the clefts of main histocompatibility complex (MHC) class I or class II molecules, they either activate cytotoxic T-lymphocytes (CTLs), CD4+ T or CD8+ T lymphocytes, which release cytokines that can suppress tumor cells growth. In cancer immunotherapies, CD8+ T lymphocytes are a major mediator of tumor repression. The effect of peptide-based vaccinations on cytokines in the activating CD8+ T cell against targeted tumor antigens is the subject of this review. It is believed that peptide-based vaccines increased IFN-γ, TNF-α, IL-2, and IL-12, secreting CTL line by interacting with dendritic cell (DC), supposed to stimulate immune system. Additionally, mechanisms of CTL activation and dysfunction were also studied. According to most of the data resulted from in vivo and in vitro research works, it is assumed that peptide-based vaccines increased IFN-γ, TNF-α, IL-2, and IL-12.

Internalization routes of cell-penetrating melanoma antigen peptides into human dendritic cells

Optimized delivery of antigens combined with sustainable maturation of dendritic cells (DCs) is crucial for generation of effective antitumoral immune responses. Multiple approaches for ex vivo antigen loading and improvement in immunogenicity have been described. We have recently established a single-step protocol consisting of a fusion peptide (a sequence of the melanoma antigen Melan-A and a cationic cell-penetrating HIV TAT domain) bound in complexes with a toll-like receptor agonist. As the exact cellular uptake mechanisms of TAT-coupled antigens have been a matter of considerable debate and significantly depend on cell type, cargo and concentrations, we evaluated internalization routes into human immature DCs in comparison with non-phagocytic cell lines. We found that Melan-A-TAT fusion peptide uptake by DCs is mainly energy dependent, superior compared with polylysine-coupled Melan-A and significantly higher in DCs as compared with Jurkat cells or HUVECs. Furthermore, we could track the uptake of the fusion peptide exclusively through early endosomes to lysosome compartments after 90 min by fluorescence microscopy and immunoelectron microscopy. Specific endocytosis inhibitors revealed major internalization of the fusion peptide by DCs via clathrin-mediated endocytosis, whereas uptake by non-phagocytic HUVECs differed significantly, involving macropinocytosis as well as clathrin-mediated endocytosis. As our understanding of the processes involved in internalization of TAT-coupled cargos by human DCs broadens, and DC activation becomes available by single-step procedures as described, further development of simultaneous DC maturation and intra-cellular peptide targeting is warranted.

Dendritic cell engineering for tumor immunotherapy: from biology to clinical translation

Dendritic cells (DCs) are the most potent APCs, with the ability to orchestrate a repertoire of immune responses. DCs play a pivotal role in the initiation, programming and regulation of tumor-specific immune responses, as they are poised to take up, process and present tumor antigens to naive or effector T lymphocytes. Although, to an extent, DC-based immunotherapeutic strategies have successfully induced specific anti-tumor responses in animal models, their clinical efficacy has rarely been translated into the clinic. This article attempts to present a complete picture of recent developments of DC-based therapeutic strategies addressing multiple components of tumor immunoenvironment. It also showcases certain practical intricacies in order to explore novel strategies for providing new impetus to DC-based cancer vaccination.

The dermis as a portal for dendritic cell-targeted immunotherapy of cutaneous melanoma

Complete surgical excision at an early stage remains the only curative treatment for cutaneous melanoma with few available adjuvant therapy options. Nevertheless, melanoma is a relatively immunogenic tumor type and particularly amenable to immunotherapeutic approaches. A dense network of cutaneous dendritic cells (DC) may account for the reported efficacy of vaccination through the skin and provide an attractive target for the immunotherapy of melanoma. Several phenotypically distinct DC subsets are discernable in the skin, among others, epidermal Langerhans cells and dermal DC. Upon appropriate activation both subsets can efficiently migrate to melanoma-draining lymph nodes (LN) to prime T cell-mediated responses. Unfortunately, from an early stage, melanoma development is characterized by strong immune suppression, facilitating unchecked tumor growth and spread. Particularly the primary tumor site and the first-line tumor-draining LN, the so-called sentinel LN, bear the brunt of this melanoma-induced immune suppression-and these are exactly the sites where anti-melanoma effector T cell responses should be primed by DC in order to prevent early metastasis. Through local immunopotentiation or through DC-targeted vaccination, the dermis may be utilized as a portal to activate DC and kick-start or boost effective T cell-mediated anti-melanoma immunity, even in the face of this immune suppression.