In vivo anti-melanoma efficacy of allo-restricted CTLs specific for melanoma expanded by artificial antigen-presenting cells

Utilizing immunogenomic approaches to prioritize targetable neoantigens for personalized cancer immunotherapy

Advancements in sequencing technologies and bioinformatics algorithms have expanded our ability to identify tumor-specific somatic mutation-derived antigens (neoantigens). While recent studies have shown neoantigens to be compelling targets for cancer immunotherapy due to their foreign nature and high immunogenicity, the need for increasingly accurate and cost-effective approaches to rapidly identify neoantigens remains a challenging task, but essential for successful cancer immunotherapy. Currently, gene expression analysis and algorithms for variant calling can be used to generate lists of mutational profiles across patients, but more care is needed to curate these lists and prioritize the candidate neoantigens most capable of inducing an immune response. A growing amount of evidence suggests that only a handful of somatic mutations predicted by mutational profiling approaches act as immunogenic neoantigens. Hence, unbiased screening of all candidate neoantigens predicted by Whole Genome Sequencing/Whole Exome Sequencing may be necessary to more comprehensively access the full spectrum of immunogenic neoepitopes. Once putative cancer neoantigens are identified, one of the largest bottlenecks in translating these neoantigens into actionable targets for cell-based therapies is identifying the cognate T cell receptors (TCRs) capable of recognizing these neoantigens. While many TCR-directed screening and validation assays have utilized bulk samples in the past, there has been a recent surge in the number of single-cell assays that provide a more granular understanding of the factors governing TCR-pMHC interactions. The goal of this review is to provide an overview of existing strategies to identify candidate neoantigens using genomics-based approaches and methods for assessing neoantigen immunogenicity. Additionally, applications, prospects, and limitations of some of the current single-cell technologies will be discussed. Finally, we will briefly summarize some of the recent models that have been used to predict TCR antigen specificity and analyze the TCR receptor repertoire.

Modulating T-cell-based cancer immunotherapy via particulate systems

Immunotherapy holds tremendous promise for improving cancer treatment in which an appropriate stimulator may naturally trigger the immune system to control cancer. Up-to-date, adoptive T-cell therapy has received two new FDA approvals that provide great hope for some cancer patient groups. Nevertheless, expense and safety-related issues require further study to obtain insight into targets for efficient immunotherapy. The development of material science was largely responsible for providing a promising horizon to strengthen immunoengineering. In this review, we focus on T-cell characteristics in the context of the immune system against cancer and discuss several approaches of exploiting engineered particles to manipulate the responses of T cells and the tumour microenvironment.

Paracrine release of IL-2 and anti-CTLA-4 enhances the ability of artificial polymer antigen-presenting cells to expand antigen-specific T cells and inhibit tumor growth in a mouse model

Accumulating evidence indicates that bead-based artificial antigen-presenting cells (aAPCs) are a powerful tool to induce antigen-specific T cell responses in vitro and in vivo. To date, most conventional aAPCs have been generated by coupling an antigen signal (signal 1) and one or two costimulatory signals, such as anti-CD28 with anti-LFA1 or anti-4-1BB (signal 2), onto the surfaces of cell-sized or nanoscale magnetic beads or polyester latex beads. The development of a biodegradable scaffold and the combined use of multiple costimulatory signals as well as third signals for putative clinical applications is the next step in the development of this technology. Here, a novel biodegradable aAPC platform for active immunotherapy was developed by co-encapsulating IL-2 and anti-CTLA-4 inside cell-sized polylactic-co-glycolic acid microparticles (PLGA-MPs) while co-coupling an H-2Kb/TRP2-Ig dimer and anti-CD28 onto the surface. Cytokines (activating signal) and antibodies (anti-inhibition signal) were efficiently co-encapsulated in PLGA-MP-based aAPCs and co-released without interfering with each other. The targeted, sustained co-release of IL-2 and anti-CTLA-4 achieved markedly enhanced, synergistic effects in activating and expanding tumor antigen-specific T cells both in vitro and in vivo, as well as in inhibiting tumor growth in a mouse melanoma model, as compared with conventional two-signal aAPCs and IL-2 or anti-CTLA-4 single-released aAPCs. These data revealed the feasibility and importance of the paracrine release of multiple costimulatory molecules and cytokines from biodegradable aAPCs and thus provide a proof of principle for the future use of polymeric aAPCs for active immunotherapy of tumors and infectious diseases.

Folate-modified Chitosan Nanoparticles Containing the IP-10 Gene Enhance Melanoma-specific Cytotoxic CD8(+)CD28(+) T Lymphocyte Responses

BACKGROUND

Adoptive immunotherapy with cytotoxic T lymphocytes (CTLs) has great potential for the treatment of some malignant cancers. Therefore, augmenting the responses of tumor-specific CTLs is significant for the adoptive immunotherapy of melanoma. This study aimed to investigate the anti-tumor response of a combination therapy employing folate-modified chitosan nanoparticles containing IP-10 (interferon-γ-inducible protein-10) plus melanoma TRP2-specific CD8(+)CD28(+) T cells.

METHODS

We prepared folate-modified chitosan nanoparticles containing the mouse IP-10 gene (FA-CS-mIP-10), and induced melanoma TRP2-specific CD8(+)CD28(+) T cells by co-culturing them with artificial antigen-presenting cells. B16-bearing mice were treated with FA-CS-mIP-10, melanoma TRP2-specific CD8(+)CD28(+) T cells, a combination of both, and the saline control. Tumor volumes and the survival time of mice were recorded. The proportion of myeloid-derived suppressor cells (MDSCs) infiltrating the tumor microenvironment and regulatory T cells (Tregs) in the spleen was analyzed by flow cytometry. We also detected the proliferation and angiogenesis of tumors by immunohistochemistry and apoptosis by TUNEL.

RESULTS

The combination therapy inhibited the progression of melanoma in vivo. Compared with other treatments, it more efficiently inhibited tumor growth and increased the survival time of mice. After treatment with combination therapy, the proportion of MDSCs and Tregs decreased, while the percentage of CXCR3(+)CD8(+) T cells increased. Furthermore, combination therapy inhibited proliferation and promoted apoptosis of tumor cells and significantly inhibited tumor angiogenesis in vivo.

CONCLUSION

We describe a novel strategy for improving the anti-tumor response of CD8(+)CD28(+) CTLs by combining them with FA-CS-mIP-10 nanoparticles.

A constructed HLA-A2-restricted pMAGE-A1(278-286) tetramer detects specific cytotoxic T lymphocytes in tumour tissues in situ

OBJECTIVE

To construct a human leucocyte antigen (HLA)-A2-restricted peptide 278-286 of melanoma-associated antigen family A, 1 (pMAGE-A1(278-286)) tetramer to analyse the distribution of cytotoxic T lymphocytes (CTLs) in tumour tissue and tumour-adjacent normal tissue.

METHODS

A HLA-A2-pMAGE-A1(278-286) tetramer was constructed. The distribution of pMAGE-A1(278-286)-specific CTLs was investigated in tumour tissues and tumour-adjacent normal tissues from patients with hepatocellular carcinoma using in situ HLA-A2-pMAGE-A1(278-286) tetramer staining.

RESULTS

Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis indicated that HLA-A2 heavy and light chain proteins were successfully obtained. The successful construction of the HLA-A2-pMAGE-A1(278-286) monomer was confirmed with Western blot analysis using W6/32 antibody. Flow cytometry confirmed the specific binding of HLA-A2-pMAGE-A1(278-286) tetramer to pMAGE-A1(278-286)-specific CTLs. In situ HLA-A2-pMAGE-A1(278-286) tetramer staining demonstrated that the number of pMAGE-A1(278-286)-specific CTLs in tumour tissues was significantly higher than in tumour-adjacent normal tissues.

CONCLUSIONS

The HLA-A2-pMAGE-A1(278-286) tetramer was useful for the detection of pMAGE-A1(278-286)-specific CTLs in both tumour tissues and tumour-adjacent normal tissues. In situ tetramer staining is a powerful tool for investigating the distribution of pMAGE-A1278-286-specific CTLs in the tumour microenvironment.

Latex bead-based artificial antigen-presenting cells induce tumor-specific CTL responses in the native T-cell repertoires and inhibit tumor growth

Cell-free artificial antigen-presenting cells (aAPCs) were generated by coupling H-2K(b)/TRP2 tetramers together with anti-CD28 and anti-4-1BB antibodies onto cell-sized latex beads and injected intravenously and subcutaneously into naïve mice and antigen-primed mice (B6, H-2K(b)). Vigorous tumor antigen-specific CTL responses in the native T-cell repertoire in each mouse model were elicited as evaluated by measuring surface CD69 and CD25, intracellular IFN-γ, tetramer staining and cytolysis of melanoma cells. Furthermore, the aAPCs efficiently inhibited subcutaneous tumor growth and markedly delayed tumor progression in tumor-bearing mice. These data suggest that bead-based aAPCs represent a potential strategy for the active immunotherapy of cancers or persistent infections.

Killer artificial antigen-presenting cells deplete alloantigen-specific T cells in a murine model of alloskin transplantation

FasL-expressing killer antigen-presenting cells (KAPCs) have the ability to delete antigen-specific T cells and, therefore, could potentially be used for the treatment of allograft rejection and autoimmunity; however, their cellular nature markedly limits their clinical use. Novel bead-based killer artificial antigen-presenting cells (KaAPCs), which are generated by coupling major histocompatibility complex (MHC) class I antigens together with the apoptosis-inducing anti-Fas monoclonal antibody (mAb) onto magnetic beads, have recently attracted more attention. KaAPCs have a number of advantages over KAPCs and are able to deplete specific T cells in cocultures. However, it remains unknown whether bead-based KaAPCs can also induce apoptosis of alloreactive or autoreactive T cells and, consequently, generate hyporesponsiveness in vivo. In this study, H-2K(b)/peptide monomers and anti-Fas mAb have been covalently coupled to latex beads and administered intravenously into BALB/c mice (H-2K(d)) that had previously been grafted with skin squares from C57BL/6 mice (H-2K(b)). Alloskin graft survival was prolonged for 6 days. A 60% decrease of H-2K(b) antigen-alloreactive T cells was demonstrated by several measures 2 days after each injection of KaAPCs, but intact immune function, including antitumor activity, was maintained. These data provide the first in vivo evidence that bead-based KaAPCs can selectively deplete antigen-specific T cells without the loss of overall immune responsiveness and, therefore, highlight the therapeutic potential of this novel strategy for the treatment of allograft rejection and autoimmune disorders.