Different types of engineered cardiac constructs are being developed nowadays by many research groups. However, the immunological properties of such artificial tissues are not yet clearly understood. Previously, we have studied microfiber scaffolds carrying iPSC-derived cardiomyocytes. In this work, we evaluated the ability of these tissue-engineered constructs to activate the expression of CD28 and CTLA-4 proteins in T-lymphocytes which are early markers of the immune response. For this purpose electrospun PLA nanofibrous scaffolds were seeded with human iPSCs-CM and cultivated for 2 weeks. After, allogeneic mononuclear cells were co-cultured during 48 hours with 3 groups of samples that were tissue-engineered constructs, pure culture of cardiomyocytes and bare scaffolds followed by analysis of CD28/CTLA-4 expression on T-lymphocytes via flow cytometry. PLA scaffolds and concanavalin A (positive control) stimulation statistically significantly increased CD28 expression on CD4+ cells (up to 61.3% and 66.3%) and on CD8+ cells (up to 17.8% and 21.7%). CD28/CTLA-4 expression didn’t increase during co-cultivation of T-lymphocytes with cardiac engineered constructs and iPSC-CM monolayers. Thus, iPSCs-CM in monolayers and on PLA nanofibrous scaffolds didn’t cause T-cell activation, which allows us to expect that such cardiac constructs are not a cause of rejection after implantation.

Immune checkpoint inhibitors (ICIs) have obtained durable responses in many cancers, making it possible to foresee their potential in improving the health of cancer patients. However, immunotherapies are limited at the moment to a minority of patients and there is a need for a better understanding of the basic molecular mechanisms and functions of pivotal immune regulatory molecules. Immune checkpoint cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and regulatory T (Treg) cells play pivotal roles in hindering the anticancer immunity. Treg cells suppress antigen-presenting cells (APCs) by depleting immune stimulating cytokines, producing immunosuppressive cytokines and constitutively expressing CTLA-4. CTLA-4 molecules bind with higher affinity to CD80 and CD86 than CD28 and act as competitive inhibitors of CD28 in APCs. The purpose of this review is to summarize state-of-the-art understanding of the molecular mechanisms underlining CTLA-4 immune regulation and the correlation of ICI response with CTLA-4 expression in Treg cells from preclinical and clinical studies for possibly improving CTLA-4-based immunotherapies, while highlighting the knowledge gap.

The complete regression of clear cell renal cell carcinoma (ccRCC) obtained pre-clinically with anti-carbonic anhydrase IX (CAIX) G36 chimeric antigen receptor (CAR) T cells in doses equivalent to 10e8 CAR T cells/ Kg renewed the potential of this target to treat ccRCC and other tumors in hypoxia. The immune checkpoint blockade (ICB) brought durable clinical responses in advanced ccRCC and other tumors. Here we tested CD8/4-1BB compared to CD28-based anti-CAIX CAR PBMCs cells-releasing anti-programmed cell death ligand-1 (PD-L1) IgG4 for human ccRCC treatment in vitro and in an orthotopic NSG mice model in vivo. Using a 10e7 CAR PBMCs cells/ Kg dose, anti-CAIX CD28 CAR T cells releasing anti-PD-L1 IgG highly decrease both tumor volume and weight in vivo, avoiding the occurrence of metastasis. This antitumoral superiority of CD28-based CAR PBMCs cells compared to 4-1BB occurred under ICB via PD-L1. Furthermore, T cell exhaustion status in peripheral CD4 T cells, additionally to CD8 was critical for CAR T cells efficiency. The lack of hepatotoxicity and nephrotoxicity upon administration of 10e7 CAR PMBCs cells/Kg dose is the basis for carrying out clinical trials using anti-CAIX CD28 CAR PBMCs cells releasing anti-PD-L1 antibodies or anti-CAIX 4-1BB CAR T cells, offering exciting new prospects for the treatment of refractory ccRCC and hypoxic tumors.