Adoptive cell transfer utilizing tumour-targeting cytotoxic T lymphocytes (CTLs) is one of the most effective immunotherapies against haematological malignancies, but significant clinical success has not yet been achieved in solid tumours due in part to the strong immunosuppressive tumour microenvironment. Here, we show that suppression of CTL killing by CD4+CD25+Foxp3+ regulatory T cell (Treg) is in part mediated by TGFβ-induced inhibition of inositol trisphosphate (IP3) production, leading to a decrease in T cell receptor (TCR)-dependent intracellular Ca2+ response. Highly selective optical control of Ca2+ signalling in adoptively transferred CTLs enhances T cell activation and IFN-γ production in vitro, leading to a significant reduction in tumour growth in mice. Altogether, our findings indicate that the targeted optogenetic stimulation of intracellular Ca2+ signal allows for the remote control of cytotoxic effector functions of adoptively transferred T cells with outstanding spatial resolution by boosting T cell immune responses at the tumour sites.

Dendritic cells (DC), which consist of several different subsets, specialize in antigen presentation and are critical for mediating the innate and adaptive immune responses. DC subsets can be classified into conventional, plasmacytoid, and monocyte-derived DC in the tumor microenvironment, and each subset plays a different role. Because of the role of intratumoral DCs in initiating antitumor immune responses with tumor-derived antigen presentation to T cells, DCs have been targeted in the treatment of cancer. By regulating the functionality of DCs, several DC-based immunotherapies have been developed, including administration of tumor-derived antigens and DC vaccines. In addition, DCs participate in the mechanisms of classical cancer therapies, such as radiation therapy and chemotherapy. Thus, regulating DCs is also important in improving current cancer therapies. Here, we will discuss the role of each DC subset in antitumor immune responses, and the current status of DC-related cancer therapies.

The outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is spreading globally, and the WHO has declared this outbreak a pandemic. Vaccines are an effective way to prevent the rapid spread of COVID-19. Furthermore, the immune response against SARS-CoV-2 infection needs to be understood for the development of an efficient and safe vaccine. Here, we review the current understanding of vaccine targets and the status of vaccine development for COVID-19. We also describe host immune responses to highly pathogenic human coronaviruses in terms of innate and adaptive immunities.

Although cancer immunotherapy is effective against hematological malignancies, it is less effective against solid tumors due in part to significant metabolic challenges present in the tumor microenvironment (TME), where infiltrated CD8+ T cells face fierce competition with cancer cells for limited nutrients. Strong metabolic suppression in the TME is often associated with impaired T cell recruitment to the tumor site and hyporesponsive effector function via T cell exhaustion. Increasing evidence suggests that mitochondria play a key role in CD8+ T cell activation, effector function, and persistence in tumors. In this study, we showed that there was an increase in overall mitochondrial function, including mitochondrial mass and membrane potential, during both mouse and human CD8+ T cell activation. CD8+ T cell mitochondrial membrane potential was closely correlated with granzyme B and IFN-γ production, demonstrating the significance of mitochondria in effector T cell function. Additionally, activated CD8+ T cells that migrate on ICAM-1 and CXCL12 consumed significantly more oxygen than stationary CD8+ T cells. Inhibition of mitochondrial respiration decreased the velocity of CD8+ T cell migration, indicating the importance of mitochondrial metabolism in CD8+ T cell migration. Remote optical stimulation of CD8+ T cells that express our newly developed “OptoMito-On” successfully enhanced mitochondrial ATP production and improved overall CD8+ T cell migration and effector function. Our study provides new insight into the effect of the mitochondrial membrane potential on CD8+ T cell effector function and demonstrates the development of a novel optogenetic technique to remotely control T cell metabolism and effector function at the target tumor site with outstanding specificity and temporospatial resolution.

Adoptive cell transfer utilizing tumor-targeting cytotoxic T lymphocytes (CTLs) is one of the most effective immunotherapies against hematological malignancies, but significant clinical success has not yet been achieved in solid tumors due in part to the strong immunosuppressive tumor microenvironment. Systemic or intratumoral delivery of an immune boosting molecule to overcome local suppression has been proposed, but the full potential is limited by non-specific stimulation of tumor growth, metastasis, and angiogenesis. Here, we show that suppression of CTL killing by CD4+CD25+Foxp3+ regulatory T cell (Treg) is mainly mediated by TGFβ-induced inhibition of inositol trisphosphate (IP3) production, leading to a decrease in T cell receptor (TCR)-dependent intracellular Ca2+ response. Both in vitro and in vivo assays revealed that highly selective optical control of Ca2+ signaling in adoptively transferred CTLs was sufficient to overcome immunosuppression at the tumor site by enhancing T cell activation, IFN-γ production and antitumor cytotoxicity, leading to a significant reduction in tumor growth in mice. Together, our findings indicate that the targeted optogenetic stimulation of intracellular Ca2+ signal allows for the remote control of cytotoxic effector functions of adoptively transferred T cells with outstanding spatial resolution by boosting T cell immune responses only at the targeted tumor sites.

Regulatory T cells (Tregs) have critical roles in the maintenance of immunological self-tolerance and in the control of antitumor immune responses. In tumor microenvironment, Tregs use several mechanisms to suppress cytotoxic T cell responses, including suppression of TCR-induced Ca2+-NFAT signaling, secretion of inhibitory cytokines and inhibition of the stimulatory capacity of antigen presenting cells. Particularly, suppression of Ca2+ signals in cytotoxic T cell is a significant challenge because Ca2+ plays pivotal roles in tumor-specific CD8+ cytotoxic T lymphocytes (CTLs) function by regulating the degranulation of CTLs, their expression of Fas ligand and production of TNF-α and IFN-γ. Here we developed a strategy for optically controlling calcium signal using Ca2+ translocating channelrhodopsin (CatCh). The Ca2+/NFAT pathway is activated upon blue light (480nm) illumination via increase in intracellular calcium in CatCh expressing CTLs. In vitro, light stimulation enhances CatCh expressing CTLs activation, IFN-γ production and tumor cytotoxicity. Importantly, CatCh expressing CTLs restore against Treg-induce immunosuppression by light stimulation. In vivo, blue LED illumination onto the melanoma improved the efficacy of adoptive T-cell transfer immunotherapy, with a significant reduction in tumor growth. Together, our findings indicate that strong intracellular calcium signals can boost T cell functions by overcoming immunosuppressive Treg responses at tumor sites.

The tumor microenvironment presents significant metabolic challenges to T cells by depleting oxygen and glucose, as well as limiting the uptake of key nutrients. Therefore, T cells and tumor cells engage in fierce metabolic competition, as the demand for both oxygen and glucose in the niche is extremely high. The transition from a resting naïve T cell into an activated and highly proliferative effector T cell requires substantial metabolic reprogramming from relying primarily on oxidative phosphorylation (OxPhos) to the rapid induction of aerobic glycolysis. However, evidence suggests that tumor infiltrating CD8+ T cells show defects in glycolytic functions. In addition, our data indicates that actively migrating effector CD8+ T cells have greater levels of OxPhos activity than stationary cells, imposing an increasing demand for oxygen during T cell migration to the tumor site. To overcome the glycolytic deficiency of the tumor-targeting T cells and boost anti-tumor effector functions at the tumor microenvironment, we developed a genetically encoded light-activated proton pump (fungal proton pump, “Mac”), namely photoactivatable OxPhos (PA-OxPhos) that is expressed in the inner mitochondrial membrane. During OxPhos, electrons enter the electron transport chain (ETC), causing protons to be pumped across the inner mitochondrial membrane to establish a proton gradient. The gradient is then used to generate ATP through complex V (CxV). Therefore, the outward proton pumping through the inner mitochondrial membrane by light stimulation of PA-OxPhos mimics the ETC function and boosts ATP generation in T cells, even in the presence of low levels of oxygen and substrates, giving T cells a metabolic competitive advantage in the tumor microenvironment. PA-OxPhos is tagged with GFP and is expressed in the mitochondria of transfected 293T cells and in activated mouse CD8+ T cells. When cells were treated with Rotenone (an inhibitor of complex I of the ETC), ATP production was decreased after 90 minutes. Importantly, light stimulation of 293T cells expressing PA-OxPhos successfully increased ATP production even in the presence of Rotenone. Our data suggests that PA-OxPhos can remotely provide a competitive metabolic advantage and boost T cell functions in the tumor microenvironment. The utilization of an alternative mechanism for ATP production in T cells could potentially dissipate the failures of T-cell-based cancer immunotherapies in destroying malignant cells of solid tumors. Citation Format: Andrea Amitrano, Brandon Walling, Kyun Do Kim, Brandon Berry, Adam Trewin, Andrew Wojtovich, Minsoo Kim. Optogenetic regulation of T cell metabolism in the tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A73.