Aldehyde Dehydrogenese-1 High Cancer Stem-like Cells/Cancer-initiating Cells Escape from Cytotoxic T Lymphocytes due to Lower Expression of Human Leukocyte Antigen Class 1

BACKGROUND/AIM

Human gastric cancer stem-like cells (CSCs)/cancer-initiating cells can be identified as aldehyde dehydrogenase-high (ALDHhigh) cells. Cancer immunotherapy employing immune checkpoint blockade has been approved for advanced gastric cancer cases. However, the effectiveness of cancer immunotherapy against gastric CSCs/CICs remains unclear. This study aimed to investigate the susceptibility of gastric CSCs/CICs to immunotherapy.

MATERIALS AND METHODS

Gastric CSCs/CICs were isolated as ALDHhigh cells using the human gastric cancer cell line, MKN-45. ALDHhigh clone cells and ALDHlow clone cells were isolated using the ALDEFLUOR assay. ALDH1A1 expression was assessed via qRT-PCR. Sphere-forming ability was evaluated to confirm the presence of CSCs/CICs. A model neoantigen, AP2S1, was over-expressed in ALDHhigh clone cells and ALDHlow clone cells, and susceptibility to AP2S1-specific TCR-T cells was assessed using IFNγ ELISPOT assay.

RESULTS

Three ALDHhigh clone cells were isolated from MKN-45 cells. ALDHhigh clone cells exhibited a stable phenotype in in vitro culture for more than 2 months. The High-36 clone cells demonstrated the highest sphere-forming ability, whereas the Low-8 cells showed the lowest sphere-forming ability. High-36 cells exhibited lower expression of HLA-A24 compared to Low-8 cells. TCR-T cells specific for AP2S1 showed lower reactivity to High-36 cells compared to Low-8 cells.

CONCLUSION

High-36 cells and Low-8 cells represent novel gastric CSCs/CICs and non-CSCs/CICs, respectively. ALDHhigh CSCs/CICs evade T cells due to lower expression of HLA class 1.

Hepatitis B virus-specific human stem cell memory T cells differentiate into cytotoxic T cells and eradicate HBV-infected hepatocytes in mice

Chronic infection with the hepatitis B virus (HBV) induces progressive hepatic impairment. Achieving complete eradication of the virus remains a formidable challenge. Cytotoxic T lymphocytes, specific to viral antigens, either exhibit a numerical deficiency or succumb to an exhausted state in individuals chronically afflicted with HBV. The comprehension of the genesis and dissemination of stem cell memory T cells (TSCMs) targeting HBV remains inadequately elucidated. We identified TSCMs in subjects with chronic HBV infection and scrutinized their efficacy in a murine model with human hepatocyte transplants, specifically the TK-NOG mice. TSCMs were discerned in all subjects under examination. Introduction of TSCMs into the HBV mouse model precipitated a severe necro-inflammatory response, resulting in the elimination of human hepatocytes. TSCMs may constitute a valuable tool in the pursuit of a remedial therapy for HBV infection.

Immunogenicity of ferroptosis in cancer: a matter of context?

Ferroptosis is a variant of regulated cell death (RCD) elicited by an imbalance of cellular redox homeostasis that culminates with extensive lipid peroxidation and rapid plasma membrane breakdown. Since other necrotic forms of RCD, such as necroptosis, are highly immunogenic, ferroptosis inducers have attracted considerable attention as potential tools to selectively kill malignant cells while eliciting therapeutically relevant tumor-targeting immune responses. However, rather than being consistently immunogenic, ferroptosis mediates context-dependent effects on anticancer immunity. The inability of ferroptotic cancer cells to elicit adaptive immune responses may arise from contextual deficiencies in intrinsic aspects of the process, such as adjuvanticity and antigenicity, or from microenvironmental defects imposed by ferroptotic cancer cells themselves or elicited by the induction of ferroptosis in immune cells.

Prediction and identification of HLA-A*0201-restricted epitopes from cancer testis antigen CT23

Cancer-testis antigen CT23 is a class of tumor-associated antigens (TAA) characterized by restricted expression in male germ cells and a variety of tumor tissues. Numerous studies have shown that CT23 is closely related to tumor cell viability, proliferation, metastasis and invasion. CT23 is immunogenic and can cause specific immune response in tumor patients. Therefore, it is considered to be one of the best target antigens for designing therapeutic tumor vaccines and T-cell-mediated tumor immunotherapy. In this study, we initially obtained seven HLA-A*0201-restricted CT23 epitope candidate peptides through the T cell epitope prediction program. Subsequently, a T2 cell binding assay revealed the potential binding of all candidate peptides with HLA-A2 molecules. Notably, peptide P7 (ALLVLCYSI) exhibited the highest affinity, as evidenced by a fluorescence index (FI) of 2.19. Dendritic cells (DCs) loaded with CT23 candidate peptide can stimulate CD8+T cell activation and proliferation, and compared with other candidate peptides, candidate peptide P7 is superior. The cytotoxic T lymphocytes (CTLs) stimulated by the peptide P7 had killing effect on tumor cells (HLA-A*0201+, CT23+), but no killing effect on tumor cells (HLA-A*0201-, CT23+). The CTLs induced by the peptide P7 also had a specific killing effect on T2 cells bearing the peptide P7. In summary, our findings suggest that the CT23 peptide P7 (ALLVLCYSI) can induce immune responses and holds potential for tumor-specific CTL therapy.

Eribulin is an immune potentiator in breast cancer that upregulates human leukocyte antigen class I expression via the induction of NOD-like receptor family CARD domain-containing 5

Eribulin inhibits microtubule polymerization and improves the overall survival of patients with recurrent metastatic breast cancer. A subgroup analysis revealed a low neutrophil to lymphocyte ratio (NLR) (<3) to be a prognostic factor of eribulin treatment. We thus hypothesized that eribulin might be related to the immune response for breast cancer cells and we analyzed the effects of eribulin on the immune system. Immunohistochemical staining revealed that human leukocyte antigen (HLA) class I expression was increased in clinical samples after eribulin treatment. In vitro assays revealed that eribulin treatment increased HLA class I expression in breast cancer line cells. RNA-sequencing demonstrated that eribulin treatment increased the expression of the NOD-like family CARD domain-containing 5 (NLRC5), a master regulator of HLA class I expression. Eribulin treatment increased the NY-ESO-1-specific T-cell receptor (TCR) transduced T (TCR-T) cell response for New York oesophageal squamous cell carcinoma 1 (NY-ESO-1) overexpressed breast cancer cells. The eribulin and TCR-T combined therapy model revealed that eribulin and immunotherapy using TCR-T cells has a synergistic effect. In summary, eribulin increases the expression of HLA class 1 via HLA class 1 transactivatior NLRC5 and eribulin combination with immunotherapy can be effective for the treatment of breast cancer.

Emerging Role of Circular RNAs in Hepatocellular Carcinoma Immunotherapy

Hepatocellular carcinoma (HCC) is a highly fatal malignancy with limited therapeutic options and high recurrence rates. Recently, immunotherapeutic agents such as immune checkpoint inhibitors (ICIs) have emerged as a new paradigm shift in oncology. ICIs, such as programmed cell death protein 1 (PD-1) inhibitors, have provided a new source of hope for patients with advanced HCC. Yet, the eligibility criteria of HCC patients for ICIs are still a missing piece in the puzzle. Circular RNAs (circRNAs) have recently emerged as a new class of non-coding RNAs that play a fundamental role in cancer pathogenesis. Structurally, circRNAs are resistant to exonucleolytic degradation and have a longer half-life than their linear counterparts. Functionally, circRNAs possess the capability to influence various facets of the tumor microenvironment, especially at the HCC tumor-immune synapse. Notably, circRNAs have been observed to control the expression of immune checkpoint molecules within tumor cells, potentially impeding the therapeutic effectiveness of ICIs. Therefore, this renders them potential cancer-immune biomarkers for diagnosis, prognosis, and therapeutic regimen determinants. In this review, the authors shed light on the structure and functional roles of circRNAs and, most importantly, highlight the promising roles of circRNAs in HCC immunomodulation and their potential as promising biomarkers and immunotherapeutic regimen determinants.

The safety and anti-tumor effect of multiple peptides-pulsed dendritic cells combined with induced specific cytotoxic T lymphocytes for patients with solid tumors

Objective

The aim of this study was to explore the safety and efficacy of multiple peptide-pulsed autologous dendritic cells (DCs) combined with cytotoxic T lymphocytes (CTLs) in patients with cancer.

Methods

Five patients diagnosed with cancer between November 2020 and June 2021 were enrolled and received DC-CTLs therapy. Peripheral blood was collected and antigenic peptides were analyzed. The phenotype and function of DC-CTLs and the immune status of patients were detected using flow cytometry or IFN-γ ELISPOT analysis.

Results

DCs acquired a mature phenotype and expressed high levels of CD80, CD86, CD83, and HLA-DR after co-culture with peptides, and the DC-CTLs also exhibited high levels of IFN-γ. Peripheral blood mononuclear cells from post-treatment patients showed a stronger immune response to peptides than those prior to treatment. Importantly, four of five patients maintained a favorable immune status, of which one patient's disease-free survival lasted up to 28.2 months. No severe treatment-related adverse events were observed.

Conclusion

Our results show that multiple peptide-pulsed DCs combined with CTLs therapy has manageable safety and promising efficacy for cancer patients, which might provide a precise immunotherapeutic strategy for cancer.

Culture filtrate proteins from BCG act as adjuvants for cytotoxic T lymphocyte induction

Mycobacterium bovis bacilli Calmette-Guerin (BCG) is a licensed vaccine against tuberculosis. It requires attenuated live bacteria to be effective, possibly because actively secreted proteins play a critical role in inducing anti-tuberculosis immunity. BCG also functions as an effective adjuvant. Moreover, the effects of BCG components as adjuvants are not important as those of attenuated live BCG, which is used in cancer immunotherapy. However, the BCG secreted proteins have not been paid attention in anticancer immunity. To understand mycobacterial secreted proteins' function, we investigate immune responses to BCG culture filtrate proteins (CFP). Here, CFP strongly induce both antigen-specific CD4+ T cells and specific CD8+ T cells, which may be functional cytotoxic T lymphocytes (CTLs). In this study, we clearly demonstrate that CFP acts as an adjuvant for CTL induction against specific co-administered proteins and propose CFP as a new protein adjuvant. The CTL response shows potent anticancer effects in mice. These findings could provide insight into the contribution of mycobacterial secreted proteins in both anticancer and antimycobacterial immunity.

Caspase activation in tumour-infiltrating lymphocytes is associated with lymph node metastasis in oral squamous cell carcinoma

Oral squamous cell carcinomas (OSCCs) are genetically heterogeneous and exhibit diverse stromal and immune microenvironments. Acquired resistance to standard chemo-, radio-, and targeted therapies remains a major hurdle in planning effective treatment modalities for OSCC patients. Since Caspase 8 (CASP8) is frequently mutated in OSCCs, we were interested to explore a potential interaction between tumour-infiltrating lymphocytes (TILs) and CASP8 activation using high-content image analysis of human tumour (n = 32) sections. Despite the lymphocyte-rich tumour microenvironment, we observed lower activation of CASP8 (0-10% of tumour area) and its downstream effector CASP3 (0-6%) in tumours than in normal oral epithelium. Conversely, we found apoptosis was high for all the lymphocyte subtypes examined (38-52% of lymphocytes within tumour islands). Tumours with higher Fas ligand (FasL) expression had a significantly higher proportion of cleaved CASP3/8 positive cytotoxic T cells within the tumour islands (p = 0.05), and this was associated with the presence of lymph node metastatic disease [odds ratio: 1.046, 95% confidence interval (1.002-1.091), p = 0.039]. Our finding of extensive activation of the extrinsic pathway of apoptosis in TILs, together with evidence of higher FasL in CASP8 mutated tumours, may be useful in predicting the course of disease in individual patients. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Coxsackievirus infection induces direct pancreatic β-cell killing but poor anti-viral CD8+ T-cell responses

Coxsackievirus B (CVB) infection of pancreatic β cells is associated with β-cell autoimmunity. We investigated how CVB impacts human β cells and anti-CVB T-cell responses. β cells were efficiently infected by CVB in vitro, downregulated HLA Class I and presented few, selected HLA-bound viral peptides. Circulating CD8+ T cells from CVB-seropositive individuals recognized only a fraction of these peptides, and only another sub-fraction was targeted by effector/memory T cells that expressed the exhaustion marker PD-1. T cells recognizing a CVB epitope cross-reacted with the β-cell antigen GAD. Infected β cells, which formed filopodia to propagate infection, were more efficiently killed by CVB than by CVB-reactive T cells. Thus, our in-vitro and ex-vivo data highlight limited T-cell responses to CVB, supporting the rationale for CVB vaccination trials for type 1 diabetes prevention. CD8+ T cells recognizing structural and non-structural CVB epitopes provide biomarkers to differentially follow response to infection and vaccination.

Hypoxic niches attract and sequester tumor-associated macrophages and cytotoxic T cells and reprogram them for immunosuppression

Glioblastoma (GBM), a highly lethal brain cancer, is notorious for immunosuppression, but the mechanisms remain unclear. Here, we documented a temporospatial patterning of tumor-associated myeloid cells (TAMs) corresponding to vascular changes during GBM progression. As tumor vessels transitioned from the initial dense regular network to later scant and engorged vasculature, TAMs shifted away from perivascular regions and trafficked to vascular-poor areas. This process was heavily influenced by the immunocompetence state of the host. Utilizing a sensitive fluorescent UnaG reporter to track tumor hypoxia, coupled with single-cell transcriptomics, we revealed that hypoxic niches attracted and sequestered TAMs and cytotoxic T lymphocytes (CTLs), where they were reprogrammed toward an immunosuppressive state. Mechanistically, we identified chemokine CCL8 and cytokine IL-1β as two hypoxic-niche factors critical for TAM trafficking and co-evolution of hypoxic zones into pseudopalisading patterns. Therefore, perturbation of TAM patterning in hypoxic zones may improve tumor control.

Analysis of Novel Immunological Biomarkers Related to Rheumatoid Arthritis Disease Severity

Rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs) are the most frequently used rheumatoid arthritis (RA) diagnostic markers, but they are unable to anticipate the patient's evolution or response to treatment. The aim of this study was to identify possible severity biomarkers to predict an upcoming flare-up or remission period. To address this objective, sera and anticoagulated blood samples were collected from healthy controls (HCs; n = 39) and from early RA (n = 10), flare-up (n = 5), and remission (n = 16) patients. We analyzed leukocyte phenotype markers, regulatory T cells, cell proliferation, and cytokine profiles. Flare-up patients showed increased percentages of cluster of differentiation (CD)3+CD4- lymphocytes (p < 0.01) and granulocytes (p < 0.05) but a decreased natural killer (NK)/T lymphocyte ratio (p < 0.05). Analysis of leukocyte markers by principal component analysis (PCA) and receiver operating characteristic (ROC) curves showed that CD45RO+ (p < 0.0001) and CD45RA+ (p < 0.0001) B lymphocyte expression can discriminate between HCs and early RA patients, while CD3+CD4- lymphocyte percentage (p < 0.0424) and CD45RA+ (p < 0.0424), CD62L+ (p < 0.0284), and CD11a+ (p < 0.0185) B lymphocyte expression can differentiate between flare-up and RA remission subjects. Thus, the combined study of these leukocyte surface markers could have potential as disease severity biomarkers for RA, whose fluctuations could be related to the development of the characteristic pro-inflammatory environment.

Cytotoxic T Lymphocytes Control Growth of B16 Tumor Cells in Collagen-Fibrin Gels by Cytolytic and Non-Lytic Mechanisms

Cytotoxic T lymphocytes (CTLs) are important in controlling some viral infections, and therapies involving the transfer of large numbers of cancer-specific CTLs have been successfully used to treat several types of cancers in humans. While the molecular mechanisms of how CTLs kill their targets are relatively well understood, we still lack a solid quantitative understanding of the kinetics and efficiency by which CTLs kill their targets in vivo. Collagen-fibrin-gel-based assays provide a tissue-like environment for the migration of CTLs, making them an attractive system to study T cell cytotoxicity in in vivo-like conditions. Budhu.et al. systematically varied the number of peptide (SIINFEKL)-pulsed B16 melanoma cells and SIINFEKL-specific CTLs (OT-1) and measured the remaining targets at different times after target and CTL co-inoculation into collagen-fibrin gels. The authors proposed that their data were consistent with a simple model in which tumors grow exponentially and are killed by CTLs at a per capita rate proportional to the CTL density in the gel. By fitting several alternative mathematical models to these data, we found that this simple "exponential-growth-mass-action-killing" model did not precisely describe the data. However, determining the best-fit model proved difficult because the best-performing model was dependent on the specific dataset chosen for the analysis. When considering all data that include biologically realistic CTL concentrations (E≤107cell/mL), the model in which tumors grow exponentially and CTLs suppress tumor's growth non-lytically and kill tumors according to the mass-action law (SiGMA model) fit the data with the best quality. A novel power analysis suggested that longer experiments (∼3-4 days) with four measurements of B16 tumor cell concentrations for a range of CTL concentrations would best allow discriminating between alternative models. Taken together, our results suggested that the interactions between tumors and CTLs in collagen-fibrin gels are more complex than a simple exponential-growth-mass-action killing model and provide support for the hypothesis that CTLs' impact on tumors may go beyond direct cytotoxicity.

Immunosuppression reduces rAAV2.5T neutralizing antibodies that limit efficacy following repeat dosing to ferret lungs

The efficacy of redosing the recombinant adeno-associated virus (rAAV) vector rAAV2.5T to ferret lung is limited by AAV neutralizing antibody (NAb) responses. While immunosuppression strategies have allowed for systemic rAAV repeat dosing, their utility for rAAV lung-directed gene therapy is largely unexplored. To this end, we evaluated two immunosuppression (IS) strategies to improve repeat dosing of rAAV2.5T to ferret lungs: (1) a combination of three IS drugs (Tri-IS) with broad coverage against cellular and humoral responses (methylprednisolone [MP], azathioprine, and cyclosporine) and (2) MP alone, which is typically used in systemic rAAV applications. Repeat dosing utilized AAV2.5T-SP183-fCFTRΔR (recombinant ferret CFTR transgene), followed 28 days later by AAV2.5T-SP183-gLuc (for quantification of transgene expression). Both the Tri-IS and MP strategies significantly improved transgene expression following repeat dosing and reduced AAV2.5T NAb responses in the bronchioalveolar lavage fluid (BALF) and plasma, while AAV2.5T binding antibody subtypes and cellular immune responses by ELISpot were largely unchanged by IS. One exception was the reduction in plasma AAV2.5T binding immunoglobulin G (IgG) in both IS groups. Only the Tri-IS strategy significantly suppressed splenocyte expression of IFNA (interferon α [IFN-α]) and IL4. Our studies suggest that IS strategies may be useful in clinical application of rAAV targeting lung genetic diseases such as cystic fibrosis.

Human papilloma virus-16-specific CD8+ T-cell expansions characterize different clinical forms of lichen planus and not lichen sclerosus et atrophicus

Lichen planus (LP) is a cutaneomucosal chronic inflammatory disease characterized by a CD8+ cytotoxic T-lymphocytes (CTL) infiltrate. In erosive oral LP, we found HPV16-specific activated CTL in lesions, supporting a pathogenic contribution of HPV16. Here, we investigated whether a similar scenario occurs in other clinical forms of LP and in lichen sclerosus et atrophicus (LSA), another chronic disease also affecting the mucosa and/or the skin. Blood CTL from LP and LSA patients expressed significant higher levels of granzyme B, perforin and CD107a proteins than healthy donors. Expansions of TCRVß3+ CTL, with presence of TCR clonotypes identical to those previously detected in erosive oral LP, were found both in blood and mucosal/skin lesions of LP, and not of LSA patients. These expansions were enriched with HPV16-specific CD8+ T-cells as shown by their recognition of the E711-20 immunodominant epitope. In LSA patients, the peripheral repertoire of CTL was oligoclonal for TCRVß6+ CTL. Finally, although patients with LP and LSA have developed antibodies against HPV16 capsid L1, antibodies against HPV16 E6 were only observed in patients with LP. Overall, our data collectively suggest an involvement of HPV16-specific CTL in different clinical forms of LP, not only in erosive oral LP, while a different scenario operates in LSA.

Lytic granule exocytosis at immune synapses: lessons from neuronal synapses

Regulated exocytosis is a central mechanism of cellular communication. It is not only the basis for neurotransmission and hormone release, but also plays an important role in the immune system for the release of cytokines and cytotoxic molecules. In cytotoxic T lymphocytes (CTLs), the formation of the immunological synapse is required for the delivery of the cytotoxic substances such as granzymes and perforin, which are stored in lytic granules and released via exocytosis. The molecular mechanisms of their fusion with the plasma membrane are only partially understood. In this review, we discuss the molecular players involved in the regulated exocytosis of CTL, highlighting the parallels and differences to neuronal synaptic transmission. Additionally, we examine the strengths and weaknesses of both systems to study exocytosis.

Fusion with type 2 macrophages induces melanoma cell heterogeneity that potentiates immunological escape from cytotoxic T lymphocytes

Evasion from immunity is a major obstacle to the achievement of successful cancer immunotherapy. Hybrids derived from cell-cell fusion are theoretically associated with tumor heterogeneity and progression by conferring novel properties on tumor cells, including drug resistance and metastatic capacity; however, their impact on immune evasion remains unknown. Here, we investigated the potency of tumor-macrophage hybrids in immune evasion. Hybrids were established by co-culture of a melanoma cell line (A375 cells) and type 2 macrophages. The hybrids showed greater migration ability and greater tumorigenicity than the parental melanoma cells. The hybrids showed heterogeneous sensitivity to New York esophageal squamous cell carcinoma-1 (NY-ESO-1)-specific T-cell receptor-transduced T (TCR-T) cells and two out of four hybrid clones showed less sensitivity to TCR-T compared with the parental cells. An in vitro tumor heterogeneity model revealed that the TCR-T cells preferentially killed the parental cells compared with the hybrids and the survival rate of the hybrids was higher than that of the parental cells, indicating that the hybrids evade killing by TCR-T cells efficiently. Analysis of a single-cell RNA sequencing dataset of patients with melanoma revealed that a few macrophages expressed RNA encoding melanoma differentiation antigens including melan A, tyrosinase, and premelanosome protein, which indicated the presence of hybrids in primary melanoma. In addition, the number of potential hybrids was correlated with a poorer response to immune checkpoint blockade. These results provide evidence that melanoma-macrophage fusion has a role in tumor heterogeneity and immune evasion. © 2023 The Pathological Society of Great Britain and Ireland.

HIV-1 Group M Capsid Amino Acid Variability: Implications for Sequence Quality Control of Genotypic Resistance Testing

BACKGROUND

With the approval of the HIV-1 capsid inhibitor, lenacapavir, capsid sequencing will be required for managing lenacapavir-experienced individuals with detectable viremia. Successful sequence interpretation will require examining new capsid sequences in the context of previously published sequence data.

METHODS

We analyzed published HIV-1 group M capsid sequences from 21,012 capsid-inhibitor naïve individuals to characterize amino acid variability at each position and influence of subtype and cytotoxic T lymphocyte (CTL) selection pressure. We determined the distributions of usual mutations, defined as amino acid differences from the group M consensus, with a prevalence ≥ 0.1%. Co-evolving mutations were identified using a phylogenetically-informed Bayesian graphical model method.

RESULTS

162 (70.1%) positions had no usual mutations (45.9%) or only conservative usual mutations with a positive BLOSUM62 score (24.2%). Variability correlated independently with subtype-specific amino acid occurrence (Spearman rho = 0.83; p < 1 × 10-9) and the number of times positions were reported to contain an HLA-associated polymorphism, an indicator of CTL pressure (rho = 0.43; p = 0.0002).

CONCLUSIONS

Knowing the distribution of usual capsid mutations is essential for sequence quality control. Comparing capsid sequences from lenacapavir-treated and lenacapavir-naïve individuals will enable the identification of additional mutations potentially associated with lenacapavir therapy.

Enhanced inhibition of MHC-I expression by SARS-CoV-2 Omicron subvariants

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) possess mutations that confer resistance to neutralizing antibodies within the Spike protein and are associated with breakthrough infection and reinfection. By contrast, less is known about the escape from CD8+ T cell-mediated immunity by VOC. Here, we demonstrated that all SARS-CoV-2 VOCs possess the ability to suppress major histocompatibility complex class I (MHC-I) expression. We identified several viral genes that contribute to the suppression of MHC I expression. Notably, MHC-I upregulation was strongly inhibited after SARS-CoV-2 but not influenza virus infection in vivo. While earlier VOCs possess similar capacity as the ancestral strain to suppress MHC-I, the Omicron subvariants exhibited a greater ability to suppress surface MHC-I expression. We identified a common mutation in the E protein of Omicron that further suppressed MHC-I expression. Collectively, our data suggest that in addition to escaping from neutralizing antibodies, the success of Omicron subvariants to cause breakthrough infection and reinfection may in part be due to its optimized evasion from T cell recognition.

5-Fluorouracil Suppresses Colon Tumor through Activating the p53-Fas Pathway to Sensitize Myeloid-Derived Suppressor Cells to FasL+ Cytotoxic T Lymphocyte Cytotoxicity

Myelosuppression is a major adverse effect of 5-fluorouracil (5-FU) chemotherapy. However, recent findings indicate that 5-FU selectively suppresses myeloid-derived suppressor cells (MDSCs), to enhance antitumor immunity in tumor-bearing mice. 5-FU-mediated myelosuppression may thus have a beneficial effect for cancer patients. The molecular mechanism underlying 5-FU's suppression of MDSCs is currently unknown. We aimed at testing the hypothesis that 5-FU suppresses MDSCs through enhancing MDSC sensitivity to Fas-mediated apoptosis. We observed that, although FasL is highly expressed in T cells, Fas is weakly expressed in myeloid cells in human colon carcinoma, indicating that downregulation of Fas is a mechanism underlying myeloid cell survival and accumulation in human colon cancer. 5-FU treatment upregulated expression of both p53 and Fas, and knocking down p53 diminished 5-FU-induced Fas expression in MDSC-like cells, in vitro. 5-FU treatment also increased MDSC-like cell sensitivity to FasL-induced apoptosis in vitro. Furthermore, we determined that 5-FU therapy increased expression of Fas on MDSCs, suppressed MDSC accumulation, and increased CTL tumor infiltration in colon tumor-bearing mice. In human colorectal cancer patients, 5-FU chemotherapy decreased MDSC accumulation and increased CTL level. Our findings determine that 5-FU chemotherapy activates the p53-Fas pathway, to suppress MDSC accumulation, to increase CTL tumor infiltration.

Resisting T cell attack: tumor-cell-intrinsic defense and reparation mechanisms

Cytotoxic T lymphocytes (CTLs) are antigen-specific killer cells equipped to identify and eliminate host cells that have been altered through infection or transformation. Both chimeric antigen-receptor (CAR) T cell therapies and immune checkpoint blockade (ICB) therapies are based on successful elimination of tumor cells by cytotoxic effectors. In this opinion article, we outline cell-intrinsic mechanisms by which tumor cells defend against CTLs, highlighting pathways that confer resistance and proposing opportunities for combination therapies. We discuss how exogenous killing entities [e.g., supramolecular attack particles (SMAPs)] offer a novel strategy to circumvent cellular resistance mechanisms. Our opinion article highlights the importance of identifying, quantifying, and targeting tumor defense mechanisms at the interface between tumor cells and CTLs as a critical consideration in the development of immunotherapy approaches.

Peripheral Immunophenotype in IgG4-Related Disease and Its Association with Clinical Phenotypes and Disease Activity

Diverse immune cell subsets have been described in IgG4-related disease (IgG4-RD). If there is a different immunophenotype according to clinical phenotype and activity status is not known. Levels of IL-4-, IL-13-, IL-5-, and IL-21-producing CD4⁺ T cells (Th2 subsets), CD4⁺ cytotoxic T lymphocytes (CD4⁺CTLs), T helper 9 cells, T follicular helper cells (Tfh; Tfh1/Tfh2/Tfh17/Tf regulatory [Tfr]), Foxp3⁺ regulatory T cells, Type 1 regulatory T cells (Tr1), T helper 3 regulatory cells (Th3), IL-10-producing regulatory B cells (Bregs), IL-10-expressing regulatory plasmacytoid dendritic (pDC IL-10⁺) cells, and M1 and M2 monocytes were determined by flow cytometry in 43 IgG4-RD patients and 12 controls. All immune subsets were higher in patients vs. controls. CD4⁺/IL-4⁺, CD4⁺/IL-5⁺, CD4⁺CTLs, Tfh2, Tfh17, Tfr, and M1 monocyte cell number was different among IgG4-RD clinical phenotypes. The pancreato-hepato-biliary phenotype was characterized by a higher CD4⁺CTLs, Tfh17, Tfh2, and Tfr and lower M1 cell number. An increased CD4⁺CTLs and Th3 cell number distinguished the head and neck-limited phenotype, while the retroperitoneal/aortic and Mikulicz/systemic phenotypes were characterized by increased Th2 subsets. Tfh17, Tr1, Th3, pDC, M1, and M2 monocytes were augmented in active patients. In summary, the clinical heterogeneity of IgG4-RD might be driven by the participation of different immunophenotypes and, consequently, by a different fibroinflammatory process.

Graphdiyne Oxide-Mediated Photodynamic Therapy Boosts Enhancive T-Cell Immune Responses by Increasing Cellular Stiffness

Purpose

Nanomaterial-based photodynamic therapy (PDT) has been commonly used for the treatment of cancerous tumors. Despite significant achievements made in this field, the intrinsic impact of nanomaterials-based PDT on the mechanical properties of oral squamous cell carcinoma (OSCC) cells is not entirely understood. Here, we used atomic force microscopy (AFM) to measure the stiffness of OSCC cells subjected to PDT in co-culture systems to evaluate the T cell-mediated cancer cell-killing effects.

Methods

In this study, AFM was used to assess the stiffness of PDT-subjected cells. The phototoxicity of graphdiyne oxide (GDYO) was assessed using confocal laser scanning microscopy (CLSM), measurements of membrane cholesterol levels, and assessments of the F-actin cytoskeleton. A co-culture system was used to evaluate the effects of CD8⁺ T cells (cytotoxic T lymphocytes), demonstrating how PDT modulates the mechanical properties of cancer cells and activates T cell responses. The antitumor immunotherapeutic effect of GDYO was further evaluated in a murine xenograft model.

Results

GDYO increased the mechanical stiffness of tumor cells and augmented T-cell cytotoxicity and inflammatory cytokine secretion (IFN-γ and TNF-α) under laser in vitro. Furthermore, GDYO-based PDT exerted inhibitory effects on OSCC models and elicited antitumor immune responses via specific cytotoxic T cells.

Conclusion

These results highlight that GDYO is a promising candidate for OSCC therapy, shifting the mechanical forces of OSCC cells and breaking through the barriers of the immunosuppressive tumor microenvironment. Our study provides a novel perspective on nanomaterial-based antitumor therapies.

Target Selection for T-Cell Therapy in Epithelial Ovarian Cancer: Systematic Prioritization of Self-Antigens

Adoptive T cell-receptor therapy (ACT) could represent a promising approach in the targeted treatment of epithelial ovarian cancer (EOC). However, the identification of suitable tumor-associated antigens (TAAs) as targets is challenging. We identified and prioritized TAAs for ACT and other immunotherapeutic interventions in EOC. A comprehensive list of pre-described TAAs was created and candidates were prioritized, using predefined weighted criteria. Highly ranked TAAs were immunohistochemically stained in a tissue microarray of 58 EOC samples to identify associations of TAA expression with grade, stage, response to platinum, and prognosis. Preselection based on expression data resulted in 38 TAAs, which were prioritized. Along with already published Cyclin A1, the TAAs KIF20A, CT45, and LY6K emerged as most promising targets, with high expression in EOC samples and several identified peptides in ligandome analysis. Expression of these TAAs showed prognostic relevance independent of molecular subtypes. By using a systematic vetting algorithm, we identified KIF20A, CT45, and LY6K to be promising candidates for immunotherapy in EOC. Results are supported by IHC and HLA-ligandome data. The described method might be helpful for the prioritization of TAAs in other tumor entities.

A standardized method to study immune responses using porcine whole blood

BACKGROUND

Peripheral blood mononuclear cells (PBMCs) are commonly used to assess in vitro immune responses. However, PBMC isolation is a time-consuming procedure, introduces technical variability, and requires a relatively large volume of blood. By contrast, whole blood assay (WBA) is faster, cheaper, maintains more physiological conditions, and requires less sample volume, laboratory training, and equipment.

OBJECTIVES

Herein, this study aimed to develop a porcine WBA for in vitro evaluation of immune responses.

METHODS

Heparinized whole blood (WB) was diluted (non-diluted, 1/2, 1/8, and 1/16) in RPMI-1640 media, followed by phorbol myristate acetate and ionomycin. After 24 h, cells were stained for interferon (IFN)-γ secreting T-cells followed by flow cytometry, and the supernatant was analyzed for tumor necrosis factor (TNF)-α. In addition, diluted WB was stimulated by lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (poly I:C), reference strain KCTC3557 (RS), field isolate (FI), of heat-killed (HK) Streptococcus suis, and porcine reproductive and respiratory syndrome virus (PRRSV).

RESULTS

The frequency of IFN-γ⁺CD3⁺ T-cells and concentration of TNF-α in the supernatant of WB increased with increasing dilution factor and were optimal at 1/8. WB TNF-α and interleukin (IL)-10 cytokine levels increased significantly following stimulation with LPS or poly I:C. Further, FI and RS induced IL-10 production in WB. Additionally, PRRSV strains increased the frequency of IFN-γ⁺CD4^-CD8⁺ cells, and IFN-γ was non-significantly induced in the supernatant of re-stimulated samples.

CONCLUSIONS

We propose that the WBA is a rapid, reliable, and simple method to evaluate immune responses and WB should be diluted to trigger immune cells.

Interdependence of sequential cytotoxic T lymphocyte and natural killer cell cytotoxicity against melanoma cells

Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells recognize and eliminate cancer cells. However, immune evasion, downregulation of immune function by the tumour microenvironment and resistance of cancer cells are major problems. Although CTL and NK cells are both important to eliminate cancer, most studies address them individually. We quantified sequential primary human CTL and NK cell cytotoxicity against the melanoma cell line SK-Mel-5. At high effector-to-target ratios, NK cells or melan-A (MART-1)-specific CTL eliminated all SK-Mel-5 cells within 24 h, indicating that SK-Mel-5 cells are not resistant initially. However, at lower effector-to-target ratios, which resemble numbers of the immune contexture in human cancer, a substantial number of SK-Mel-5 cells survived. Pre-exposure to CTL induced resistance in surviving SK-Mel-5 cells to subsequent CTL or NK cell cytotoxicity, and pre-exposure to NK cells induced resistance in surviving SK-Mel-5 cells to NK cells. Higher human leucocyte antigen class I expression or interleukin-6 levels were correlated with resistance to NK cells, whereas reduction in MART-1 antigen expression was correlated with reduced CTL cytotoxicity. The CTL cytotoxicity was rescued beyond control levels by exogenous MART-1 antigen. In contrast to the other three combinations, CTL cytotoxicity against SK-Mel-5 cells was enhanced following NK cell pre-exposure. Our assay allows quantification of sequential CTL and NK cell cytotoxicity and might guide strategies for efficient CTL-NK cell anti-melanoma therapies. KEY POINTS: Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells eliminate cancer cells. Both CTL and NK cells attack the same targets, but most studies address them individually. In a sequential cytotoxicity model, the interdependence of antigen-specific CTL and NK cell cytotoxicity against melanoma is quantified. High numbers of antigen-specific CTL and NK cells eliminate all melanoma cells. However, lower numbers induce resistance if secondary CTL or NK cell exposure follows initial CTL exposure or if secondary NK cell exposure follows initial NK cell exposure. On the contrary, if secondary CTL exposure follows initial NK cell exposure, cytotoxicity is enhanced. Alterations in human leucocyte antigen class I expression and interleukin-6 levels are correlated with resistance to NK cells, whereas a reduction in antigen expression is correlated with reduced CTL cytotoxicity; CTL cytotoxicity is rescued beyond control levels by exogenous antigen. This assay and the results on interdependencies will help us to understand and optimize immune therapies against cancer.

CTLs: Killers of intracellular bacteria

Many microbial pathogens have evolved a range of capabilities to evade host immune defense mechanisms and to survive and multiply in host cells. The presence of host intracellular bacteria makes it difficult for specific antibodies to function. After the intracellular bacteria escape the attack of the innate immune system, such as phagocytes, they survive in cells, and then adaptive immunity comes into play. Cytotoxic T lymphocytes (CTLs) play an important role in eliminating intracellular bacteria. The regulation of key transcription factors could promote CD4+/CD8+ T cells to acquire cytolytic ability. The TCR-CD3 complex transduces activation signals generated by TCR recognition of antigen and promotes CTLs to generate multiple pathways to kill intracellular bacteria. In this review, the mechanism of CD4/CD8 CTLs differentiation and how CD4/CD8 CTLs kill intracellular bacteria are introduced. In addition, their application and prospects in the treatment of bacterial infections are discussed.

In vivo bioluminescence imaging of granzyme B activity in tumor response to cancer immunotherapy

Cancer immunotherapy has revolutionized the treatment of cancer, but only a small subset of patients benefits from this new treatment regime. Imaging tools are useful for early detection of tumor response to immunotherapy and probing the dynamic and complex immune system. Here, we report a bioluminescence probe (GBLI-2) for non-invasive, real-time, longitudinal imaging of granzyme B activity in tumors receiving immune checkpoint inhibitors. GBLI-2 is made of the mouse granzyme B tetrapeptide IEFD substrate conjugated to D-luciferin through a self-immolative group. GBLI-2 was evaluated for imaging the dynamics of the granzyme B activity and predicting therapeutic efficacy in a syngeneic mouse model of CT26 murine colorectal carcinoma. The GBLI-2 signal correlated with the change in the population of PD-1- and granzyme B-expressing CD8+ T cells in tumors.

Evaluating the Safety and Quality of Life of Colorectal Cancer Patients Treated by Autologous Immune Enhancement Therapy (AIET) in Vinmec International Hospitals

(1) Colorectal cancer (CRC) is an increasingly prevalent disease with a high mortality rate in recent years. Immune cell-based therapies have received massive attention among scientists, as they have been proven effective as low-toxicity treatments. This study evaluated the safety and effectiveness of autologous immune enhancement therapy (AIET) for CRC. (2) An open-label, single-group study, including twelve patients diagnosed with stages III and IV CRC, was conducted from January 2016 to December 2021. Twelve CRC patients received one to seven infusions of natural killer (NK)-cell and cytotoxic T-lymphocyte (CTL). Multivariate modelling was used to identify factors associated with health-related quality-of-life (HRQoL) scores. (3) After 20−21 days of culture, the NK cells increased 3535-fold, accounting for 85% of the cultured cell population. Likewise, CTLs accounted for 62.4% of the cultured cell population, which was a 1220-fold increase. Furthermore, the QoL improved with increased EORTC QLQ-C30 scores, decreased symptom severity, and reduced impairment in daily living caused by these symptoms (MDASI-GI report). Finally, a 14.3 ± 14.1-month increase in mean survival time was observed at study completion. (4) AIET demonstrated safety and improved survival time and HRQoL for CRC patients in Vietnam.

ATF3 and CH25H regulate effector trogocytosis and anti-tumor activities of endogenous and immunotherapeutic cytotoxic T lymphocytes

Effector trogocytosis between malignant cells and tumor-specific cytotoxic T lymphocytes (CTLs) contributes to immune evasion through antigen loss on target cells and fratricide of antigen-experienced CTLs by other CTLs. The mechanisms regulating these events in tumors remain poorly understood. Here, we demonstrate that tumor-derived factors (TDFs) stimulated effector trogocytosis and restricted CTLs' tumoricidal activity and viability in vitro. TDFs robustly altered the CTL's lipid profile, including depletion of 25-hydroxycholesterol (25HC). 25HC inhibited trogocytosis and prevented CTL's inactivation and fratricide. Mechanistically, TDFs induced ATF3 transcription factor that suppressed the expression of 25HC-regulating gene-cholesterol 25-hydroxylase (CH25H). Stimulation of trogocytosis in the intratumoral CTL by the ATF3-CH25H axis attenuated anti-tumor immunity, stimulated tumor growth, and impeded the efficacy of chimeric antigen receptor (CAR) T cell adoptive therapy. Through use of armored CAR constructs or pharmacologic agents restoring CH25H expression, we reversed these phenotypes and increased the efficacy of immunotherapies.

NKG7 Enhances CD8+ T Cell Synapse Efficiency to Limit Inflammation

Cytotoxic lymphocytes are essential for anti-tumor immunity, and for effective responses to cancer immunotherapy. Natural killer cell granule protein 7 (NKG7) is expressed at high levels in cytotoxic lymphocytes infiltrating tumors from patients treated with immunotherapy, but until recently, the role of this protein in cytotoxic lymphocyte function was largely unknown. Unexpectedly, we found that highly CD8+ T cell-immunogenic murine colon carcinoma (MC38-OVA) tumors grew at an equal rate in Nkg7^+/+ and Nkg7^-/- littermate mice, suggesting NKG7 may not be necessary for effective CD8+ T cell anti-tumor activity. Mechanistically, we found that deletion of NKG7 reduces the ability of CD8+ T cells to degranulate and kill target cells in vitro. However, as a result of inefficient cytotoxic activity, NKG7 deficient T cells form a prolonged immune synapse with tumor cells, resulting in increased secretion of inflammatory cytokines, including tumor necrosis factor alpha (TNF). By deleting the TNF receptor, TNFR1, from MC38-OVA tumors, we demonstrate that this hyper-secretion of TNF compensates for reduced synapse-mediated cytotoxic activity against MC38-OVA tumors in vivo, via increased TNF-mediated tumor cell death. Taken together, our results demonstrate that NKG7 enhances CD8+ T cell immune synapse efficiency, which may serve as a mechanism to accelerate direct cytotoxicity and limit potentially harmful inflammatory responses.

HLA-B∗46 associates with rapid HIV disease progression in Asian cohorts and prominent differences in NK cell phenotype

Human leukocyte antigen (HLA) alleles have been linked to HIV disease progression and attributed to differences in cytotoxic T lymphocyte (CTL) epitope representation. These findings are largely based on treatment-naive individuals of European and African ancestry. We assessed HLA associations with HIV-1 outcomes in 1,318 individuals from Thailand and found HLA-B∗46:01 (B∗46) associated with accelerated disease in three independent cohorts. B∗46 had no detectable effect on HIV-specific T cell responses, but this allele is unusual in containing an HLA-C epitope that binds inhibitory receptors on natural killer (NK) cells. Unbiased transcriptomic screens showed increased NK cell activation in people with HIV, without B∗46, and simultaneous single-cell profiling of surface proteins and transcriptomes revealed a NK cell subset primed for increased responses in the absence of B∗46. These findings support a role for NK cells in HIV pathogenesis, revealed by the unique properties of the B∗46 allele common only in Asia.

Microbial Metabolite 3-Indolepropionic Acid Mediates Immunosuppression

The microbial-derived metabolite, 3-indolepropionic acid (3-IPA), has been intensely studied since its origins were discovered in 2009; however, 3-IPA's role in immunosuppression has had limited attention. Untargeted metabolomic analyses of T-cell exhaustion and immunosuppression, represented by dysfunctional under-responsive CD8⁺ T cells, reveal a potential role of 3-IPA in these responses. T-cell exhaustion was examined via infection of two genetically related mouse strains, DBA/1J and DBA/2J, with lymphocytic choriomeningitis virus (LCMV) Clone 13 (Cl13). The different mouse strains produced disparate outcomes driven by their T-cell responses. Infected DBA/2J presented with exhausted T cells and persistent infection, and DBA/1J mice died one week after infection from cytotoxic T lymphocytes (CTLs)-mediated pulmonary failure. Metabolomics revealed over 70 metabolites were altered between the DBA/1J and DBA/2J models over the course of the infection, most of them in mice with a fatal outcome. Cognitive-driven prioritization combined with statistical significance and fold change were used to prioritize the metabolites. 3-IPA, a tryptophan-derived metabolite, was identified as a high-priority candidate for testing. To test its activity 3-IPA was added to the drinking water of the mouse models during LCMV Cl13 infection, with the results showing that 3-IPA allowed the mice to survive longer. This negative immune-modulation effect might be of interest for the modulation of CTL responses in events such as autoimmune diseases, type I diabetes or even COVID-19. Moreover, 3-IPA's bacterial origin raises the possibility of targeting the microbiome to enhance CTL responses in diseases such as cancer and chronic infection.

The Robustness of Cellular Immunity Determines the Fate of SARS-CoV-2 Infection

Two years after the appearance of the SARS-CoV-2 virus, the causal agent of the current global pandemic, it is time to analyze the evolution of the immune protection that infection and vaccination provide. Cellular immunity plays an important role in limiting disease severity and the resolution of infection. The early appearance, breadth and magnitude of SARS-CoV-2 specific T cell response has been correlated with disease severity and it has been thought that T cell responses may be sufficient to clear infection with minimal disease in COVID-19 patients with X-linked or autosomal recessive agammaglobulinemia. However, our knowledge of the phenotypic and functional diversity of CD8+ cytotoxic lymphocytes, CD4+ T helper cells, mucosal-associated invariant T (MAIT) cells and CD4+ T follicular helper (Tfh), which play a critical role in infection control as well as long-term protection, is still evolving. It has been described how CD8+ cytotoxic lymphocytes interrupt viral replication by secreting antiviral cytokines (IFN-γ and TNF-α) and directly killing infected cells, negatively correlating with stages of disease progression. In addition, CD4+ T helper cells have been reported to be key pieces, leading, coordinating and ultimately regulating antiviral immunity. For instance, in some more severe COVID-19 cases a dysregulated CD4+ T cell signature may contribute to the greater production of pro-inflammatory cytokines responsible for pathogenic inflammation. Here we discuss how cellular immunity is the axis around which the rest of the immune system components revolve, since it orchestrates and leads antiviral response by regulating the inflammatory cascade and, as a consequence, the innate immune system, as well as promoting a correct humoral response through CD4+ Tfh cells. This review also analyses the critical role of cellular immunity in modulating the development of high-affinity neutralizing antibodies and germinal center B cell differentiation in memory and long-lived antibody secreting cells. Finally, since there is currently a high percentage of vaccinated population and, in some cases, vaccine booster doses are even being administered in certain countries, we have also summarized newer approaches to long-lasting protective immunity and the cross-protection of cellular immune response against SARS-CoV-2.

Activation of cytotoxic T lymphocytes by self-differentiated myeloid-derived dendritic cells for killing breast cancer cells expressing folate receptor alpha protein

Adoptive cell transfer (ACT) is a promising approach for cancer treatment. Activation of T lymphocytes by self-differentiated myeloid-derived antigen-presenting-cells reactive against tumor (SmartDC) resulted in specific anti-cancer function. Folate receptor alpha (FRα) is highly expressed in breast cancer (BC) cells and thus potential to be a target antigen for ACT. To explore the SmartDC technology for treatment of BC, we create SmartDC expressing FRα antigen (SmartDC-FRα) for activation of FRα-specific T lymphocytes. Human primary monocytes were transduced with lentiviruses containing tri-cistronic complementary DNA sequences encoding granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-4 (IL-4), and FRα to generate SmartDC-FRα. Autologous T lymphocytes were activated by SmartDC-FRα by coculture. The activated T lymphocytes exhibited enhanced cytotoxicity against FRα-expressing BC cell cultures. Up to 84.9 ± 6.2% of MDA-MB-231 and 89.7 ± 1.9% of MCF-7 BC cell lines were specifically lysed at an effector-to-target ratio of 20:1. The cytotoxicity of T lymphocytes activated by SmartDC-FRα was also demonstrated in three-dimensional (3D) spheroid culture of FRα-expressing BC cells marked by size reduction and spheroid disruption. This study thus portray the potential development of T lymphocytes activated by SmartDC-FRα as ACT in FRα-expressing BC treatment.

Greek Fire, Poison Arrows, and Scorpion Bombs: How Tumor Cells Defend Against the Siege Weapons of Cytotoxic T Lymphocytes

CD8⁺ cytotoxic T lymphocytes (CTLs) are the main cellular effectors of the adaptive immune response against cancer cells, which in turn have evolved sophisticated cellular defense mechanisms to withstand CTL attack. Herein we provide a critical review of the pertinent literature on early and late attack/defense events taking place at the CTL/target cell lytic synapse. We examine the earliest steps of CTL-mediated cytotoxicity (“the poison arrows”) elicited within seconds of CTL/target cell encounter, which face commensurately rapid synaptic repair mechanisms on the tumor cell side, providing the first formidable barrier to CTL attack. We examine how breach of this first defensive barrier unleashes the inextinguishable “Greek fire” in the form of granzymes whose broad cytotoxic potential is linked to activation of cell death executioners, injury of vital organelles, and destruction of intracellular homeostasis. Herein tumor cells deploy slower but no less sophisticated defensive mechanisms in the form of enhanced autophagy, increased reparative capacity, and dysregulation of cell death pathways. We discuss how the newly discovered supra-molecular attack particles (SMAPs, the “scorpion bombs”), seek to overcome the robust defensive mechanisms that confer tumor cell resistance. Finally, we discuss the implications of the aforementioned attack/defense mechanisms on the induction of regulated cell death (RCD), and how different contemporary RCD modalities (including apoptosis, pyroptosis, and ferroptosis) may have profound implications for immunotherapy. Thus, we propose that understanding and targeting multiple steps of the attack/defense process will be instrumental to enhance the efficacy of CTL anti-tumor activity and meet the outstanding challenges in clinical immunotherapy.

Development of a Dendritic Cell/Tumor Cell Fusion Cell Membrane Nano-Vaccine for the Treatment of Ovarian Cancer

Ovarian cancer (OC) is a malignant tumor that seriously affects women’s health. In recent years, immunotherapy has shown great potential in tumor treatment. As a major contributor of immunotherapy, dendritic cells (DCs) - based tumor vaccine has been demonstrated to have a positive effect in inducing immune responses in animal experiments. However, the effect of tumor vaccines in clinical trials is not ideal. Therefore, it is urgent to improve the existing tumor vaccines for tumor treatment. Here, we developed a fusion cell membrane (FCM) nano-vaccine FCM-NPs, which is prepared by fusing DCs and OC cells and coating the FCM on the poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with the immune adjuvant CpG-oligodeoxynucleotide (CpG-ODN). The fusion process promoted the maturation of DCs, thus up-regulating the expression of costimulatory molecule CD80/CD86 and accelerating lymph node homing of DCs. Furthermore, FCM-NPs has both the immunogenicity of tumor cells and the antigen presenting ability of DCs, it can stimulate naive T lymphocytes to produce a large number of tumor-specific cytotoxic CD8⁺ T lymphocytes. FCM-NPs exhibited strong immuno-activating effect both in vitro and in vivo. By establishing subcutaneous transplanted tumor model, patient-derived xenograft tumor model and abdominal metastatic tumor model, FCM-NPs was proved to have the effect of delaying the growth and inhibiting the metastasis of OC. FCM-NPs is expected to become a new tumor vaccine for the treatment of ovarian cancer.

Anti-hepatoma Effect of DC2.4 Cells Transfected with Tumor-Associated Antigen Cdc25C In Vitro

OBJECTIVE

Cell division cyclin 25 homolog C (Cdc25C) is a tumor-associated antigen candidate gene, and this may be used as an effective target in cancer treatment. The present study aims to evaluate the lysis effect of cytotoxic T lymphocytes (CTLs) induced by dendritic cell line DC2.4 overexpressing Cdc25C, and the feasibility of Cdc25C as a component in hepatoma immunotherapy.

METHODS

The mouse Cdc25C gene was ligated into a lentiviral vector, and transfected into DC2.4 cells. The DC2.4 cell phenotype and cytokine secretion were determined by flow cytometry and ELISA, respectively. CD8⁺ T cells were sorted from the spleens of C57BL/6 mice using a magnetic bead sorting kit obtained from Miltenyi Biotech, Germany, and co-cultured with DC2.4 cells for one week as effector cells. Then, IL-2, granzyme B and perforin were detected in the CTL culture medium by ELISA. Next, time-resolved fluorescence immunoassay was used to detect the immune killing effect of Cdc25C-specific CTLs on target cells. Meanwhile, the effect of blocking MHC-I sites on target cells with a monoclonal anti-MHC-I antibody was evaluated.

RESULTS

The results revealed that Cdc25C could be stably overexpressed in DC2.4 cells by LV-Cdc25C infection. DC2.4 cells transfected with LV-Cdc25C secreted more IL-6, IL-12, TNF-α and IFN-γ, and had higher expression levels of CD40, CD86, CCR7 and MHC-II than unaltered DC2.4 cells. The elevated Cdc25C in dendritic cells also further increased the secretion of IL-2, granzyme B and perforin to elicit Cdc25C-specific CTLs, and induced the higher cytotoxicity in Hepa1-6 cell lines (P<0.05), but this had no effect on the target cells when MHC-I monoclonal antibodies were blocked.

CONCLUSION

DC2.4 cells transfected with LV-Cdc25C can induce specific CTLs, and result in a strong cellular immune response. The dendritic cells that overexpress Cdc25C may be useful for hepatoma immunotherapy.

Epitope length variants balance protective immune responses and viral escape in HIV-1 infection

Cytotoxic T lymphocyte (CTL) and natural killer (NK) cell responses to a single optimal 10-mer epitope (KK10) in the human immunodeficiency virus type-1 (HIV-1) protein p24Gag are associated with enhanced immune control in patients expressing human leukocyte antigen (HLA)-B∗27:05. We find that proteasomal activity generates multiple length variants of KK10 (4-14 amino acids), which bind TAP and HLA-B∗27:05. However, only epitope forms ≥8 amino acids evoke peptide length-specific and cross-reactive CTL responses. Structural analyses reveal that all epitope forms bind HLA-B∗27:05 via a conserved N-terminal motif, and competition experiments show that the truncated epitope forms outcompete immunogenic epitope forms for binding to HLA-B∗27:05. Common viral escape mutations abolish (L136M) or impair (R132K) production of KK10 and longer epitope forms. Peptide length influences how well the inhibitory NK cell receptor KIR3DL1 binds HLA-B∗27:05 peptide complexes and how intraepitope mutations affect this interaction. These results identify a viral escape mechanism from CTL and NK responses based on differential antigen processing and peptide competition.

Regeneration of antigen-specific T cells by using induced pluripotent stem cell (iPSC) technology

In currently ongoing adoptive T-cell therapies, T cells collected from the patient are given back to the patient after ex vivo cell activation and expansion. In some cases, T cells are transduced with chimeric antigen receptor (CAR) or T-cell receptor (TCR) genes during the ex vivo culture period. Although such strategies have been shown to be effective in some types of cancer, there remain issues to be solved; these methods (i) are time-consuming, (ii) are costly and (iii) it is difficult to guarantee the quality because the products depend on patient-derived T cells. To address these issues, several groups including ours have developed methods in which cytotoxic cells are mass-produced by using induced pluripotent stem cell (iPSC) technology. For the regeneration of T cells, the basic idea is as follows: iPSCs produced from T cells inherit rearranged TCR genes, and thus all regenerated T cells should express the same TCR. Based on this idea, various types of T cells have been regenerated, including conventional cytotoxic T lymphocytes (CTLs), γδT cells, NKT cells and mucosal-associated invariant T (MAIT) cells. On the other hand, any cytotoxic cells can be used as the base cells into which CAR is introduced, and thus iPSC-derived NK cells have been developed. To apply the iPSC-based cell therapy in an allogeneic setting, the authors' group developed a method in which non-T-cell-derived iPSCs are transduced with exogenous TCR genes (TCR-iPSC method). This approach is being prepared for a clinical trial to be realized in Kyoto University Hospital, in which acute myeloid leukemia patients will be treated by the regenerated WT1 antigen-specific CTLs.

Applications of Magnetite Nanoparticles in Cancer Immunotherapies: Present Hallmarks and Future Perspectives

Current immuno-oncotherapeutic protocols that inhibit tumor immune evasion have demonstrated great clinical success. However, the therapeutic response is limited only to a percentage of patients, and the immune-related adverse events can compromise the therapeutic benefits. Therefore, improving cancer immunotherapeutic approaches that pursue high tumor suppression efficiency and low side effects turn out to be a clinical priority. Novel magnetite nanoparticles (MNPs) exhibit great potential for therapeutic and imaging applications by utilizing their properties of superparamagnetism, good biocompatibility, as well as the easy synthesis and modulation/functionalization. In particular, the MNPs can exert magnetic hyperthermia to induce immunogenic cell death of tumor cells for effective antigen release and presentation, and meanwhile polarize tumor-associated macrophages (TAMs) to M1 phenotype for improved tumor killing capability, thus enhancing the anti-tumor immune effects. Furthermore, immune checkpoint antibodies, immune-stimulating agents, or tumor-targeting agents can be decorated on MNPs, thereby improving their selectivity for the tumor or immune cells by the unique magnetic navigation capability of MNPs to promote the tumor killing immune therapeutics with fewer side effects. This mini-review summarizes the recent progress in MNP-based immuno-oncotherapies, including activation of macrophage, promotion of cytotoxic T lymphocyte (CTL) infiltration within tumors and modulation of immune checkpoint blockade, thus further supporting the applications of MNPs in clinical therapeutic protocols.

Tumor-Infiltrating Cytotoxic T Cells and Tumor-Associated Macrophages Correlate With the Outcomes of Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer

BACKGROUND

Tumor-infiltrating immune cells (TIICs) play a key role in immunoregulatory networks and are related to tumor development. Emerging evidence shows that these cells are associated with sensitivity to chemotherapy and radiotherapy. However, the predictive role of TIICs in the outcomes of neoadjuvant chemoradiotherapy (nCRT) for locally advanced rectal cancer (LARC) is unclear.

METHODS

Imaging mass cytometry (IMC) was performed to comprehensively assess the immune status before nCRT in 6 patients with LARC (3 achieved pathological complete response (pCR), 3 did not) with matched clinicopathological parameters. Immunohistochemistry (IHC) for CD8, CD163 and Foxp3 on biopsy samples from 70 patients prior to nCRT and logistic regression analysis were combined to further evaluate its predictive value for treatment responses in an independent validation group.

RESULTS

A trend of increased CD8+ cytotoxic T lymphocytes (CTLs) and decreased CD163+ tumor-associated macrophages (TAMs) and Foxp3+ regulatory T cells (Tregs) in the pCR group was revealed by IMC. In the validation group, CTLs and TAMs were strong predictors of the clinical response to nCRT. High levels of CTLs were positively associated with the pCR ratio (OR=1.042; 95% CI: 1.015~1.070, p=0.002), whereas TAMs were correlated with a poor response (OR=0.969; 95% CI: 0.941~0.998, p=0.036). A high density of TAMs was also associated with an advanced cN stage.

CONCLUSION

CTLs in the tumor microenvironment (TME) may improve the response to nCRT, whereas TAMs have the opposite effect. These results suggest that these cells might be potential markers for the clinical outcomes of nCRT and aid in the clinical decision-making of LARC for improved clinical outcomes.

Developing Acid-Responsive Glyco-Nanoplatform Based Vaccines for Enhanced Cytotoxic T-lymphocyte Responses Against Cancer and SARS-CoV-2

Cytotoxic T-lymphocytes (CTLs) are central for eliciting protective immunity against malignancies and infectious diseases. Here, for the first time, partially oxidized acetalated dextran nanoparticles (Ox-AcDEX NPs) with an average diameter of 100 nm are fabricated as a general platform for vaccine delivery. To develop effective anticancer vaccines, Ox-AcDEX NPs are conjugated with a representative CTL peptide epitope (CTLp) from human mucin-1 (MUC1) with the sequence of TSAPDTRPAP (referred to as Mp1) and an immune-enhancing adjuvant R837 (referred to as R) via imine bond formation affording AcDEX-(imine)-Mp1-R NPs. Administration of AcDEX-(imine)-Mp1-R NPs results in robust and long-lasting anti-MUC1 CTL immune responses, which provides mice with superior protection from the tumor. To verify its universality, this nanoplatform is also exploited to deliver epitopes from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to prevent coronavirus disease 2019 (COVID-19). By conjugating Ox-AcDEX NPs with the potential CTL epitope of SARS-CoV-2 (referred to as Sp) and R837, AcDEX-(imine)-Sp-R NPs are fabricated for anti-SARS-CoV-2 vaccine candidates. Several epitopes potentially contributing to the induction of potent and protective anti-SARS-CoV-2 CTL responses are examined and discussed. Collectively, these findings shed light on the universal use of Ox-AcDEX NPs to deliver both tumor-associated and virus-associated epitopes.

Detection of granzyme B in CD3-positive cells infiltrated in lesional skin of a dog with erythema multiforme associated with zonisamide

In human erythema multiforme (EM), cytotoxic T lymphocytes (CTLs) play an essential role in the pathogenesis. In canine EM, immunohistochemical staining with anti-CD8 antibody using frozen sections has shown the involvement of CTLs; however, CTL infiltration has never been quantitatively analyzed. We herein quantitatively analyzed CTL infiltration by immunohistochemical staining with granzyme B and CD3 antibodies using paraffin sections of a dog with EM associated with zonisamide. The present results indicated approximately 70% of cells at the border between the epidermis and dermis consisted of CTLs. Detection of granzyme B and CD3 using paraffin sections employed in this study can be a clinically applicable method for detecting CTLs.

Identification of HLA-A2-Restricted Mutant Epitopes from Neoantigens of Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC), one of the deadliest gastrointestinal cancers, has had limited effective therapeutic strategies up to now. Accumulating evidence suggests that effective immunotherapy in cancer patients has been associated with T cells responsive to mutant peptides derived from neoantigens. Here, we selected 35 human leukocyte antigen-A2 (HLA-A2)-restricted mutant (MUT) peptides stemmed from neoantigens of ESCC. Among them, seven mutant peptides had potent binding affinity to HLA-A*0201 molecules and could form a stable peptide/HLA-A*0201 complex. Three mutant peptides (TP53-R267P, NFE2L2-D13N, and PCLO-E4090Q) of those were immunogenic and could induce the cytotoxic T lymphocytes (CTLs) recognizing mutant peptides presented on transfected cells in an HLA-A2-restricted and MUT peptide-specific manner. In addition, the CTL response in immunized HLA-A2.1/K^b transgenic (Tg) mice was enhanced by coupling MUT peptides to peptide WH, a peptide delivery carrier targeting Clec9a⁺ DCs. Then, the possible binding model conversions between the WT and MUT candidate peptides were analyzed by docking with the pockets of HLA-A*0201 molecule. We therefore propose a novel strategy and epitopes for immunotherapy of ESCC based on neoantigens.

Spatially fractionated radiotherapy: tumor response modelling including immunomodulation

A mathematical tumor response model has been developed, encompassing the interplay between immune cells and cancer cells initiated by either partial or full tumor irradiation. The iterative four-compartment model employs the linear-quadratic radiation response theory for four cell types: active and inactive cytotoxic T lymphocytes (immune cells, CD8⁺T cells in particular), viable cancer cells (undamaged and reparable cells) and doomed cells (irreparably damaged cells). The cell compartment interactions are calculated per day, with total tumor volume (TV) as the main quantity of interest. The model was fitted to previously published data on syngeneic xenografts (67NR breast carcinoma and Lewis lung carcinoma; (Markovskyet al2019Int. J. Radiat. Oncol. Biol. Phys.103697-708)) subjected to single doses of 10 or 15 Gy by 50% (partial) or 100% (full) TV irradiation. The experimental data included effects from anti-CD8⁺antibodies and immunosuppressive drugs. Using a new optimization method, promising fits were obtained where the lowest and highest root-mean-squared error values were observed for anti-CD8⁺treatment and unirradiated control data, respectively, for both cell types. Additionally, predictive capabilities of the model were tested by using the estimated model parameters to predict scenarios for higher doses and different TV irradiation fractions. Here, mean relative deviations in the range of 19%-34% from experimental data were found. However, more validation data is needed to conclude on the model's predictive capabilities. In conclusion, the model was found useful in evaluating the impact from partial and full TV irradiation on the immune response and subsequent tumor growth. The model shows potential to support and guide spatially fractionated radiotherapy in future pre-clinical and clinical studies.

Association of human leukocyte antigen-B*13:01 with dapsone-induced liver injury

Human leukocyte antigens (HLA) have been linked to adverse drug reactions. Generally, HLA association is phenotype specific and is related to either liver or skin injury. HLA-A*13:01 has been linked to dapsone-induced severe cutaneous drug reactions and its role in drug-induced liver injury (DILI) is unclear. In our series, all of the four patients with immunoallergic dapsone DILI were carrying HLA-B*13:01 compared to its prevalence of 1-12% among Indians. HLA-B*13:01 plays a role not only in dapsone-induced severe cutaneous adverse reaction (SCAR) but also in dapsone-induced liver injury with immunoallergic features and highlights the role of adaptive immune response in the pathogenesis of both liver and skin injury and associated other organ involvement.

Expression of HLA-DR in Cytotoxic T Lymphocytes: A Validated Predictive Biomarker and a Potential Therapeutic Strategy in Breast Cancer

Simple Summary

More than 50% of breast cancer (BC) patients selected for neoadjuvant chemotherapy (NACT) are subjected to at least a 6-month regimen of this treatment without a clear benefit, probably delaying more effective therapeutic strategies and being exposed to potential treatment-associated toxicity. Thus, it is urgent to implement reliable predictive biomarkers, as well as novel treatments for NACT non-responder patients. This study validates that the HLA-DR level in cytotoxic T lymphocytes (CTLs) is an independent and robust predictive factor of BC patients’ response to NACT, as previously proposed. Hence, a predictive probability model of response was developed as a new tool to improve treatment decisions. HLA-DR level in CTLs also have a general prognostic value, which might be relevant for long-term BC management. In addition, our results suggest that increasing the expression of HLA-DR in CTLs of non-responders could be a promising therapeutic strategy to ameliorate BC response to NACT.

Abstract

Neoadjuvant chemotherapy (NACT) is common in breast cancer (BC) treatment, though more than half of the patients lack an effective response. Therefore, new predictive biomarkers and alternative therapies are crucial. Previously, we proposed HLA-DR-expressing cytotoxic T lymphocytes (CTLs) as a potential biomarker of the response to NACT. To validate this observation and further investigate these cells, 202 BC patients were enrolled. Flow cytometry analyses were performed in 61 biopsies and 41 blood samples pre-NACT and 100 non-NACT tumor samples. All the patients were followed up for 34 months. Blood-isolated immune cells were cultured with BC cell lines in a 3D system. We confirmed that HLA-DR level in CTLs is a highly sensitive, specific, and independent biomarker to predict response to NACT and developed a predictive probability model. This biomarker was also associated with progression-free survival, regardless of the treatment. The clinical observations are substantiated by the anti-tumor properties of HLA-DR-expressing CTLs. Intriguingly, HLA-DR level in CTLs can be modulated ex vivo, boosting their capacity to kill tumor cells synergistically with doxorubicin. Thus, HLA-DR expression in CTLs is a validated tool to select patients that will actually benefit from NACT, and its stimulation might be a novel therapeutic approach for BC.

Morphological profiling of human T and NK lymphocytes by high-content cell imaging

The immunological synapse is a complex structure that decodes stimulatory signals into adapted lymphocyte responses. It is a unique window to monitor lymphocyte activity because of development of systematic quantitative approaches. Here we demonstrate the applicability of high-content imaging to human T and natural killer (NK) cells and develop a pipeline for unbiased analysis of high-definition morphological profiles. Our approach reveals how distinct facets of actin cytoskeleton remodeling shape immunological synapse architecture and affect lytic granule positioning. Morphological profiling of CD8⁺ T cells from immunodeficient individuals allows discrimination of the roles of the ARP2/3 subunit ARPC1B and the ARP2/3 activator Wiskott-Aldrich syndrome protein (WASP) in immunological synapse assembly. Single-cell analysis further identifies uncoupling of lytic granules and F-actin radial distribution in ARPC1B-deficient lymphocytes. Our study provides a foundation for development of morphological profiling as a scalable approach to monitor primary lymphocyte responsiveness and to identify complex aspects of lymphocyte micro-architecture.

Novel myeloperoxidase-derived HLA-A2-restricted peptides as therapeutic targets against myeloid leukemia

BACKGROUND AIMS

Human myeloperoxidase has been shown to be overexpressed in many types of leukemia, such as chronic myeloid leukemia, acute myeloid leukemia and myelodysplastic syndrome. The authors identified two myeloperoxidase-derived HLA-A2-restricted peptides, MY4 and MY8, as novel leukemia-associated antigens.

METHODS

Ex vivo-elicited MY4- and MY8-specific cytotoxic T lymphocytes were generated, and tested for leukemia cell lysis in vitro and in NOD/SCID AML xenograft model.

RESULTS

These MY4- and MY8-specific cytotoxic T lymphocytes killed leukemic blasts while sparing healthy donor bone marrow cells. In addition, co-injection of MY4- and MY8-specific cytotoxic T lymphocytes into nonobese diabetic/severe combined immunodeficiency mice with acute myeloid leukemia drastically reduced tumor burden in vivo. The authors also found that MY4- and MY8-specific T cells could be detected in the peripheral blood mononuclear cells of allogeneic stem cell transplant recipients.

CONCLUSIONS

These antigen-specific T cells were significantly increased in blood samples from patients compared with healthy donors, suggesting that both MY4 and MY8 are immunogenic and that MY4- and MY8-specific cytotoxic T lymphocytes may play a role in reducing leukemia in vivo. Thus, the discovery of MY4 and MY8 as novel leukemia-associated antigens paves the way for targeting these antigens in immunotherapy against myeloid leukemia.