Granzyme B production distinguishes recently activated CD8(+) memory cells from resting memory cells

Granzyme B May Act as an Effector Molecule to Control the Inflammatory Process in COPD

Chronic obstructive pulmonary disease (COPD) is caused by smoking, but only a small proportion of smokers have disease severe enough to develop COPD. COPD is not always progressive. The question then arises as to what explains the different trajectories of COPD. The role of autoimmunity and regulatory T (Treg) cells in the pathogenesis of COPD is increasingly being recognized. Nine published studies on Treg cells in the lung tissue or bronchoalveolar lavage fluid have shown that smokers with COPD have fewer Treg cells than smokers without COPD or nonsmokers. Three studies showed a positive correlation between Treg cell count and FEV1%, suggesting an important role for Treg cells in COPD progression. Treg cells can regulate immunological responses via the granzyme B (GzmB) pathway. Immunohistochemical staining for GzmB in surgically resected lungs with centrilobular emphysema showed that the relationship between the amount of GzmB+ cells and FEV1% was comparable to that between Treg cell count and FEV1% in the COPD lung, suggesting that GzmB could be a functional marker for Treg cells. The volume fraction of GzmB+  cells in the small airways, the number of alveolar GzmB+ cells, and GzmB expression measured by enzyme-linked immunosorbent assay in the lung tissue of smokers were significantly correlated with FEV1%. These results suggest that the GzmB content in lung tissue may determine the progression of COPD by acting as an effector molecule to control inflammatory process. Interventions to augment GzmB-producing immunosuppressive cells in the early stages of COPD could help prevent or delay COPD progression.

Progressively Enhancing Stemness of Adoptively Transferred T Cells with PI3Kδ Blockade Improves Metabolism and Antitumor Immunity

Generating stem-like memory T cells (TSCM) is a potential strategy to improve adoptive immunotherapy. Elucidating optimal ways to modulate signaling pathways that enrich TSCM properties could identify approaches to achieve this goal. We discovered herein that blocking the PI3Kδ pathway pharmaceutically to varying degrees can generate T cells with increasingly heightened stemness properties, based on the progressive enrichment of the transcription factors Tcf1 and Lef1. T cells with enhanced stemness features exhibited metabolic plasticity, marked by improved mitochondrial function and glucose uptake after tumor recognition. Conversely, T cells with low or medium stemness were less metabolically dynamic, vulnerable to antigen-induced cell death, and expressed more inhibitory checkpoint receptors. Only T-cell receptor-specific or chimeric antigen receptor (CAR)-specific T cells with high stemness persisted in vivo and mounted protective immunity to tumors. Likewise, the strongest level of PI3Kδ blockade in vitro generated human tumor-infiltrating lymphocytes and CAR T cells with elevated stemness properties, in turn bolstering their capacity to regress human solid tumors. The stemness level of T cells in vitro was important, ultimately impacting their efficacy in mice bearing three distinct solid tumors. Lef1 and Tcf1 sustained antitumor protection by donor high CD8+ TSCM or CD4+ Th17SCM, as deletion of either one compromised the therapeutic efficacy. Collectively, these findings highlight the importance of strategic modulation of PI3Kδ signaling in T cells to induce stemness and lasting protective responses to solid tumors.

SIGNIFICANCE

Elevating T-cell stemness by progressively blocking PI3Kδ signaling during ex vivo manufacturing of adoptive cell therapies alters metabolic and functional properties to enhance antitumor immunity dependent on Tcf1 and Lef1.

Immune Checkpoint Inhibitors in pMMR/MSS Colorectal Cancer

BACKGROUND

Immune checkpoint inhibitors have recently replaced over chemotherapy as the first-line treatment for microsatellite instability-high or mismatch repair deficient (dMMR/MSI-H) stage 4 colorectal cancers. Considering this success, many studies have tried to replicate the use of immune checkpoint inhibitors, either as a single agent or in combination with other therapeutic agents, in the treatment of proficient mismatch repair (pMMR/MSS) stage 4 colorectal cancers. This review summarizes the seminal clinical data about the immune checkpoint inhibitors used in pMMR/MSS colorectal cancers and some future directions.

RESULTS

Studies concerning the use of immune checkpoint inhibitors as a single agent or in combination with other immune checkpoint inhibitors, targeted therapy, chemotherapy, or radiotherapy have proven inefficient in the treatment of pMMR/MSS colorectal cancer. However, a small subset of patients with pMMR/MSS colorectal cancer who has a mutation in POLE and POLD1 enzymes may respond to immunotherapy. Moreover, patients without liver metastasis appear to have a better chance of response. New immune checkpoint targets are being identified, such as VISTA, TIGIT, LAG3, STING signal pathway, and BTLA, and studies are ongoing to determine their efficiency in this disease type.

CONCLUSION

Immune checkpoint inhibitor-based regimens have not yet shown any meaningful positive outcomes for most pMMR/MSS colorectal cancers. A beneficial effect among a minority of these patients has been observed, but concrete biomarkers of response are lacking. Understanding the underlying mechanisms of immune resistance should guide further research for overcoming these obstacles.

Immunological Misfiring and Sex Differences/Similarities in Early COVID-19 Studies: Missed Opportunities of Making a Real IMPACT

COVID-19-associated intensive care unit (ICU) admissions were recognized as critical health issues that contributed to morbidity and mortality in SARS-CoV-2-infected patients. Severe symptoms in COVID-19 patients are often accompanied by cytokine release syndrome. Here, we analyzed publicly available data from the Yale IMPACT cohort to address immunological misfiring and sex differences in early COVID-19 patients. In 2020, SARS-CoV-2 was considered far more pathogenic and lethal than other circulating respiratory viruses, and the inclusion of SARS-CoV-2 negative patients in IMPACT cohorts confounds many findings. We ascertained the impact of several important biological variables such as days from symptom onset (DFSO); pre-existing risk factors, including obesity; and early COVID-19 treatments on significantly changed immunological measures in ICU-admitted COVID-19 patients that survived versus those that did not. Deceased patients had 19 unique measures that were not shared with ICU patients including increased granzyme-B-producing GzB+CD8+ T cells and interferon-γ. Male COVID-19 patients in ICU experienced many more changes in immunological and clinical measures than female ICU patients (25% vs. ~16%, respectively). A total of 13/124 measures including CCL5, CCL17, IL-18, IFNα2, Fractalkine, classical monocytes, T cells, and CD4Temra exhibited significant sex differences in female vs. male COVID-19 patients. A total of nine measures including IL-21, CCL5, and CD4Temra differed significantly between female and male healthy controls. Immunosuppressed patients experienced the most decreases in CD4Temra and CD8Tem cell numbers. None of the early COVID-19 treatments were effective in reducing levels of IL-6, a major component of the cytokine storm. Obesity (BMI >30) was the most impactful risk factor for COVID-19-related deaths and worst clinical outcomes. Our analysis highlights the contribution of biological sex, risk factors, and early treatments with respect to COVID-19-related ICU admission and progression to morbidity and mortality.

A method for polyclonal antigen-specific T cell-targeted genome editing (TarGET) for adoptive cell transfer applications

Adoptive cell therapy of donor-derived, antigen-specific T cells expressing native T cell receptors (TCRs) is a powerful strategy to fight viral infections in immunocompromised patients. Determining the fate of T cells following patient infusion hinges on the ability to track them in vivo. While this is possible by genetic labeling of parent cells, the applicability of this approach has been limited by the non-specificity of the edited T cells. Here, we devised a method for CRISPR-targeted genome integration of a barcoded gene into Epstein-Barr virus-antigen-stimulated T cells and demonstrated its use for exclusively identifying expanded virus-specific cell lineages. Our method facilitated the enrichment of antigen-specific T cells, which then mediated improved cytotoxicity against Epstein-Barr virus-transformed target cells. Single-cell and deep sequencing for lineage tracing revealed the expansion profile of specific T cell clones and their corresponding gene expression signature. This approach has the potential to enhance the traceability and the monitoring capabilities during immunotherapeutic T cell regimens.

Potency assessment of IFNγ-producing SARS-CoV-2-specific T cells from COVID-19 convalescent subjects

The development of new therapies for COVID-19 high-risk patients remains necessary to prevent additional deaths. Here, we studied the phenotypical and functional characteristics of IFN-γ producing-SARS-CoV-2-specific T cells (SC2-STs), obtained from 12 COVID-19 convalescent donors, to determine their potency as an off-the-shelf T cell therapy product. We found that these cells present mainly an effector memory phenotype, characterized by the basal expression of cytotoxicity and activation markers, including granzyme B, perforin, CD38, and PD-1. We demonstrated that SC2-STs could be expanded and isolated in vitro, and they exhibited peptide-specific cytolytic and proliferative responses after antigenic re-challenge. Collectively, these data demonstrate that SC2-STs can be a suitable candidate for the manufacture of a T cell therapy product aimed to treat severe COVID-19.

The degree of T cell stemness differentially impacts the potency of adoptive cancer immunotherapy in a Lef-1 and Tcf-1 dependent manner

Generating stem memory T cells (T _SCM ) is a key goal for improving cancer immunotherapy. Yet, the optimal way to modulate signaling pathways that enrich T _SCM properties remains elusive. Here, we discovered that the degree to which the PI3Kδ pathway is blocked pharmaceutically can generate T cells with differential levels of stemness properties. This observation was based on the progressive enrichment of transcriptional factors of stemness (Tcf-1 and Lef-1). Additional investigation revealed that T cells with high stemness features had enhanced metabolic plasticity, marked by heightened mitochondrial function and glucose uptake. Conversely, T cells with low or medium features of stemness expressed more inhibitory checkpoint receptors (Tim-3, CD39) and were vulnerable to antigen-induced cell death. Only TCR-antigen specific T cells with high stemness persisted following adoptive transfer in vivo and mounted protective immunity to melanoma tumors. Likewise, the strongest level of PI3Kδ blockade in vitro generated human tumor infiltrating lymphocytes (TILs) and CAR T cells with heightened stemness properties, in turn bolstering their capacity to regress human mesothelioma tumors. We find that the level of stemness T cells possess in vitro differentially impacts their potency upon transfer in three tumor models. Mechanistically, both Lef-1 and Tcf-1 sustain anti-tumor protection by high T _SCM , as deletion of either one compromised cellular therapy. Collectively, these findings highlight the therapeutic potential of carefully modulating PI3Kδ signaling in T cells to confer high stemness and mediate protective responses to solid tumors.

Wnt5A signaling supports antigen processing and CD8 T cell activation

Antigen processing and antigen-specific CD8 T cell activation form part and parcel of cell-mediated immunity to infections. Yet, several lacunae remain in our understanding of how antigen processing and CD8 T cell response are coordinated. In this study, using mouse bone marrow-derived dendritic cells (BMDC) as antigen-presenting cells and Ovalbumin (OVA)/DQ-Ovalbumin (DQ-OVA) as model antigen we demonstrated that Wnt5A signaling in BMDC supports antigen processing/presentation and concomitant CD8 T cell activation through regulation of actin and proteasome dynamics. Recombinant Wnt5A conditioning of BMDC and associated actin assembly facilitated DQ-OVA processing, which was inhibited by the proteasome inhibitor MG132. Moreover, Wnt5A depletion led to a significant reduction in OVA processing and presentation. Impaired DQ-OVA processing in Wnt5A depleted BMDC correlated with altered dynamics of both actin and the proteasome regulator PA28α-PA28β, and reduced association of DQ-OVA with actin and proteasome subunits. Inhibited OVA processing/presentation in the Wnt5A depleted BMDC also resulted in subdued activation of OVA-sensitized CD8 T cells in co-culture with the BMDC. In concurrence with these findings, we demonstrated reduced OVA processing and impaired CD8 T cell response to OVA immunization in Wnt5A heterozygous mice lacking a copy of the Wnt5A gene in comparison to the wild-type cohorts. Taken together, our results reveal a crucial requirement of Wnt5A signaling in antigen processing/presentation and CD8 T cell activation, thus unveiling a vital regulatory node of cell-mediated immunity, unidentified thus far.

SARS CoV-2 mRNA vaccination exposes latent HIV to Nef-specific CD8+ T-cells

Efforts to cure HIV have focused on reactivating latent proviruses to enable elimination by CD8+ cytotoxic T-cells. Clinical studies of latency reversing agents (LRA) in antiretroviral therapy (ART)-treated individuals have shown increases in HIV transcription, but without reductions in virologic measures, or evidence that HIV-specific CD8+ T-cells were productively engaged. Here, we show that the SARS-CoV-2 mRNA vaccine BNT162b2 activates the RIG-I/TLR - TNF - NFκb axis, resulting in transcription of HIV proviruses with minimal perturbations of T-cell activation and host transcription. T-cells specific for the early gene-product HIV-Nef uniquely increased in frequency and acquired effector function (granzyme-B) in ART-treated individuals following SARS-CoV-2 mRNA vaccination. These parameters of CD8+ T-cell induction correlated with significant decreases in cell-associated HIV mRNA, suggesting killing or suppression of cells transcribing HIV. Thus, we report the observation of an intervention-induced reduction in a measure of HIV persistence, accompanied by precise immune correlates, in ART-suppressed individuals. However, we did not observe significant depletions of intact proviruses, underscoring challenges to achieving (or measuring) HIV reservoir reductions. Overall, our results support prioritizing the measurement of granzyme-B-producing Nef-specific responses in latency reversal studies and add impetus to developing HIV-targeted mRNA therapeutic vaccines that leverage built-in LRA activity.

CXCR2 inhibition enables NASH-HCC immunotherapy

OBJECTIVE

Hepatocellular carcinoma (HCC) is increasingly associated with non-alcoholic steatohepatitis (NASH). HCC immunotherapy offers great promise; however, recent data suggests NASH-HCC may be less sensitive to conventional immune checkpoint inhibition (ICI). We hypothesised that targeting neutrophils using a CXCR2 small molecule inhibitor may sensitise NASH-HCC to ICI therapy.

DESIGN

Neutrophil infiltration was characterised in human HCC and mouse models of HCC. Late-stage intervention with anti-PD1 and/or a CXCR2 inhibitor was performed in murine models of NASH-HCC. The tumour immune microenvironment was characterised by imaging mass cytometry, RNA-seq and flow cytometry.

RESULTS

Neutrophils expressing CXCR2, a receptor crucial to neutrophil recruitment in acute-injury, are highly represented in human NASH-HCC. In models of NASH-HCC lacking response to ICI, the combination of a CXCR2 antagonist with anti-PD1 suppressed tumour burden and extended survival. Combination therapy increased intratumoural XCR1+ dendritic cell activation and CD8+ T cell numbers which are associated with anti-tumoural immunity, this was confirmed by loss of therapeutic effect on genetic impairment of myeloid cell recruitment, neutralisation of the XCR1-ligand XCL1 or depletion of CD8+ T cells. Therapeutic benefit was accompanied by an unexpected increase in tumour-associated neutrophils (TANs) which switched from a protumour to anti-tumour progenitor-like neutrophil phenotype. Reprogrammed TANs were found in direct contact with CD8+ T cells in clusters that were enriched for the cytotoxic anti-tumoural protease granzyme B. Neutrophil reprogramming was not observed in the circulation indicative of the combination therapy selectively influencing TANs.

CONCLUSION

CXCR2-inhibition induces reprogramming of the tumour immune microenvironment that promotes ICI in NASH-HCC.

Tumor-Infiltrating Lymphocytes (TILs) as a Biomarker of Abscopal Effect of Cryoablation in Breast Cancer: A Pilot Study

Background

Morphological evaluation of tumor-infiltrating lymphocytes (TILs) in breast cancer is gaining momentum as an immunological biomarker. This experiment evaluates the role of TILs in distant tumors as a measure of abscopal effect from cryoablation of breast cancer.

Methods

BALB/c mice underwent bilateral orthotopic transplant with 4T1-12B (triple-negative) cells. At 2 weeks, left tumors were treated by either resection (standard of care group) or cryoablation (intervention group) followed by resection of the distant right tumors 1 week posttreatment. TIL scores were calculated from hematoxylin and eosin-stained sections and phenotyped for cytotoxic T-lymphocyte (CTL) markers by immunofluorescence. Primarily resected tumors served as baseline (Tbaseline), whereas resected distant right-sided served as the readout for abscopal effect (AbsRes or AbsCryo). Mice were monitored for tumor recurrence and metastasis.

Results

The AbsCryo had a significant mean (SD) increase in stromal (2.8 [1.1]%; p = 0.015) and invasive margin TILs (50 [12]%; p = 0.02) compared with TBaseline (1.0 [0]% and 31 [4.9]%, respectively). CTL phenotyping revealed a significant increase in mean (SD) CD8+ T cells (15.7 [12.1]; p = 0.02) and granzyme B (4.8 [3.6]; p = 0.048) for the AbsCryo compared with TBaseline (5.2 [4.7] and 2.4 [0.9], respectively). Posttreatment, the cryoablation group had no recurrence or metastasis, whereas the resected group showed local recurrence and lung metastasis in 40% of the mice. Postprocedure increase in TIL score of distant tumors was associated with decrease in tumor relapse (p = 0.02).

Conclusions

Cryoablation induced a robust tumor-specific TIL response compared with resection, suggesting an abscopal effect leading to the prevention of cancer recurrence and metastasis.

Non-severe burn injury increases cancer incidence in mice and has long-term impacts on the activation and function of T cells

Background

Recent evidence suggests that burn patients are at increased risk of hospital admission for infection, mental health conditions, cardiovascular disease and cancer for many years after discharge for the burn injury itself. Burn injury has also been shown to induce sustained immune system dysfunction. This change to immune function may contribute to the increased risk of chronic disease observed. However, the mechanisms that disrupt long-term immune function in response to burn trauma, and their link to long-term morbidity, remain unknown. In this study we investigated changes to immune function after burn injury using a murine model of non-severe injury.

Methods

An established mouse model of non-severe burn injury (full thickness burn equivalent to 8% total body surface area) was used in combination with an orthotopic model of B16 melanoma to investigate the link between burns and cancer. Considering that CD8⁺ T cells are important drivers of effective tumour suppression in this model, we also investigated potential dysregulation of this immune population using mouse models of burn injury in combination with herpes simplex virus infection. Flow cytometry was used to detect and quantify cell populations of interest and changes in immune function.

Results

We demonstrate that 4 weeks after a non-severe burn injury, mice were significantly more susceptible to tumour development than controls using an orthotopic model of B16 melanoma. In addition, our results reveal that CD8⁺ T cell expansion, differentiation and memory potential is significantly impaired at 1 month post-burn.

Conclusions

Our data suggests that CD8⁺ T cell-mediated immunity may be dysfunctional for a sustained period after even non-severe burn injury. Further studies in patients to validate these findings may support clinical intervention to restore or protect immunity in patients after burn injury and reduce the increased risk of secondary morbidities observed.

EGCG Inhibits Tumor Growth in Melanoma by Targeting JAK-STAT Signaling and Its Downstream PD-L1/PD-L2-PD1 Axis in Tumors and Enhancing Cytotoxic T-Cell Responses

Over the last decade, therapies targeting immune checkpoints, such as programmed death-1 (PD-1), have revolutionized the field of cancer immunotherapy. However, low response rates and immune-related adverse events remain a major concern. Here, we report that epigallocatechin gallate (EGCG), the most abundant catechin in green tea, inhibits melanoma growth by modulating an immune response against tumors. In vitro experiments revealed that EGCG treatment inhibited interferon-gamma (IFN-γ)-induced PD-L1 and PD-L2 expression and JAK-STAT signaling. We confirmed that this effect was driven by inhibiting STAT1 gene expression and STAT1 phosphorylation, thereby downregulating the PD-L1/PD-L2 transcriptional regulator IRF1 in both human and mouse melanoma cells. Animal studies revealed that the in vivo tumor-inhibitory effect of EGCG was through CD8+ T cells and that the inhibitory effect of EGCG was comparable to anti-PD-1 therapy. However, their mechanisms of action were different. Dissimilar to anti-PD-1 treatment that blocks PD-1/PD-L1 interaction, EGCG inhibited JAK/STAT signaling and PD-L1 expression in tumor cells, leading to the re-activation of T cells. In summary, we demonstrate that EGCG enhances anti-tumor immune responses by inhibiting JAK-STAT signaling in melanoma. EGCG could be used as an alternative treatment strategy to target the PD-L1/PD-L2-PD-1 axis in cancers.

Thymus Gland: A Double Edge Sword for Coronaviruses

The thymus is the main lymphoid organ that regulates the immune and endocrine systems by controlling thymic cell proliferation and differentiation. The gland is a primary lymphoid organ responsible for generating mature T cells into CD4+ or CD8+ single-positive (SP) T cells, contributing to cellular immunity. Regarding humoral immunity, the thymic plasma cells almost exclusively secrete IgG1 and IgG3, the two main complement-fixing effector IgG subclasses. Deformity in the thymus can lead to inflammatory diseases. Hassall’s corpuscles’ epithelial lining produces thymic stromal lymphopoietin, which induces differentiation of CDs thymocytes into regulatory T cells within the thymus medulla. Thymic B lymphocytes produce immunoglobulins and immunoregulating hormones, including thymosin. Modulation in T cell and naive T cells decrement due to thymus deformity induce alteration in the secretion of various inflammatory factors, resulting in multiple diseases. Influenza virus activates thymic CD4+ CD8+ thymocytes and a large amount of IFNγ. IFNs limit virus spread, enhance macrophages’ phagocytosis, and promote the natural killer cell restriction activity against infected cells. Th2 lymphocytes-produced cytokine IL-4 can bind to antiviral INFγ, decreasing the cell susceptibility and downregulating viral receptors. COVID-19 epitopes (S, M, and N proteins) with ≥90% identity to the SARS-CoV sequence have been predicted. These epitopes trigger immunity for antibodies production. Boosting the immune system by improving thymus function can be a therapeutic strategy for preventing virus-related diseases. This review aims to summarize the endocrine-immunoregulatory functions of the thymus and the underlying mechanisms in the prevention of COVID-19.

A Single-Cell Atlas of Lymphocyte Adaptive Immune Repertoires and Transcriptomes Reveals Age-Related Differences in Convalescent COVID-19 Patients

COVID-19 disease outcome is highly dependent on adaptive immunity from T and B lymphocytes, which play a critical role in the control, clearance and long-term protection against SARS-CoV-2. To date, there is limited knowledge on the composition of the T and B cell immune receptor repertoires [T cell receptors (TCRs) and B cell receptors (BCRs)] and transcriptomes in convalescent COVID-19 patients of different age groups. Here, we utilize single-cell sequencing (scSeq) of lymphocyte immune repertoires and transcriptomes to quantitatively profile the adaptive immune response in COVID-19 patients of varying age. We discovered highly expanded T and B cells in multiple patients, with the most expanded clonotypes coming from the effector CD8⁺ T cell population. Highly expanded CD8⁺ and CD4⁺ T cell clones show elevated markers of cytotoxicity (CD8: PRF1, GZMH, GNLY; CD4: GZMA), whereas clonally expanded B cells show markers of transition into the plasma cell state and activation across patients. By comparing young and old convalescent COVID-19 patients (mean ages = 31 and 66.8 years, respectively), we found that clonally expanded B cells in young patients were predominantly of the IgA isotype and their BCRs had incurred higher levels of somatic hypermutation than elderly patients. In conclusion, our scSeq analysis defines the adaptive immune repertoire and transcriptome in convalescent COVID-19 patients and shows important age-related differences implicated in immunity against SARS-CoV-2.

Non-invasive Detection of Immunotherapy-Induced Adverse Events

PURPOSE

Cancer immunotherapy has markedly improved the prognosis of patients with a broad variety of malignancies. However, benefits are weighed against unique toxicities, with immune-related adverse events (irAE) that are frequent and potentially life-threatening. The diagnosis and management of these events are challenging due to heterogeneity of timing onset, multiplicity of affected organs, and lack of non-invasive monitoring techniques. We demonstrate the use of a granzyme B-targeted PET imaging agent (GZP) for irAE identification in a murine model.

EXPERIMENTAL DESIGN

We generated a model of immunotherapy-induced adverse events in Foxp3-DTR-GFP mice bearing MC38 tumors. GZP PET imaging was performed to evaluate organs non-invasively. We validated imaging with ex vivo analysis, correlating the establishment of these events with the presence of immune infiltrates and granzyme B upregulation in tissue. To demonstrate the clinical relevance of our findings, the presence of granzyme B was identified through immunofluorescence staining in tissue samples of patients with confirmed checkpoint inhibitor-associated adverse events.

RESULTS

GZP PET imaging revealed differential uptake in organs affected by irAEs, such as colon, spleen, and kidney, which significantly diminished after administration of the immunosuppressor dexamethasone. The presence of granzyme B and immune infiltrates were confirmed histologically and correlated with significantly higher uptake in PET imaging. The presence of granzyme B was also confirmed in samples from patients that presented with clinical irAEs.

CONCLUSIONS

We demonstrate an interconnection between the establishment of irAEs and granzyme B presence and, for the first time, the visualization of those events through PET imaging.

Fundamentals of T Cell Metabolism and Strategies to Enhance Cancer Immunotherapy

Emerging reports show that metabolic pathways can be targeted to enhance T cell-mediated immunity to tumors. Yet, tumors consume key metabolites in the host to survive, thus robbing T cells of these nutrients to function and thrive. T cells are often deprived of basic building blocks for energy in the tumor, including glucose and amino acids needed to proliferate or produce cytotoxic molecules against tumors. Immunosuppressive molecules in the host further compromise the lytic capacity of T cells. Moreover, checkpoint receptors inhibit T cell responses by impairing their bioenergetic potential within tumors. In this review, we discuss the fundamental metabolic pathways involved in T cell activation, differentiation and response against tumors. We then address ways to target metabolic pathways to improve the next generation of immunotherapies for cancer patients.

HIV-specific T cell responses reflect substantive in vivo interactions with antigen despite long-term therapy

Antiretroviral therapies (ARTs) abrogate HIV replication; however, infection persists as long-lived reservoirs of infected cells with integrated proviruses, which reseed replication if ART is interrupted. A central tenet of our current understanding of this persistence is that infected cells are shielded from immune recognition and elimination through a lack of antigen expression from proviruses. Efforts to cure HIV infection have therefore focused on reactivating latent proviruses to enable immune-mediated clearance, but these have yet to succeed in reducing viral reservoirs. Here, we revisited the question of whether HIV reservoirs are predominately immunologically silent from a new angle: by querying the dynamics of HIV-specific T cell responses over long-term ART for evidence of ongoing recognition of HIV-infected cells. In longitudinal assessments, we show that the rates of change in persisting HIV Nef-specific responses, but not responses to other HIV gene products, were associated with residual frequencies of infected cells. These Nef-specific responses were highly stable over time and disproportionately exhibited a cytotoxic, effector functional profile, indicative of recent in vivo recognition of HIV antigens. These results indicate substantial visibility of the HIV-infected cells to T cells on stable ART, presenting both opportunities and challenges for the development of therapeutic approaches to curing infection.

CTL ELISPOT Assay and T Cell Detection

Enzyme-linked immune absorbent spot (Elispot) is a quantitative method for measuring relevant parameters of T-cell activation. The sensitivity of Elispot allows the detection of low-frequency antigen-specific T-cells that secrete cytokines and effector molecules, such as granzyme B and perforin. Cytotoxic T-cell (CTL) studies have taken advantage with this high-throughput technology by providing insights of quantity and immune kinetics. Accuracy, sensitivity, reproducibility, and robustness of Elispot resulted in a wide range of applications in research as well as in diagnostic field. Actually, CTL monitoring by Elispot is a gold standard for the evaluation of antigen-specific T-cell immunity in clinical trials and vaccine candidates where the ability to detect rare antigen-specific T-cells is of relevance for immune diagnostic. The most utilized Elispot assay is the Interferon-gamma (IFN-γ) test, a marker for CD8⁺ CTL activation, but Elispot can be also used to distinguish different subsets of activated T-cells by using other cytokines such as T-helper (Th) 1 type cells (characterized by the production of IFN-γ, IL-2, IL-6, IL-12, IL-21 and TNF-α), Th2 (producing cytokines like IL-4, IL-5, IL-10 and IL-13), and Th17 (IL-17) cells.The reliability of Elispot generated data, by the evaluation of T-cell frequency recognizing individual antigen/peptide, is the core of this method currently applied widely to investigate specific immune responses in cancer, infections, allergies, and autoimmune diseases. The Elispot Assay is competing with other methods measuring single-cell cytokine production, e.g., intracellular cytokine by FACS or Milteny cytokine secretion assay. Other types of lymphocyte frequency and function assays include limiting dilution assay (LDA), cytotoxic T-cell assay (CTL), and tetramer staining. Compared with respect to sensitivity the Elispot Assay is outranking other methods to define frequency of antigen-specific lymphocytes. The method described herein would like to offer helpful and clear protocols for researchers that apply Elispot. IFN-γ and Perforin Elispot assays will be described.

Modulating the Tumour Microenvironment by Intratumoural Injection of Pattern Recognition Receptor Agonists

Signalling through pattern recognition receptors (PRRs) leads to strong proinflammatory responses, enhancing the activity of antigen presenting cells and shaping adaptive immune responses against tumour associated antigens. Unfortunately, toxicities associated with systemic administration of these agonists have limited their clinical use to date. Direct injection of PRR agonists into the tumour can enhance immune responses by directly modulating the cells present in the tumour microenvironment. This can improve local antitumour activity, but importantly, also facilitates systemic responses that limit tumour growth at distant sites. As such, this form of therapy could be used clinically where metastatic tumour lesions are accessible, or as neoadjuvant therapy. In this review, we summarise current preclinical data on intratumoural administration of PRR agonists, including new strategies to optimise delivery and impact, and combination studies with current and promising new cancer therapies.

Glut1 expression is increased by p53 reduction to switch metabolism to glycolysis during osteoblast differentiation

The glycolytic system is selected for ATP synthesis not only in tumor cells but also in differentiated cells. Differentiated osteoblasts also switch the dominant metabolic pathway to aerobic glycolysis. We found that primary osteoblasts increased expressions of glycolysis-related enzymes such as Glut1, hexokinase 1 and 2, lactate dehydrogenase A and pyruvate kinase M2 during their differentiation. Osteoblast differentiation decreased expression of tumor suppressor p53, which negatively regulates Glut1 expression, and enhanced phosphorylation of AKT, which is regulated by phosphoinositol-3 kinase (PI3K). An inhibitor of PI3K enhanced p53 expression and repressed Glut1 expression. Luciferase reporter assay showed that p53 negatively regulated transcriptional activity of solute carrier family 2 member 1 gene promoter region. Inhibition of glycolysis in osteoblasts reduced ATP contents more significantly than inhibition of oxidative phosphorylation by carbonyl cyanide m-chlorophenyl hydrazine. These results have indicated that osteoblasts increase Glut1 expression through the down-regulation of p53 to switch their metabolic pathway to glycolysis during differentiation.

Cuprizone-induced demyelination triggers a CD8-pronounced T cell recruitment

The loss of myelinating oligodendrocytes is a key characteristic of many neurological diseases, including Multiple Sclerosis (MS). In progressive MS, where effective treatment options are limited, peripheral immune cells can be found at the site of demyelination and are suggested to play a functional role during disease progression. In this study, we hypothesize that metabolic oligodendrocyte injury, caused by feeding the copper chelator cuprizone, is a potent trigger for peripheral immune cell recruitment into the central nervous system (CNS). We used immunohistochemistry and flow cytometry to evaluate the composition, density, and activation status of infiltrating T lymphocytes in cuprizone-intoxicated mice and post-mortem progressive MS tissues. Our results demonstrate a predominance of CD8⁺ T cells along with high proliferation rates and cytotoxic granule expression, indicating an antigenic and pro-inflammatory milieu in the CNS of cuprizone-intoxicated mice. Numbers of recruited T cells and the composition of lymphocytic infiltrates in cuprizone-intoxicated mice were found to be comparable to those found in progressive MS lesions. Finally, amelioration of the cuprizone-induced pathology by treating mice with laquinimod significantly reduces the number of recruited T cells. Overall, this study provides strong evidence that toxic demyelination is a sufficient trigger for T cells to infiltrate the demyelinated CNS. Further investigation of the mode of action and functional consequence of T cell recruitment might offer promising new therapeutic approaches for progressive MS.

The Role of Granzyme B Containing Cells in the Progression of Chronic Obstructive Pulmonary Disease

Background

Lung inflammation plays a vital role in the pathogenesis of chronic obstructive pulmonary disease (COPD), but the characteristics of the inflammatory process remain unclear. There is growing interest in the role of granzyme B (GzmB) because CD8⁺ T cells can induce apoptosis of target cells by releasing GzmB, which in turn may cause tissue injury and remodeling. However, GzmB is also expressed by regulatory cells, which are able to suppress CD8⁺ T cell. The role of GzmB⁺ cells needs to be defined in COPD.

Methods

GzmB⁺ and CD8⁺ cells on alveolar wall of surgically resected lungs of microscopically classified 12 nonsmoking control, 12 panlobular emphysema (PLE) and 30 centrilobular emphysema (CLE) subjects were localized by immunohistochemical method. Positively stained cells on alveolar wall were counted and length of corresponding alveolar wall was measured. The results were expressed as mean number of positively stained cells per mm of alveolar wall in each subject.

Results

The number of GzmB⁺ and CD8⁺ cells on alveolar wall of CLE was greater than that of control or PLE subjects (p<0.05 and p<0.001, respectively). There was a positive relationship between the number of alveolar GzmB⁺ cells and forced expiratory volume in 1 second (FEV₁) (r=0.610, p=0.003) in CLE subjects. The number of alveolar GzmB⁺ cells progressively decreased with decline of FEV₁.

Conclusion

Our finding that number of alveolar GzmB⁺ cells was associated with FEV₁ suggests that GzmB⁺ cells might have protective role in the progression of lung destruction and airflow limitation in CLE, which is the predominant emphysema subtype of COPD.

Comprehensive analyses of immunodynamics and immunoreactivity in response to treatment in ALK-positive non-small-cell lung cancer

Background

EML4-ALK is a distinct molecular entity that is highly sensitive to ALK tyrosine kinase inhibitors (TKIs). Immune checkpoint inhibitors (ICIs) have not proved efficacy in ALK-positive non-small cell lung cancer so far. In this study, we performed a mouse clinical trial using EML4-ALK transgenic mice model to comprehensively investigate immunomodulatory effects of ALK TKI and to investigate the mechanisms of resistance to ICIs.

Methods

EML4-ALK transgenic mice were randomized to three treatment arms (arm A: antiprogrammed death cell protein-1 (PD-1), arm B: ceritinib, arm C: anti-PD-1 and ceritinib), and tumor response was evaluated using MRI. Progression-free survival and overall survival were measured to compare the efficacy. Flow cytometry, multispectral imaging, whole exome sequencing and RNA sequencing were performed from tumors obtained before and after drug resistance.

Results

Mouse clinical trial revealed that anti-PD-1 therapy was ineffective, and the efficacy of ceritinib and anti-PD-1 combination was not more effective than ceritinib alone in the first line. Dynamic changes in immune cells and cytokines were observed following each treatment, while changes in T lymphocytes were not prominent. A closer look at the tumor immune microenvironment before and after ceritinib resistance revealed increased regulatory T cells and programmed death-ligand 1 (PD-L1)-expressing cells both in the tumor and the stroma. Despite the increase of PD-L1 expression, these findings were not accompanied by increased effector T cells which mediate antitumor immune responses.

Conclusions

ALK-positive tumors progressing on ceritinib is not immunogenic enough to respond to immune checkpoint inhibitors.

Trial watch: IDO inhibitors in cancer therapy

Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes the first, rate-limiting step of the so-called “kynurenine pathway”, which converts the essential amino acid L-tryptophan (Trp) into the immunosuppressive metabolite L-kynurenine (Kyn). While expressed constitutively by some tissues, IDO1 can also be induced in specific subsets of antigen-presenting cells that ultimately favor the establishment of immune tolerance to tumor antigens. At least in part, the immunomodulatory functions of IDO1 can be explained by depletion of Trp and accumulation of Kyn and its derivatives. In animal tumor models, genetic or pharmacological IDO1 inhibition can cause the (re)activation of anticancer immune responses. Similarly, neoplasms expressing high levels of IDO1 may elude anticancer immunosurveillance. Therefore, IDO1 inhibitors represent promising therapeutic candidates for cancer therapy, and some of them have already entered clinical evaluation. Here, we summarize preclinical and clinical studies testing IDO1-targeting interventions for oncologic indications.

Trial watch: TLR3 agonists in cancer therapy

Toll-like receptor 3 (TLR3) is a pattern recognition receptor that senses exogenous (viral) as well as endogenous (mammalian) double-stranded RNA in endosomes. On activation, TLR3 initiates a signal transduction pathway that culminates with the secretion of pro-inflammatory cytokines including type I interferon (IFN). The latter is essential not only for innate immune responses to infection but also for the initiation of antigen-specific immunity against viruses and malignant cells. These aspects of TLR3 biology have supported the development of various agonists for use as stand-alone agents or combined with other therapeutic modalities in cancer patients. Here, we review recent preclinical and clinical advances in the development of TLR3 agonists for oncological disorders.

Abbreviations

cDC, conventional dendritic cell; CMT, cytokine modulating treatment; CRC, colorectal carcinoma; CTL, cytotoxic T lymphocyte; DC, dendritic cell; dsRNA, double-stranded RNA; FLT3LG, fms-related receptor tyrosine kinase 3 ligand; HNSCC, head and neck squamous cell carcinoma; IFN, interferon; IL, interleukin; ISV, in situ vaccine; MUC1, mucin 1, cell surface associated; PD-1, programmed cell death 1; PD-L1, programmed death-ligand 1; polyA:U, polyadenylic:polyuridylic acid; polyI:C, polyriboinosinic:polyribocytidylic acid; TLR, Toll-like receptor.

Clinical efficacy and biomarker analysis of neoadjuvant atezolizumab in operable urothelial carcinoma in the ABACUS trial

Antibodies targeting PD-1 or its ligand 1 PD-L1 such as atezolizumab, have great efficacy in a proportion of metastatic urothelial cancers^1,2. Biomarkers may facilitate identification of these responding tumors³. Neoadjuvant use of these agents is associated with pathological complete response in a spectrum of tumors, including urothelial cancer^4-7. Sequential tissue sampling from these studies allowed for detailed on-treatment biomarker analysis. Here, we present a single-arm phase 2 study, investigating two cycles of atezolizumab before cystectomy in 95 patients with muscle-invasive urothelial cancer (ClinicalTrials.gov identifier: NCT02662309). Pathological complete response was the primary endpoint. Secondary endpoints focused on safety, relapse-free survival and biomarker analysis. The pathological complete response rate was 31% (95% confidence interval: 21-41%), achieving the primary efficacy endpoint. Baseline biomarkers showed that the presence of preexisting activated T cells was more prominent than expected and correlated with outcome. Other established biomarkers, such as tumor mutational burden, did not predict outcome, differentiating this from the metastatic setting. Dynamic changes to gene expression signatures and protein biomarkers occurred with therapy, whereas changes in DNA alterations with treatment were uncommon. Responding tumors showed predominant expression of genes related to tissue repair after treatment, making tumor biomarker interpretation challenging in this group. Stromal factors such as transforming growth factor-β and fibroblast activation protein were linked to resistance, as was high expression of cell cycle gene signatures after treatment.

Natural T cell autoreactivity to melanoma antigens: clonally expanded melanoma-antigen specific CD8 + memory T cells can be detected in healthy humans

We used four-color ImmunoSpot® assays, in conjunction with peptide pools that cover the sequence of tyrosinase (Tyr), melanoma-associated antigen A3 (MAGE-A3), melanocyte antigen/melanoma antigen recognized by T cells 1 (Melan-A/MART-1), glycoprotein 100 (gp100), and New York esophageal squamous cell carcinoma-1 (NY-ESO-1) to characterize the melanoma antigen (MA)-specific CD8 + cell repertoire in PBMC of 40 healthy human donors (HD). Tyr triggered interferon gamma (IFN-γ)-secreting CD8 + T cells in 25% of HD within 24 h of antigen stimulation ex vivo. MAGE-A3, Melan-A/MART-1, and gp100 also induced recall responses in 10%, 7.5%, and 2.5% of HD, respectively. At this time point, these CD8 + T cells did not yet produce GzB (granzyme B). However, they engaged in GzB production after 72 h of antigen stimulation. By this 72-h time point, 57.5% of the HD responded to at least one, and typically several, of the MA. A closer characterization of the Tyr-specific CD8 + T cell repertoire indicated that it was low-affinity, and to primarily entail a stem cell-like subpopulation. Collectively, our data reveal pre-existing endogenous T cell immunity against melanoma antigens in healthy donors, and analogous to natural autoantibodies, we have termed this "natural T cell autoreactivity".

Soluble markers of neutrophil, T-cell and monocyte activation are associated with disease severity and parasitemia in falciparum malaria

Background

The immune response during P. falciparum infection is a two-edged sword, involving dysregulation of the inflammatory responses with several types of immune cells participating. Here we examined T-cell, monocyte/macrophage and neutrophil activation during P. falciparum infection by using soluble activation markers for these leukocyte subsets.

Methods

In a prospective cross-sectional study clinical data and blood samples were collected from adults in Mozambique with P. falciparum infection, with (n = 70) and without (n = 61) co-infection with HIV-1, as well as HIV-infected patients with similar symptoms but without malaria (n = 58) and healthy controls (n = 52). Soluble (s)CD25, sCD14, sCD163 and myeloperoxidase (MPO) as markers for T-cell, monocyte/macrophage and neutrophil activation, respectively as well as CX3CL1, granzyme B and TIM-3 as markers of T-cell subsets and T-cell exhaustion, were analyzed.

Results

All patient groups had raised levels of activation markers compared with healthy controls. Levels of sCD25 and MPO increased gradually from patient with HIV only to patient with malaria only, with the highest levels in the HIV/malaria group. In the malaria group as a whole, MPO, sCD14 and in particular sCD25 were correlated with disease severity. sCD163, sCD25 and in particular MPO correlated with the degree of parasitemia as assessed by qPCR. Patients with falciparum malaria also had signs of T-cell subset activation (i.e. increased granzyme B and CX3CL1) and T-cell exhaustion as assessed by high levels of TIM-3 particularly in patients co-infected with HIV.

Conclusion

Our data support a marked immune activation in falciparum malaria involving all major leukocyte subsets with particular enhanced activation of neutrophils and T-cells in patients co-infected with HIV. Our findings also support a link between immune activation and immune exhaustion during falciparum malaria, particularly in relation to T-cell responses in patients co-infected with HIV.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3593-8) contains supplementary material, which is available to authorized users.

PD-L1 immunostaining scoring for non-small cell lung cancer based on immunosurveillance parameters

Non-Small Cell Lung Cancer (NSCLC) is the leading cause of cancer death globally, and new immunotherapies developed and under development targeting PD-1/PD-L1 checkpoint inhibition require accurate patient selection to assure good clinical outcome. PD-L1 immunohistochemistry is the current biomarker assay used for patient selection, but still imprecise in predicting therapy response. Exploring this issue, we performed computational tissue analysis of PD-L1 immunostaining in procured NSCLC tissues (n = 50) using the Merck KGaA anti-PD-L1 clone MKP1A07310. Staining patterns and PD-L1 cut-off points were interrogated using relevant cancer immune-surveillance biomarkers. Groups with high PD-L1 expression levels (above 25/50% staining cut-off points) were enriched for a biomarker profile in the tumor-nest and microenvironment indicating escape from host-immunity, as represented by increased numbers of cells positive for CD8 and Granzyme B (immune-effectors), FOXP3 (immune-suppressive), and CD68 (P < 0.05). Manual analysis of PD-L1 staining patterns identified tumors with an immune-induced reactive pattern relevant for immunotherapy that would ordinarily be excluded by the arbitrary 25% staining threshold (P < 0.05). Conversely, some cases with completely or predominantly immune-independent constitutive PD-L1 staining patterns that indicate insensitivity to immunotherapy may have been incorrectly selected using this staining cut-off point criterion. Therefore, we propose differentiation of reactive vs constitutive PD-L1 staining patterns to improve the accuracy of this biomarker assay in selecting NSCLC patients for PD-1/PD-L1 immunotherapy.

Direct Detection of T- and B-Memory Lymphocytes by ImmunoSpot® Assays Reveals HCMV Exposure that Serum Antibodies Fail to Identify

It is essential to identify donors who have not been infected with human cytomegalovirus (HCMV) in order to avoid transmission of HCMV to recipients of blood transfusions or organ transplants. In the present study, we tested the reliability of seronegativity as an indicator for the lack of HCMV exposure in healthy human blood donors. Eighty-two HCMV seronegative individuals were identified, and their peripheral blood mononuclear cells (PBMC) were tested in ImmunoSpot® assays for the presence of HCMV-specific T- and B-memory lymphocytes. Eighty-two percent (67 of 82) of these HCMV seronegative individuals featured at least one memory cell that was lineage specific for HCMV, with the majority of these subjects possessing CD4+ and CD8+ T cells, as well as B cells, providing three independent lines of evidence for having developed immunity to HCMV. Only 15 of these 82 donors (18%) showed neither T- nor B-cell memory to HCMV, consistent with immunological naïveté to the virus. The data suggest that measurements of serum antibodies frequently fail to reveal HCMV exposure in humans, which may be better identified by direct detection of HCMV-specific memory lymphocytes.

Four Color ImmunoSpot® Assays for Identification of Effector T-Cell Lineages

Single color IFN-γ ELISPOT assays have evolved as a highly sensitive T cell immune monitoring platform. By detecting individual T cells that secrete IFN-γ in response to antigen exposure, these assays permit the measurement of the frequency of antigen-specific T cells among white blood cells. These assays therefore are well suited to assess clonal expansions, that is, whether a (Th1) T cell response has been induced to an antigen in a test subject. Single color IFN-γ ELISPOT assays are not suited, however, to provide information on the Th2/Th17 quality of the T cell response, nor do they provide insights into the differentiation state of CD8 cells. Recently it has been established that co-expression profiles of IL-2, TNF-α, and granzyme B along with IFN-γ permit to identify CD8 cell subpopulations. Naïve CD8 cells, central CD8 memory cells, CD8 terminal effector cells, polyfunctional CD8 cells, stem-cell like CD8 memory cells, dysfunctional- and senescent CD8 cells all differ in the extent they produce these molecules upon antigen re-encounter. We therefore have developed, and introduce here, a four color T cell ELISPOT assay in which the co-expression levels of IFN-γ, IL-2, TNF-α, and granzyme B can be established for individual antigen-specific CD8 cells, thereby identifying the activation/differentiation state of these cells.

Multiplexing T- and B-Cell FLUOROSPOT Assays: Experimental Validation of the Multi-Color ImmunoSpot® Software Based on Center of Mass Distance Algorithm

Over the past decade, ELISPOT has become a highly implemented mainstream assay in immunological research, immune monitoring, and vaccine development. Unique single cell resolution along with high throughput potential sets ELISPOT apart from flow cytometry, ELISA, microarray- and bead-based multiplex assays. The necessity to unambiguously identify individual T and B cells that do, or do not co-express certain analytes, including polyfunctional cytokine producing T cells has stimulated the development of multi-color ELISPOT assays. The success of these assays has also been driven by limited sample/cell availability and resource constraints with reagents and labor. There are few commercially available test kits and instruments available at present for multi-color FLUOROSPOT. Beyond commercial descriptions of competing systems, little is known about their accuracy in experimental settings detecting individual cells that secrete multiple analytes vs. random overlays of spots. Here, we present a theoretical and experimental validation study for three and four color T- and B-cell FLUOROSPOT data analysis. The ImmunoSpot^® Fluoro-X™ analysis system we used includes an automatic image acquisition unit that generates individual color images free of spectral overlaps and multi-color spot counting software based on the maximal allowed distance between centers of spots of different colors or Center of Mass Distance (COMD). Using four color B-cell FLUOROSPOT for IgM, IgA, IgG1, IgG3; and three/four color T-cell FLUOROSPOT for IL-2, IFN-γ, TNF-α, and GzB, in serial dilution experiments, we demonstrate the validity and accuracy of Fluoro-X™ multi-color spot counting algorithms. Statistical predictions based on the Poisson spatial distribution, coupled with scrambled image counting, permit objective correction of true multi-color spot counts to exclude randomly overlaid spots.

Impact of Aging and Cytomegalovirus on Immunological Response to Influenza Vaccination and Infection

The number of people over the age of 60 is expected to double by 2050 according to the WHO. This emphasizes the need to ensure optimized resilience to health stressors in late life. In older adults, influenza is one of the leading causes of catastrophic disability (defined as the loss of independence in daily living and self-care activities). Influenza vaccination is generally perceived to be less protective in older adults, with some studies suggesting that the humoral immune response to the vaccine is further impaired in cytomegalovirus (CMV)-seropositive older people. CMV is a β-herpes virus infection that is generally asymptomatic in healthy individuals. The majority of older adults possess serum antibodies against the virus indicating latent infection. Age-related changes in T-cell-mediated immunity are augmented by CMV infection and may be associated with more serious complications of influenza infection. This review focuses on the impact of aging and CMV on immune cell function, the response to influenza infection and vaccination, and how the current understanding of aging and CMV can be used to design a more effective influenza vaccine for older adults. It is anticipated that efforts in this field will address the public health need for improved protection against influenza in older adults, particularly with regard to the serious complications leading to loss of independence.

Nuclear PKC-θ facilitates rapid transcriptional responses in human memory CD4+ T cells through p65 and H2B phosphorylation

Memory T cells are characterized by their rapid transcriptional programs upon re-stimulation. This transcriptional memory response is facilitated by permissive chromatin, but exactly how the permissive epigenetic landscape in memory T cells integrates incoming stimulatory signals remains poorly understood. By genome-wide ChIP-sequencing ex vivo human CD4⁺ T cells, here, we show that the signaling enzyme, protein kinase C theta (PKC-θ) directly relays stimulatory signals to chromatin by binding to transcriptional-memory-responsive genes to induce transcriptional activation. Flanked by permissive histone modifications, these PKC-enriched regions are significantly enriched with NF-κB motifs in ex vivo bulk and vaccinia-responsive human memory CD4⁺ T cells. Within the nucleus, PKC-θ catalytic activity maintains the Ser536 phosphorylation on the p65 subunit of NF-κB (also known as RelA) and can directly influence chromatin accessibility at transcriptional memory genes by regulating H2B deposition through Ser32 phosphorylation. Furthermore, using a cytoplasm-restricted PKC-θ mutant, we highlight that chromatin-anchored PKC-θ integrates activating signals at the chromatin template to elicit transcriptional memory responses in human memory T cells.

Summary: Memory T cells have a rapid transcriptional program upon re-stimulation. Chromatin-anchored PKC-θ integrates activating signals at the chromatin template to elicit this transcriptional memory in T cells.

Cellular Interferon Gamma and Granzyme B Responses to Cytomegalovirus-pp65 and Influenza N1 Are Positively Associated in Elderly

Morbidity and mortality in the elderly are associated with viral infections, including influenza and cytomegalovirus (CMV). With increasing age, cellular immunity gains importance in protection to influenza, but latent CMV is highly prevalent and associated with immune dysfunction. An insight into the association between immunity against influenza and CMV adds to the understanding of healthy aging. Here we first aimed to measure influenza-specific cellular immunity using granzyme B (GrzB) and interferon-gamma (IFN-γ)-ELISpot. Next, influenza-specific cellular immunity was associated with humoral and cellular CMV-specific immunity in healthy 65+ elderly. Vaccine trial participants gave additional blood samples 3 weeks after receiving a H1N1 containing vaccine. CMV serology was determined and peripheral blood mononuclear cells were stimulated with influenza N1 or CMV pp65-derived peptide pools for 7 days and rechallenged to assess antigen-specific GgrzB and IFN-γ responses using ELISpot assays. Results were compared using chi-square and correlation analysis. Eighty-three individuals (60% men, 65% CMV IgG+, age range 65-78y) participated. We found significant positive associations between IFN-γ and GrzB responses to both influenza and CMV, but also between a positive CMV serostatus and an influenza N1-specific activation marker response (p = 0.013). CMV pp65 responses were detected in CMV IgG+ individuals, but remarkably also in CMV IgG- individuals (27%). In this study, following influenza vaccination, elderly with cellular immunity against CMV were more likely to have cellular immunity against influenza vaccine N1 antigen. These findings stress the need to continue exploring the possible role of CMV in immunosenescence.

Low intratumoral regulatory T cells and high peritumoral CD8(+) T cells relate to long-term survival in patients with pancreatic ductal adenocarcinoma after pancreatectomy

The prognosis for pancreatic ductal adenocarcinoma (PDAC) remains extremely poor. Recent studies have focused on the role of lymphocytes in the PDAC microenvironment. Using immunohistochemistry, our study explored the clinical significance of intratumoral or peritumoral CD4(+)Foxp3(+) regulatory T cells (Tregs) and CD8(+) T cells in the tumor microenvironment and analyzed their relation to the prognosis of PDAC in a consecutive series of 92 patients after resection. CD8(+) T cells were more frequently seen within peritumoral sites, while CD4(+)Foxp3(+) Tregs were more frequent within intratumoral areas. Neither exhibited any relationship with other clinicopathologic factors. Patients with low levels of intratumoral Tregs had longer disease-free survival than those with higher levels (DFS 22.2 vs. 11.2 months, p < 0.001), and patients with higher levels of peritumoral CD8(+) T cells had longer overall survival than those with lower levels (OS 31.0 vs. 14.2 months, p < 0.001). Multivariate analysis demonstrated that intratumoral Tregs (hazard ratio, HR 3.39, p = 0.010) and peritumoral CD8(+) T cells (HR 0.10, p < 0.001) are related to DFS and OS, respectively. These results indicate that intratumoral Tregs are a negative predictor of DFS, while peritumoral CD8(+) T cells are a positive predictor of OS for PDAC patients with pancreatectomy.

ELISPOT Assays in 384-Well Format: Up to 30 Data Points with One Million Cells

Comprehensive immune monitoring requires that frequencies of T cells, producing different cytokines, are measured to establish the magnitude of Th1, Th2, and Th17 components of cell-mediated immunity. Antigen titration provides additional information about the affinity of T cell response. In tumor immunity, it is also advisable to account for determinant spreading by testing multiple epitopes. Efforts for comprehensive immune monitoring would require substantial numbers of PBMC to run the above tests systematically, which in most test cases is limiting. Immune monitoring with ELISPOT assays have been performed, thus far, in a 96-well format. In this study we show that one can increase cell utilization by performing the assay in 384-well plates whose membrane surface area is one third that of 96-well plates. Systematic testing of PBMC for antigen-specific T cell response in the two formats demonstrated that the 384-well assay corresponds to a one-in-three miniaturization of the 96-well assay. The lowest number of cells that can be used in the 384-well format, while allowing for sufficient contact with APC, is 33,000 PBMC/well. Therefore, with one million PBMC typically obtained from 1 mL of blood, a 30 well T cell ELISPOT assay can be performed in a 384-well format.

ELISPOTs Produced by CD8 and CD4 Cells Follow Log Normal Size Distribution Permitting Objective Counting

Each positive well in ELISPOT assays contains spots of variable sizes that can range from tens of micrometers up to a millimeter in diameter. Therefore, when it comes to counting these spots the decision on setting the lower and the upper spot size thresholds to discriminate between non-specific background noise, spots produced by individual T cells, and spots formed by T cell clusters is critical. If the spot sizes follow a known statistical distribution, precise predictions on minimal and maximal spot sizes, belonging to a given T cell population, can be made. We studied the size distributional properties of IFN-γ, IL-2, IL-4, IL-5 and IL-17 spots elicited in ELISPOT assays with PBMC from 172 healthy donors, upon stimulation with 32 individual viral peptides representing defined HLA Class I-restricted epitopes for CD8 cells, and with protein antigens of CMV and EBV activating CD4 cells. A total of 334 CD8 and 80 CD4 positive T cell responses were analyzed. In 99.7% of the test cases, spot size distributions followed Log Normal function. These data formally demonstrate that it is possible to establish objective, statistically validated parameters for counting T cell ELISPOTs.

High Reproducibility of ELISPOT Counts from Nine Different Laboratories

The primary goal of immune monitoring with ELISPOT is to measure the number of T cells, specific for any antigen, accurately and reproducibly between different laboratories. In ELISPOT assays, antigen-specific T cells secrete cytokines, forming spots of different sizes on a membrane with variable background intensities. Due to the subjective nature of judging maximal and minimal spot sizes, different investigators come up with different numbers. This study aims to determine whether statistics-based, automated size-gating can harmonize the number of spot counts calculated between different laboratories. We plated PBMC at four different concentrations, 24 replicates each, in an IFN-γ ELISPOT assay with HCMV pp65 antigen. The ELISPOT plate, and an image file of the plate was counted in nine different laboratories using ImmunoSpot® Analyzers by (A) Basic Count™ relying on subjective counting parameters set by the respective investigators and (B) SmartCount™, an automated counting protocol by the ImmunoSpot® Software that uses statistics-based spot size auto-gating with spot intensity auto-thresholding. The average coefficient of variation (CV) for the mean values between independent laboratories was 26.7% when counting with Basic Count™, and 6.7% when counting with SmartCount™. Our data indicates that SmartCount™ allows harmonization of counting ELISPOT results between different laboratories and investigators.

CTL ELISPOT assay

Enzyme-linked immune absorbent spot (Elispot) is a quantitative method for measuring relevant parameters of T cell activation. The sensitivity of Elispot allows the detection of low-frequency antigen-specific T cells that secrete cytokines and effector molecules, such as granzyme B and perforin. Cytotoxic T cell (CTL) studies have taken advantage with this high-throughput technology by providing insights into quantity and immune kinetics. Accuracy, sensitivity, reproducibility, and robustness of Elispot resulted in a wide range of applications in research as well as in diagnostic field. Actually, CTL monitoring by Elispot is a gold standard for the evaluation of antigen-specific T cell immunity in clinical trials and vaccine candidates where the ability to detect rare antigen-specific T cells is of relevance for immune diagnostic. The most utilized Elispot assay is the interferon-gamma (IFN-γ) test, a marker for CD8(+) CTL activation, but Elispot can also be used to distinguish different subsets of activated T cells by using other cytokines such as T-helper (Th) 1-type cells (characterized by the production of IFN-γ, IL-2, IL-6, IL-12, IL-21, and TNF-α), Th2 (producing cytokines like IL-4, IL-5, IL-10, and IL-13), and Th17 (IL-17) cells. The reliability of Elispot-generated data, by the evaluation of T cell frequency recognizing individual antigen/peptide, is the core of this method currently applied widely to investigate specific immune responses in cancer, infections, allergies, and autoimmune diseases. The Elispot assay is competing with other methods measuring single-cell cytokine production, e.g., intracellular cytokine by FACS or Miltenyi cytokine secretion assay. Other types of lymphocyte frequency and function assays include limiting dilution assay (LDA), cytotoxic T cell assay (CTL), and tetramer staining. Compared with respect to sensitivity the Elispot assay is outranking other methods to define frequency of antigen-specific lymphocytes. The method described herein would like to offer helpful and clear protocols for researchers that apply Elispot. IFN-γ and perforin Elispot assays are described.

Memory CD8(+) T cells elicited by HIV-1 lipopeptide vaccines display similar phenotypic profiles but differences in term of magnitude and multifunctionality compared with FLU- or EBV-specific memory T cells in humans

Differentiation marker, multifunctionality and magnitude analyses of specific-CD8(+) memory T cells are crucial to improve development of HIV vaccines designed to generate cell-mediated immunity. Therefore, we fully characterized the HIV-specific CD8(+) T cell responses induced in volunteers vaccinated with HIV lipopeptide vaccines for phenotypic markers, tetramer staining, cytokine secretion, and cytotoxic activities. The frequency of ex vivo CD8(+) T cells elicited by lipopeptide vaccines is very rare and central-memory phenotype and functions of these cells were been shown to be important in AIDS immunity. So, we expanded them using specific peptides to compare the memory T cell responses induced in volunteers by HIV vaccines with responses to influenza (FLU) or Epstein Barr virus (EBV). By analyzing the differentiation state of IFN-γ-secreting CD8(+) T cells, we found a CCR7(-)CD45RA(-)CD28(+int)/CD28(-) profile (>85%) belonging to a subset of intermediate-differentiated effector T cells for HIV, FLU, and EBV. We then assessed the quality of the response by measuring various T cell functions. The percentage of single IFN-γ T cell producers in response to HIV was 62% of the total of secreting T cells compared with 35% for FLU and EBV, dual and triple (IFN-γ/IL-2/CD107a) T cell producers could also be detected but at lower levels (8% compared with 37%). Finally, HIV-specific T cells secreted IFN-γ and TNF-α, but not the dual combination like FLU- and EBV-specific T cells. Thus, we found that the functional profile and magnitude of expanded HIV-specific CD8(+) T precursors were more limited than those of to FLU- and EBV-specific CD8(+) T cells. These data show that CD8(+) T cells induced by these HIV vaccines have a similar differentiation profile to FLU and EBV CD8(+) T cells, but that the vaccine potency to induce multifunctional T cells needs to be increased in order to improve vaccination strategies.

Resting of Cryopreserved PBMC Does Not Generally Benefit the Performance of Antigen-Specific T Cell ELISPOT Assays

T cell monitoring is increasingly performed using cryopreserved PBMC. It has been suggested that resting of PBMC after thawing, that is, culturing them overnight in test medium, produces higher antigen-induced spot counts in ELISPOT assays. To evaluate the importance of overnight resting, we systematically tested cryopreserved PBMC from 25 healthy donors. CEF peptides (comprising CMV, EBV and flu antigens) were used to stimulate CD8 cells and mumps antigen to stimulate CD4 cells. The data show that resting significantly increased antigen-elicited T cell responses only for CEF high responder PBMC. The maximal gain observed was doubling of spot counts. For CEF low responders, and for mumps responders of either low- or high reactivity levels, resting had no statistically significant effect on the observed spot counts. Therefore, resting is not a generally applicable approach to improve ELISPOT assay performance, but can be recommended only for clinical subject cohorts and antigens for which it has a proven benefit. Because resting invariably leads to losing about half of the PBMC available for testing, and because doubling the PBMC numbers plated into the assay reliably doubles the antigen-induced spot counts, we suggest the latter approach as a simple and reliable alternative to resting for enhancing the performance of ELISPOT assays. Our data imply that resting is not required if PBMC were cryopreserved and thawed under conditions that minimize apoptosis of the cells. Therefore, this study should draw attention to the need to optimize freezing and thawing conditions for successful T cell work.

Cytomegalovirus (CMV)-Specific Perforin and Granzyme B ELISPOT Assays Detect Reactivation of CMV Infection in Inflammatory Bowel Disease

The role of cytomegalovirus (CMV) infection in the pathogenesis and exacerbation of Inflammatory Bowel Disease (IBD) has been unresolved. Typically, the CMV genome remains dormant in infected cells, but a breakdown of immune surveillance can lead to re-activation of viral replication in the gut mucosa, which is not necessarily associated with viremia or changes in antibody titers. We hypothesized that the detection of CMV-specific CD8 effector T cells should permit the distinction between dormant and active CMV infection. As CD8 effector T cells, unlike memory CD8 T cells, have perforin (PFN) and granzyme B (GzB) preformed in their cytoplasmic granules, we employed single cell resolution ELISPOT assays to measure the CMV antigen-triggered release of these molecules by CD8 T cells isolated from subjects with IBD, and age-matched healthy controls. The frequencies of CMV-specific (GzB) and PFN-producing CD8 T cells were increased in IBD patients compared to healthy controls. Furthermore, the increased CMV reactivity was associated with active IBD disease and with longer disease duration. Notably, PCR on serum frequently failed to detect CMV DNA during flares. The data show that during active IBD there is a flare of CD8 T cell activity against CMV in a substantial proportion of IBD patients, suggesting CMV reactivation that serum PCR does not detect. While it remains open whether CMV reactivation is a cause or consequence of IBD, our data suggest that monitoring CMV antigen-specific effector CD8 T cells with GzB and PFN ELISPOT analysis can provide novel insights into the role of CMV infection in IBD. Additionally, our data have implications for the fields of transplantation, HIV, cancer, and autoimmune diseases, in all of which patient care critically depends on sensitive and reliable detection of a reactivation of CMV infection.

Immunodominance: a pivotal principle in host response to viral infections

We encounter pathogens on a daily basis and our immune system has evolved to mount an immune response following an infection. An interesting phenomenon that has evolved in response to clearing bacterial and viral infections is called immunodominance. Immunodominance refers to the phenomenon that, despite co-expression of multiple major histocompatibility complex class I alleles by host cells and the potential generation of hundreds of distinct antigenic peptides for recognition following an infection, a large portion of the anti-viral cytotoxic T lymphocyte population targets only some peptide/MHC class I complexes. Here we review the main factors contributing to immunodominance in relation to influenza A and HIV infection. Of special interest are the factors contributing to immunodominance in humans and rodents following influenza A infection. By critically reviewing these findings, we hope to improve understanding of the challenges facing the discovery of new factors enabling better anti-viral vaccine strategies in the future.

Objective, user-independent ELISPOT data analysis based on scientifically validated principles

ELISPOT results used to be evaluated visually which, however, is inevitably subjective, inaccurate, and cumbersome. Even when applying automated image analysis to this end, the results are highly variable if the counting parameters are set subjectively. Since objective, accurate, and reproducible measurements are fundamental to science, major efforts have been undertaken over the last decade at CTL to understand the scientific principles behind ELISPOT data and to develop "intelligent" image analysis algorithms based on these principles. Thus, a spot recognition and gating algorithm was developed to automatically recognize the signatures of defined cell populations, such as T cells, discerning them from irrelevant cell types and noise. In this way, the science of ELISPOT data analysis has been introduced, permitting exact frequency measurement against background. As ELISPOT assays become a gold standard for monitoring antigen-specific T-cell immunity in clinical trials, the need has surfaced to make ELISPOT data transparent, reproducible, and tamper-proof, complying with Good Laboratory Practice (GLP) and Code for Federal Regulations (CFR) Part 11 guidelines. Flow cytometry-based and other immune monitoring assay platforms face the same challenge. In this chapter, we provide an overview of how CTL's ImmunoSpot(®) platform for ELISPOT data analysis, management, and documentation meets these challenges.

Statistical analysis of ELISPOT assays

Cytokine ELISPOT assays have emerged as a powerful tool for the detection of rare antigen-specific T cells in freshly isolated cell material, such as blood. While ELISPOT assays allow one to directly visualize and count extremely low frequencies of cytokine-secreting T cells among millions of nonsecreting bystander cells, the interpretation of ELISPOT data can become ambiguous when (a) spot numbers in antigen-containing wells are low, (b) spot counts in negative control wells are elevated, and particularly (c) when both of the above occur simultaneously. Thus, the primary task, even before statistics are employed, must be the optimization of the basic assay parameters and reagents such that the assay yields low background signal in the negative-control wells and the maximal number of antigen-induced spots in test wells, i.e., the signal-to-noise ratio is maximized. Furthermore, the use of proper spot-size gating parameters for data analysis is indispensable for screening out irrelevant background spots, and thus increasing the signal-to-noise ratio. The goal of most ELISPOT experiments is to identify positive T-cell responses as defined by a significantly elevated spot count in antigen-stimulated wells over the nonstimulated medium-control or negative-control antigen. In this chapter, we conclude that - with some limitations - the T-Test and related statistical methods which rely on the assumption of normal distribution are suitable for identifying positive ELISPOT results.

Autologous mesenchymal stromal cells and kidney transplantation: a pilot study of safety and clinical feasibility

BACKGROUND AND OBJECTIVES

Mesenchymal stromal cells (MSCs) abrogate alloimmune response in vitro, suggesting a novel cell-based approach in transplantation. Moving this concept toward clinical application in organ transplantation should be critically assessed.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

A safety and clinical feasibility study (ClinicalTrials.gov, NCT00752479) of autologous MSC infusion was conducted in two recipients of kidneys from living-related donors. Patients were given T cell-depleting induction therapy and maintenance immunosuppression with cyclosporine and mycophenolate mofetil. On day 7 posttransplant, MSCs were administered intravenously. Clinical and immunomonitoring of MSC-treated patients was performed up to day 360 postsurgery.

RESULTS

Serum creatinine levels increased 7 to 14 days after cell infusion in both MSC-treated patients. A graft biopsy in patient 2 excluded acute graft rejection, but showed a focal inflammatory infiltrate, mostly granulocytes. In patient 1 protocol biopsy at 1-year posttransplant showed a normal graft. Both MSC-treated patients are in good health with stable graft function. A progressive increase of the percentage of CD4+CD25highFoxP3+CD127- Treg and a marked inhibition of memory CD45RO+RA-CD8+ T cell expansion were observed posttransplant. Patient T cells showed a profound reduction of CD8+ T cell activity.

CONCLUSIONS

Findings from this study in the two patients show that MSC infusion in kidney transplant recipients is feasible, allows enlargement of Treg in the peripheral blood, and controls memory CD8+ T cell function. Future clinical trials with MSCs to look with the greatest care for unwanted side effects is advised.

In vitro stimulation of human influenza-specific CD8+ T cells by dendritic cells pulsed with an influenza virus-like particle (VLP) vaccine

The purpose of this in vitro study was to determine if a virus-like particle (VLP) influenza vaccine stimulated human CD8(+) T cells in a dendritic cell (DC): T cell co-culture system. VLP-pulsed DCs were co-cultured with autologous CD8(+) T cells from five donors. Functional CD8(+) T cells were detected via cell surface and intracellular cytokine staining. T cells from four of the five donors showed >or=2-fold increase over background in the % activated CD8(+) cells. These results indicate that the influenza VLP vaccine can stimulate CD8(+) T cells via DC antigen presentation, likely through the MHC-I pathway, thus broadening the immunological response induced by this promising influenza vaccine.