LFA-1 activation enriches tumor-specific T cells in a cold tumor model and synergizes with CTLA-4 blockade.

The inability of CD8+ effector T cells (Teffs) to reach tumor cells is an important aspect of tumor resistance to cancer immunotherapy. The recruitment of these cells to the tumor microenvironment (TME) is regulated by integrins, a family of adhesion molecules that are expressed on T cells. Here, we show that 7HP349, a small-molecule activator of lymphocyte function-associated antigen-1 (LFA-1) and very late activation antigen-4 (VLA-4) integrin cell-adhesion receptors, facilitated the preferential localization of tumor-specific T cells to the tumor and improved antitumor response. 7HP349 monotherapy had modest effects on anti-programmed death 1-resistant (anti-PD-1-resistant) tumors, whereas combinatorial treatment with anti-cytotoxic T lymphocyte-associated protein 4 (anti-CTLA-4) increased CD8+ Teff intratumoral sequestration and synergized in cooperation with neutrophils in inducing cancer regression. 7HP349 intratumoral CD8+ Teff enrichment activity depended on CXCL12. We analyzed gene expression profiles using RNA from baseline and on treatment tumor samples of 14 melanoma patients. We identified baseline CXCL12 gene expression as possibly improving the likelihood or response to anti-CTLA-4 therapies. Our results provide a proof-of-principle demonstration that LFA-1 activation could convert a T cell-exclusionary TME to a T cell-enriched TME through mechanisms involving cooperation with innate immune cells.

Interleukin-6 blockade abrogates immunotherapy toxicity and promotes tumor immunity.

Immune checkpoint blockade (ICB) therapy frequently induces immune-related adverse events. To elucidate the underlying immunobiology, we performed a deep immune analysis of intestinal, colitis, and tumor tissue from ICB-treated patients with parallel studies in preclinical models. Expression of interleukin-6 (IL-6), neutrophil, and chemotactic markers was higher in colitis than in normal intestinal tissue; T helper 17 (Th17) cells were more prevalent in immune-related enterocolitis (irEC) than T helper 1 (Th1). Anti-cytotoxic T-lymphocyte-associated antigen 4 (anti-CTLA-4) induced stronger Th17 memory in colitis than anti-program death 1 (anti-PD-1). In murine models, IL-6 blockade associated with improved tumor control and a higher density of CD4+/CD8+ effector T cells, with reduced Th17, macrophages, and myeloid cells. In an experimental autoimmune encephalomyelitis (EAE) model with tumors, combined IL-6 blockade and ICB enhanced tumor rejection while simultaneously mitigating EAE symptoms versus ICB alone. IL-6 blockade with ICB could de-couple autoimmunity from antitumor immunity.

Tox2 is required for the maintenance of GC TFH cells and the generation of memory TFH cells.

Memory T follicular helper (TFH) cells play an essential role to induce secondary antibody response by providing help to memory and naïve B cells. Here, we show that the transcription factor Tox2 is vital for the maintenance of TFH cells in germinal centers (GCs) and the generation of memory TFH cells. High Tox2 expression was almost exclusive to GC TFH cells among human tonsillar and blood CD4+ T cell subsets. Tox2 overexpression maintained the expression of TFH-associated genes in T cell receptor­stimulated human GC TFH cells and inhibited their spontaneous conversion into TH1-like cells. Tox2-deficient mice displayed impaired secondary TFH cell expansion upon reimmunization with an antigen and upon secondary infection with a heterologous influenza virus. Collectively, our study shows that Tox2 is highly integrated into establishment of durable GC TFH cell responses and development of memory TFH cells in mice and humans.

Immune Profiling Mass Cytometry Assay Harmonization: Multicenter Experience from CIMAC-CIDC.

PURPOSE: The Cancer Immune Monitoring and Analysis Centers - Cancer Immunologic Data Commons (CIMAC-CIDC) Network is supported by the NCI to identify biomarkers of response to cancer immunotherapies across clinical trials using state-of-the-art assays. A primary platform for CIMAC-CIDC studies is cytometry by time of flight (CyTOF), performed at all CIMAC laboratories. To ensure the ability to generate comparable CyTOF data across labs, a multistep cross-site harmonization effort was undertaken. EXPERIMENTAL DESIGN: We first harmonized standard operating procedures (SOPs) across the CIMAC sites. Because of a new acquisition protocol comparing original narrow- or new wide-bore injector introduced by the vendor (Fluidigm), we also tested this protocol across sites before finalizing the harmonized SOP. We then performed cross-site assay harmonization experiments using five shared cryopreserved and one lyophilized internal control peripheral blood mononuclear cell (PBMC) with a shared lyophilized antibody cocktail consisting of 14 isotype-tagged antibodies previously validated, plus additional liquid antibodies. These reagents and samples were distributed to the CIMAC sites and the data were centrally analyzed by manual gating and automated methods (Astrolabe). RESULTS: Average coefficients of variation (CV) across sites for each cell population were reported and compared with a previous multisite CyTOF study. We reached an intersite CV of under 20% for most cell subsets, very similar to a previously published study. CONCLUSIONS: These results establish the ability to reproduce CyTOF data across sites in multicenter clinical trials, and also highlight the importance of quality control procedures, such as the use of spike-in control samples, for tracking variability in this assay.

Cytokines in the Treatment of Melanoma.

PURPOSE OF REVIEW: The use of cytokines in harnessing the immune system to eradicate cancer has been an important treatment modality. However, the dose-limiting toxicities of these cytokines limited their usage in clinic. Here, we review the basic biology of cytokines involved in the treatment of melanoma and discuss their therapeutic applications. Moreover, we describe several innovative technological approaches that have been developed to improve the pharmacokinetics, safety, and efficacy of these cytokines. RECENT FINDINGS: The safety and the anti-tumor activity of newly engineered cytokines including PEGylated IL-2 (NKTR-214), PEGylated IL-10 (AM0010), and IL-15 super agonist (ALT-803) have been evaluated in clinical trials with encouraging clinical activity and acceptable safety profile, both as single agents and in combination with immuno-oncology agents. A greater understanding of the mechanisms of action and effective dosing of these newly engineered cytokine together with determination of optimum combination therapy regimens may yield greater clinical benefits in the future.

Tilsotolimod with Ipilimumab Drives Tumor Responses in Anti-PD-1 Refractory Melanoma.

Many patients with advanced melanoma are resistant to immune checkpoint inhibition. In the ILLUMINATE-204 phase I/II trial, we assessed intratumoral tilsotolimod, an investigational Toll-like receptor 9 agonist, with systemic ipilimumab in patients with anti-PD-1- resistant advanced melanoma. In all patients, 48.4% experienced grade 3/4 treatment-emergent adverse events. The overall response rate at the recommended phase II dose of 8 mg was 22.4%, and an additional 49% of patients had stable disease. Responses in noninjected lesions and in patients expected to be resistant to ipilimumab monotherapy were observed. Rapid induction of a local IFNα gene signature, dendritic cell maturation and enhanced markers of antigen presentation, and T-cell clonal expansion correlated with clinical response. A phase III clinical trial with this combination (NCT03445533) is ongoing. SIGNIFICANCE: Despite recent developments in advanced melanoma therapies, most patients do not experience durable responses. Intratumoral tilsotolimod injection elicits a rapid, local type 1 IFN response and, in combination with ipilimumab, activates T cells to promote clinical activity, including in distant lesions and patients not expected to respond to ipilimumab alone.This article is highlighted in the In This Issue feature, p. 1861.

Bempegaldesleukin (NKTR-214) plus Nivolumab in Patients with Advanced Solid Tumors: Phase I Dose-Escalation Study of Safety, Efficacy, and Immune Activation (PIVOT-02).

This single-arm, phase I dose-escalation trial (NCT02983045) evaluated bempegaldesleukin (NKTR-214/BEMPEG), a CD122-preferential IL2 pathway agonist, plus nivolumab in 38 patients with selected immunotherapy-naïve advanced solid tumors (melanoma, renal cell carcinoma, and non-small cell lung cancer). Three dose-limiting toxicities were reported in 2 of 17 patients during dose escalation [hypotension (n = 1), hyperglycemia (n = 1), metabolic acidosis (n = 1)]. The most common treatment-related adverse events (TRAE) were flu-like symptoms (86.8%), rash (78.9%), fatigue (73.7%), and pruritus (52.6%). Eight patients (21.1%) experienced grade 3/4 TRAEs; there were no treatment-related deaths. Total objective response rate across tumor types and dose cohorts was 59.5% (22/37), with 7 complete responses (18.9%). Cellular and gene expression analysis of longitudinal tumor biopsies revealed increased infiltration, activation, and cytotoxicity of CD8+ T cells, without regulatory T-cell enhancement. At the recommended phase II dose, BEMPEG 0.006 mg/kg plus nivolumab 360 mg every 3 weeks, the combination was well tolerated and demonstrated encouraging clinical activity irrespective of baseline PD-L1 status. SIGNIFICANCE: These data show that BEMPEG can be successfully combined with a checkpoint inhibitor as dual immunotherapy for a range of advanced solid tumors. Efficacy was observed regardless of baseline PD-L1 status and baseline levels of tumor-infiltrating lymphocytes, suggesting therapeutic potential for patients with poor prognostic risk factors for response to PD-1/PD-L1 blockade.See related commentary by Rouanne et al., p. 1097.This article is highlighted in the In This Issue feature, p. 1079.

Bempegaldesleukin selectively depletes intratumoral Tregs and potentiates T cell-mediated cancer therapy.

High dose interleukin-2 (IL-2) is active against metastatic melanoma and renal cell carcinoma, but treatment-associated toxicity and expansion of suppressive regulatory T cells (Tregs) limit its use in patients with cancer. Bempegaldesleukin (NKTR-214) is an engineered IL-2 cytokine prodrug that provides sustained activation of the IL-2 pathway with a bias to the IL-2 receptor CD122 (IL-2Rß). Here we assess the therapeutic impact and mechanism of action of NKTR-214 in combination with anti-PD-1 and anti-CTLA-4 checkpoint blockade therapy or peptide-based vaccination in mice. NKTR-214 shows superior anti-tumor activity over native IL-2 and systemically expands anti-tumor CD8+ T cells while inducing Treg depletion in tumor tissue but not in the periphery. Similar trends of intratumoral Treg dynamics are observed in a small cohort of patients treated with NKTR-214. Mechanistically, intratumoral Treg depletion is mediated by CD8+ Teff-associated cytokines IFN-γ and TNF-α. These findings demonstrate that NKTR-214 synergizes with T cell-mediated anti-cancer therapies.

A First-in-Human Study and Biomarker Analysis of NKTR-214, a Novel IL2Rßγ-Biased Cytokine, in Patients with Advanced or Metastatic Solid Tumors.

NKTR-214 (bempegaldesleukin) is a novel IL2 pathway agonist, designed to provide sustained signaling through heterodimeric IL2 receptor ßγ to drive increased proliferation and activation of CD8+ T and natural killer cells without unwanted expansion of T regulatory cells (Treg) in the tumor microenvironment. In this first-in-human multicenter phase I study, NKTR-214 administered as an outpatient regimen was well tolerated and showed clinical activity including tumor shrinkage and durable disease stabilization in heavily pretreated patients. Immune activation and increased numbers of immune cells were observed in the periphery across all doses and cycles with no loss of NKTR-214 activity with repeated administration. On-treatment tumor biopsies demonstrated that NKTR-214 promoted immune cell increase with limited increase of Tregs. Transcriptional analysis of tumor biopsies showed that NKTR-214 engaged the IL2 receptor pathway and significantly increased genes associated with an effector phenotype. Based on safety and pharmacodynamic markers, the recommended phase II dose was determined to be 0.006 mg/kg every three weeks. SIGNIFICANCE: We believe that IL2- and IL2 pathway-targeted agents such as NKTR-214 are key components to an optimal immunotherapy treatment algorithm. Based on its biological activity and tolerability, NKTR-214 is being studied with approved immuno-oncology agents including checkpoint inhibitors.See related commentary by Sullivan, p. 694.This article is highlighted in the In This Issue feature, p. 681.

Molecular Mechanisms Regulating T Helper 1 versus T Follicular Helper Cell Differentiation in Humans.

IL-12 is important for the differentiation of T follicular helper (Tfh) cells, as well as Th1 cells in humans. Still, how IL-12 signals regulate Tfh versus Th1 cell differentiation remains poorly characterized. Here we aimed to determine the molecular mechanisms that regulate the differentiation and the function of IL-12-stimulated human naive CD4(+) T cells. We found that T-bet promoted the expression of CXCR5 in human CD4(+) T cells. We provide evidence that T-bet does not strongly inhibit the Tfh cell differentiation program per se but diminishes the functions to provide help to B cells. This study also suggests that IRF4 plays an important role in driving the early differentiation of IL-12-stimulated CD4(+) T cells toward Tfh and away from Th1 by inhibiting the expression of Eomesodermin. Thus, the fate of IL-12-stimulated CD4(+) T cells is determined through interplay of multiple transcription factors at early stages.

ICOS(+)PD-1(+)CXCR3(+) T follicular helper cells contribute to the generation of high-avidity antibodies following influenza vaccination.

The immune mechanism leading to the generation of protective antibody responses following influenza trivalent inactivated vaccine (TIV) vaccinations remains largely uncharacterized. We recently reported that TIV vaccination induced a transient increase of circulating ICOS(+)PD-1(+)CXCR3(+) T follicular helper (cTfh) cells in blood, which positively correlated with the induction of protective antibody responses measured at day 28. However, whether and how these T cells directly contribute to antibody response remains unclear. In this study, we analyzed the changes after TIV vaccination in the amount and the avidity of the polyclonal antibodies specific for the HA1 subunit of the pandemic H1N1 virus, and analyzed the correlation with the increase of ICOS(+)PD-1(+)CXCR3(+) cTfh cells. We found that both the amount and the avidity of specific antibodies rapidly increased during the first 7 days after TIV. Importantly, the increase of ICOS(+)PD-1(+)CXCR3(+) cTfh cells strongly correlated with the increase in the avidity of antibodies, particularly in subjects who did not have high affinity antibodies at baseline. We propose that ICOS(+)PD-1(+)CXCR3(+) Tfh cells directly contribute to the generation of high-avidity antibodies after TIV vaccinations by selectively interacting with high affinity B cells at extrafollicular sites.

Analysis of human blood memory T follicular helper subsets.

Human blood contains a memory counterpart of T follicular helper (T(FH)) cells. Blood T(FH) cells are composed of subsets that differ in phenotype and function. Recent studies show that analysis of blood circulating memory T(FH) cells can provide clues to understand the mode of actions of vaccines and the pathogenesis of human autoimmune diseases. We will describe here a detailed protocol to analyze the memory T(FH) subsets in human whole blood samples. We will also describe a protocol to assess the helper capacity of blood memory T(FH) subsets.

The cytokine TGF-ß co-opts signaling via STAT3-STAT4 to promote the differentiation of human TFH cells.

Understanding the developmental mechanisms of follicular helper T cells (TFH cells) in humans is relevant to the clinic. However, the factors that drive the differentiation of human CD4+ helper T cells into TFH cells remain largely undefined. Here we found that transforming growth factor-ß (TGF-ß) provided critical additional signals for the transcription factors STAT3 and STAT4 to promote initial TFH differentiation in humans. This mechanism did not appear to be shared by mouse helper T cells. Developing human TFH cells that expressed the transcriptional repressor Bcl-6 also expressed RORγt, a transcription factor typically expressed by the TH17 subset of helper T cells. Our study documents a mechanism by which TFH cells and TH17 cells emerge together in inflammatory environments in humans, as is often observed in many human autoimmune diseases.

Phenotype and functions of memory Tfh cells in human blood.

Our understanding of the origin and functions of human blood CXCR5(+) CD4(+) T cells found in human blood has changed dramatically in the past years. These cells are currently considered to represent a circulating memory compartment of T follicular helper (Tfh) lineage cells. Recent studies have shown that blood memory Tfh cells are composed of phenotypically and functionally distinct subsets. Here, we review the current understanding of human blood memory Tfh cells and the subsets within this compartment. We present a strategy to define these subsets based on cell surface profiles. Finally, we discuss how increased understanding of the biology of blood memory Tfh cells may contribute insight into the pathogenesis of autoimmune diseases and the mode of action of vaccines.

IL-12 receptor ß1 deficiency alters in vivo T follicular helper cell response in humans.

Antibody responses represent a key immune protection mechanism. T follicular helper (Tfh) cells are the major CD4(+) T-cell subset that provides help to B cells to generate an antibody response. Tfh cells together with B cells form germinal centers (GCs), the site where high-affinity B cells are selected and differentiate into either memory B cells or long-lived plasma cells. We show here that interleukin-12 receptor ß1 (IL-12Rß1)-mediated signaling is important for in vivo Tfh response in humans. Although not prone to B cell-deficient-associated infections, subjects lacking functional IL-12Rß1, a receptor for IL-12 and IL-23, displayed substantially less circulating memory Tfh and memory B cells than control subjects. GC formation in lymph nodes was also impaired in IL-12Rß1-deficient subjects. Consistently, the avidity of tetanus toxoid-specific serum antibodies was substantially lower in these subjects than in age-matched controls. Tfh cells in tonsils from control individuals displayed the active form of signal transducer and activator of transcription 4 (STAT4), demonstrating that IL-12 is also acting on Tfh cells in GCs. Thus, our study shows that the IL-12-STAT4 axis is associated with the development and the functions of Tfh cells in vivo in humans.

Induction of ICOS+CXCR3+CXCR5+ TH cells correlates with antibody responses to influenza vaccination.

Seasonal influenza vaccine protects 60 to 90% of healthy young adults from influenza infection. The immunological events that lead to the induction of protective antibody responses remain poorly understood in humans. We identified the type of CD4+ T cells associated with protective antibody responses after seasonal influenza vaccinations. The administration of trivalent split-virus influenza vaccines induced a temporary increase of CD4+ T cells expressing ICOS, which peaked at day 7, as did plasmablasts. The induction of ICOS was largely restricted to CD4+ T cells coexpressing the chemokine receptors CXCR3 and CXCR5, a subpopulation of circulating memory T follicular helper cells. Up to 60% of these ICOS+CXCR3+CXCR5+CD4+ T cells were specific for influenza antigens and expressed interleukin-2 (IL-2), IL-10, IL-21, and interferon-γ upon antigen stimulation. The increase of ICOS+CXCR3+CXCR5+CD4+ T cells in blood correlated with the increase of preexisting antibody titers, but not with the induction of primary antibody responses. Consistently, purified ICOS+CXCR3+CXCR5+CD4+ T cells efficiently induced memory B cells, but not naïve B cells, to differentiate into plasma cells that produce influenza-specific antibodies ex vivo. Thus, the emergence of blood ICOS+CXCR3+CXCR5+CD4+ T cells correlates with the development of protective antibody responses generated by memory B cells upon seasonal influenza vaccination.

Human tonsil B-cell lymphoma 6 (BCL6)-expressing CD4+ T-cell subset specialized for B-cell help outside germinal centers.

T follicular helper (Tfh) cells represent a Th subset engaged in the help of B-cell responses in germinal centers (GCs). Tfh cells abundantly express the transcription repressor B-cell lymphoma 6 (Bcl6), a factor that is necessary and sufficient for their development in vivo. Whether Tfh or Tfh-committed cells are involved in the help of B cells outside GCs remains unclear, particularly in humans. In this study, we identified a previously undefined BCL6-expressing CD4(+) T-cell subset in human tonsils. This subset expressed IL-7 receptor and chemokine receptor 5 (CXCR5) and inducible costimulator (ICOS) at low levels (CXCR5(lo)ICOS(lo)), and it was found exclusively outside GCs. CXCR5(lo)ICOS(lo) CD4(+) T cells secreted larger amounts of IL-21 and IL-10 than CXCR5(hi)ICOS(hi) GC-Tfh cells upon activation, and they induced proliferation and differentiation of naïve B cells into Ig-producing cells more efficiently than GC-Tfh cells. However, this subset lacked the capacity to help GC-B cells because of the induction of apoptosis of GC-B cells through the FAS/FAS-ligand interaction. CXCR5(lo)ICOS(lo) CD4(+) T cells expressed equivalent amounts of BCL6 transcript with CXCR5(hi)ICOS(hi) GC-Tfh cells, but they expressed less Bcl6 protein. Collectively, our study indicates that CXCR5(lo)ICOS(lo) CD4(+) T cells in human tonsils represent Tfh lineage-committed cells that provide help to naïve and memory B cells outside GCs.

Human blood CXCR5(+)CD4(+) T cells are counterparts of T follicular cells and contain specific subsets that differentially support antibody secretion.

Although a fraction of human blood memory CD4(+) T cells expresses chemokine (C-X-C motif) receptor 5 (CXCR5), their relationship to T follicular helper (Tfh) cells is not well established. Here we show that human blood CXCR5(+)CD4(+) T cells share functional properties with Tfh cells and appear to represent their circulating memory compartment. Blood CXCR5(+)CD4(+) T cells comprised three subsets: T helper 1 (Th1), Th2, and Th17 cells. Th2 and Th17 cells within CXCR5(+), but not within CXCR5(-), compartment efficiently induced naive B cells to produce immunoglobulins via interleukin-21 (IL-21). In contrast, Th1 cells from both CXCR5(+) and CXCR5(-) compartments lacked the capacity to help B cells. Patients with juvenile dermatomyositis, a systemic autoimmune disease, displayed a profound skewing of blood CXCR5(+) Th cell subsets toward Th2 and Th17 cells. Importantly, the skewing of subsets correlated with disease activity and frequency of blood plasmablasts. Collectively, our study suggests that an altered balance of Tfh cell subsets contributes to human autoimmunity.

Human dendritic cells induce the differentiation of interleukin-21-producing T follicular helper-like cells through interleukin-12.

T follicular helper (Tfh) cells help development of antibody responses via interleukin-21 (IL-21). Here we show that activated human dendritic cells (DCs) induced naive CD4(+) T cells to become IL-21-producing Tfh-like cells through IL-12. CD4(+) T cells primed with IL-12 induced B cells to produce immunoglobulins in a fashion dependent on IL-21 and inducible costimulator (ICOS), thus sharing fundamental characteristics with Tfh cells. The induction of Tfh-like cells by activated DCs was inhibited by neutralizing IL-12. IL-12 induced two different IL-21-producers: IL-21(+)IFN-gamma(+)T-bet(+) Th1 cells and IL-21(+)IFN-gamma(-)T-bet(-) non-Th1 cells, in a manner dependent on signal transducer and activator of transcription 4 (STAT4). IL-12 also regulated IL-21 secretion by memory CD4(+) T cells. Thus, IL-12 produced by activated DCs regulates antibody responses via developing IL-21-producing Tfh-like cells and inducing IL-21 secretion from memory CD4(+) T cells. These data suggest that the developmental pathway of Tfh cells differs between mice and humans, which have considerable implications for vaccine development.