Systemic immunostimulation induces glucocorticoid-mediated thymic involution succeeded by rebound hyperplasia which is impaired in aged recipients.

The thymus is the central organ involved with T-cell development and the production of naïve T cells. During normal aging, the thymus undergoes marked involution, reducing naïve T-cell output and resulting in a predominance of long-lived memory T cells in the periphery. Outside of aging, systemic stress responses that induce corticosteroids (CS), or other insults such as radiation exposure, induce thymocyte apoptosis, resulting in a transient acute thymic involution with subsequent recovery occurring after cessation of the stimulus. Despite the increasing utilization of immunostimulatory regimens in cancer, effects on the thymus and naïve T cell output have not been well characterized. Using both mouse and human systems, the thymic effects of systemic immunostimulatory regimens, such as high dose IL-2 (HD IL-2) with or without agonistic anti-CD40 mAbs and acute primary viral infection, were investigated. These regimens produced a marked acute thymic involution in mice, which correlated with elevated serum glucocorticoid levels and a diminishment of naïve T cells in the periphery. This effect was transient and followed with a rapid thymic "rebound" effect, in which an even greater quantity of thymocytes was observed compared to controls. Similar results were observed in humans, as patients receiving HD IL-2 treatment for cancer demonstrated significantly increased cortisol levels, accompanied by decreased peripheral blood naïve T cells and reduced T-cell receptor excision circles (TRECs), a marker indicative of recent thymic emigrants. Mice adrenalectomized prior to receiving immunotherapy or viral infection demonstrated protection from this glucocorticoid-mediated thymic involution, despite experiencing a substantially higher inflammatory cytokine response and increased immunopathology. Investigation into the effects of immunostimulation on middle aged (7-12 months) and advance aged (22-24 months) mice, which had already undergone significant thymic involution and had a diminished naïve T cell population in the periphery at baseline, revealed that even further involution was incurred. Thymic rebound hyperplasia, however, only occurred in young and middle-aged recipients, while advance aged not only lacked this rebound hyperplasia, but were entirely absent of any indication of thymic restoration. This coincided with prolonged deficits in naïve T cell numbers in advanced aged recipients, further skewing the already memory dominant T cell pool. These results demonstrate that, in both mice and humans, systemic immunostimulatory cancer therapies, as well as immune challenges like subacute viral infections, have the potential to induce profound, but transient, glucocorticoid-mediated thymic involution and substantially reduced thymic output, resulting in the reduction of peripheral naive T cells. This can then be followed by a marked rebound effect with naïve T cell restoration, events that were shown not to occur in advanced-aged mice.

JAK2/mTOR Inhibition Fails to Prevent Acute GVHD Despite Reduced Th1/Th17 cells: Final Phase II Trial Results.

Our phase I graft-versus-host disease (GVHD) prevention trial of JAK2 inhibitor, pacritinib, (recommended phase II dose: 100mg po BID day 0 to +70) plus sirolimus and tacrolimus (PAC/SIR/TAC) demonstrated the regimen was safe and free of pan-JAK myelosuppression after allogeneic hematopoietic cell transplantation (alloHCT). PAC inhibits IL-6 receptor activity and pathogenic Th1/Th17 differentiation in preclinical models and the phase I trial. Herein we report on our completed phase II trial of PAC/SIR/TAC after 8/8-HLA matched alloHCT. This single-arm phase II trial (NCT02891603) was powered to determine if PAC/SIR/TAC suppressed %pSTAT3+ CD4+ T cells at day +21 (primary endpoint: %pSTAT3+ CD4+ T cells ≤ 35%) and estimated grade II-IV acute GVHD by day +100. The impact of PAC/SIR/TAC on T cell subsets, CD28 (pS6 and pH3ser10), and IL-2 receptor (pSTAT5) signal transduction was also evaluated. Eligible patients (n=28) received alloHCT for hematologic malignancies or myeloproliferative neoplasms. Reduced or myeloablative intensity conditioning was permitted. PAC/SIR/TAC met the primary endpoint, reducing %pSTAT3+ CD4+ T cells to 9.62% at day +21. Th1/Th17 cells were decreased at day +21, increasing the ratio of Tregs to Th1 and Th17 cells with PAC/SIR/TAC at RP2D PAC compared to dose level 1 PAC. The cumulative incidence of grade II-IV acute GVHD by day +100 with PAC/SIR/TAC was similar to historic SIR/TAC values (46 v 43%). While PAC/SIR/TAC suppressed pSTAT3 and Th1/Th17 cells, the regimen did not improve acute GVHD prevention.

Chronic graft-versus-host disease: unresolved complication or ancient history?

ABSTRACT: Chronic graft-versus-host disease (cGVHD) is associated with morbidity, mortality, impaired quality of life, prolonged immunosuppressive therapy, and infection risk after allogeneic hematopoietic cell transplantation (HCT). Major strides have occurred in the understanding of cGVHD biology; National Institutes of Health Consensus meetings have refined rigorous approaches to diagnosis, staging, and response criteria; major interventional trials have established standard benchmarks for treatment outcome; and 3 agents to date have been US Food and Drug Administration approved for treating corticosteroid-refractory cGVHD. Promising results from several recent trials have led some, but not others, to conclude that the risk of developing cGVHD is sufficiently low to be considered a major post-HCT complication of the past. We propose that it is time to critically examine the results of contemporary graft-versus-host disease (GVHD) prophylaxis regimens and discuss the state of the science and associated controversies in the spectrum of conclusions reached as to the risk of cGVHD. With these data, the current cGVHD incidence can be most precisely determined, and the present and future burden of cGVHD-affected patients can be accurately modeled. Through review of existing evidence, we highlight unresolved needs and opportunities to refine best GVHD prophylaxis or preemptive therapy approaches and optimize established cGVHD therapy, and make the argument that support of preclinical and clinical research is critical in improving patient outcomes.

Anti-PD-1 cancer immunotherapy induces central nervous system immune-related adverse events by microglia activation.

Cancer treatment with anti-PD-1 immunotherapy can cause central nervous system immune-related adverse events (CNS-irAEs). The role of microglia in anti-PD-1 immunotherapy-induced CNS-irAEs is unclear. We found that anti-PD-1 treatment of mice caused morphological signs of activation and major histocompatibility complex (MHC) class II up-regulation on microglia. Functionally, anti-PD-1 treatment induced neurocognitive deficits in mice, independent of T cells, B cells, and natural killer cells. Instead, we found that microglia mediated these CNS-irAEs. Single-cell RNA sequencing revealed major transcriptional changes in microglia upon anti-PD-1 treatment. The anti-PD-1 effects were mediated by anti-PD-1 antibodies interacting directly with microglia and were not secondary to peripheral T cell activation. Using a proteomics approach, we identified spleen tyrosine kinase (Syk) as a potential target in activated microglia upon anti-PD-1 treatment. Syk inhibition reduced microglia activation and improved neurocognitive function without impairing anti-melanoma effects. Moreover, we analyzed CNS tissue from a patient cohort that had received anti-PD-1 treatment. Imaging mass cytometry revealed that anti-PD-1 treatment of patients was associated with increased surface marker expression indicative of microglia activation. In summary, we identified a disease-promoting role for microglia in CNS-irAEs driven by Syk and provide an inhibitor-based approach to interfere with this complication after anti-PD-1 immunotherapy.

Calcineurin inhibition rescues alloantigen-specific central memory T cell subsets that promote chronic GVHD.

Calcineurin inhibitors (CNIs) constitute the backbone of modern acute graft-versus-host disease (aGVHD) prophylaxis regimens but have limited efficacy in the prevention and treatment of chronic GVHD (cGVHD). We investigated the effect of CNIs on immune tolerance after stem cell transplantation with discovery-based single-cell gene expression and T cell receptor (TCR) assays of clonal immunity in tandem with traditional protein-based approaches and preclinical modeling. While cyclosporin and tacrolimus suppressed the clonal expansion of CD8+ T cells during GVHD, alloreactive CD4+ T cell clusters were preferentially expanded. Moreover, CNIs mediated reversible dose-dependent suppression of T cell activation and all stages of donor T cell exhaustion. Critically, CNIs promoted the expansion of both polyclonal and TCR-specific alloreactive central memory CD4+ T cells (TCM) with high self-renewal capacity that mediated cGVHD following drug withdrawal. In contrast to posttransplant cyclophosphamide (PT-Cy), CSA was ineffective in eliminating IL-17A-secreting alloreactive T cell clones that play an important role in the pathogenesis of cGVHD. Collectively, we have shown that, although CNIs attenuate aGVHD, they paradoxically rescue alloantigen-specific TCM, especially within the CD4+ compartment in lymphoid and GVHD target tissues, thus predisposing patients to cGVHD. These data provide further evidence to caution against CNI-based immune suppression without concurrent approaches that eliminate alloreactive T cell clones.

Oncogenic Calreticulin Induces Immune Escape by Stimulating TGFß Expression and Regulatory T-cell Expansion in the Bone Marrow Microenvironment.

Increasing evidence supports the interplay between oncogenic mutations and immune escape mechanisms. Strategies to counteract the immune escape mediated by oncogenic signaling could provide improved therapeutic options for patients with various malignancies. As mutant calreticulin (CALR) is a common driver of myeloproliferative neoplasms (MPN), we analyzed the impact of oncogenic CALRdel52 on the bone marrow (BM) microenvironment in MPN. Single-cell RNA sequencing revealed that CALRdel52 led to the expansion of TGFß1-producing erythroid progenitor cells and promoted the expansion of FoxP3+ regulatory T cells (Treg) in a murine MPN model. Treatment with an anti-TGFß antibody improved mouse survival and increased the glycolytic activity in CD4+ and CD8+ T cells in vivo, whereas T-cell depletion abrogated the protective effects conferred by neutralizing TGFß. TGFß1 reduced perforin and TNFα production by T cells in vitro. TGFß1 production by CALRdel52 cells was dependent on JAK1/2, PI3K, and ERK activity, which activated the transcription factor Sp1 to induce TGFß1 expression. In four independent patient cohorts, TGFß1 expression was increased in the BM of patients with MPN compared with healthy individuals, and the BM of patients with MPN contained a higher frequency of Treg compared with healthy individuals. Together, this study identified an ERK/Sp1/TGFß1 axis in CALRdel52 MPNs as a mechanism of immunosuppression that can be targeted to elicit T-cell-mediated cytotoxicity. Significance: Targeting the mutant calreticulin/TGFß1 axis increases T-cell activity and glycolytic capacity, providing the rationale for conducting clinical trials on TGFß antagonists as an immunotherapeutic strategy in patients with myeloproliferative neoplasms.

Oncogene-induced TIM-3 ligand expression dictates susceptibility to anti-TIM-3 therapy in mice.

Leukemia relapse is a major cause of death after allogeneic hematopoietic cell transplantation (allo-HCT). We tested the potential of targeting T cell (Tc) immunoglobulin and mucin-containing molecule 3 (TIM-3) for improving graft-versus-leukemia (GVL) effects. We observed differential expression of TIM-3 ligands when hematopoietic stem cells overexpressed certain oncogenic-driver mutations. Anti-TIM-3 Ab treatment improved survival of mice bearing leukemia with oncogene-induced TIM-3 ligand expression. Conversely, leukemia cells with low ligand expression were anti-TIM-3 treatment resistant. In vitro, TIM-3 blockade or genetic deletion in CD8+ Tc enhanced Tc activation, proliferation, and IFN-γ production while enhancing GVL effects, preventing Tc exhaustion, and improving Tc cytotoxicity and glycolysis in vivo. Conversely, TIM-3 deletion in myeloid cells did not affect allogeneic Tc proliferation and activation in vitro, suggesting that anti-TIM-3 treatment-mediated GVL effects are Tc induced. In contrast to anti-programmed cell death protein 1 (anti-PD-1) and anti-cytotoxic T lymphocyte-associated protein 4 (anti-CTLA-4) treatment, anti-TIM-3-treatment did not enhance acute graft-versus-host disease (aGVHD). TIM-3 and its ligands were frequently expressed in acute myeloid leukemia (AML) cells of patients with post-allo-HCT relapse. We decipher the connections between oncogenic mutations found in AML and TIM-3 ligand expression and identify anti-TIM-3 treatment as a strategy for enhancing GVL effects via metabolic and transcriptional Tc reprogramming without exacerbation of aGVHD. Our findings support clinical testing of anti-TIM-3 Ab in patients with AML relapse after allo-HCT.

Targeting TGFß-activated kinase-1 activation in microglia reduces CAR T immune effector cell-associated neurotoxicity syndrome.

Cancer immunotherapy with chimeric antigen receptor (CAR) T cells can cause immune effector cell-associated neurotoxicity syndrome (ICANS). However, the molecular mechanisms leading to ICANS are not well understood. Here we examined the role of microglia using mouse models and cohorts of individuals with ICANS. CD19-directed CAR (CAR19) T cell transfer in B cell lymphoma-bearing mice caused microglia activation and neurocognitive deficits. The TGFß-activated kinase-1 (TAK1)-NF-κB-p38 MAPK pathway was activated in microglia after CAR19 T cell transfer. Pharmacological TAK1 inhibition or genetic Tak1 deletion in microglia using Cx3cr1CreER:Tak1fl/fl mice resulted in reduced microglia activation and improved neurocognitive activity. TAK1 inhibition allowed for potent CAR19-induced antilymphoma effects. Individuals with ICANS exhibited microglia activation in vivo when studied by translocator protein positron emission tomography, and imaging mass cytometry revealed a shift from resting to activated microglia. In summary, we prove a role for microglia in ICANS pathophysiology, identify the TAK1-NF-κB-p38 MAPK axis as a pathogenic signaling pathway and provide a rationale to test TAK1 inhibition in a clinical trial for ICANS prevention after CAR19 T cell-based cancer immunotherapy.

CD8+ T-cell differentiation and dysfunction inform treatment response in acute myeloid leukemia.

ABSTRACT: The interplay between T-cell states of differentiation, dysfunction, and treatment response in acute myeloid leukemia (AML) remains unclear. Here, we leveraged a multimodal approach encompassing high-dimensional flow cytometry and single-cell transcriptomics and found that early memory CD8+ T cells are associated with therapy response and exhibit a bifurcation into 2 distinct terminal end states. One state is enriched for markers of activation, whereas the other expresses natural killer (NK)-like and senescence markers. The skewed clonal differentiation trajectory toward CD8+ senescence was also a hallmark indicative of therapy resistance. We validated these findings by generating an AML CD8+ single-cell atlas integrating our data and other independent data sets. Finally, our analysis revealed that an imbalance between CD8+ early memory and senescent-like cells is linked to AML treatment refractoriness and poor survival. Our study provides crucial insights into the dynamics of CD8+ T-cell differentiation and advances our understanding of CD8+ T-cell dysfunction in AML.

The Adverse Event Landscape of Stem Cell Transplant: Evidence for aGVHD Driving Early Transplant Associated Toxicities.

Although unrelated-donor (URD) hematopoietic cell transplantation (HCT) is associated with many toxicities, a detailed analysis of adverse events, as defined by the Common Terminology Criteria for Adverse Events (CTCAE), has not previously been curated. This represents a major unmet need, especially as it relates to assessing the safety of novel agents. We analyzed a detailed AE database from the "ABA2" randomized, double-blind, placebo-controlled clinical trial of abatacept for acute graft-versus-host disease (aGVHD) prevention, for which the FDA mandated a detailed AE assessment through Day +180, and weekly neutrophil and platelet counts through Day +100. These were analyzed for their relationship to key transplant outcomes, with a major focus on the impact of aGVHD on the development/severity of AEs. A total of 2102 AEs and 1816 neutrophil/platelet counts were analyzed from 142 8/8-HLA-matched URD HCT recipients on ABA2 (placebo cohort, n = 69, abatacept cohort, n = 73). This analysis resulted in 2 major observations. (1) Among graft source, conditioning intensity, age, and Grade 2 to 4 aGVHD, only aGVHD impacted Grade 3 to 5 AE acquisition after the first month post-transplant. (2) The development of Grade 3 to 4 aGVHD was associated with thrombocytopenia. We have created a detailed resource for the transplant community by which to contextualize clinical toxicities after transplant. It has identified aGVHD as a major driver of post-HCT Grade 3 to 5 AEs, and underscored a link between aGVHD and thrombocytopenia. This establishes a critical safety framework upon which the impact of novel post-transplant aGVHD therapeutics should be evaluated. This trial was registered at www.clinicaltrials.gov (#NCT01743131).

Alloengraftment without significant toxicity or GVHD in CD45 antibody-drug conjugate-conditioned Fanconi anemia mice.

ABSTRACT: Fanconi anemia (FA) is an inherited DNA repair disorder characterized by bone marrow (BM) failure, developmental abnormalities, myelodysplasia, leukemia, and solid tumor predisposition. Allogeneic hematopoietic stem cell transplantation (allo-HSCT), a mainstay treatment, is limited by conditioning regimen-related toxicity and graft-versus-host disease (GVHD). Antibody-drug conjugates (ADCs) targeting hematopoietic stem cells (HSCs) can open marrow niches permitting donor stem cell alloengraftment. Here, we report that single dose anti-mouse CD45-targeted ADC (CD45-ADC) facilitated stable, multilineage chimerism in 3 distinct FA mouse models representing 90% of FA complementation groups. CD45-ADC profoundly depleted host stem cell enriched Lineage-Sca1+cKit+ cells within 48 hours. Fanca-/- recipients of minor-mismatched BM and single dose CD45-ADC had peripheral blood (PB) mean donor chimerism >90%; donor HSCs alloengraftment was verified in secondary recipients. In Fancc-/- and Fancg-/- recipients of fully allogeneic grafts, PB mean donor chimerism was 60% to 80% and 70% to 80%, respectively. The mean percent donor chimerism in BM and spleen mirrored PB results. CD45-ADC-conditioned mice did not have clinical toxicity. A transient <2.5-fold increase in hepatocellular enzymes and mild-to-moderate histopathological changes were seen. Under GVHD allo-HSCT conditions, wild-type and Fanca-/- recipients of CD45-ADC had markedly reduced GVHD lethality compared with lethal irradiation. Moreover, single dose anti-human CD45-ADC given to rhesus macaque nonhuman primates on days -6 or -10 was at least as myeloablative as lethal irradiation. These data suggest that CD45-ADC can potently promote donor alloengraftment and hematopoiesis without significant toxicity or severe GVHD, as seen with lethal irradiation, providing strong support for clinical trial considerations in highly vulnerable patients with FA.

Corticosteroids impair epithelial regeneration in immune-mediated intestinal damage.

Corticosteroid treatment (CST) failure is associated with poor outcomes for patients with gastrointestinal (GI) graft-versus-host disease (GVHD). CST is intended to target the immune system, but the glucocorticoid receptor (GR) is widely expressed, including within the intestines, where its effects are poorly understood. Here, we report that corticosteroids (CS) directly targeted intestinal epithelium, potentially worsening immune-mediated GI damage. CS administered to mice in vivo and intestinal organoid cultures ex vivo reduced epithelial proliferation. Following irradiation, immediate CST mitigated GI damage but delayed treatment attenuated regeneration and exacerbated damage. In a murine steroid-refractory (SR) GVHD model, CST impaired epithelial regeneration, worsened crypt loss, and reduced intestinal stem cell (ISC) frequencies. CST also exacerbated immune-mediated damage in organoid cultures with SR, GR-deficient T cells or IFN-γ. These findings correlated with CS-dependent changes in apoptosis-related gene expression and STAT3-related epithelial proliferation. Conversely, IL-22 administration enhanced STAT3 activity and overcame CS-mediated attenuation of regeneration, reducing crypt loss and promoting ISC expansion in steroid-treated mice with GVHD. Therefore, CST has the potential to exacerbate GI damage if it fails to control the damage-inducing immune response, but this risk may be countered by strategies augmenting epithelial regeneration, thus providing a rationale for clinical approaches combining such tissue-targeted therapies with immunosuppression.

Overlap chronic GVHD is associated with adverse survival outcomes compared to classic chronic GVHD.

Chronic graft-versus-host-disease (cGVHD) is divided into two subtypes: classic (absence of acute GVHD features) and overlap cGVHD ('ocGVHD'), in which both chronic and acute GVHD clinical features are present simultaneously. While worse outcomes with ocGVHD have been reported, there are few recent analyses. We performed a secondary analysis of data from the ABA2 trial (N = 185), in which detailed GVHD data were collected prospectively and systematically adjudicated. Analyses included cumulative incidence of classic versus ocGVHD, their specific organ manifestations, global disease severity scores, non-relapse mortality (NRM), disease-free survival (DFS) and overall survival (OS) in these two cGVHD subtypes. Of 92 patients who developed cGVHD, 35 were classified as ocGVHD. The 1-year cumulative incidence, organ involvement, and global severity of classic and ocGVHD were similar between ABA2 patients receiving CNI/MTX+placebo and CNI/MTX+abatacept; thus, cohorts were combined for ocGVHD evaluation. This analysis identified ocGVHD as having significantly higher severity at presentation and at maximum global severity compared to classic cGVHD. OS and DFS were significantly lower for ocGVHD versus classic cGVHD. OcGVHD is associated with increased cGVHD severity scores, and is associated with decreased OS and DFS compared to classic cGVHD, underscoring the high risks with this cGVHD subtype.

Autophagy prevents graft failure during murine graft-versus-host disease.

ABSTRACT: Autophagy is an intracellular survival process that has established roles in the long-term survival and function of hematopoietic stem cells (HSC). We investigated the contribution of autophagy to HSC fitness during allogeneic transplantation and graft-versus-host disease (GVHD). We demonstrate in vitro that both tumor necrosis factor and IL-1ß, major components of GVHD cytokine storm, synergistically promote autophagy in both HSC and their more mature hematopoietic progenitor cells (HPC). In vivo we demonstrate that autophagy is increased in donor HSC and HPC during GVHD. Competitive transplant experiments demonstrated that autophagy-deficient cells display reduced capacity to reconstitute the hematopoietic system compared to wild-type counterparts. In a major histocompatibility complex-mismatched model of GVHD and associated cytokine dysregulation, we demonstrate that autophagy-deficient HSC and progenitors fail to establish durable hematopoiesis, leading to primary graft failure and universal transplant related mortality. Using several different models, we confirm that autophagy activity is increased in early progenitor and HSC populations in the presence of T-cell-derived inflammatory cytokines and that these HSC populations require autophagy to survive. Thus, autophagy serves as a key survival mechanism in HSC and progenitor populations after allogeneic stem cell transplant and may represent a therapeutic target to prevent graft failure during GVHD.

ROCK1/2 signaling contributes to corticosteroid-refractory acute graft-versus-host disease.

Patients with corticosteroid-refractory acute graft-versus-host disease (aGVHD) have a low one-year survival rate. Identification and validation of novel targetable kinases in patients who experience corticosteroid-refractory-aGVHD may help improve outcomes. Kinase-specific proteomics of leukocytes from patients with corticosteroid-refractory-GVHD identified rho kinase type 1 (ROCK1) as the most significantly upregulated kinase. ROCK1/2 inhibition improved survival and histological GVHD severity in mice and was synergistic with JAK1/2 inhibition, without compromising graft-versus-leukemia-effects. ROCK1/2-inhibition in macrophages or dendritic cells prior to transfer reduced GVHD severity. Mechanistically, ROCK1/2 inhibition or ROCK1 knockdown interfered with CD80, CD86, MHC-II expression and IL-6, IL-1ß, iNOS and TNF production in myeloid cells. This was accompanied by impaired T cell activation by dendritic cells and inhibition of cytoskeletal rearrangements, thereby reducing macrophage and DC migration. NF-κB signaling was reduced in myeloid cells following ROCK1/2 inhibition. In conclusion, ROCK1/2 inhibition interferes with immune activation at multiple levels and reduces acute GVHD while maintaining GVL-effects, including in corticosteroid-refractory settings.

Galectin-3 predicts acute GvHD and overall mortality post reduced intensity allo-HCT: a BMT-CTN biorepository study.

Identifying plasma biomarkers early after allo-HCT may become crucial to prevent and treat severe aGvHD. We utilized samples from 203 allo-HCT patients selected from the Blood & Marrow Transplant Clinical Trials Network (BMT CTN) to identify new biomarker models to predict aGvHD and overall mortality. Two new biomarkers (Gal-3 and LAG-3), and previously identified biomarkers (ST2/IL33R, IL6, Reg3A, PD-1, TIM-3, TNFR1) were screened. Increased Gal-3 levels measured at Day +7 post-transplant predicted the development of aGvHD (grade 2-4) in the total population [AUC: 0.602; P = 0.045] while higher Day +14 levels predicted overall mortality due to toxicity among patients receiving reduced intensity conditioning [P = 0.028] but not myeloablative conditioning. Elevated LAG-3 levels (Day +21) were associated with less severe aGvHD [159.1 ng/mL vs 222.0 ng/mL; P = 0.046]. We developed a model utilizing Gal-3, LAG-3, and PD-1 levels at Days +14 and +21 with an improved performance to predict aGvHD and overall non-relapse mortality. We confirmed four informative biomarkers (Reg3A, ST2, TIM-3, and TNFR1) predict severe aGvHD at day +14 and day +21 (grade 3-4). In conclusion, the combination of Gal-3 alone or in combination with LAG-3, and PD-1 is a new informative model to predict aGvHD development and overall non-relapse mortality after allo-HCT.

A tissue-intrinsic IL-33/EGF circuit promotes epithelial regeneration after intestinal injury.

Intestinal stem cells (ISCs) maintain the epithelial lining of the intestines, but mechanisms regulating ISCs and their niche after damage remain poorly understood. Utilizing radiation injury to model intestinal pathology, we report here that the Interleukin-33 (IL-33)/ST2 axis, an immunomodulatory pathway monitored clinically as an intestinal injury biomarker, regulates intrinsic epithelial regeneration by inducing production of epidermal growth factor (EGF). Three-dimensional imaging and lineage-specific RiboTag induction within the stem cell compartment indicated that ISCs expressed IL-33 in response to radiation injury. Neighboring Paneth cells responded to IL-33 by augmenting production of EGF, which promoted ISC recovery and epithelial regeneration. These findings reveal an unknown pathway of niche regulation and crypt regeneration whereby the niche responds dynamically upon injury and the stem cells orchestrate regeneration by regulating their niche. This regenerative circuit also highlights the breadth of IL-33 activity beyond immunomodulation and the therapeutic potential of EGF administration for treatment of intestinal injury.

Regulation of human and mouse bystander T cell activation responses by PD-1.

Bystander activation of memory T cells occurs via cytokine signaling alone in the absence of T cell receptor (TCR) signaling and provides a means of amplifying T cell effector responses in an antigen-nonspecific manner. While the role of Programmed Cell Death Protein 1 (PD-1) on antigen-specific T cell responses is extensively characterized, its role in bystander T cell responses is less clear. We examined the role of the PD-1 pathway during human and mouse non-antigen-specific memory T cell bystander activation and observed that PD-1+ T cells demonstrated less activation and proliferation than activated PD-1- populations in vitro. Higher activation and proliferative responses were also observed in the PD-1- memory population in both mice and patients with cancer receiving high-dose IL-2, mirroring the in vitro phenotypes. This inhibitory effect of PD-1 could be reversed by PD-1 blockade in vivo or observed using memory T cells from PD-1-/- mice. Interestingly, increased activation through abrogation of PD-1 signaling in bystander-activated T cells also resulted in increased apoptosis due to activation-induced cell death (AICD) and eventual T cell loss in vivo. These results demonstrate that the PD-1/PD-Ligand 1 (PD-L1) pathway inhibited bystander-activated memory T cell responses but also protected cells from AICD.

Validated graft-specific biomarkers identify patients at risk for chronic graft-versus-host disease and death.

BACKGROUNDChronic graft-versus-host disease (cGVHD) is a serious complication of allogeneic hematopoietic cell transplantation (HCT). More accurate information regarding the risk of developing cGVHD is required. Bone marrow (BM) grafts contribute to lower cGVHD, which creates a dispute over whether risk biomarker scores should be used for peripheral blood (PB) and BM.METHODSDay 90 plasma proteomics from PB and BM recipients developing cGVHD revealed 5 risk markers that were added to 8 previous cGVHD markers to screen 982 HCT samples of 2 multicenter Blood and Marrow Transplant Clinical Trials Network (BMTCTN) cohorts. Each marker was tested for its association with cause-specific hazard ratios (HRs) of cGVHD using Cox-proportional-hazards models. We paired these clinical studies with biomarker measurements in a mouse model of cGVHD.RESULTSSpearman correlations between DKK3 and MMP3 were significant in both cohorts. In BMTCTN 0201 multivariate analyses, PB recipients with 1-log increase in CXCL9 and DKK3 were 1.3 times (95% CI: 1.1-1.4, P = 0.001) and 1.9 times (95%CI: 1.1-3.2, P = 0.019) and BM recipients with 1-log increase in CXCL10 and MMP3 were 1.3 times (95%CI: 1.0-1.6, P = 0.018 and P = 0.023) more likely to develop cGVHD. In BMTCTN 1202, PB patients with high CXCL9 and MMP3 were 1.1 times (95%CI: 1.0-1.2, P = 0.037) and 1.2 times (95%CI: 1.0-1.3, P = 0.009) more likely to develop cGVHD. PB patients with high biomarkers had increased likelihood to develop cGVHD in both cohorts (22%-32% versus 8%-12%, P = 0.002 and P < 0.001, respectively). Mice showed elevated circulating biomarkers before the signs of cGVHD.CONCLUSIONBiomarker levels at 3 months after HCT identify patients at risk for cGVHD occurrence.FUNDINGNIH grants R01CA168814, R21HL139934, P01CA158505, T32AI007313, and R01CA264921.