HLA-DR Expression Research Articles

Neutrophil extracellular trap-induced intermediate monocytes trigger macrophage activation syndrome in adult-onset Still’s disease

BackgroundAdult-onset Still’s disease (AOSD) is a systemic autoinflammatory disease characterized by innate immune system activation, with a high risk for macrophage activation syndrome (MAS). MAS development is associated with monocyte/macrophage activation and cytokine storm. Monocytes consist of three different subsets, classical monocytes (CMs, CD14brightCD16 −), intermediate monocytes (IMs, CD14brightCD16 +), and non-classical monocytes (NCMs, CD14dimCD16 +), each has distinct roles in inflammatory regulation. However, the frequencies and regulatory mechanism of monocyte subsets in AOSD patients have not been identified.MethodsWe performed flow cytometry, RNA sequencing, phagocytosis analysis, and enzyme-linked immunosorbent assay to evaluate monocyte subsets, cell functions, and potential biomarkers. The effect of neutrophil extracellular traps (NETs) on monocytes was determined by evaluating mRNA levels of DNA sensors, surface CD16 expression, and inflammasome pathway activation.ResultsHigher proportions of intermediate monocytes (IMs) were identified in active AOSD patients. IMs displayed higher expression of CD80, CD86, HLA-DR, and CD163 than CMs and NCMs. CD163 upregulation was noted on AOSD IMs, accompanied by increased phagocytic activity and elevated cytokine/chemokine production, including IL-1β, IL-6, CCL8, and CXCL10. The frequencies of IMs were correlated with disease activity and higher in AOSD patients with MAS (AOSD-MAS). CCL8 and CXCL10 were highly expressed in RNA sequencing of monocytes from AOSD-MAS patients and plasma CXCL10 level could serve as a potential biomarker for AOSD-MAS. Moreover, DNA-sensing pathway was activated in monocytes from AOSD-MAS patients. Stimulation with NETs derived from AOSD induced DNA sensor expression, the expansion of IMs, and inflammasome pathway activation. These effects can be abrogated by DNase I treatment.ConclusionsOur results demonstrated that the proportions of IMs were elevated in AOSD and associated with MAS. The DNA component in NETs from AOSD plays an important role in the formation of IMs, shedding new light for the therapeutic target.

Dynamic MAIT Cell Recovery after Severe COVID-19 Is Transient with Signs of Heterogeneous Functional Anomalies.

Mucosal-associated invariant T (MAIT) cells are an abundant population of unconventional T cells in humans and play important roles in immune defense against microbial infections. Severe COVID-19 is associated with strong activation of MAIT cells and loss of these cells from circulation. In the present study, we investigated the capacity of MAIT cells to recover after severe COVID-19. In longitudinal paired analysis, MAIT cells initially rebounded numerically and phenotypically in most patients at 4 mo postrelease from the hospital. However, the rebounding MAIT cells displayed signs of persistent activation with elevated expression of CD69, CD38, and HLA-DR. Although MAIT cell function was restored in many patients, a subgroup displayed a predominantly PD-1high functionally impaired MAIT cell pool. This profile was associated with poor expression of IFN-γ and granzyme B in response to IL-12 + L-18 and low levels of polyfunctionality. Unexpectedly, although the overall T cell counts recovered, normalization of the MAIT cell pool failed at 9-mo follow-up, with a clear decline in MAIT cell numbers and a further increase in PD-1 levels. Together, these results indicate an initial transient period of inconsistent recovery of MAIT cells that is not sustained and eventually fails. Persisting MAIT cell impairment in previously hospitalized patients with COVID-19 may have consequences for antimicrobial immunity and inflammation and could potentially contribute to post-COVID-19 health problems.

Study on the biological properties of SMILE-derived corneal stromal lenticules after long-term cryopreservation in nutrient capsules

PurposeTo investigate the long-term preservation effects of nutrient capsules on the physiological activity, collagen fiber structure and transmittance of corneal stromal lenticules derived from small incision lenticule extraction (SMILE). MethodsA new nutrient capsule was constructed for long-term preservation of SMILE-derived corneal stromal lenticules. The lenticules were randomly divided into 99% anhydrous glycerol, and hydrogel nutrient capsules. After preserving for 1 year at −80 °C, lenticules were compared with fresh lenticules. The optical transmittance, tissue morphology, ultrastructure, cells activity and immunogenicity of the lenticules was detected and compared between different groups. ResultsThe rate of apoptotic cells was significantly higher in the glycerol group compared with the nutrient capsule group (P < 0.0001). More viable cells were present in the lenticules after nutrient capsule preservation compared to the glycerol group (P = 0.0003). The mean transmittance of the lenticules in the glycerol group (50 ± 18%) was significantly lower (P = 0.0008) compared to the control group (75 ± 11%), and the lenticules transmittance of the nutrient capsule group (64 ± 15%) after long-term preservation was not significantly different (P = 0.23) compared to the control group. The structure of HE staining showed that the collagen fibers in the nutrient capsule group were arranged in parallel and neatly, and a few cavitation vesicles were visible inside the tissue. There was no significant difference in the number of lenticular collagen fibers in the nutritional capsule group compared to the fresh lenticule group (P = 0.06). HLA-DR, HLA-ABC, CD45, CD25 and CD69 expression was low in all groups of lenticules after preservation. ConclusionsNutrient capsules can preserve lenticules for a long time and maintain the transmission structure and cells activity of lenticules.

Taming the SARS-CoV-2-mediated proinflammatory response with BromAc®.

In the present study, the impact of BromAc®, a specific combination of bromelain and acetylcysteine, on the SARS-CoV-2-specific inflammatory response was evaluated. An in vitro stimulation system was standardized using blood samples from 9 healthy donors, luminex assays and flow cytometry were performed. BromAc® demonstrated robust anti-inflammatory activity in human peripheral blood cells upon SARS-CoV-2 viral stimuli, reducing the cytokine storm, composed of chemokines, growth factors, and proinflammatory and regulatory cytokines produced after short-term in vitro culture with the inactivated virus (iSARS-CoV-2). A combined reduction in vascular endothelial growth factor (VEGF) induced by SARS-CoV-2, in addition to steady-state levels of platelet recruitment-associated growth factor-PDGFbb, was observed, indicating that BromAc® may be important to reduce thromboembolism in COVID-19. The immunophenotypic analysis of the impact of BromAc® on leukocytes upon viral stimuli showed that BromAc® was able to downmodulate the populations of CD16+ neutrophils and CD14+ monocytes observed after stimulation with iSARS-CoV-2. Conversely, BromAc® treatment increased steady-state HLA-DR expression in CD14+ monocytes and preserved this activation marker in this subset upon iSARS-CoV-2 stimuli, indicating improved monocyte activation upon BromAc® treatment. Additionally, BromAc® downmodulated the iSARS-CoV-2-induced production of TNF-a by the CD19+ B-cells. System biology approaches, utilizing comprehensive correlation matrices and networks, showed distinct patterns of connectivity in groups treated with BromAc®, suggesting loss of connections promoted by the compound and by iSARS-CoV-2 stimuli. Negative correlations amongst proinflammatory axis and other soluble and cellular factors were observed in the iSARS-CoV-2 group treated with BromAc® as compared to the untreated group, demonstrating that BromAc® disengages proinflammatory responses and their interactions with other soluble factors and the axis orchestrated by SARS-CoV-2. These results give new insights into the mechanisms for the robust anti-inflammatory effect of BromAc® in the steady state and SARS-CoV-2-specific immune leukocyte responses, indicating its potential as a therapeutic strategy for COVID-19.

Persistence of circulating CD169+monocytes and HLA-DR downregulation underline the immune response impairment in PASC individuals: the potential contribution of different COVID-19 pandemic waves

The use of CD169 as a marker of viral infection has been widely discussed in the context of COVID-19, and in particular, its crucial role in the early detection of SARS-CoV-2 infection and its association with the severity and clinical outcome of COVID-19 were demonstrated. COVID-19 patients show relevant systemic alteration and immunological dysfunction that persists in individuals with post-acute sequelae of SARS-CoV-2 infection (PASC). It is critical to implement the characterization of the disease, focusing also on the possible impact of the different COVID-19 waves and the consequent effects found after infection. On this basis, we evaluated by flow cytometry the expression of CD169 and HLA-DR on monocytes from COVID-19 patients and PASC individuals to better elucidate their involvement in immunological dysfunction, also evaluating the possible impact of different pandemic waves. The results confirm CD169 RMFI is a good marker of viral infection. Moreover, COVID-19 patients and PASC individuals showed high percentage of CD169+ monocytes, but low percentage of HLA-DR+ monocytes and the alteration of systemic inflammatory indices. We have also observed alterations of CD169 and HLA-DR expression and indices of inflammation upon different COVID-19 waves. The persistence of specific myeloid subpopulations suggests a role of CD169+ monocytes and HLA-DR in COVID-19 disease and chronic post-infection inflammation, opening new opportunities to evaluate the impact of specific pandemic waves on the immune response impairment and systemic alterations with the perspective to provide new tools to monitoring new variants and diseases associated to emerging respiratory viruses.

Comparative analysis of monocyte-derived dendritic cell phenotype and T cell stimulatory function in patients with acute-on-chronic liver failure with different clinical parameters.

Acute-on-Chronic Liver Failure (ACLF) patients experience systemic inflammation as well as immune dysfunction and exhaustion. The phenotype and functionality of monocyte-derived dendritic cells in ACLF patients with different clinical parameters have not been elucidated. This study included 37 cases of ACLF, 20 cases of Chronic Hepatitis B (CHB) patients, and 12 healthy controls. Demographic and laboratory parameters were collected from the enrolled patients. Peripheral blood samples were obtained from the participants. Monocyte-derived dendritic cells were induced and cultured, followed by co-culturing with T cells from the patients. Cell surface markers and intracellular markers were analyzed using flow cytometry. The relationship between these markers and clinical parameters was compared. Our study found that ACLF patients had lower expression levels of HLA-DR, CD86, and CD54 on monocyte-derived dendritic cells compared to both CHB patients and healthy controls. IL-4, GM-CSF, and alcohol were found to promote the expression of HLA-DR, CD86, and CD54 on monocyte-derived dendritic cells. In ACLF patients, higher levels of procalcitonin (PCT), lower levels of albumin, decreased prothrombin activity and deceased patients were associated with lower expression of HLA-DR, CD86, and CD54 on monocyte-derived dendritic cells. Peripheral blood mononuclear cells (PBMCs), after removing adherent cells, were co-cultured with monocyte-derived DC. Our study revealed that patients with infection and low albumin levels exhibited a decreased proportion of T cell subsets within PBMCs. Additionally, these patients' T cells showed lower levels of Ki-67 and interferon-gamma (IFN-γ) production. ACLF patients exhibit varying clinical states, with differences in the phenotype and the ability of monocyte-derived dendritic cells to stimulate T cells. Alcohol can stimulate the maturation of monocyte-derived dendritic cells.

Abstract A052: Comprehensive EBV-specific T cell profiling and multi-omics analysis of nasopharyngeal carcinoma CD8 T cells reveals novel cancer-associated phenotype

Abstract Nasopharyngeal carcinoma (NPC) is a high mortality, Epstein-Barr virus (EBV)-driven cancer with limited treatment options. Although EBV is highly antigenic and detectable in nearly all NPC tumor cells, it remains unclear why NPC tumors evade immune targeting despite high levels of immune infiltration. Here, we investigate the phenotypes of peripheral EBV-specific T cells with the purpose of identifying clinically relevant, cancer-associated EBV-specific T cell phenotypes. We developed a 34-marker mass cytometry and multiplexed MHC-I tetramer panel to detect and phenotype CD8 T cells of up to 55 antigen-specificities, including EBV and other known viral and cancer-antigen epitopes. We used this approach to profile peripheral blood mononuclear cells (PBMCs) from treatment-naïve NPC patients (n=51). Compared to other antigen-specific T cells detected in NPC patients and EBV-specific T cells in healthy individuals, EBV-specific T cells in NPC patients expressed high levels of activation markers (CD38, HLA-DR), co-inhibitory markers (CD39, TIGIT, PD-1), and migratory markers (ITB7, CD103). Using unsupervised clustering, we found that the frequency of EBV-specific T cells in a phenotypic cluster characterized by high CD103, CD39, HLA-DR, and CD38 expression positively correlated with plasma EBV-DNA titer and gross tumor volume. Remarkably, we observed that regardless of antigen specificity, NPC patients had a higher frequency of total CD8 T cells with this activated/exhausted cluster phenotype. CD8 frequencies of this cluster were also positively correlated with plasma EBV-DNA titer and stage (TNM). To investigate the gene expression profiles and TCR clonal diversity of this cancer-associated phenotype, we performed single-cell multi-omics analysis on peripheral CD8 T cells from NPC patients (n=17). We identified that cell subsets within this phenotype had distinct gene expression patterns indicative of potential associations with the tumor and we also assessed the clonality of these subpopulations. Overall, this study identified a unique cancer-associated peripheral EBV-specific T cell phenotype in the context of nasopharyngeal carcinoma that is positively correlated with advanced disease. Frequencies of peripheral T cells with this phenotype could also be useful as a blood-based prognostic marker for NPC. Citation Format: Nandita Kumar, Long Nguyen, Saumya Jani, Darren WT Lim, Joe PS Yeong, Melvin LK Chua, Amit Jain, Evan W Newell. Comprehensive EBV-specific T cell profiling and multi-omics analysis of nasopharyngeal carcinoma CD8 T cells reveals novel cancer-associated phenotype [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A052.

Abstract LB_B05: Mapping therapy resistant phenotypes in SCLC liquid biopsies with single-cell proteomics at a personalized level

Abstract Small-cell lung cancer (SCLC) accounts for ~15% cases of all lung cancer cases and is characterized by aggressive growth and dismal prognosis. Although patients initially respond favorably to platinum and immune checkpoint blockade therapy, most develop therapy resistance and relapse within 1 year. Leveraging liquid biopsies and circulating tumor cells (CTCs) for evaluating SCLC status is regarded as a promising approach especially in SCLC where biopsies are scarce. SCLC CTC numbers are higher compared to other cancers, presenting a unique opportunity to utilize them for assessing SCLC therapy response and resistance and identifying new targetable markers. In this study we leverage mass cytometry (i.e., CyTOF), a multiplex cytometric approach that enables interrogation of 30-50 protein markers per single cell, allowing us to identify and analyze a significant number of CTCs and their heterogeneous expression profiles. Our goal was to utilize CyTOF to help us map changes in CTC expression profiles in the treatment naïve and relapsed setting and thus be able to assess therapy response and resistance at a personalized level. To achieve this, we optimized a CyTOF antibody panel by using SCLC cell lines and blood specimens from healthy donors and SCLC patients. We show that by using this approach, we are able to identify and phenotype SCLC CTCs by using the combination of CD45 (negative expression) and CD56 positive expression with further validation achieved by TTF1 and SCLC subtype transcription factor expression (e.g. NEUROD1, POU2F3). This approach avoids enriching for specific CTC epithelial phenotypes that express surface markers that fluctuate during epithelial-mesenchymal transition (EMT) (e.g. EpCAM, a common marker for isolating CTCs). We also evaluated markers that describe immune suppression activity (PD-L1), EMT status (E-Cadherin, Vimentin, MUC1, Slug), as well as markers that can be therapeutically targeted/are indicative of resistance (e.g., p-YAP). For parallel immune profiling we assessed among others CD8/CD4 (T-cytotoxic/T-helpers respectively) and CD11b and HLA-DR (Myeloid-derived suppressor cells, MDSCs) expression. We found that p-YAP and MUC1 are significantly increased in CTCs detected in blood specimens from SCLC relapsed patients compared to treatment naïve patients. Both YAP and MUC1 have been shown to be play a role in therapy resistance and YAP inhibition is considered a promising therapeutic target. Our analysis also showed a significant increase of MDSC (CD33+CD11b+HLA-DR-) percentages and a decrease in the CD4/CD8 T cell ratio in the relapsed setting. Finally, when we used PHENOSTAMP, a previously developed reference EMT map for assessing EMT phenotypes in lung cancer clinical specimens at a personalized level, we observed an increase of EMT heterogeneity in CTCs in relapsed patients. Our data highlight the translational power of our approach in tracking therapy resistant cells during therapy directly in SCLC patient liquid biopsies towards assessing therapy resistance at a personalized level. Citation Format: Sayantan Bhattacharyya, Catherine A Stewart, Ashley M Victorian, Shafqat F Ehsan, Ester F Lujan, Alberto Duarte, John V Heymach, Jing Wang, Lauren A Byers, Loukia G Karacosta. Mapping therapy resistant phenotypes in SCLC liquid biopsies with single-cell proteomics at a personalized level [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_B05.

Monocyte Subpopulations and Their Expression of HLA-DR and CD300e after Allogeneic Stem Cell Transplantation in Patients with or without GvHD

Introduction: Graft versus host disease (GvHD) is a complex immune process that can affect up to 50% of patients undergoing allogeneic stem cell transplantation (allo-SCT). Even though prophylactic immunosuppressive regimens have been established over the last decades, GvHD is still one of the main causes of morbidity and mortality among these patients. Monocytes are cells of the innate immune system, that represent, as professional antigen-presenting cells, a connection to the adaptive immune system, and play a role in several autoimmune disorders. They are classified according to the expression of CD14 and CD16 into classical (CD14++/CD16-), intermediate (CD14++/CD16+), and non-classical (CD14+/CD16++) monocytes. Previous research has shown higher levels of intermediate monocytes in pediatric patients with GvHD. Furthermore, non-classical monocytes in allogenic bone marrow grafts have also been correlated with the development of GvHD. The expression of other surface markers such as HLA-DR and CD300e (IREM-2) are related to monocyte function and engagement in inflammatory processes. Nevertheless, the role of CD300e in GvHD remains unclear. Here, we present a description of monocyte subgroups and their expression of HLA-DR and CD300e in allo-SCT patients with or without GvHD as well as in healthy subjects. Methods: Transversal observational study with patients undergoing allo-SCT. Peripheral blood of patients was collected once after engraftment. Both acute and chronic GvHD patients were enrolled. Five healthy volunteers served as controls. Flow cytometry was performed to determine the immunophenotype of monocytes according to their expression of CD14 and CD16 stratifying into classical, intermediate, and non-classical subgroups as described above. In addition, the expression of HLA-DR and CD300e was analyzed for all monocytes and individual subgroups. Clinical characteristics are described in the table below. Statistical analysis was performed using GraphPad Prism 9. Comparisons between groups were made using non-parametrical tests and tests for multiple comparisons (Mann-Whitney and Kruskal-Wallis respectively). Results: 29 patients were enrolled. Two patients with GvHD were excluded due to neutropenia. 19 patients presented GvHD grade II or higher. Of those, ten had acute GvHD, five had prolonged acute GvHD, two had late onset acute GvHD, and two had chronic GvHD. Eight patients did not show GvHD or had only mild skin disease (grade one). The mean age was 60 years for all patients, 62.5 and 58.5 years among GvHD and non-GvDH patients, respectively. The image summarizes patient characteristics and comparisons. We compared transplant recipients with and without GvHD which each other and with healthy controls. In single comparisons, patients with GvHD showed significantly lower percentages of total monocytes as well as CD14+/HLA-DR+, total HLA-DR+, and intermediate monocytes compared to patients without GvHD. In addition, we observed a trend toward lower levels of CD16+/HLA-DR+ and CD300e-expressing monocytes in GvHD patients. When compared to healthy controls, allogeneic recipients without GvHD showed significantly higher levels of total monocytes, intermediate monocytes, and CD16+/HLA-DR+ monocytes and lower levels of classical and non-classical monocytes. Compared to controls, patients with GvHD showed significantly lower levels of total monocytes expressing CD300e (also true in all subgroups) as well as lower levels of classical monocytes, but higher levels of intermediate and non-classical monocytes. P values are shown in Table 1. Means and ranges for all groups are represented in Image 1. Conclusions: In our cohort, patients with GvHD showed higher levels of intermediate and non-classical monocytes compared to controls, however, these populations were lower when compared to allogeneic recipients without GvHD. This could indicate a consumption process similar to that observed in COVID-19 patients and a direct involvement of these monocytes in the GvHD process. In addition, we report for the first time the involvement of CD300e in GvHD, which was significantly lower expressed in the GvHD patients, compared to controls. However, there was only a strong trend compared to transplanted non-GvHD patients. This indicates a possible contribution of CD300e in the pathogenesis of GvHD. Further studies are needed in order to confirm these findings.

LSD1 Inhibition Enhances Antigen Presentation and Co-Stimulation in AML to Promote T Cell-Mediated Anti-Leukemia Immune Responses

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) can provide a curative treatment option for acute myeloid leukemia (AML). Donor T cells play an important role in the curative potential of allo-HSCT by recognizing and eliminating residual leukemic cells, inducing the desirable graft-versus-leukemia (GVL) effect. Evading from this effect of donor T cell immune surveillance through the downregulation of human leukocyte antigen class II (HLA-II) molecules has been shown to contribute to AML relapse after allo-HSCT. Lysine-specific demethylase 1 (LSD1) is an emerging epigenetic therapeutic target in AML due to its role in regulating myeloid differentiation pathways. We hypothesized that LSD1 inhibition has the potential to enhance anti-leukemic immune responses by differentiating AML cells and inducing the acquisition of markers typical for antigen-presenting cells. We have studied these effects by treating human AML cell lines with the LSD1 inhibitor bomedemstat and investigated the expression of antigen-presenting molecules by flow cytometry and quantitative PCR (qPCR). At a concentration of 100 nM, bomedemstat upregulated the expression of CIITA by a log2 fold change of 2.23 ± 0.68 (p &amp;lt; 0.01) in OCI-AML3, 2.17 ± 0.28 (p &amp;lt; 0.01) in HL60 and 1.80 ± 0.67 (p &amp;lt; 0.05) in MOLM-13. To assess if the observed upregulation of CIITA can lead to a re-expression of HLA-DR in these HLA-DR negative cell lines, we then treated these cell lines with 100 nM of bomedemstat with additional IFN-γ stimulation. Expression of HLA-DR and the co-stimulatory molecule CD86 was determined by flow cytometry. Bomedemstat increased the expression of HLA-DR and CD86 across all three cell lines leading to the generation of 26.63 ± 3.07% (p &amp;lt; 0.0001) HLA-DR +/CD86 + cells in OCI-AML3, 4.19 ± 1.68% (p &amp;lt; 0.001) HLA-DR +/CD86 + cells in HL-60 and 14.67 ± 2.03% (p &amp;lt; 0.001) HLA-DR +/CD86 + cells in MOLM-13. We further assessed the effects of bomedemstat treatment on cytokine production by qPCR. Notably, bomedemstat treatment increased the expression of CXCL-10 by a log2 fold change of 2.59 ± 0.66 (p &amp;lt; 0.001) in MOLM-13 and 4.12 ± 0.88 (p &amp;lt; 0.001) in HL-60 at 100 nM concentration. The upregulation of CXCL-10 was also validated using bead-based ELISA assays. To investigate the molecular mechanism of the observed concomitant upregulation of MHC-II molecules and CD86, we then used murine myeloid progenitor cells transformed by overexpression of Hoxa9 and Meis1 (H9M) or MN1. In H9M-transformed cells, bomedemstat concurrently upregulated MHC-II (I-A/I-E) and CD86 even in the absence of IFN-γ stimulation, leading to an increase in MHC-II +/CD86 + cells from 2.52 ± 1.22% at baseline to 29.95 ± 14.11 (p &amp;lt; 0.05). This effect was not observed in MN1-transformed cells. H9M-transformed progenitor cells from Irf8 knockout mice (H9M- Irf8-KO) did not show any upregulation of MHC-II, pointing towards a role for Irf8 in this process. To interrogate whether the concurrent upregulation of MHC-II and CD86 can enhance CD4 + T cell activation, we used ovalbumin-expressing H9M-transformed cells that were co-cultured with OT-II T cells after bomedemstat treatment. We could show that bomedemstat-treatment enhanced the ability of H9M-OVA cells to activate T cells as demonstrated by an enhanced expression of the T cell activation markers CD25 and CD69. Furthermore, bomedemstat also increased the immune killing of OVA-peptide pulsed H9M cells at an effector-to-target (E:T) ratio of 1:1 from 1.12 ± 4.01 to 19.70 ± 6.20% (p &amp;lt; 0.01). It also enhanced the killing of OVA-expressing H9M cells from 5.80 ± 2.95% to 17.70 ± 3.16% (p &amp;lt; 0.05). No significant killing effect was observed for MN1 cells. In conclusion, we demonstrate both phenotypically and functionally that LSD1 inhibition by bomedemstat can enhance the immunogenicity of human and murine AML models. These findings point towards a potential role of LSD1 inhibition as a maintenance therapy after allo-HSCT.

Transfer of mRNA Encoding CEBPA in Lipid Nanoparticles to CEBPA Mutated Leukemia Cell Line KO52 and Primary AML Reduces Cell Growth and Induces Myeloid Differentiation

There are known constitutional mutations associated with bone marrow failure and progression to malignancy, including myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). For the majority of the defects associated with clonal hematopoiesis and progression to MDS/AML, there are no specific treatments. We sought to determine if messenger RNA (mRNA) transfer can restore expression of the normal proteins, modulate abnormal proliferation and differentiation, and enhance response to chemotherapy and targeted agents. CCAAT enhancer-binding protein alpha (CEBPA) is a transcription factor involved in myeloid differentiation that is mutated in ~7-20% of patients with AML (Su L et al., Frontier Oncol. 2022). A germline alteration was identified in 4.5% of AML patients with CEBPA mutation (Ho PA et al., Blood 2009). While it was originally believed that biallelic mutations of CEBPA confer favorable prognosis, more recently it was realized that a single basic region leucine zipper (bZIP) mutation in the C terminal region suffices to confer favorable risk, as categorized by ELN2022. There are currently no targeted therapies for mutated CEBPA, and no known specific therapy for patients with constitutional or acquired CEBPA mutations. Although most patients with mutated CEBPA achieve initial CR, there is a moderate relapse rate (30-50%). The objective of this study was to determine if restoration of normal CEBPA mRNA would result in expression of normal CEBPA protein in AML cell lines (e.g.-U937), as well as an AML cell line with mutated CEBPA (KO52), and in primary AML blasts, including those with mutated CEBPA. We tested whether expression of normal CEBPA would lead to phenotypic changes including overcoming differentiation block, induce apoptosis, and eliminate leukemic blasts. There are normally two translation initiation sites, leading to production of the CEBPA-p42 or CEBPA-p30 proteins. U937 has high level expression of normal CEBPA-p42, while the KO52 cell line has two CEBPA mutations, p.E50* and p.L324P, the former leading to decrease in CEBPA-p30. To study the consequences of mRNA transfer, we performed immunofluorescence, multicolor flow cytometry (MFC), and Western blot (WB) analysis for non-transfected control cells, GreenLantern mRNA lipid nanoparticle (LNP) transfected control cells, and cells transfected with two types of CEBPA mRNA LNP (#1 and #2). We observed transfection efficiencies of 90-97% in cell lines and 20-95% in primary cells. Figure 1A shows the mean fluorescence intensity (MFI) of Alexa Fluor® 647-labeled monoclonal antibody to the C-terminus of CEBPA. Wild-type CEBPA-p42 was expressed in U937 and KO52 cell lines at 2-4 times control levels by WB quantitation. With two additions of LNP at 0h and 48h, the induced CEBPA protein maintained stable expression up to 5 days. Immunofluorescence demonstrated staining of CEBPA in the nucleus, co-localizing with nuclear DAPI fluorescence. To evaluate the functional consequences of CEBPA introduction, we analyzed morphology by Wright/Giemsa staining, proliferation by cell counting, apoptosis by Annexin V staining, cell cycle using BrdU labeling assay, and immunophenotype with stem and lineage markers including CD45, CD34, CD38, CD123, CD117, HLA-DR, CD13, CD33, CD16, CD11b, CD64, CD14. Strikingly, the enhanced expression of CEBPA was associated with decrease in proliferation and fraction in S phase, and increase in apoptosis and myeloid differentiation, suggesting induction of differentiation that could have therapeutic implications similar to ATRA in acute promyelocytic leukemia. The myeloid differentiation was evident by MFC showing decreased expression of primitive markers CD34, CD117 and HLA-DR, with increased expression of CD64 (Figure 1B), CD38, and CD11b. With this method we have also transfected primary AML patient blasts including a sample that harbored 4 CEBPA mutations. We observed 95% transfection efficiency and &amp;gt;50% decrease in cell number relative to controls with increased myeloid differentiation. Studies of the combination of CEBPA mRNA LNP transfection with targeted inhibitors to the other mutations present in this sample are in progress. Our findings reveal a novel therapeutic strategy using CEBPA mRNA LNP applicable to inherited or acquired disorders of CEBPA. This approach of restoration of normal mRNA could have potential for therapy of many pre-malignant and malignant disorders.

Dysregulation of Cellular Immunity in High-Risk Multiple Myeloma

Introduction: Multiple myeloma (MM) is the second most prevalent hematological malignancy, characterized by the abnormal proliferation of plasma cells in the bone marrow. Approximately 20% of MM patients present with high-risk (HR) clinical and genetic features that are associated with aggressive disease course and poor prognosis. Novel immune therapies are changing the paradigm of MM treatment. A comprehensive understanding of immune dysregulation within the tumor microenvironment (TME) of HR vs standard risk (SR) MM patients could inform the development of targeted immunotherapeutic strategies for HR MM. Methods: 55 HR and 25 SR patients were selected from the Mt. Sinai Hematologic Malignancies Tissue Bank (IRB# STUDY-11-01978). HR included one or more cytogenic abnormalities (HRCA) such as translocations t(4;14), deletion of chromosome 17 (del17p), and gain/amplification of 1q (1q+/++) based on the Second Revised International Staging System (R2-ISS). We also included nine patients with t(14;16) translocation alone or combined with one or two of the other HRCA. We performed comprehensive immune phenotyping of the bone marrow micro-environment on specimens from HR and SR patients using mass cytometry (CyTOF) and single cell RNA sequencing (scRNASeq) of bone marrow mononuclear cells (BMMC) depleted of CD138 positive MM cells. Results: ScRNAseq of BMMC from HR MM patients revealed a robust cytotoxic and cytolytic signature on CD4+ T cells relative to SR, characterized by the upregulation of genes such as GNLY, NKG7, PRF1, and IFNG, and a higher frequency of Granzyme K-positive (GZMK+) CD8+ T cells, previously described as progenitors of exhausted cells. Both CD4 and CD8 T cells, along with monocytes, exhibited high expression of a group of Interferon-stimulated genes (ISGs) including IFI27, IFIT3, IFI44L, IFITM1/3, and OASL. Notably, high expression of this group of ISGs was associated with T cell exhaustion and poor prognosis in the setting of immune checkpoint inhibitor therapy for solid tumors. Mass cytometry analysis confirmed the activated state of T cells in HR MM patients, with increased expression of immune activation markers HLA-DR, CD38, and the senescence marker CD57. Furthermore, HR patients exhibited higher frequencies of mast cells, CD14+ Monocytes and plasmacytoid dendritic cells compared to SR, suggesting an inflammatory and immunosuppressive environment that may dampen effective antitumor immune responses. Conclusions: These results indicate distinct bone marrow microenvironments of HR and SR MM. CD4 and CD8 T cells appear to be more activated in HR patients compared to SR. However, the higher frequencies of mast cells and plasmacytoid dendritic cells, and the prominent expression of ISGs associated with inhibition of anti-tumor immunity suggest dysregulation and exhaustion of T cell activity in HR patients. Collectively, these findings highlight the complex immune dynamics in HR MM and provide insights into the underlying immune dysfunction which may contribute to disease progression and therapy resistance in HR MM. Such insights have the potential to inform the design of targeted therapeutic interventions aimed at modulating the immune response and improving treatment outcomes for HR MM patients.

IRF4 Expression in Germinal Center and Lymphoma B Cells Regulates Antigen-Dependent Immune Response

A substantial subset of follicular lymphoma (FL) patients has an early relapse with a poor outcome. We showed that this unfavorable group displays increased expression of IRF4, dysregulated immune signaling and an immunosuppressive microenvironment. At the molecular level, IRF4 controls expression of antigen presentation and immune molecules (e.g. HLA-DR, CD40, PDL1). Furthermore, silencing of IRF4 triggers anti-lymphoma immunity ( Mondello P et al, Blood 2022;140 Suppl 1:168-169). However, little is known on the molecular mechanisms whereby IRF4 controls the crosstalk between B and T cells. To address this question, first we performed RNA-seq, ATAC-seq and CUT&amp;TAG of active (H3K27Ac, H3K4me3) and repressive (H3K27me3, H3K4me1) histone marks in TMD8 and HBL1 (lymphoma cells with high IRF4 expression) transfected with two pairs of siIRF4 or siCtr for 72 hours. Gene expression revealed a broad change in transcription, with 432 upregulated genes and 136 downregulated genes in siIRF4 compared to siCtr. Notably, the genes with increased expression following IRF4 silencing coded for antigen presentation, immune molecules and cytokines (e.g. HLA-DR, CD86, IL6, IL10). Accordingly, we observed significant enrichment of antigen presentation, interferon and immune response signatures ( Fig 1A). Integrating RNA-seq with chromatin accessibility showed a significant shift towards transcriptional upregulation at genes nearest to upregulated ATAC peaks, with significant enrichment at enhancers (n=771). Conversely, transcriptional suppression was enriched at enhancers (n=2,458) of downregulated peaks. k-means analyses of all union peaks, generated by merging ATAC with CUT&amp;TAG peaks, revealed a significant gain of H3K4me3, with concordant loss of H3K4me1 at enhancers with upregulated gene expression. In contrast, H3K4me3 was severely decreased at suppressed peaks. TF motif analysis revealed an enrichment for PU.1 and E2A at IRF4-bound regions, suggesting their cooperation in regulating immune signaling. Since antigen presentation and other immune molecules are critical components of the immune synapse, we explored the role of IRF4 on the interaction between germinal center (GC) B and T cells by crossing irf4 fl/fl mice with conditional deletion of irf4 ( Klein et al, Nat Immunol 2006) and Cγ 1cre mice ( Cγ 1cre; irf4 fl/fl) to induce recombination in GC B cells. After 10 days of immunization (GC reaction peak), Cγ 1cre; irf4 fl/fl and Cγ 1cre; irf4 fl/+ GC B cells showed significant increase of HLA-DR and CD40 expression compared to WT. As expected, Cγ 1cre; irf4 fl/fl mice displayed a significantly skewed light-zone:dark-zone ratio in favor of increased dark-zone, which are the cells that most reflect the action of BCL6, with concordant suppression of plasma cells. Additionally, we observed a significant increase of CD4 + T cells after partial or complete deletion of irf4, with upregulation of T FH cells and decrease of T reg cells ( Fig 1B). Notably, mice with loss of irf4 showed a significant decrease in exhausted T FH cells. To test if this effect was dependent on MHC:TCR interaction, we cocultured CD4 + T cells with TMD8 cells transfected with two siIRF4 or siCtr in presence of blocking antibodies for MHC class I, MHC class II or both. Blocking one or the other MHC class I or II partially rescued the IRF4 effect on T reg and T FH cells respectively as well as reduced anti-lymphoma cytotoxicity. Further experiments blocking IRF4-dependent IL6 and IL10 identified these two cytokines as responsible for the additional effects on T cells. To confirm this as an antigen-dependent immune response we coculture sorted GC B cells from NP-OVA-immunized Cγ 1cre; irf4 fl/fl, Cγ 1cre; irf4 fl/+ and WT mice with CSFE-labeled OVA-specific OT-II CD4 + T cells at a ratio of 2:1 in an organoid system for 5 days. We observed induced antigen specific proliferation of CD4 + T cells in the presence of Cγ 1cre; irf4 fl/fl and Cγ 1cre; irf4 fl/+ GC B cellscompared to WT,as indicated by decrease in CSFE expression . We confirmed an increase of T FH cells and a decrease of T reg cells, supporting the conclusion that IRF4 directly controls the antigen-dependent immune response . In summary, IRF4 expression in GC and lymphoma B cells regulates immune signaling with PU.1 and E2A, thereby modulating antigen-dependent immune responses with potential implications for lymphomagenesis. Future studies investigating targeting of IRF4 in lymphoma are warranted.

Immunomodulatory Effects of Chemo-Immunotherapy ± Idelalisib in Chronic Lymphocytic Leukaemia (CLL)

Introduction: Chronic lymphocytic leukaemia (CLL) is characterised by a dysfunctional immune profile. However, the precise impact of therapy on this altered immune state, both short and long term, remains unclear. The collection of pre-treatment and longitudinal blood samples in the NCRI phase III RIAltO trial (NCT01678430) offered a unique opportunity to address this question in the context of frontline chemo-immunotherapy (CIT) containing bendamustine or chlorambucil. The factorial randomisation to idelalisib versus placebo also provided a framework for investigating the immunomodulatory effects of PI3Kδ inhibition in this setting. Methods: We conducted mass cytometry analysis on samples obtained from CLL patients enrolled in the RIAltO trial. Patients were randomly assigned to receive ofatumumab plus either bendamustine or chlorambucil, with or without idelalisib. Samples were collected before treatment and at early (median 5.9 [IQR 5.7 - 6.4] months) and late (18.5 [16.1 - 22.6] months) post-treatment timepoints. Three healthy controls (HC) were included for comparison. CD3 + T cells were analysed using a customised CyTOF panel comprising 36 markers. Uniform manifold approximation and projection (UMAP) and manual gating analysis were utilised to evaluate global and specific T-cell changes. Results: In all, 177 samples from 79 CLL patients, obtained before or after CIT, were analysed. Baseline characteristics were similar between the different treatment arms. Compared to HC, treatment-naïve CLL patients exhibited a distinct T-cell profile with increased regulatory T cells, decreased naïve and central memory (CM) cells, elevated effector memory (EM) cells, reduced non-senescent cells, and increased expression of HLA-DR, PD-1, TOX, T-bet, and Eomes. Following CIT, the T-cell profile was significantly altered but remained distinct from that of HCs. CIT-induced changes persisted at the late post-treatment timepoint, indicating a sustained effect. Analysis of specific T-cell populations showed that, although some CLL-associated features became less prominent following CIT (expression of PD-1, TOX and TIGIT), most were enhanced (shift from naïve and CM cells towards a terminal effector phenotype; shift from a non-senescent to a terminally senescent phenotype; increased HLA-DR and T-bet expression). The post-treatment immune profiles were similar in patients receiving bendamustine or chlorambucil. Despite its immunomodulatory effects when used as a single agent, idelalisib also induced minimal additional changes. Furthermore, the post-treatment immune profile was similar in patients achieving minimal residual disease (MRD) negativity versus those who remained MRD positive, suggesting a direct pharmacodynamic effect. Finally, non-metric multidimensional scaling (NMDS) analysis demonstrated that CIT shifted the overall CLL-associated immune profile further away from that of HC, and that the shift was independent of chemotherapy allocation, idelalisib, or the level of CLL cytoreduction achieved. Conclusion: CIT results in profound immune changes that persists up to 18.5 [16.1 - 22.6] months following treatment. Furthermore, the overall effect of these changes further differentiates the CLL-associated immune profile from that of HC, deepening the existing T-cell dysfunction irrespective of chemotherapy choice, or the addition of idelalisib. Our study has important potential implications for patients receiving CIT in a range of clinical settings and supports the move towards more targeted agents that are less likely to cause indiscriminate immune perturbation.

Clinical, Cytogenetic and Immunophenotypic Spectra of Post-Transplant Relapse Following Allogeneic Hematopoietic Stem Cell Transplantation for Myelodysplastic Syndrome

Introduction Allogeneic hematopoietic stem cell transplantation (HCT) is a curative therapy used to treat myelodysplastic syndrome (MDS). Relapse post-HCT confers poor outcomes and subsequent therapy is not standardized. Like acute myeloid leukemia (AML), several mechanisms are known to be involved in post-HCT relapse including clonal evolution in favor of chemotherapy-resistant clones and tumor immune escape. Systemic reviews are scarce in the MDS post-HCT relapse population. Accordingly, the present study aimed to investigate clinical, cytogenetic, and immunophenotypic (IP) spectra for MDS post-HCT relapse patients (pts), along with subsequent therapies, and clinical outcomes following post-HCT relapse. Patients and methods A retrospective study was conducted and found that 231 MDS pts received HCT between April 2010 and September 2022 at the Princess Margaret Cancer Centre (PMCC). The primary endpoint was overall survival (OS) following post-HCT relapse. Secondary endpoints explored time to relapse (TTR), relapse presentation (i.e., MDS or AML), clonal evolution (i.e., changes in cytogenetics or IP profiles), and therapeutic strategies delivered after relapse. Results Of the 231 MDS pts treated with HCT, 52 (23%) relapsed in a median of 4.5 months (range 0.9-59.8 months). Twenty-five (48%) pts relapsed with MDS (i.e., blast &amp;lt;20%), while 27 (52%) relapsed with AML (i.e., blast ≥20%) in the marrow. Fifteen (65%) pts showed cytogenetic changes at the time of post-HCT relapse. Eleven (48%) of which presented with more aggressive findings (i.e., additional structural abnormalities and monosomal karyotype). Ten of 17 (59%) pts presented with changes in their IP profile at post-HCT relapse, 7 (70%) of which relapsed with AML. Combined these findings give evidence of clonal evolution in favor of more aggressive malignant clones that are often responsible for post-HCT relapse. Treatment with hypomethylating agents (HMA) alone or in combination after post-HCT relapse increased OS to 5.6 months in comparison to those not receiving HMA of whom OS was 1.4 months (p=0.0003). Stratified by disease presentation cytogenetic clonal evolution was seen in 6/12 (50%) of the post-HCT MDS relapses, and 9/11 (82%) of the post-HCT AML relapses. Cytogenetic abnormalities at diagnosis and post-HCT relapse, respectively included in descending order: structural abnormalities (n=14/23, 61%; n=20/23, 87%), complex karyotype (n=12/23, 52%; 17/23, 74%), -5/del(5q) (n=11/23, 48%; n=10/23, 43%), -7/del(7q) (n=8/23, 35%; n=11/23, 48%), monosomy karyotype (n=8/23, 35%; n=11/23, 48%), -17 (n=3/23, 13%; n=5/23, 22%), der(5)/t(5;17) (n=2/23, 9%; n=5/23, 22%), -20 (n=2/23, 9%; n=3/23, 13%), and inv(3) (n=1/23, 4%, n=2/23, 9%). Seventeen pts had paired IP profiles available both prior to HCT and at post-HCT relapse, of which 10 (59%) had profile changes of at least 1 antigen. Seven of 10 (70%) pts that relapsed with AML post-HCT had IP expression changes, compared to 3/7 (42.9%) pts that relapsed with MDS post-HCT. Summarized IP findings include reduced expression of CD7 (n=2/6, 33%), altered expression of CD34 (n=3/15, 20%), altered expression of CD117 (n=3/14, 21%), and reduced expression of HLA DR (n=4/15, 27%). The presence of IP expression changes at post-HCT relapse suggests evidence of clonal evolution or immune escape as the mechanism behind the relapsed disease. Overall survival duration was 3.97 months; the 12-month OS rate was 20.0% (10.0-32.5%). Post-HCT relapse treatments included hypomethylating agents (HMA; n=13/46, 28%), HMA with donor lymphocyte infusion (DLI; n= 7/46, 15%), HMA with Venetoclax (VEN; n=7/46, 15%), chemotherapy (n=9/46, 19%), best supportive care (8/46, 17%) and second HCT (n=2/46, 4%). Patients that received HMA with or without DLI or VEN had a longer survival duration of 5.6 months (95% CI [3.4-13.2 months]) compared to those not receiving HMA 1.4 months (95% CI [0.6-0.39 months, p=0.0003]). The 12-month survival rate was also significantly in favor of pts that received HMA following post-HCT relapse (35.3% [95% CI 17.2-54.0%] vs 4.3% [95% CI 0.3-18.0%]). Conclusion Patients with MDS undergoing HCT may relapse with either MDS or AML. The relapsed disease often shows evidence of clonal evolution in its immunophenotype and/or cytogenetic profile toward a more aggressive disease. Approaches to post-HCT relapse remain heterogenous but HMA is beneficial.

Multiparametric Flow Cytometry-MRD Assay: Lesson from Phase II Trail REL AML 001

Background: Core-binding factor (CBF) AML with RUNX1/RUNX1T1 (AML1/ETO) and CBFB/MYH11 fusion genes is known as a heterogenous group, accounting for about 10% to 15% of AML. In the Phase II Trial REL AML 001 (EudraCT Number 2017-002094-18; ClinicalTrials ID: NCT 03686345) adult CBF leukemia patients treated with a continuation therapy with Midostaurin were included, and the measurable residual disease (MRD) was performed by molecular MRD assessment (qPCR) and multiparametric flow cytometric-MRD (MCF-MRD) assay. The findings of MCF-MRD assay were compared to qPCR. Methods: 31 patients with AML1/ETO (n=15) and CBFB/MYH11 (n=16) were evaluated between December 2018 to July 2022 with both techniques. A total of 145 determinations (n. AML1/ETO = 56 and n. CBFB/MYH11= 89) were performed. MCF panel included 2 10-color tubes: CD15 FITC/ CD56 PE/ CD34 PerCP-cy5.5/ CD117 PE-cy7/ CD7 APC/ CD13 APC-R700/ CD19 APC H7/ HLADR V450/ CD45 V500C/ CD33 BV630, specific for RUNX1/RUNX1T1 cases and CD64 FITC/ CD2 PE/ CD34 PerCP-cy5.5/ CD117 PE-cy7/ CD200 APC/ CD13 APC-R700/ CD14 APC H7/ HLADR V450/ CD45 V500C/ CD33 BV630, specific for CBFB/MYH11 cases. A mean of 1,733,240 CD45 positive events were acquired, with a mean lower limit of detection (LLOD) of 0.001% (ranging 0.01-0.0003%). In 10 cases (6 RUNX1 and 4 CBFB/MYH11) the molecular and phenotypical features at onset were not available. MCF analyses were performed by InfinicytTM software and reference image tool was used wherever possible. Results: We found a concordance of 76% between MCF cases and RUNX1/RUNX1T1 qPCR, and a concordance of 83% between MCF cases and CBFB/MYH11 qPCR (Tables 1a and 1b). In relapsed cases we observed a dynamic and continuous increase of abnormal MCF events, that was not found in cases without clinical relapse although with positive qPCR (Table 2). The HLADR expression evaluated as the geo mean intensity at presentation and/or at relapse resulted higher in RUNX1/RUNX1T1 patients than in CBFB/MYH11 cases (29845 vs 8979, respectively, p=0.0039 Figure 1). Interestingly, we found in a single case with atypical CBFB/MYH11 fusion gene a high value of HLADR geo mean (44522). The down-regulated expression of HLADR in CBFB/MYH11 blasts may be a useful clue to distinguish AML blasts from the scarcely represented normal CD2 positive myeloid precursors, and from the strongly HLADR positive elements that are found in a regenerating bone marrow background. Conclusion: Although MCF-MRD assay showed lower sensitivity than CBF qPCR, MCF offered interesting informations about the dynamics of the abnormal clone size with time, evaluated as the increasing number of MRD clustering events, which may predict an impending relapse.

Preliminary Findings of a Phase Ib/II Trial Indicate Manageable Safety and Promising Efficacy for Mosunetuzumab in Combination with Lenalidomide (M+Len) in Previously Untreated (1L) Follicular Lymphoma (FL)

Background: First-line FL treatments typically include an anti-CD20 monoclonal antibody with alkylator-based chemotherapy. Despite encouraging efficacy, most patients (pts) eventually relapse; novel therapies that improve outcomes and prolong remission in 1L FL are needed. Also, chemotherapy-containing regimens may have substantial toxicities, emphasizing the need for new therapies with improved safety. Mosunetuzumab (M), a CD20xCD3 bispecific antibody that redirects T cells to eliminate malignant B cells, has shown manageable safety with high complete remission rates in pts with relapsed/refractory (R/R) FL after ≥2 prior lines of therapy (Budde et al. Lancet Oncol 2022). Lenalidomide (Len), a potent immunomodulatory agent, may have synergistic effects with M. Initial results from the CO41942 Phase Ib/II trial (NCT04246086) showed that M (intravenous) combined with Len had a manageable safety profile and encouraging chemotherapy-free anti-lymphoma activity in pts with R/R FL who had ≥1 prior line of therapy (Morschhauser et al. ASH 2021). We present preliminary safety, efficacy, and biomarker data from this ongoing trial of M (subcutaneous [SC]) combined with oral Len in pts with 1L FL who require systemic therapy. Methods: Pts with 1L FL requiring systemic therapy (investigator-assessed using GELF criteria) with an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-2 are included; target enrollment is 40 pts. Pts received 12 cycles of M+Len (cycle [C] 1, 21 days; C2-12, 28 days); in C1, 5mg of M was given on Day (D) 1, with the target dose (45mg) given on C1D8, C1D15, and on D1 of C2-12; Len (20mg) was given on D1-21 of C2-12 ( Figure A). Cytokine release syndrome (CRS) was reported using ASTCT criteria (Lee et al. Biol Blood Marrow Transplant 2019). Responses by PET-CT were investigator-assessed using Lugano 2014 criteria (Cheson et al. J Clin Oncol 2014). Flow cytometry (fluorescence-activated cell sorting) on whole blood was used to assess peripheral biomarkers. Results: At clinical cutoff date (CCOD; May 2, 2023), 37 pts were enrolled: 21 (56.8%) had been on the study for 0-3 months, 12 (32.4%) for 3-6 months, and 4 (10.8%) for 6-9 months. Median age was 62.0 (range 28-83) years and 20 (54.1%) pts were male. All pts had a baseline ECOG PS of ≤1; 32 (86.5%) had Ann Arbor stage III-IV; and 7 (18.9%), 13 (35.1%), and 17 (45.9%) had a FL International Prognostic Index score of 0-1 (low), 2 (intermediate), and 3-5 (high risk), respectively. All pts reported ≥1 treatment-emergent adverse event (TEAE); 12 (32.4%) had ≥1 serious TEAE. Two pts discontinued study treatment after the C1D15 dose, one pt due to uveitis and one pt due to tumor flare. TEAEs related to M or Len occurred in 36 (97.3%) and 29 (78.4%) pts, respectively. At least one Grade (Gr) 3-4 TEAE occurred in 16 (43.2%) pts, the most common being neutropenia (seven pts). No pts reported Gr 5 AEs. CRS occurred in 20 (54.1%) pts; all were Gr 1, except for one pt with Gr 2 CRS, and all events resolved (median CRS duration: 2 days [range 1-26]). CRS frequency was highest after C1D1 (32.4%), and steadily declined over subsequent days and cycles. No immune effector cell-associated neurotoxicity syndrome events were observed. To date, 27 pts were efficacy evaluable ( Figure B). Of 24 (88.9%) responders, 22 (81.5%) had a complete metabolic response (21 achieved by the first response assessment at end of C3), and two (7.4%) had a partial metabolic response. One pt (3.7%) had no response assessment by CCOD, and two (7.4%) had progressive disease but were recognized to have biopsy-proven transformed FL during C1 and C2. All responses were maintained at CCOD. Preliminary biomarker analyses of pt blood samples showed: increased CD69 and sustained HLA-DR expression in CD8 T cells, with modulation of CD8 subsets favoring central/effector memory phenotypes; sustained natural killer-cell activity; and minimal effects on CD4 T cells (except for lower PD-1 expression). Conclusions: This fixed-duration, chemotherapy-free M+Len regimen offers a convenient means for outpatient SC administration, and has a manageable early safety profile with promising anti-lymphoma activity in pts with 1L FL requiring systemic therapy, based on the preliminary data. Advancing M+Len into the first-line setting offers potential benefits in chemotherapy-naïve pts. Safety, efficacy, biomarker, and pharmacokinetic data from the complete cohort (40 pts) will be presented.

Intradermal Vaccination with Vididencel in MRD+ AML-Patients Leads to Increase in Antigen Presenting Cells and T-Cells to the Injection Site, Visualized Using Imaging Mass Cytometry, Showing Local Immune Cell Interactions Leading to Systemic Immune Responses

Background. Vididencel is an allogeneic leukemia-derived dendritic cell vaccine being developed as maintenance treatment in AML patients. Intradermal vaccination using vididencel is known to induce a local skin reaction, with local antigen processing by skin dendritic cells and direct presentation to T cells as well as dendritic cells, crawling out of the skin and presentation of the antigen in the draining lymph nodes for a full-blown immune response. It was previously shown that vididencel is able to induce an influx of immune cells in the skin using standard immunohistochemistry (van de Loosdrecht, 2018). In a phase 2 study vididencel was investigated as AML maintenance treatment after induction of CR1 with chemotherapy (ADVANCE-II, Clintrials.gov: NCT03697707). Using imaging mass cytometry up to 43 markers can be assessed in the same tissue section, to allow in depth analysis of the immune cells on a single cell level infiltrating in the dermis at the injection site. Methods. AML patients, in first complete remission with measurable residual disease (MRD +) and not planned for HSCT at inclusion, received 4 biweekly doses of vididencel followed by 2 booster doses at week 14 and 18. Skin biopsies of the injection site were taken 2 days after the 1 st, 4 th and 6 th vaccination. Control samples were collected from unvaccinated/unaffected skin in two patients and from healthy controls. Samples were fixed and embedded in paraffin, and stained by standard immunohistochemistry for immune cell markers like CD4, CD8 and CD68 in the central lab. For patients treated at Haukeland University Hospital (N=6), tissue sections were prepared, mounted and stained with the panel of 29 antibodies labelled with heavy metal isotopes for use in the Hyperion mass cytometry imaging. For each sample a region of interest (ROI) of 2.8mm 2 was scanned based on the localization of the immune infiltrates, guided by standard H&amp;E staining from neighboring slides. Results In 88.5% of patients injection site reactions were reported in this phase 2 study, characterized by redness, swelling and warmth at the site of intradermal injection, which were mild (maximum grade 1 or 2), and were of short duration (generally resolved within 12 days). Skin biopsies of a subset of 6 patients were analyzed using Hyperion. In standard single stain immunohistochemistry a large influx of CD4, CD8 and CD68 cells was observed in contrast to normal skin. Imaging mass cytometry confirmed these dense immune infiltrations. Using additional markers to characterize monocytes, dendritic cells and T-cells revealed that these cells are in close proximity and suggestive for cell-to-cell interaction (Figure 1). At sites of dense immune infiltration, influx of GranzymeB expressing CD8 T-cells and CD38 positive CD4 T-cells were observed as well as CD1c+ or CD141+ dendritic cells with high HLA-DR expression. These T-cells and dendritic cells are in close contact suggestive for patients' dendritic cells migrating from blood to skin, inducing a local immune response. Conclusion/discussion. Vaccination with vididencel triggered an inflammatory skin reaction in the majority of patients, with redness, warmth and swelling, of short duration, indicative for an active immune response at the site of injection. Skin biopsies using standard immunohistochemistry showed influx of activated CD4 and CD8 T cells as well as antigen presenting cell, including dendritic cells.Extended analysis with multiparameter imaging mass cytometry showed specific immune cell subsets infiltrating in these site of injection sites. The observed co-localization of the different immune subsets following vaccination supports the hypothesis of local antigen capturing by blood derived and local antigen presenting cells (Zuo et al, 2021). The local immune response may ultimately leads to a systemic immune response and disease control.

Sitagliptin Induces Tolerogenic Human Dendritic Cells

Sitagliptin, an anti-diabetic drug, is a dipeptidyl peptidase (DPP)-4/CD26 inhibitor with additional anti-inflammatory and immunomodulatory properties. In this study, we investigated for the first time the effect of sitagliptin on the differentiation and functions of human dendritic cells generated from monocytes (MoDCs) for 4 days using the standard GM-CSF/IL-4 procedure. LPS/IFN-γ treatment for an additional 24 h was used for maturation induction of MoDCs. Sitagliptin was added at the highest non-cytotoxic concentration (500 µg/mL) either at the beginning (sita 0d protocol) or after MoDC differentiation (sita 4d protocol). Sitagliptin impaired differentiation and maturation of MoDCs as judged with the lower expression of CD40, CD83, CD86, NLRP3, and HLA-DR, retention of CD14 expression, and inhibited production of IL-β, IL-12p70, IL-23, and IL-27. In contrast, the expression of CD26, tolerogenic DC markers (ILT4 and IDO1), and production of immunoregulatory cytokines (IL-10 and TGF-β) were increased. Generally, the sita 0d protocol was more efficient. Sitagliptin-treated MoDCs were poorer allostimulators of T-cells in MoDC/T-cell co-culture and inhibited Th1 and Th17 but augmented Th2 and Treg responses. Tolerogenic properties of sitagliptin-treated MoDCs were additionally confirmed by an increased frequency of CD4+CD25+CD127- FoxP3+ Tregs and Tr1 cells (CD4+IL-10+FoxP3-) in MoDC/T-cell co-culture. The differentiation of IL-10+ and TGF-β+ Tregs depended on the sitagliptin protocol used. A Western blot analysis showed that sitagliptin inhibited p65 expression of NF-kB and p38MAPK during the maturation of MoDCs. In conclusion, sitagliptin induces differentiation of tolerogenic DCs, and the effect is important when considering sitagliptin for treating autoimmune diseases and allotransplant rejection.

Comprehensive transcriptomic analyses identify the immunosuppressive effects of LLDT-8 in ART-treated SIV-infected rhesus macaques

BackgroundChronic immune activation plays a significant role in the pathogenesis and disease progression of human immunodeficiency virus (HIV), and the existing interventions to address this issue are limited. In a phase II clinical trial, (5R)-5-hydroxytriptolide (LLDT-8) demonstrated promising potential in enhancing CD4+ T cell recovery. However, the therapeutical effects of LLDT-8 remained to be systemic explored. MethodsTo assess the treatment effects of LLDT-8, we conducted flow cytometry and RNA-seq analyses on eight Chinese rhesus monkeys infected with simian immunodeficiency virus (SIV). Additionally, we performed comprehensive transcriptomic analyses, including cross-sectional and longitudinal differentially expressed gene (DEG) analysis, gene set enrichment analysis (GSEA), weighted gene co-expression network analysis (WGCNA), and deconvolution analysis using peripheral blood mononuclear cell (PBMC) samples from 14-time points. These findings were further validated with RNA-seq analysis on patients who received LLDT-8 treatment, along with in vitro cellular experiments using human PBMCs. ResultsFlow cytometry analysis revealed that LLDT-8 treatment significantly reduced the percentage of HLA-DR+CD38+CD8+ T cells in SIV-infected rhesus monkeys (P < 0.001). The cross-sectional and longitudinal analysis identified 2531 and 1809 DEGs, respectively. GSEA analysis indicated that LLDT-8 treatment led to significant downregulation of proliferation-related pathways, such as E2F targets, G2M checkpoint, and mitotic spindle pathways. WGCNA analysis identified two modules and 202 hub genes associated with CD8 activation levels. Deconvolution analysis showed a significant decrease in the proportion of CD8+ T cells and activated CD4+ T cells during LLDT-8 treatment. Gene ontology results demonstrated that the common DEGs between LLDT-8-treated patients and rhesus monkeys were primarily enriched in cell activation and cell cycle progression. Furthermore, in vitro cellular experiments validated the consistent impact of LLDT-8 in inhibiting proliferation, activation (HLA-DR and CD38 expression), exhaustion (PD-1 expression), and IFN-γ production in human CD4+ and CD8+ T cells. ConclusionLLDT-8 exhibited notable efficacy in alleviating immune activation in both an in vivo animal model and in vitro human cell experiments. These findings suggest that LLDT-8 may hold potential as a drug for managing systemic immune activation associated with SIV/HIV infection, warranting further prospective clinical exploration.