Citations

Abstract Introduction: Chronic lymphocytic leukemia (CLL) is marked by impaired T cell responses that limit the efficacy of immunotherapies. CD19-directed chimeric antigen receptor T cell therapy (CART19) received FDA approval to treat CLL in 2024. However, itsefficacy in CLL patients remains low, with durable remission rate of ~20%. Ibrutinib, a Bruton tyrosine kinase inhibitor, has shown synergy with CART19 in preclinical and early clinical studies. We aimed to study the impact of ibrutinib on CART19 utilizing clinical samples from the pivotal clinical trial E1912 (NCT02048813) of ibrutinib/rituximab (IR) vs fludarabine/cyclophosphamide/rituximab (FCR). This trial led to the FDA approval of first line ibrutinib in CLL. Methods: We generated CART19 incorporating either CD28 (28ζ) or 41BB (BBζ) costimulatory domains from T cells isolated from patients with CLL treated with IR or FCR on the E1912 trial. IR samples were collected at baseline (pretreatment), 6- or 12-months during treatment, or at progression. FCR samples were collected at baseline, 15-18 months during treatment, or at progression. For animal experiments, NOD-SCID-γ-/- (NSG) mice were intravenously (i.v.) engrafted with 1×10⁶ luciferase⁺ CD19⁺ JeKo-1 cells. Upon tumor establishment (~10⁸ photons/sec by bioluminescence imaging), mice were randomized and treated i.v. with 1×10⁶ 28ζ or BBζ derived from longitudinal IR- or FCR-treated patient samples. To further assess the impact of prolonged ibrutinib exposure on CART19 function, we chronically stimulated healthy donor-derived 28ζ or BBζ in vitro for 22 days with JeKo-1 cells and 100nM ibrutinib or vehicle control and then tested CART19 functions. Finally, we performed single cell RNA sequencing (scRNAseq) of longitudinal patient T cell samples treated with IR. Results: Ex vivo T cell expansion was significantly enhanced following IR compared to FCR. BBζ generated from IR-treated patients after 6 months of ibrutinib exhibited enhanced in vitro expansion (p=0.016) and antigen-specific proliferation (p=0.038) in the presence of JeKo-1 cells. This corresponded with significantly improved antitumor efficacy and prolonged survival in vivo compared to cells generated at disease progression (p=0.017). In contrast, 28ζ showed no significant differences in efficacy across IR studied treatment timepoints. BBζ from FCR-treated patients did not show differences in tumor control based on treatment timepoints but demonstrated shorter survival compared to BBζ from IR-treated patients. 28ζ from FCR-treated patients generated at disease progression demonstrated significantly reduced tumor control and shorter survival compared to 28ζ produced at baseline (p=0.0002), indicating detrimental effects of FCR treatment on the therapeutic potential of CART products. To further investigate the impact of prolonged ibrutinib exposure, we utilized in vitro models of CART exhaustion. We found that, after repeated antigen stimulation with JeKo-1 cells, ibrutinib-treated BBζ had significantly increased antigen-specific degranulation (p=0.005), and cytokine production (IL-2, p=0.045; TNF-α, p=0.003; IFN-γ, p=0.001), compared to BBζ treated with vehicle control. In contrast, 28ζ did not show improved degranulation or cytokine production in cocultures with ibrutinib. Prolonged ibrutinib exposure led to downregulation of FOXO3, a transcription factor associated with T cell exhaustion which has been shown to cause dysfunction specifically in BBζ. These results further indicate that ibrutinib may be more beneficial to BBζ. Indeed, scRNAseq revealed that after ≥ 6 months of ibrutinib, T cells showed downregulation of inflammatory, oxidative stress, and apoptosis pathways, paralleled by modest activation of MYC and E2F targets. However, at disease progression, T cells under ibrutinib treatment displayed marked upregulation of interferon signaling, inflammation responses, and stress-related programs, indicating a shift toward immune reactivation or dysfunction.Conclusion: Our study shows that BBζ, but not 28ζ, generated 6 months during ibrutinib treatment has superior antitumor activity and persistence compared to similar later timepoints or FCR-treated counterparts. Prolonged ibrutinib exposure enhances BBζ function by modulating stress and apoptotic pathways. These findings highlight the importance of pre-CART treatment timing and support ibrutinib as a potential enhancer of CART cell fitness in CLL.

Abstract INTRODUCTION: Warm autoimmune hemolytic anemia (wAIHA) is a rare, autoimmune-mediated hematologic disorder associated with significant morbidity and mortality and may occur as a primary condition or secondary to an underlying disorder. It is the most common subtype of autoimmune hemolytic anemia (AIHA), accounting for 75-80% of AIHA cases. Older adults with wAIHA are particularly vulnerable, as they often have multiple comorbidities and are already at elevated risk of death. This study aimed to assess mortality associated with wAIHA. METHODS: Adults with wAIHA (wAIHA cohort) and without AIHA (non-AIHA cohort) were identified from the 100% Medicare Fee-for-Service database (10/01/2019–12/31/2023). Evidence of wAIHA was defined as one of the following: 1) a primary wAIHA diagnosis (International Classification of Diseases, Tenth Revision, Clinical Modification [ICD-10-CM]: D59.11) in the inpatient setting (first instance of wAIHA diagnosis defined the index date), 2) ≥2 wAIHA diagnosis in any setting ≥30 days apart (second instance of wAIHA diagnosis defined the index date), or 3) a wAIHA diagnosis preceded ≥30 days by any AIHA diagnosis (ICD-10-CM: D59.10, D59.19, D59.8, D59.9; first instance of wAIHA diagnosis defined the index date). Patients in the wAIHA cohort were excluded if they had a diagnosis for cold or mixed-type AIHA (ICD-10-CM: D59.12, D59.13) during the baseline period (12 months before index). The non-AIHA cohort had no diagnoses for any AIHA during the study period; a random index date during continuous Medicare eligibility was selected and patients were matched 1:10 with the wAIHA cohort based on age on index date. Using overlap weighting, age-matched cohorts were further weighted on sex, race, region, index year, and baseline comorbidities associated with mortality, excluding conditions defining secondary wAIHA. Mortality during the follow-up period was evaluated between the weighted cohorts using the Kaplan-Meier method and Cox proportional hazard models. Patients whose death was not observed were censored at the earlier of the end of continuous Medicare eligibility or data availability. RESULTS: 3,112 and 31,120 patients were included in the wAIHA and non-AIHA cohorts, respectively. After weighting, among the wAIHA vs non-AIHA cohorts, mean [standard deviation; SD] age was 74.4 [11.6] vs 74.6 [11.2] years, the proportion of female were 56.1% vs 56.1%, mean [SD] Quan-CCI without secondary wAIHA-defining conditions was 1.9 [2.0] vs 1.9 [2.1], and mean [SD] follow-up time was 17.2 [11.7] vs 14.9 [11.4] months, respectively. In addition, 53.7% of the wAIHA cohort had secondary wAIHA. The most common secondary wAIHA-defining conditions were autoimmune and inflammatory diseases (wAIHA cohort: 27.8%; non-AIHA cohort: 11.0%), hematologic and lymphoproliferative disorders (wAIHA cohort: 23.8%; non-AIHA cohort: 1.3%), and solid tumors (wAIHA cohort: 16.8%; non-AIHA cohort: 12.6%). The most common comorbidities for both cohorts were hypertension (wAIHA cohort: 77.4%; non-AIHA cohort: 78.3%) and dyslipidemia (wAIHA cohort: 72.2%; non-AIHA cohort: 74.7%). Survival rates in the wAIHA and non-AIHA cohorts were 80.3% vs 84.0% at 12 months, 70.7% vs 77.6% at 24 months, and 63.7% vs 73.1% at 36 months, respectively (all p<0.001). Patients with wAIHA were at 20%, 27%, and 30% higher risk of death at 12, 24, and 36 months, respectively, compared to patients without AIHA (hazard ratios: 1.20, 1.27, and 1.30; all p<0.001). CONCLUSIONS: This large retrospective study is the first to assess real-world incremental mortality associated with wAIHA among Medicare beneficiaries. Patients with wAIHA were at significantly greater risk of death following the initial diagnosis. These results may point to potential gaps in early diagnosis and effective disease management, which could contribute to increased mortality. Future research should focus on specific subgroups within the wAIHA cohort to identify differences in mortality as well as characteristics that may be associated with death.

Abstract Recent studies have highlighted the important but pleiotropic role of IL-4 in response to chimeric antigen receptor T (CART) cell therapy. IL-4 was identified as a regulator of dysfunction in CD19-targeting CART cells with a CD28 costimulatory domain (CART19-28ζ) through a genome-wide CRISPR knockout screen as well as RNA and ATAC sequencing of baseline and exhausted healthy donor CART19-28ζ cells and pre-infusion CART19-28ζ cell products from responders and non-responders in the ZUMA-1 trial (Stewart et al, Nat Commun., 2024). However, interrogation of a single-cell atlas fromactivated pre-infusion CART cell products from patients with acute lymphoblastic leukemia revealed a beneficial role for IL-4 and other type 2 cytokines in the promotion of long-term response (Bai et al, Nature, 2024). In this report, we aim to further understand how IL-4 can be detrimental to CART cell therapy. To study the regulation of CART19-28ζ cells by IL-4, we performed RNA sequencing on CART19-28ζ cells that were stimulated with CD19+target cells in the presence of either 20 ng/mL hrIL-4 or diluent for 24 hours, one week, or two weeks in an in vitro model for exhaustion as previously described (Stewart et al, Nat Commun., 2024). We observed that hrIL-4 treatment drove the development of a distinct transcriptomic profile after chronic stimulation for one week (up genes = 3253 and down genes = 3645) or two weeks (up genes = 6435 and down genes = 6224) but not following 24 hours of activation (up genes = 0 and down genes = 0). Gene set enrichment analysis on the differentially expressed genes following two weeks of chronic stimulation showed that hrIL-4 treatment pushes CART cells to a more exhausted and less naïve phenotype (FDR = 0.015) and leads to a broad downregulation in cytokine signaling (FDR = 0.012). To investigate transcription factors associated with IL-4-induced CART cell dysfunction, we used BETA analysis with publicly available transcription factor binding sites for STAT6, GATA3, and EOMES and our differential expression data. EOMES (p = 0.039), but not STAT6 (p = 0.999) nor GATA3 (p = 0.999) significantly regulated the differentially expressed genes. In support of these findings, the addition of hrIL-4 also significantly upregulated EOMES expression after one (p < 0.0001) and two (p < 0.0001) weeks of chronic stimulation and downregulated the expression of TBX21 (p < 0.0001), a binding competitor of EOMES, following two weeks of chronic stimulation. To evaluate if EOMES is critical for IL-4-induced CART cell dysfunction, we treated either control or EOMES CRISPR knockdown CART cells with 20ng/mL hrIL-4 during chronic stimulation. EOMES knockdown reduced IL-4-induced CART19-28ζ cell dysfunction as seen by an increase in antigen-specific expansion (p = 0.046) and an increase in cytokine production including IL-2 (p < 0.0001), TNF-α (p = 0.006), and IFN-γ (p = 0.020). Having identified that EOMES is at least partially responsible for IL-4-induced CART cell dysfunction, we evaluated EOMES binding sites in human CART19-28ζ cells with CUT&RUN sequencing. Our analysis revealed EOMES binding at hypersensitivity site 2 (HS2) in the IL-4 locus which, in a previous study, was more accessible in both exhausted healthy donor CART19-28ζ cells and pre-infusion CART cell products from non-responders in the ZUMA-1 clinical trial (Stewart et al, Nat Commun., 2024). To determine how HS2 can impact CART cell functions, we generated CART19-28ζ cells from either wildtype (HS2+/+) or HS2-deleted (HS2-/-) murine T-cells and tested them in a syngeneic model of lymphoma generated by engrafting C57BL6 mice with luciferase+ TBL12 cells (1x106, tail vein injection on Day -3) following preconditioning (250mg/kg cyclophosphamide, intraperitoneal injection on Day -4). Following randomization of mice via tumor burden (n = 5 per group), mice were treated with either HS2+/+ or HS2-/- CART19-28ζ cells (1x106 cells, tail vein injection). In this model, HS2-/- CART cells showed enhanced expansion (p = 0.022), increased anti-tumor activity (p = 0.018), and improved overall survival (p = 0.003). Together, our study shows that IL-4 induces a distinct cellular fate in CART19-28ζ cells in the presence of chronic antigen-specific stimulation at least partially through the upregulation of EOMES. Further, the epigenetic regulation of CART cells by the IL-4 enhancer HS2 can significantly influence CART cell activity, and deletion of HS2 can improve CART cell therapy.

Abstract Introduction: CLL disease control and survival outcomes have improved since the introduction of Bruton tyrosine kinase inhibitors (BTKis). Since CLL often requires treatments, understanding patient preferences is critical in optimizing adherence and overall satisfaction. However, there are limited published data on how Korean patients prioritize treatment efficacy, safety and the convenience of administration. To address this gap, a discrete choice experiment (DCE) methodology was applied in a comprehensive quantitative analysis to evaluate patient preferences for BTKi treatment attributes among patients with CLL in Korea. Methods: Adult patients (≥18 years of age) with a confirmed diagnosis of CLL in Korea were recruited by The Korea Blood Disease & Cancer Association to participate in an online DCE survey questionnaire from April 30, 2025 to May 22, 2025. Treatment attributes and levels were identified based on published literature and clinical inputs. Efficacy attributes included progression-free survival (PFS); safety attributes included impacts of adverse events (AEs), including diarrhea, headache, atrial fibrillation and hypertension, on quality of life (QoL); convenience attributes included formulation type (including tablet or capsule) and dosing frequency (including once daily or twice daily). Preference data was analyzed using a conditional logistic regression. Relative importance of BTKi treatment attributes were calculated to measure the importance of each attribute in treatment decision-making. Additionally, subgroup analyses were conducted among patients aged <60 years and ≥60 years, those who received 2 or more lines (2L+) of treatments, and those who experienced AEs from CLL treatment. Results: A total of 57 patients completed the survey. The mean age was 61 years, with 46% aged <60 years and 54% aged ≥60 years. Female patients comprise 35% of the sample. Around 33% had a high school education or less, and 23% were employed full-time. More than half (54%) reported no comorbid conditions, and 70% were diagnosed ≥5 years ago (26% diagnosed 1 to <5 years ago; 4% diagnosed less than a year ago). In terms of treatment experience, 11% were treatment naive, while 89% received ≥1 treatment (61% first-line, 21% second-line and 7% third-line or later). In the context of CLL treatment preferences, patients showed a significant preference (P < .05) for therapies that minimized the impact of AEs on QoL, offered longer PFS, and required less frequent dosing. Formulation type did not have a statistically significant impact on treatment choice. Overall, patients placed greater importance on how treatment-related attributes affect their QoL and dosing frequency. The highest-ranked factors were the impact of headache (22%) and diarrhea (21%) on QoL, followed by dosing frequency (19%), the impact of atrial fibrillation (16%) and hypertension (14%) on QoL, PFS (7%), and formulation type (0.6%). Results from the subgroup analyses were generally consistent with the full sample analysis, with impacts of AEs on QoL being the most important factors for treatment decision-making, especially among older patients, although the relative ranking of impacts of AEs varied by age groups and treatment experience. Regarding efficacy, younger patients (<60 years of age) valued PFS slightly more than older patients (≥60 years of age), ranking it 4th and 6th out of the 10 attributes, respectively. Additionally, preference on dosing frequency was more important for 2L+ patients, reflecting the treatment burden experienced from previous regimens. Conclusions: This study provides valuable insights into the treatment preferences of Korean patients with CLL, highlighting the importance of QoL considerations for treatment decision-making. Among the evaluated attributes, patients placed the greatest weight on minimizing the impacts of AEs, particularly headache and diarrhea, on daily functioning, followed by dosing frequency. These preferences underscore the need for patient-centered care that prioritizes not only clinical efficacy but also tolerability and convenience. These insights can inform shared decision-making and support the development of personalized treatment strategies that better align with patient needs and expectations in Korea.

Abstract B cell maturation antigen (BCMA)-targeted chimeric antigen receptor T (CART) cell therapies have emerged as a potentially curative treatment for multiple myeloma (MM). However, 50-70% of patients relapse within 3 years. The MM tumor microenvironment (TME) is highly immunosuppressive with an abundance of bone marrow (BM) cancer-associated fibroblasts (CAFs), which contribute to BCMA-CART cell failure. Therapeutic targeting of BM-CAFs has been beset by 1) an incomplete understanding of CAF interactions with CART cells and other BM cells and 2) toxicity risks due to prolonged depletion of healthy fibroblasts and inefficient drug delivery to the BM. To elucidate how BM-CAFs drive BCMA-CART resistance, we performed single cell RNA sequencing (scRNAseq) of baseline BM aspirates from responders (R, n = 6) and non-responders (NR, n = 6) to BCMA-CART cell therapy. NR BMs were enriched for inhibitory CAFs (iCAFs) that highly express fibroblast activation protein (FAP). Spatial analyses of BM cells revealed greater iCAF-iCAF and iCAF-inhibitory macrophage interactions in NR. These findings suggest that FAP+ iCAFs in NR are abundant in the BM and exhibit significant interactions with immunosuppressive macrophages. Next, we sought to validate our scRNAseq data in preclinical models. Xenograft mice were intravenously (IV) engrafted with luciferase+ (luc+) BCMA+ OPM2 cells and/or patient-derived (pd) BM-CAFs (1x106 each). Following engraftment, mice received 1x106 BCMA-CART cells (IV). BCMA-CART cells eradicated tumors in mice engrafted with OPM2 cells, but not in mice engrafted with pdBM-CAFs and OPM2 cells (p<0.01). In NSG and humanized mice (NSG mice engrafted with human CD34+ cells in the first 48 hours of life), tumor growth was significantly accelerated in the presence of pdBM-CAFs (NSG: p<0.01; humanized: p<0.001). BCMA-CART, OPM2, and pdBM-CAF co-cultures also showed significant increases in immunosuppressive cytokines including IL-1Rα, IL-4 and IL-10 and inhibited CART cell proliferation compared to co-cultures without pdBM-CAFs (IL-1Rα, IL-10: p<0.01; IL-4: p<0.001; proliferation: p<0.05). To overcome CAF-mediated CART dysfunction, we engineered BCMA-CART cells to secrete molecules to target BM FAP+ iCAFs and remodel the MM-TME (STriKEs). We designed two BCMA-CART-STriKE strategies: 1) a tri-specific composed of IL-15, anti-FAP, and anti-CD16 molecules to activate innate immune cells to kill CAFs and 2) bi-specific anti-FAP, anti-SIRPα molecules linked to an antibody Fc region (Fc fusion) targeting the CD47/SIRPα axis to induce phagocytosis of FAP+ iCAFs. We hypothesized that BCMA-CART-STriKEs would surmount CAF-mediated immunosuppression without toxicity. We generated BCMA-CART-STriKEs from healthy human donor T cells. CAR expression, STriKE secretion, and binding were confirmed via flow cytometry. Co-cultures of BCMA-CART-STriKEs, donor-matched macrophages, OPM2 cells or BCMA+ MM1S cells, and pdBM-CAFs showed significantly higher OPM2 or MM1S killing (p<0.001), immune cell activation (p<0.01), and phagocytosis (p<0.05), compared to control BCMA-CART cells secreting IL-15 or Fc fusions targeting only FAP or only SIRPα. Next, we assessed BCMA-CART-STriKE efficacy in vivo. NOD-SCID-γ-/- (NSG) mice received 1x106 pdBM-CAFs and 1x106 luc+ OPM2 or luc+ MM1S cells via IV or subcutaneous (SQ) injection. Mice were randomized after confirming tumor engraftment (via bioluminescence imaging for IV or tumor caliper for SQ) and received IV treatment with 1x106 BCMA-CART-STriKEs (or controls) and 5x105 donor-matched macrophages or CD16+ immune cells. BCMA-CART-STriKE-treated mice achieved total tumor clearance. Treatment with BCMA-CART cells secreting IL-15 led to lethal weight loss despite tumor clearance while BCMA-CART cells secreting Fc fusions targeting only FAP or SIRPα failed to eradicate tumors. Lastly, we assessed the potential toxicities of BCMA-CART-STriKEs in humanized mice engrafted with OPM2 cells and pdBM-CAFs (1x106 each). CART cells expressing BCMA and FAP CARs (BCMA-FAP CART) served as a control. BCMA-FAP CART treatment resulted in significant toxicity and weight loss while BCMA-CART-STriKE treatment did not (p<0.01). In summary, we have identified iCAF interactions with immunosuppressive immune cells as key contributors to BCMA-CART cell failure and designed novel BCMA-CART-STriKEs that overcome this failure in MM preclinical models. These findings support the translation of BCMA-CART-STriKEs to a phase I clinical trial.

Abstract Introduction: The epidemiology and clinical characteristics of familial myelodysplastic syndromes/acute myeloid leukemia (MDS/AML) remain poorly understood, particularly among Native Hawaiians and Other Pacific Islanders (NHOPI). Methods: To investigate the real-world evidence in this area, we conducted a retrospective study at the Queen's Medical Center (QMC), Hawaii's largest tertiary referral hospital. The data was gathered from QMC's electronic medical record. Familial MDS or familial AML patients in this study were defined as MDS or AML occurring in a patient with a family history of MDS and/or AML. Patients with acute promyelocytic leukemia (APL), as well as those with a family history of APL, were excluded given the differences in disease characteristics and its genetic phenotype from other AML subtypes. Unspecified leukemia was defined when a patient had a family history of leukemia but the specific subtype was unavailable. Some patients underwent comprehensive panel testing, while others had targeted next-generation sequencing (NGS) assays ordered at the discretion of their treating physicians. NGS was performed at Clinical Laboratory Improvement Amendments (CLIA)-certified commercial laboratories. NGS panels typically included the following genes: ASXL1, BCOR, BRAF, CEBPA, CSF3R, DNMT3A, ETV6, EZH2, FLT3, HRAS, IDH1, IDH2, JAK2, KIT, KRAS, MLL, NPM1, NRAS, PDGFRA, PHF6, PML, PTPN11, RUNX1, SETBP1, STAG2, TET2, TP53, and WT1. Results: Among 1,686 MDS/AML patients presented between January 2012 and July 2023, 12 (0.71 %) had familial MDS/AML and 25 (1.48%) had a family history of unspecified leukemia. While no NHOPI were identified among familial MDS/AML cases, 20% of patients with a family history of unspecified leukemia were NHOPI. The median age at diagnosis of familial MDS/AML was 70 years, and 50% of familial MDS patients had MDS with low blasts based on the World Health Organization 2022 classification. Based on International Consensus Classification 2022 criteria, 25% had MDS, not otherwise specified (NOS) with multilineage dysplasia, and 25% had MDS, NOS with single lineage dysplasia. Among the eight patients with familial MDS, the median overall survival (OS) was 12.7 years, with an estimated 5-year OS rate of 75.0% (95% CI: 12.8–96.1), based on Kaplan–Meier analysis. In contrast, the three patients with familial AML had a median survival of 10.2 months and a 3-year OS estimate of 33.3% (95% CI: 0.90–77.4). For patients with a family history of unspecified leukemia, the median survival was not reached during the follow-up period. The estimated 5-year OS rate was 53.3% (95% CI: 12.5–82.7) for the 10 familial MDS cases and 53.3% (95% CI: 20.9–77.3) for the 13 familial AML cases. When combining all familial cases, the median OS for familial MDS (n = 18) was 12.7 years with a 5-year OS rate of 61.9% (95% CI: 26.8–84.0). The median OS for familial AML (n = 16) was 0.90 years, and the estimated 5-year OS rate was 48.2% (95% CI: 20.8–71.3). When all cases were combined, there was no statistically significant difference in overall survival between patients with familial AML (n = 16) and those with familial MDS (n = 18), based on the log-rank test (p = 0.22). Regarding NGS, ASXL1 mutations were the most frequent in the cohort, detected in six of the 32 NGS tests performed (18.8%). Among patients with familial MDS, recurrent somatic mutations were observed in several genes. ASXL1 mutations were identified in two patients; one had a brother with MDS, and the other had a maternal uncle with unspecified leukemia. DNMT3A mutations were also found in two patients with familial MDS; one had a brother with MDS, and the other had a paternal uncle with MDS. SRSF2 mutations were detected in two patients; one had a brother with MDS, and the other had a granddaughter with leukemia. Additionally, SF3B1 mutations were found in two patients; one had a mother with MDS, and the other had a paternal uncle with MDS. Two patients with familial AML were found to have ASXL1 mutation, both with fathers who had unspecified leukemia. Otherwise, no other repeated mutations were found. None of the cases involved NHOPI patients. Conclusion: Our study offers new insights into familial MDS/AML within Hawaii's multiethnic population. Although no NHOPI patients were identified among the familial cases, our findings underscore the genetic heterogeneity and clinical variability of these disorders.

Abstract Description The live-attenuated measles virus (MeV) vaccine is one of the most efficacious vaccines ever developed and has the potential to eradicate MeV from the human population. While having been administered to millions of children over the past 60 years, the molecular mechanisms of its attenuation remain elusive. To determine these mechanisms, we have performed a comparative study of wild type (WT) and vaccine strain MeV infections in peripheral blood mononuclear cells (PBMCs) from human donors, the natural target cells of MeV. We performed in vitro growth kinetics, high-parameter spectral flow cytometry, next generation RNA-seq, and protein analyses. We found that the vaccine strain specifically activated cell intrinsic innate immunity signaling cascades causing a strong type-I interferon (IFN) signature. This resulted in 100-fold reduced titers of vaccine compared to WT virus. Surprisingly, while MeV vaccine infected B and T cells expressing the natural MeV receptor CD150 with similar efficiency as the WT virus, we found a subset of CD150-negative, CD11b+CD11c+CD123+ myeloid cells to become infected with the vaccine strain. We propose that these innate immune cells are highly specialized in pathogen sensing and prime the IFN response preventing vaccine from productive replication and generation of progeny virus in PBMCs. We currently investigate whether altered cell entry or innate immune control mechanisms are the underlying cause of attenuation. Funding Sources Supported by the German Research Foundation (DFG) Collaborative Research Center (SFB) 1021 (Project number 197785619/B12), internal funding of the German Ministry of Health, and by Mayo Clinic. Topic Categories Viral Immunology (VIR)

Pediatric central nervous system tumors are the leading cause of cancer-related deaths in children. The five-year survival rate for high-grade glioma in children is less than 20%. The development of new treatments is dependent upon multi-institutional collaborative clinical trials requiring reproducible and accurate centralized response assessment. We present the results of the BraTS-PEDs 2023 challenge, the first Brain Tumor Segmentation (BraTS) challenge focused on pediatric brain tumors. This challenge utilized data acquired from multiple international consortia dedicated to pediatric neuro-oncology and clinical trials. BraTS-PEDs 2023 aimed to evaluate volumetric segmentation algorithms for pediatric brain gliomas from magnetic resonance imaging using standardized quantitative performance evaluation metrics employed across the BraTS 2023 challenges. The top-performing AI approaches for pediatric tumor analysis included ensembles of nnU-Net and Swin UNETR, Auto3DSeg, or nnU-Net with a self-supervised framework. The BraTS-PEDs 2023 challenge fostered collaboration between clinicians (neuro-oncologists, neuroradiologists) and AI/imaging scientists, promoting faster data sharing and the development of automated volumetric analysis techniques. These advancements could significantly benefit clinical trials and improve the care of children with brain tumors.