High-dimensional Flow Research Articles

IMMU-06. CAR DESIGN SHAPES THE BRAIN TUMOR IMMUNE MICROENVIRONMENT: IMPACT ON ACTIVITY AND PERSISTENCE OF ANTI-GLIOMA ADOPTIVE T CELL IMMUNOTHERAPY

Abstract BACKGROUND B7-H3 CAR T-cells effectively eradicate brain tumors in xenograft models and have proven safe in clinical trials, yet no objective responses were observed in patients. The limited efficacy is partly attributed to the immunosuppressive tumor microenvironment (TME), a characteristic not fully recapitulated in investigations using xenograft models. In this study, we set to optimize B7-H3 CAR structure and examine the effects of CAR design on the brain TME using an immunocompetent glioma model. METHODS We generated a panel of fully murine B7-H3 CARs with variations in transmembrane, co-stimulatory, and activation domains. This enabled us to comprehensively investigate their effector functions within the intact immune system. High-dimensional flow cytometry and single-cell RNA sequencing were then used to investigate changes in the brain TME following CAR T-cell therapy. RESULTS While five out of six B7-H3 CARs with single co-stimulatory domains exhibited potent functionality in vitro, optimizing co-stimulation and signaling failed to enhance their anti-glioma efficacy in vivo. To further enhance therapeutic effectiveness and persistence, we incorporated 4-1BB and CD28 co-stimulation through transgenic expression of 4-1BBL on CD28-based CAR T-cells. Although this design significantly improved anti-glioma efficacy in vitro, it conferred no additional benefits in vivo. Analysis of the TME revealed that CAR T-cell therapy influenced the immune composition of the brain TME. Successful anti-tumor responses were dictated by the recruitment, activation, and spatial localization of unique inflammatory ‘immune hubs’ containing specific subsets of macrophages and endogenous T-cells. Interestingly, depletion of brain macrophages using CSF1R inhibitor markedly inhibited CAR T-cell anti-tumor activity. CONCLUSION Our study highlights the critical role of CAR structural design and its modulation of the TME in mediating the efficacy of CAR T-cell therapy in brain tumors. Yet, more specific targeting and/or reprogramming of the TME is warranted for the successful design of effective adoptive immunotherapies for high-grade glioma.

Deep JKO: Time-implicit particle methods for general nonlinear gradient flows

We develop novel neural network-based implicit particle methods to compute high-dimensional Wasserstein-type gradient flows with linear and nonlinear mobility functions. The main idea is to use the Lagrangian formulation in the Jordan–Kinderlehrer–Otto (JKO) framework, where the velocity field is approximated using a neural network. We leverage the formulations from the neural ordinary differential equation (neural ODE) in the context of continuous normalizing flow for efficient density computation. Additionally, we make use of an explicit recurrence relation for computing derivatives, which greatly streamlines the backpropagation process. Our methodology demonstrates versatility in handling a wide range of gradient flows, accommodating various potential functions and nonlinear mobility scenarios. Extensive experiments demonstrate the efficacy of our approach, including an illustrative example from Bayesian inverse problems. This underscores that our scheme provides a viable alternative solver for the Kalman-Wasserstein gradient flow.

A Novel Finite Element-Based Method for Predicting the Permeability of Heterogeneous and Anisotropic Porous Microstructures.

Permeability is a fundamental property of porous media. It quantifies the ease with which a fluid can flow under the effect of a pressure gradient in a network of connected pores. Porous materials can be natural, such as soil and rocks, or synthetic, such as a densified network of fibres or open-cell foams. The measurement of permeability is difficult and time-consuming in heterogeneous and anisotropic porous media; thus, a numerical approach based on the calculation of the tensor components on a 3D image of the material can be very advantageous. For this type of microstructure, it is important to perform calculations on large samples using boundary conditions that do not suppress the transverse flows that occur when flow is forced out of the principal directions. Since these are not necessarily known in complex media, the permeability determination method must not introduce bias by generating non-physical flows. A new finite element-based method proposed in this study allows us to solve very high-dimensional flow problems while limiting the biases associated with boundary conditions and the small size of the numerical samples addressed. This method includes a new boundary condition, full permeability tensor identification based on the multiscale homogenization approach, and an optimized solver to handle flow problems with a large number of degrees of freedom. The method is first validated against academic test cases and against the results of a recent permeability benchmark exercise. The results underline the suitability of the proposed approach for heterogeneous and anisotropic microstructures.

HETEROGENEOUS EXPANSION OF POLYMORPHONUCLEAR MYELOID-DERIVED SUPPRESSOR CELLS DISTINGUISHES HIGH-RISK SEPSIS IMMUNOPHENOTYPES IN UGANDA.

Background: Understanding of immune cell phenotypes associated with inflammatory and immunosuppressive host responses in sepsis is imprecise, particularly in low- and middle-income countries, where the global sepsis burden is concentrated. In these settings, elucidation of clinically relevant immunophenotypes is necessary to determine the relevance of emerging therapeutics and refine mechanistic investigations of sepsis immunopathology. Methods: In a prospective cohort of adults hospitalized with suspected sepsis in Uganda (N = 43; median age 46 years [IQR 36-59], 24 [55.8%] living with HIV, 16 [37.2%] deceased at 60 days), we combined high-dimensional flow cytometry with unsupervised machine learning and manual gating to define peripheral immunophenotypes associated with increased risk of 60-day mortality. Results: Patients who died showed heterogeneous expansion of polymorphonuclear myeloid-derived suppressor cells, with increased and decreased abundance of CD16 - PD-L1 dim and CD16 bright PD-L1 bright subsets, respectively, significantly associated with mortality. While differences between CD16 - PD-L1 dim cell abundance and mortality risk appeared consistent throughout the course of illness, those for the CD16 bright PD-L1 bright subset were more pronounced early after illness onset. Independent of HIV co-infection, depletion of CD4 + T cells, dendritic cells, and CD56 - CD16 bright NK cells were significantly associated with mortality risk, as was expansion of immature, CD56 + CD16 - CD11c + NK cells. Abundance of T cells expressing inhibitory checkpoint proteins (PD-1, CTLA-4, LAG-3) was similar between patients who died versus those who survived. Conclusions: This is the first study to define high-risk immunophenotypes among adults with sepsis in sub-Saharan Africa, an immunologically distinct region where biologically informed treatment strategies are needed. More broadly, our findings highlight the clinical importance and complexity of myeloid derived suppressor cell expansion during sepsis and support emerging data that suggest a host-protective role for PD-L1 myeloid checkpoints in acute critical illness.

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

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

Increased Natural Killer (NK)-cell cytotoxicity and Trypanosoma cruzi-specific memory B cells in subjects with discordant serology for Chagas disease

The presence of memory T cell specific for Trypanosoma cruzi in subjects with discordant serology for Chagas disease supports a cleared infection in these subjects. Using high-dimensional flow cytometry, ELISPOT assays and quantitative PCR, antibody-secreting cells and memory B cells specific for T. cruzi, total B-cell phenotypes, innate immune responses and parasite DNA were evaluated in serodiscordant, seropositive and seronegative subjects for T. cruzi infection. T. cruzi-specific memory B cells but no antibody-secreting cells specific for T. cruzi, increased proportion of nonclassical monocytes and increased levels of polyfunctional NK cells were found in serodiscordant compared with seropositive subjects. None of the serodiscordant subjects evaluated showed detectable parasite DNA, most of them did not show cardiac abnormalities and a group of them had had confirmed positive serology for Chagas disease. The unique immune profiles in serodiscordant subjects support that T. cruzi infection was cleared or profoundly controlled in these subjects.

Time dimension feature extraction and classification of high-dimensional large data streams based on unsupervised learning

In order to solve the problem of low accuracy of time dimension feature extraction and classification of high-dimensional large data streams, this paper proposes a time dimension feature extraction and classification algorithm of high-dimensional large data streams based on unsupervised learning. Analyze the trend of high-dimensional data flow changes under machine learning, and achieve dimensionality reduction of high-dimensional large traffic time dimensional data through local save projection. Analyze the spatial relationship between feature attributes and feature space, segment and fit high-dimensional big data streams and time dimensional feature data streams, further segment time dimensional sequences using sliding windows, and complete feature extraction through discrete dyadic wavelet transform. According to the clustering algorithm, cluster the time dimension feature data stream, calculate the cosine similarity of the feature data, model the time dimension feature stream of training samples, use the feature classification function to minimize the classification loss, and use unsupervised learning to achieve the final classification task. The test results show that this method can improve the temporal feature extraction and classification accuracy streams.

Abstract PO1-13-04: Distinct immune signatures discriminate between patients defined as exceptional survivors of metastatic breast cancer compared to those with rapidly progressing treatment resistant breast cancers

Abstract Background: "Atypical responders" can encompass three sub- categories of patients: "exceptional responders" (those with an unusually favourable treatment response), "rapid progressors" (unusually poor or no response), and "exceptional/long-term survivors" (outlived initial prognosis). Here, we aim to investigate the drivers of immune surveillance mechanisms (local, lymphoid and peripheral) and the nature of immunological tumour recognition in exceptional survivors of stage 4 metastatic disease following standard-of-care chemo- and targeted therapies. Methods: We conducted a complementary multi-platform immune profiling study to define differences in the phenotypic immune landscape including mass-spectrometry-based proteomics on peripheral blood mononuclear cells (PBMCs), multiplex cytokine profiling of patient serum, and high-dimensional flow cytometry on whole blood samples. By staining 500μl of whole blood using 2 panels, 353 immune-cell-related parameters were obtained for comparisons among the following groups: "exceptional survivors," "exceptional responders," "rapid progressors," "non-exceptional metastatic patients," "early breast cancer patients," and "healthy volunteers". Patients were matched for age, breast cancer receptor status, and sites of metastases where possible. Results: Preliminary analysis of serum biomarkers and proteome of the PBMCs of the exceptional survivors showed elevated levels of NK-cell-related proteins such as KCTD10 and RBBP7. Flow cytometry analysis revealed the presence of increased activated CD56dim NK cells, CD56bright NK cells, and central memory (CM) (CD45RA-CD27+) CD8 T cells in both the exceptional survivors and the rapid progressors. However, expression of CD25 appears to be the main mode of activation in rapid progressors compared with increased NKG2D expression in exceptional survivors. Additionally, activation of the unconventional gd T cells was evident in both groups with terminally differentiated effector memory cells re-expressing CD45RA (TEMRA) Vd1 cell predominating in the exceptional survivors. In the rapid progressors, the increased CD25+ TEMRA Vd2 cells coupled with elevated serum IL-17A and IL-1b suggest their ability to generate IL-17. Th2 cytokines, IL-5 and IL-13 were also enriched in rapid progressors and concomitant increase in CD25+ Th2 cells reveals a strong Th2-driven immune signature in these patients. Finally increased CD86+ atypical double negative (DN) B cells, mostly comprised of the DN2 subset were also significantly enriched in the rapid progressors compared to the exceptional survivors where DN1 B cells were prevalent. Conclusion: The multi-platform approach to investigating immune responses present in atypical responders has identified several distinct immunophenotypes in which the extreme outliers differ in their potential immune surveillance mechanisms. Functional validation of these findings through activation and cytotoxicity assays is currently underway and future work aims to understand the spatial biology of these circulating immune cells within the context of their primary tumours, metastases, and lymph nodes. Citation Format: Helen Kakkassery, Thanussuyah Alaguthurai, Zuza Kozik, Paul Buckley, Ruifang Lu, Esme Carpenter, Rosalind Graham, Gheed Alhity, Farhana Hossain, Sadiyah Mukhtar, Syed Haider, Jyoti Choudhary, Sheeba Irshad. Distinct immune signatures discriminate between patients defined as exceptional survivors of metastatic breast cancer compared to those with rapidly progressing treatment resistant breast cancers [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-13-04.

Targeting the Dendritic Cell-Secreted Immunoregulatory Cytokine CCL22 Alleviates Radioresistance.

Radiation-mediated immune suppression limits efficacy and is a barrier in cancer therapy. Radiation induces negative regulators of tumor immunity including regulatory T cells (Treg). Mechanisms underlying Treg infiltration after radiotherapy (RT) are poorly defined. Given that conventional dendritic cells (cDC) maintain Treg, we sought to identify and target cDC signaling to block Treg infiltration after radiation. Transcriptomics and high dimensional flow cytometry revealed changes in murine tumor cDC that not only mediate Treg infiltration after RT but also associate with worse survival in human cancer datasets. Antibodies perturbing a cDC-CCL22-Treg axis were tested in syngeneic murine tumors. A prototype interferon-anti-epidermal growth factor receptor fusion protein (αEGFR-IFNα) was examined to block Treg infiltration and promote a CD8+ T cell response after RT. Radiation expands a population of mature cDC1 enriched in immunoregulatory markers that mediates Treg infiltration via the Treg-recruiting chemokine CCL22. Blocking CCL22 or Treg depletion both enhanced RT efficacy. αEGFR-IFNα blocked cDC1 CCL22 production while simultaneously inducing an antitumor CD8+ T cell response to enhance RT efficacy in multiple EGFR-expressing murine tumor models, including following systemic administration. We identify a previously unappreciated cDC mechanism mediating Treg tumor infiltration after RT. Our findings suggest blocking the cDC1-CCL22-Treg axis augments RT efficacy. αEGFR-IFNα added to RT provided robust antitumor responses better than systemic free interferon administration and may overcome clinical limitations to interferon therapy. Our findings highlight the complex behavior of cDC after RT and provide novel therapeutic strategies for overcoming RT-driven immunosuppression to improve RT efficacy. See related commentary by Kalinski et al., p. 4260.

Bispecific T cell engager therapy for refractory rheumatoid arthritis.

Bispecific T cell engagers (BiTEs) kill B cells by engaging T cells. BiTEs are highly effective in acute lymphoblastic leukemia. Here we treated six patients with multidrug-resistant rheumatoid arthritis (RA) with the CD19xCD3 BiTE blinatumomab under compassionate use. Low doses of blinatumomab led to B cell depletion and concomitant decrease of T cells, documenting their engager function. Treatment was safe, with brief increase in body temperature and acute phase proteins during first infusion but no signs of clinically relevant cytokine-release syndrome. Blinatumomab led to a rapid decline in RA clinical disease activity in all patients, improved synovitis in ultrasound and FAPI-PET-CT and reduced autoantibodies. High-dimensional flow cytometry analysis of B cells documented an immune reset with depletion of activated memory B cells, which were replaced by nonclass-switched IgD-positive naïve B cells. Together, these data suggest the feasibility and potential for BiTEs to treat RA. This approach warrants further exploration on other B-cell-mediated autoimmune diseases.

Osteomyelitis is associated with increased anti-inflammatory response and immune exhaustion.

Osteomyelitis (OMS) is a bone infection causing bone pain and severe complications. A balanced immune response is critical to eradicate infection without harming the host, yet pathogens manipulate immunity to establish a chronic infection. Understanding OMS-driven inflammation is essential for disease management, but comprehensive data on immune profiles and immune cell activation during OMS are lacking. Using high-dimensional flow cytometry, we investigated the detailed innate and adaptive systemic immune cell populations in OMS and age- and sex-matched controls. Our study revealed that OMS is associated with increased levels of immune regulatory cells, namely T regulatory cells, B regulatory cells, and T follicular regulatory cells. In addition, the expression of immune activation markers HLA-DR and CD86 was decreased in OMS, while the expression of immune exhaustion markers TIM-3, PD-1, PD-L1, and VISTA was increased. Members of the T follicular helper (Tfh) cell family as well as classical and typical memory B cells were significantly increased in OMS individuals. We also found a strong correlation between memory B cells and Tfh cells. We conclude that OMS skews the host immune system towards the immunomodulatory arm and that the Tfh memory B cell axis is evident in OMS. Therefore, immune-directed therapies may be a promising alternative for eradication and recurrence of infection in OMS, particularly in individuals and areas where antibiotic resistance is a major concern.

Signatures of CD4+ T and B cells are associated with distinct stages of chronic chagasic cardiomyopathy.

Chagas disease is a neglected parasitic disease caused by Trypanosoma cruzi. While most patients are asymptomatic, around 30% develop Chronic Chagasic Cardiomyopathy (CCC). Here, we employed high-dimensional flow cytometry to analyze CD4+ T and B cell compartments in patients during the chronic phase of Chagas disease, presenting the asymptomatic and mild or moderate/severe cardiac clinical forms. Effector CD27-CD4+ T cells were expanded in both CCC groups, and only mild CCC patients showed higher frequencies of effector memory and T follicular helper (Tfh) cells than healthy donors (CTL) and asymptomatic patients. Unsupervised analysis confirmed these findings and further revealed the expansion of a specific subpopulation composed of Tfh, transitional, and central memory CD4+ T cells bearing a phenotype associated with strong activation, differentiation, and exhaustion in patients with mild but not moderate/severe CCC. In contrast, patients with mild and moderate/severe CCC had lower frequencies of CD4+ T cells expressing lower levels of activation markers, suggesting resting status, than CTL. Regarding the B cell compartment, no alterations were found in naïve CD21-, memory cells expressing IgM or IgD, marginal zone, and plasma cells in patients with Chagas disease. However, expansion of class-switched activated and atypical memory B cells was observed in all clinical forms, and more substantially in mild CCC patients. Taken together, our results showed that T. cruzi infection triggers changes in CD4+ T and B cell compartments that are more pronounced in the mild CCC clinical form, suggesting an orchestrated cellular communication during Chagas disease. Overall, these findings reinforce the heterogeneity and complexity of the immune response in patients with chronic Chagas disease and may provide new insights into disease pathology and potential markers to guide clinical decisions.

Tumor-targeted therapy with BRAF-inhibitor recruits activated dendritic cells to promote tumor immunity in melanoma

BackgroundTumor-targeted therapy causes impressive tumor regression, but the emergence of resistance limits long-term survival benefits in patients. Little information is available on the role of the myeloid cell network, especially...

Deep learning reconstruction of high-Reynolds-number turbulent flow field around a cylinder based on limited sensors

It is of significant importance to reconstruct the high-dimensional global flow field using limited sensor data, considering that sensors are often local and limited in full-scale measurements. In the literature, the reconstruction of laminar flows at low Reynolds number (Re) was mostly investigated. This study focuses on high-Re turbulent flows around a body, and aims to systematically investigate the reconstruction performance of deep learning models, including multilayer perceptron (MLP), convolutional neural network (CNN), and generative adversarial neural network (GAN). The extensive assessment encompasses the prediction accuracy of the instantaneous, phase-averaged, and mean flow fields, and the training efficiency. Results shows that GAN demonstrates a obvious advantage in reconstructing small-scale vortex structures. MLP is slightly better at reconstructing time-averaged flow fields (3%) and has a significant advantage in reconstruction efficiency. We also examine the generalization ability by applying transfer learning at different Re. Additionally, sensitivity of sensor number, training data size, and optimization of sensor layout are studied to further augment the accuracy of flow field reconstruction.

TSPAN8+ myofibroblastic cancer-associated fibroblasts promote chemoresistance in patients with breast cancer.

Cancer-associated fibroblasts (CAFs) are abundant stromal cells in the tumor microenvironment that promote cancer progression and relapse. However, the heterogeneity and regulatory roles of CAFs underlying chemoresistance remain largely unclear. Here, we performed a single-cell analysis using high-dimensional flow cytometry analysis and identified a distinct senescence-like tetraspanin-8 (TSPAN8)+ myofibroblastic CAF (myCAF) subset, which is correlated with therapeutic resistance and poor survival in multiple cohorts of patients with breast cancer (BC). TSPAN8+ myCAFs potentiate the stemness of the surrounding BC cells through secretion of senescence-associated secretory phenotype (SASP)-related factors IL-6 and IL-8 to counteract chemotherapy. NAD-dependent protein deacetylase sirtuin 6 (SIRT6) reduction was responsible for the senescence-like phenotype and tumor-promoting role of TSPAN8+ myCAFs. Mechanistically, TSPAN8 promoted the phosphorylation of ubiquitin E3 ligase retinoblastoma binding protein 6 (RBBP6) at Ser772 by recruiting MAPK11, thereby inducing SIRT6 protein destruction. In turn, SIRT6 down-regulation up-regulated GLS1 and PYCR1, which caused TSPAN8+ myCAFs to secrete aspartate and proline, and therefore proved a nutritional niche to support BC outgrowth. By demonstrating that TSPAN8+SIRT6low myCAFs were tightly associated with unfavorable disease outcomes, we proposed that the combined regimen of anti-TSPAN8 antibody and SIRT6 activator MDL-800 is a promising approach to overcome chemoresistance. These findings highlight that senescence contributes to CAF heterogeneity and chemoresistance and suggest that targeting TSPAN8+ myCAFs is a promising approach to circumvent chemoresistance.

182 Purification and Characterization of Human Neural Stem and Progenitor Cells

INTRODUCTION: The human brain undergoes rapid development at mid-gestation from a pool of neural stem and progenitor cells (NSPCs) that give rise to the neurons, oligodendrocytes, and astrocytes of the mature brain. Functional study of these cell types has been hampered by a lack of precise purification methods. METHODS: We combine high-dimensional flow cytometry with single cell transcriptomics to comprehensively purify and functionally characterize NSPCs from the developing human brain during mid-gestation. We utilize index sorting based on the combinatorial expression of cell-surface markers (immunophenotype) to directly link surface-marker expression to the expressed transcriptomes of single cells, allowing for rigorous validation of sort purity. We further demonstrate the functional properties of each identified cell type in vitro and in vivo. RESULTS: CD24-THY1-/lo cells were enriched for radial glia, which robustly engrafted and differentiated into all three neural lineages in the mouse brain.THY1hi cells marked unipotent oligodendrocyte precursors committed to an oligodendroglial fate, and CD24+ THY1-/lo cells marked committed excitatory and inhibitory neuronal lineages. Notably, we identify and functionally characterize a novel transcriptomically distinct THY1hiEGFRhiPDGFRA- bipotent glial progenitor cell, which is lineage-restricted to astrocytes and oligodendrocytes, but not to neurons. CONCLUSIONS: The results presented here are strong proof-of-concept that distinct cell types from the developing brain can be prospectively isolated based on the expression of multiple surface markers. The combined results from scRNA-seq, in vitro differentiation, and in vivo transplantation offers the most rigorous interrogation of NSPCs’ transcriptomic identities and functional behavior. The modular nature of our antibody panel allows for the easy expansion or simplification of the panel, based on the cell-type of interest, thus providing a valuable tool for future investigation of both molecular and functional NSPC heterogeneity.

Randomized Phase II Study Evaluating the Addition of Pembrolizumab to Radium-223 in Metastatic Castration-resistant Prostate Cancer.

The checkpoint immunotherapeutic pembrolizumab induces responses in a small minority of patients with metastatic castration-resistant prostate cancer (mCRPC). Radium-223 (R223) may increase immunogenicity of bone metastases and increase pembrolizumab (P) activity. In a randomized phase II study, we assessed the effect of R223+P compared with R223 on tumor immune infiltration, safety, and clinical outcomes in patients with mCRPC. The primary endpoint was differences in CD4+ and CD8+ T-cell infiltrate in 8-week versus baseline bone metastasis biopsies; secondary endpoints were safety, radiographic progression-free survival (rPFS), and overall survival (OS). Of the 42 treated patients (29 R223+P, 13 R223), 18 R223+P and 8 R223 patients had evaluable paired tumor biopsies. Median fold-change of CD4+ T cells was -0.7 (range: -9.3 to 4.7) with R223+P and 0.1 (-11.1 to 3.7) with R223 (P = 0.66); for CD8+ T cells, median fold-change was -0.6 (-7.4 to 5.3) with R223+P and -1.3 (-3.1 to 4.8) with R223 (P = 0.66). Median rPFS and OS was 6.1 (95% confidence interval: 2.7-11.0) and 16.9 months [12.7-not reached (NR)], respectively, with R223+P and 5.7 (2.6-NR) and 16.0 (9.0-NR), respectively, with R223. Although R223+P was well tolerated with no unexpected toxicity, the combination did not improve efficacy. High-dimensional flow cytometry demonstrated minimal immune modulation with R223, whereas R223+P induced CTLA-4 expression on circulating CD4+ T cells. Clinical responders possessed lower circulating frequencies of Ki67+ T and myeloid cells at baseline and higher circulating frequencies of TIM-3+ T and myeloid cells by week 9. Although R223+P did not induce T-cell infiltration into the tumor microenvironment, exhaustion of induced peripheral T-cell immune responses may dampen the combination's clinical activity.

Multiple sclerosis endophenotypes identified by high-dimensional blood signatures are associated with distinct disease trajectories.

One of the biggest challenges in managing multiple sclerosis is the heterogeneity of clinical manifestations and progression trajectories. It still remains to be elucidated whether this heterogeneity is reflected by discrete immune signatures in the blood as a surrogate of disease pathophysiology. Accordingly, individualized treatment selection based on immunobiological principles is still not feasible. Using two independent multicentric longitudinal cohorts of patients with early multiple sclerosis (n = 309 discovery and n = 232 validation), we were able to identify three distinct peripheral blood immunological endophenotypes by a combination of high-dimensional flow cytometry and serum proteomics, followed by unsupervised clustering. Longitudinal clinical and paraclinical follow-up data collected for the cohorts revealed that these endophenotypes were associated with disease trajectories of inflammation versus early structural damage. Investigating the capacity of immunotherapies to normalize endophenotype-specific immune signatures revealed discrete effect sizes as illustrated by the limited effect of interferon-β on endophenotype 3-related immune signatures. Accordingly, patients who fell into endophenotype 3 subsequently treated with interferon-β exhibited higher disease progression and MRI activity over a 4-year follow-up compared with treatment with other therapies. We therefore propose that ascertaining a patient's blood immune signature before immunomodulatory treatment initiation may facilitate prediction of clinical disease trajectories and enable personalized treatment decisions based on pathobiological principles.

Intranodal Injection of Immune Activator Demonstrates Antitumor Efficacy in an Adjuvant Approach.

The tumor-draining lymph nodes (tdLN) are the initial site of metastases and are the prime site for generating robust antitumor responses. In this study, we explored the efficacy of a universal immune activator (ImmAct) targeted to the tdLN. This approach can be viewed as an attempt to turn a cold, unresponsive tdLN into a hot, responsive site. The adjuvant antitumor efficacy of our novel intranodal injection was evaluated in an aggressive metastatic mammary carcinoma murine model. The cancer cells were inoculated subcutaneously in the lower quadrant of the mouse to provoke the tdLN (inguinal lymph node). The study encompasses a range of methodologies, including in vivo and in vitro assays and high-dimensional flow cytometry analysis. Our findings demonstrated that intranodal administration of ImmAct following the dissection of the primary tumor led to improved tumor-free survival and minimized weight loss. ImmAct led to both local and systemic alterations in the cellular and humoral immunity. Additionally, after ImmAct treatment, non-responders showed a higher rate of exhausted CD8+ T cells compared to responders. Indeed, our innovative approach surpassed the gold standard surgery of sentinel lymph node excision. Overall, intranodal administration of ImmAct yielded a robust antitumor immune response, offering protection against micrometastases and relapse.

Abstract 3959: Unraveling the anti-tumor partnership of CD169+ macrophages and CD8+ T cells in a preclinical breast cancer model

Abstract In this study, we describe both the individual and the cooperative mechanisms by which CD169+ macrophages (MP) and CD8+ T cells support an anti-tumor immune response against breast cancer tumors. Breast cancer is the second leading cause of death in women of all ages each year, thus a deeper understanding of the molecular determinants that promote tumor development and suppress the anti-tumor immune response is still greatly needed. Here we use high dimensional flow cytometry, functional assays, and new mouse models to investigate the MP - T cell anti-tumor partnership. With our collaborators, we developed a preclinical mouse model of breast cancer by genetically engineering mammary stem cells to harbor three cancer driver mutations that are frequently associated in human patients: functional loss of the tumor suppressor genes p53 and mixed-lineage leukemia protein 3, and constitutive activation of the PI3 kinase. To characterize the immune cells in this tumor model, we developed a powerful 30-color high dimensional spectral flow cytometry panel to track and phenotype most known immune cell subsets. We found that CD169+ MP rapidly infiltrated and outnumbered all other populations during tumor growth, suggesting that they play an important role in shaping the tumor microenvironment. Surprisingly, although current literature describes breast cancer MP to be highly immunosuppressive, our phenotypic analysis showed only low expression of the pro-tumor MP markers TREM2 and CD206, but extremely high expression of the anti-tumor markers FOLR2 and CD64. To further investigate if these MP promoted or prevented tumor growth, we selectively depleted CD169+ MP in tumor-bearing mice and observed significantly accelerated tumor growth compared to the non-depleted control group, suggesting that these MP promoted anti-tumor responses. MP depletion also affected tumor-infiltrating CD8+ T cells, which produced lower effector functions (e.g., secretion of IFNγ, CCL3, TNF), indicating that MP may also boost anti-tumor CD8+ T cell responses. To further test if CD8+ T cells control tumor growth, we depleted either CD8+ or CD4+ T cells in tumor-bearing mice and observed that only CD8+ but not CD4+ T cell depletion accelerated tumor growth compared to the control group. MP have been documented to provide type I IFN signals to CD8+ T cells via the triggering of the STING pathway. To explore this mechanism in our model, we created a CD169creSTINGflox/KO mouse in which MP lack functional STING. Tumors in these mice grew much faster compared to those in the control group, consistent with the hypothesis that STING sensing occurs in tumor MP and promotes anti-tumor effector CD8+ T cell responses. Overall, our data provide evidence for an unexpected anti-tumor role for CD169+ MP in breast tumors, presumably through enhancing anti-tumor effector CD8+ T cell responses. Citation Format: Nicole Couturier, Marie Boutet, Kenta Nishitani, Wenjun Guo, Gregoire Lauvau. Unraveling the anti-tumor partnership of CD169+ macrophages and CD8+ T cells in a preclinical breast cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3959.