Antigen Processing Research Articles

Blood mir-331-3p is a potential diagnostic marker for giant panda (Ailuropoda melanoleuca) testicular tumor.

In recent years, several giant pandas have suffered from testicular tumor, which has seriously affected giant panda health. However, the pathogenesis of testicular tumor in giant panda is still unclear. Studies have shown that miRNAs are involved in the occurrence and development of a variety of cancers. However, the effect of miRNAs on giant panda testicular tumor has been little studied. Therefore, this study explored the pathogenesis of giant panda testicular tumor through miRNA and mRNA sequencing, and screened out diagnostic markers of testicular tumor. Combined with phenotypic symptoms and pathological section results, three giant pandas were diagnosed with testicular tumor and divided into tumor group, and three other giant pandas were divided into normal group. A total of 29 differentially expressed miRNAs (DEmiRNAs) were screened by blood miRNA-seq, and 3149 target gene candidates were predicted. Functional enrichment analysis showed that the target genes were mainly involved in intermembrane lipid transfer and ATP-dependent chromatin remodeling. However, only 5 DEmiRNAs were screened by miRNA-seq of blood-derived exosomes and 364 target genes were predicted, which were mainly involved in antigen processing and presentation. In addition, 216 differentially expressed genes (DEGs) were screened by RNA-seq, and functional enrichment analysis showed that tumor-specific DEGs significantly enriched to protein phosphorylation. Spearman correlation analysis of miRNA-mRNA showed that the expressions of miR-331-3p and PKIG were significantly positively correlated (spearman = 0.943, p < 0.01), while the expressions of miR-331-3p and ENSAMEG00000013628 were significantly negatively correlated (spearman= -0.829, p < 0.05). RT-PCR showed that the expression of miR-331-3p was significantly decreased in giant panda with tumor (p < 0.01). blood miRNAs and exosomal miRNAs exhibit distinct regulatory patterns concerning giant panda testicular tumor, potentially reflecting divergent biological processes in the disease's etiology. Meanwhile, miR-331-3p could be used as a potential diagnostic marker for giant panda testicular tumor. Our findings are conducive to the rapid clinical diagnosis of testicular tumor in giant pandas, and are also expected to provide scientific reference for further research on the pathogenesis of testicular tumor.

B cell adapter for PI 3-kinase (BCAP) coordinates antigen internalization and trafficking through the B cell receptor.

B cell adapter for PI 3-kinase (BCAP) is an adaptor molecule associated with signaling through multiple immune receptors, including the B cell receptor (BCR). However, B cell-intrinsic role of BCAP in antibody responses is unclear. We investigated the role of BCAP in B cell response to viral particles and found a previously unidentified mechanism by which BCAP regulates antigen-specific responses. B cell-specific deletion of BCAP in mice leads to decreases in antigen-specific responses through defects in BCR-antigen endocytosis. BCAP is necessary to orchestrate actin reorganization around the antigen for efficient endocytosis through BCR and intracellular processing of antigens. Therefore, loss of BCAP from B cells leads to defects in antigen endocytosis, hampering the propagation of antigen-derived signals and decreasing the ability of B cells to present antigens to T cells. Thus, our study clarifies how BCAP regulates B cell responses to complex antigens and elucidates that antigen positioning inside B cells determines different B cell activation outcomes.

Proteomic profiling of oral squamous cell carcinoma tissues reveals altered immune-related proteins: implications for personalized therapy

ABSTRACT Objectives Oral squamous cell carcinoma poses a substantial global health challenge marked by rising mortality rate. Recently, immunotherapy has shown promising results in cancer management by enhancing immune response. Thus, identifying additional immune-related markers is critical for advancing immunotherapy treatments. Methods Data-independent acquisition (DIA) mass spectrometry approach was used to explore differentially expressed immune-related proteins in oral cancer tissues compared to adjacent non-cancerous tissues. Functional significance was identified through Gene Ontology, pathway, and network analysis. Gene expression of identified proteins was validated using transcriptomic data. Results DIA analysis identified 29,459 precursors corresponding to 3429 proteins. Among these, 1060 proteins were differentially expressed, with 166 being immune-related. Differentially regulated proteins were involved in innate immune response, mitochondrial ATP synthesis, and neutrophil degranulation. Pathway analysis of immune-related proteins showed perturbation in anti-tumor immunity-related pathways such as interferon signaling, TCR signaling, PD-1 signaling, and antigen processing and presentation. Significance of these pathways was further reinforced by the strong interactions identified in the protein–protein interaction network analysis. Additionally, gene expression analysis showed similar mRNA expression patterns for key proteins involved in altered pathways, including ISG15, IFIT1/3, HLA-A/C and OAS2/3. Conclusions Further validation of these proteins could establish them as potential targets for personalized therapy.

Abstract 4137296: Single-cell Atlas of Human Epicardial Adipose Tissue Reveals Aging IL4R + Naive B cell Contributing To Atrial Fibrillation

Background: Numerous recent evidence suggested a role of epicardial adipose tissue (EAT), the visceral fat depot of the heart, in the development of Atrial Fibrillation (AF). However, the cellular and molecular mechanisms underlying the association remain elusive. Methods: We performed single-nucleus RNA sequencing on eleven EAT samples collected from 2 groups of subjects: patients with nonvalvular AF undergoing coronary bypass surgery for severe CAD (n=7), and a control group of patients without concomitant AF (n=4). Comparative analyses were performed between the groups, including cellular compositional analysis, cell type–resolved transcriptomic changes, and functional analysis. Results: Unsupervised clustering of 92734 nuclei identified 11 clusters, encompassing all known cell types in the adipose tissue. Pseudobulk differential expression analysis between the AF and control groups revealed pronounced differences in a select subset of genes located on the X and Y chromosomes, including XIST and TSIX. Subsequent pathway analysis identified that the most significantly impacted pathways were those associated with immune cell functions. Meanwhile, differences in cellular composition and transcriptomic profiles, particularly concerning B cells, were observed between normal and AF conditions, highlighting distinct immune cell dynamics. Comparison of pathways across different B cell states revealed the enrichment of distinct pathways within each state, including those involved in cellular senescence, antigen processing and presentation, and programmed cell death signatures. Notably, aging IL4R + naive B cell and inflammatory ITGB1 + memory B cell were identified as important regulators potentially involved in functional changes of EAT and AF pathogenesis. Conclusions: We built a complete single-nucleus transcriptomic atlas of human EAT in normal and AF conditions. Our study lays the foundation for developing novel therapeutic strategies for treating AF by targeting and modifying B cell functions within EAT.

Abstract 4136692: Spatial Transcriptomics Identifies Novel Clinical Markers to Classify the Etiology of Rare and Aggressive Cardiac Sarcomas

Background: Cardiac sarcomas, such as leiomyosarcoma (LMS), synovial sarcoma (SS), and undifferentiated pleomorphic sarcoma (UPS), lack sufficient diagnostic markers for early diagnosis and tailored therapeutic interventions. Understanding their molecular signatures with spatial-temporal resolution compared to normal heart tissue is crucial. Hypothesis: Spatial transcriptomics will reveal a comprehensive set of novel clinical markers, including changes in cellular composition, stemness, and metabolic profiles unique for each cardiac sarcoma subtypes. Aims: Identify novel molecular markers for the accurate diagnosis of cardiac sarcoma subtypes. Methods: Using 10X Visium spatial transcriptomics, we analyzed three cardiac sarcoma subtypes (LMS, SS, UPS) and compared them with normal heart tissue. Differential expression analysis identified novel target genes suitable for clinical disease stratification. Subsequently, machine learning models reveal an unbiased transcriptomic profile to distinguish normal from sarcoma tissues. Finally, immunohistochemistry analysis validated the differential marker gene expression. Results: We identify several novel clinical markers, such as IGKC, PCOLCE, NET1, TLE2, MDFI, BGN, TNNC1, and CNN3, that classify normal heart tissue from sarcoma subtypes. Machine learning models and immunostaining analysis confirm the transcriptomic signature in each sarcoma subtype. Pathway enrichment analysis show LMS enriched in antigen processing and B cell-mediated immunity, SS in protein folding and response to incorrect proteins, and UPS in axon development and Wnt signaling regulation. Trajectory Reconstruction Analysis indicate higher stemness scores in all sarcomas, with SS highest, followed by UPS and LMS. Additional cell cycling analysis show LMS cells in G2M phase, SS in G1, and UPS in S phase. SS express a high number of cancer stem markers (EZH2, BMI1, KDM5B, LGR5, HIF1A), while UPS express KDM5B and CTNNB1, and LMS show fewer stem-related marker genes (EZH2, BMI1, KDM5B, CTNNB1). Both SS and LMS express CD44. Glucose and oxidative pathways are also differentially regulated in each sarcoma subtype. Conclusion: Spatial transcriptomics uncovers distinct clinical markers, stemness characteristics, and metabolic activity profiles in cardiac sarcomas, offering insights for fast, accurate and improved diagnostics and therapeutics.

Abstract 4120290: Sex-specific Impact of Early to Mid-gestational Testosterone Excess on Sheep Fetal and Adult Offspring Lungs

Using the translationally relevant sheep model of prenatal testosterone (T) excess, we previously reported intrauterine growth retardation (IUGR) in both sexes, adverse sex specific programming of fetal heart and cardiometabolic dysfunction in adult female offspring. Because of the intricate reciprocal relationship between the heart and lungs, we hypothesized that gestational T excess will have detrimental sex-specific effects on offspring lungs beginning as early as fetal life and extending into adulthood. Pregnant ewes were intramuscularly injected with 100 mg of testosterone propionate twice weekly from gestational days (GD) 30-90 (term 147 days) and offspring lungs were harvested at GD120, 30 days after cessation of T treatment; (n=4-7/group) and in adulthood (n=4-6/group) and processed for molecular and histological analyses. Data was analyzed by student T test within each sex and Cohen (d) effect size was calculated (Cohens d&gt;0.8 represents large effect size. Lung collagen was significantly increased in T-male fetuses (TM) vs control males (CM) (p=0.01, d=1.99) that persisted into adulthood (TM vs CM: p=0.01, d=1.83). The effects of gestational T excess was evidenced as an increase in collagen only in the lungs of adult T-female fetuses (TF) relative to control females (CF) (p=0.003, d=2.38), but not during fetal life. Gestational T excess induced significant parallel increases in TUNEL positive nuclei/frame in TM fetuses relative to CM (n=3/group, p=0.01, d=3.35) persisting as a large magnitude increase of TUNEL positive nuclei/frame in adult TM (p=0.12, d=0.96). In TF females, apoptotic changes were not noted in fetal lungs but an increase of TUNEL positive nuclei/frame was evidenced in adult TF (p=0.08, d=1.14). At the molecular level prenatal T excess induced an increase in histone deacetylase 1 (HDAC1) expression in fetal TM vs CM (p=0.04, d=1.50), and decrease in HDAC1 in TF vs CF (p=0.10, d=1.09) suggestive of T-induced epigenetic alteration. Transcriptomic analysis of fetal lungs revealed upregulation of pathways associated with estrogen signaling and neuroactive ligand receptor interaction, and downregulation of pathways associated with protein processing in endoplasmic reticulum and antigen processing&amp;presentation (unadjusted p&lt; 0.05, log FC&gt;1.5) in both sexes. Overall, early to mid-gestational exposure to testosterone adversely reprograms the lungs in sex specific fashion as early as fetal life extending into postnatal adult life.

IMMU-07. THE IMMUNE LANDSCAPE OF PEDIATRIC BRAIN TUMORS: A TRANSCRIPTOMIC ANALYSIS

Abstract Despite standard-of-care therapy, pediatric brain tumors are now the leading cause of cancer-related death in children, highlighting an urgent need for the development of new treatments. Immunotherapy is actively being evaluated as a therapeutic approach to pediatric brain tumors, however, more research is needed to reveal additional antigenic targets that exist in these malignancies. In this study, our team performed a transcriptomic analysis of pediatric brain tumor RNA sequencing data within the Children’s Brain Tumor Network (CBTN) to identify intra and extracellular antigens that are highly expressed across major tumor types. Interestingly, our team observed that most tumors had high gene expression of a group of antigens that were unique to that specific tumor type. Specifically, our analysis revealed that diffuse midline gliomas (DMGs) highly expressed the extracellular antigens CA9, CTCFL, and ST8SIA1, whereas atypical rhabdoid tumors (ATRTs) highly expressed MUC1 and TEK. Other tumors that displayed high gene expression for a variety of antigenic targets included H3-wildtype high-grade gliomas (HGGs), and ependymomas (EPNs). Strikingly, we observed minimal difference in antigen expression in primary tumors when compared to patient-matched recurrences. Beyond antigen expression, we evaluated the expression of antigen processing machinery (APM) which includes major histocompatibility complexes (MHCs). Our findings revealed that DMGs had the lowest level of APM expression, however, these tumors uniquely expressed high levels of the immune checkpoints ADORA2A, CD276, and KLRC1. Contrarily, ATRTs showed a high expression of immune checkpoints CD274 (PD-L1), PVR, and CD80. Other tumors included in our analysis had unique expression patterns of antigen, as well as APM and immune checkpoints. Our findings illustrate that pediatric brain tumors have distinct expression patterns of antigens, APM, and immune checkpoints that are specific to tumor type, emphasizing diverse, rather than general, immunotherapeutic approaches must be considered for childhood brain tumors.

Fibroblast Heterogeneity in Hepatocellular Carcinoma and Identification of Prognostic Markers Based on Single-cell Transcriptome Analysis.

HCC is a malignant tumor with high morbidity and mortality. Fibroblasts play a key role in the tumor microenvironment (TME). However, the transcriptional regulatory mechanisms of fibroblasts remained unclear in HCC. The aim of this study was to explore the complex role of fibroblasts in hepatocellular carcinoma (HCC) and to reveal their transcriptional regulatory mechanisms. The goal of this study was to discover potential prognostic markers for HCC by analyzing the genetic variations and differentiation process of fibroblasts. Single-cell transcriptome data from the non-tumor liver site and primary tumor site of HCC were acquired from GSE149614, processed, and clustered using the Seurat pipeline. The inferCNV algorithm was applied to infer copy number variations (CNVs) in fibroblasts. Subsequently, the mechanism underlying the interaction between fibroblasts and other cells in the TME of HCC was analyzed using CellChat software. The trajectory of cellular differentiation of fibroblasts from normal state to malignant state was examined using Monocle 2. SCENIC analysis was performed to identify key transcription factors (TFs) in fibroblasts and assess their correlation with HCC prognosis. Finally, qRT-PCR and Transwell assays were carried out to analyze the mRNA expression and cell metastasis. We identified a total of nine different cell types (B cells, cycling cells, endothelial cells, epithelial cells, fibroblasts, hepatocytes, macrophages, plasma cells, and T cells) based on the single-cell transcriptomic data of HCC. Among them, fibroblasts were highly enriched at the primary tumor site, and their number increased with advanced stages. In addition, significant deletions were detected on chromosome 6p of fibroblasts, and genes in this region were remarkably enriched in pathways associated with antigen processing and presentation. Intercellular communication showed that epithelial cells regulated fibroblasts the most. The differentiation of fibroblasts was mainly accompanied by a transition from normal to malignant state. Importantly, CEBPD and FOSB, the TFs most associated with the putative timing of fibroblasts, were under-expressed in human hepatocytes and showed a significant correlation with HCC prognosis. Overexpressed CEBPD inhibited HCC cell migration and invasion. In conclusion, our study revealed that fibroblast recruitment and differentiation, as well as copy number loss at chromosome 6p, were associated with a higher degree of malignancy and immune dysfunction in HCC. The current discoveries provided new insights into the clinical treatment and diagnosis of HCC.

Co-regulated ceRNA network mediated by circRNA and lncRNA in patients with gouty arthritis

Numerous studies have demonstrated the involvement of messenger RNAs (mRNAs) and non-coding RNAs, including long non-coding RNAs (lncRNA), circular RNAs (circRNAs) and microRNA (miRNAs), in gouty arthritis onset; however, the regulatory mechanism has not yet been elucidated. Here, we applied whole-transcriptome sequencing to identify the differentially expressed circRNAs, lncRNAs, miRNAs and mRNAs between the gout patients and normal people, and constructed co-regulated networks of circRNAs and lncRNAs according to the competitive endogenous RNA (ceRNA) theory for gouty arthritis onset to improve our understanding of the pathogenesis of this disease. The most significant finding of this study is the co-regulated ceRNA network of circRNAs and lncRNAs in gouty arthritis. The circRNA novel_circ_0030384 and the lncRNAs AAMP, TRIM16, PKN1, XLOC_184579 and XLOC_189826 were upstream genes in the co-regulated network. These upstream genes upregulated miR550a-5p and miR550a-3-5p, which downregulated PSME1 and FERMT3 expression. These mRNAs participated in proteasome dynamics, antigen processing and presentation, and platelet activation, which are associated with inflammation in gouty arthritis. In addition, the circRNA and lncRNAs upregulated miR550a-5p, which downregulated GRK2 and OS9 expression. Also, it proved that the down-regulated of PSME1, FERMT3, GRK2 and OS9 can aggravate gouty arthritis in vitro. In summary, these genes mediate inflammation in gouty arthritis through chemokine signaling to regulate neutrophil function.

Transcriptomics analysis of differential gene expression and immune and inflammatory response mechanisms in patients with typical and non-criteria obstetric antiphospholipid syndrome (OAPS and NC-OAPS)

In this study, we investigated the molecular differences between patients with typical obstetric antiphospholipid syndrome (OAPS) and patients with non-criteria obstetric antiphospholipid syndrome (NC-OAPS) patients through transcriptome sequencing of peripheral blood samples from ten OAPS patients and ten NC-OAPS patients. Differentially expressed genes (DEGs) were identified, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, protein-protein interaction (PPI) analysis, and competitive endogenous RNA (ceRNA) network construction to identify hub genes. Verification was performed via Quantitative Real-time PCR (qPCR) in OAPS (n=9) and NC-OAPS (n=12) samples. We identified 240 DEGs in two groups. GO and KEGG analyses reviewed upregulated in pathways related to the inflammatory response; immune response; antigen processing and presentation; Th1, Th2, and Th17 cell differentiation; and NK cell-mediated cytotoxicity in OAPS patients. PPI and ceRNA network analyses identified key genes, with significant upregulation of CXCR2, JAK2, and MPO found in the OAPS group, which correlated with severe inflammation, JAK-STAT pathway activation, and increased NET activity in neutrophils. Other genes such as CD4, IL2RB, and NKG7, are involved in T-cell and NK cell regulation. Our results indicate enhanced inflammatory and immune responses in OAPS patients, suggesting more severe immune activity than in NC-OAPS patients, providing a basis for precise diagnostic and therapeutic strategies.

Neoantigen prioritization based on antigen processing and presentation

Somatic mutations in tumor cells give rise to mutant proteins, fragments of which are often presented by MHC and serve as neoantigens. Neoantigens are tumor-specific and not expressed in healthy tissues, making them attractive targets for T-cell-based cancer immunotherapy. On the other hand, since most somatic mutations differ from patient to patient, neoantigen-targeted immunotherapy is personalized medicine and requires their identification in each patient. Computational algorithms and machine learning methods have been developed to prioritize neoantigen candidates. In fact, since the number of clinically relevant neoantigens present in a patient is generally limited, this process is like finding a needle in a haystack. Nevertheless, MHC presentation of neoantigens is not random but follows certain rules, and the efficiency of neoantigen detection may be further improved with technological innovations. In this review, we discuss current approaches to the detection of clinically relevant neoantigens, with a focus on antigen processing and presentation.

Regulation of cell-mediated immune responses in dairy bulls via long non-coding RNAs from submandibular lymph nodes, peripheral blood, and the spleen

Cell-mediated immune responses (CMIRs) are critical to building a robust immune system and reducing disease susceptibility in cattle. Long non-coding RNAs (lncRNAs) regulate various biological processes. However, to the best of our knowledge, the characterization and functions of lncRNAs and their regulations on the bovine CMIR have not been investigated comprehensively. In this study, experimental bulls were immunized with a heat-killed preparation of Candida albicans (HKCA) to induce delayed-type hypersensitivity (DTH). Three bulls were classified as high- CMIR responders and three were low-CMIR responders, based on their classical DTH skin reactions. LncRNAs were identified in the submandibular lymph nodes, peripheral blood, and spleen of high- and low-CMIR animals using strand-specific RNA sequencing. A total of 21,003 putative lncRNAs were identified across tissues, and 420, 468, and 599 lncRNAs were differentially expressed between the two groups in the submandibular lymph node, peripheral blood, and spleen tissues, respectively. Functional analysis of the differentially expressed lncRNA (DElncRNA) target genes showed that a number of immune-related Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were enriched, including immune response, cell adhesion, nucleosome, DNA packaging, antigen processing and presentation, and complement and coagulation cascades. Tissue specificity analysis indicated that lncRNA transcripts have stronger tissue specificity than mRNA. Furthermore, an interaction network was constructed based on DElncRNAs and DEGs, and 11, 14, and 11 promising lncRNAs were identified as potential candidate genes influencing immune response regulation in submandibular lymph nodes, peripheral blood, and spleen tissues, respectively. These results provide a foundation for further research into the biological functions of lncRNAs associated with bovine CMIR and identify candidate lncRNA markers for cell-mediated immune responses.

The pore-forming apolipoprotein APOL7C drives phagosomal rupture and antigen cross-presentation by dendritic cells.

Conventional dendritic cells (cDCs) generate protective cytotoxic T lymphocyte (CTL) responses against extracellular pathogens and tumors. This is achieved through a process known as cross-presentation (XP), and, despite its biological importance, the mechanism(s) driving XP remains unclear. Here, we show that a cDC-specific pore-forming protein called apolipoprotein L 7C (APOL7C) is up-regulated in response to innate immune stimuli and is recruited to phagosomes. Association of APOL7C with phagosomes led to phagosomal rupture and escape of engulfed antigens to the cytosol, where they could be processed via the endogenous MHC class I antigen processing pathway. Accordingly, mice deficient in APOL7C did not efficiently prime CD8+ T cells in response to immunization with bead-bound and cell-associated antigens. Together, our data indicate the presence of dedicated apolipoproteins that mediate the delivery of phagocytosed proteins to the cytosol of activated cDCs to facilitate XP.

PRR adjuvants restrain high stability peptides presentation on APCs.

Adjuvants can affect APCs function and boost adaptive immune responses post-vaccination. However, whether they modulate the specificity of immune responses, particularly immunodominant epitope responses, and the mechanisms of regulating antigen processing and presentation remain poorly defined. Here, using overlapping synthetic peptides, we screened the dominant epitopes of Th1 responses in mice post-vaccination with different adjuvants and found that the adjuvants altered the antigen-specific CD4+ T-cell immunodominant epitope hierarchy. MHC-II immunopeptidomes demonstrated that the peptide repertoires presented by APCs were significantly altered by the adjuvants. Unexpectedly, no novel peptide presentation was detected after adjuvant treatment, whereas peptides with high binding stability for MHC-II presented in the control group were missing after adjuvant stimulation, particularly in the MPLA- and CpG-stimulated groups. The low-stability peptide present in the adjuvant groups effectively elicited robust T-cell responses and formed immune memory. Collectively, our results suggest that adjuvants (MPLA and CpG) inhibit high-stability peptide presentation instead of revealing cryptic epitopes, which may alter the specificity of CD4+ T-cell-dominant epitope responses. The capacity of adjuvants to modify peptide-MHC (pMHC) stability and antigen-specific T-cell immunodominant epitope responses has fundamental implications for the selection of suitable adjuvants in the vaccine design process and epitope vaccine development.

PRR adjuvants restrain high stability peptides presentation on APCs

Adjuvants can affect APCs function and boost adaptive immune responses post-vaccination. However, whether they modulate the specificity of immune responses, particularly immunodominant epitope responses, and the mechanisms of regulating antigen processing and presentation remain poorly defined. Here, using overlapping synthetic peptides, we screened the dominant epitopes of Th1 responses in mice post-vaccination with different adjuvants and found that the adjuvants altered the antigen-specific CD4+ T-cell immunodominant epitope hierarchy. MHC-II immunopeptidomes demonstrated that the peptide repertoires presented by APCs were significantly altered by the adjuvants. Unexpectedly, no novel peptide presentation was detected after adjuvant treatment, whereas peptides with high binding stability for MHC-II presented in the control group were missing after adjuvant stimulation, particularly in the MPLA- and CpG-stimulated groups. The low-stability peptide present in the adjuvant groups effectively elicited robust T-cell responses and formed immune memory. Collectively, our results suggest that adjuvants (MPLA and CpG) inhibit high-stability peptide presentation instead of revealing cryptic epitopes, which may alter the specificity of CD4+ T-cell-dominant epitope responses. The capacity of adjuvants to modify peptide–MHC (pMHC) stability and antigen-specific T-cell immunodominant epitope responses has fundamental implications for the selection of suitable adjuvants in the vaccine design process and epitope vaccine development.

Comprehensive single-cell profiling of monocytes in HLA-B27-positive ankylosing spondylitis with acute anterior uveitis.

Acute anterior uveitis (AAU) is a common extra-articular manifestation of ankylosing spondylitis (AS), particularly in patients positive for the human leucocyte antigen (HLA)-B27 genetic marker. To explore the underlying mechanisms of HLA-B27+ AS-associated AAU, we employed single-cell RNA sequencing to profile the transcriptomes of peripheral blood mononuclear cells in three HLA-B27+ AS-associated AAU patients and three healthy controls (HCs). We identified 11 distinct immune cell clusters, with a particular focus on monocytes, revealing six subsets, including three previously unidentified subsets, namely, GTPase immune-associated proteins, Th17-related, and lncRNA monocytes, with unique gene expression patterns. Significant differences in monocyte composition, activation states, and gene expression were observed between patients and HCs, particularly within HLA monocyte subpopulations. Notably, enhanced expression of X-inactive specific transcript and myeloid cell nuclear differentiation antigen genes was validated across monocyte subclusters in patients. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis highlighted significant enrichment in antigen processing and presentation pathways, shedding light on the disease's molecular mechanisms. These findings provide novel insights into the molecular mechanisms of HLA-B27+ AS-associated AAU and may contribute to the development of targeted diagnostic and therapeutic strategies. Further clinical validation is essential.

Integrating single cell and bulk RNA sequencing data identifies RBM17 as a novel response biomarker for immunotherapy in bladder cancer.

Checkpoint inhibitors (CPIs) have been widely applied in the treatment of patients with bladder cancer (BLCA). However, there is still unmet need to dissect response predict biomarkers. To uncover CPI response-related marker genes in cancer cells, we utilized SCISSOR, integrating single-cell RNA and bulk RNA sequencing data. Transcriptomic and clinical data from IMvigor210, UNC-108, and BCAN/HCRN datasets were collected to evaluate and validate the identified biomarkers and signatures. Additionally, we analyzed TCGA-BLCA and local-BLCA RNA-seq data to investigate alternative splicing events (ASEs). Cell viability was assessed in T24 and UMUC3 cells with RBM17 upregulation or downregulation. Through SCISSOR analysis, we discovered that the expression levels of RBM17, TAP1, and PSMB8 were significantly associated with CPI response. Since PSMB8 displayed a highly positive correlation with TAP1, we developed a CPI response score (CRS) signature based on the expression profiles of RBM17 and TAP1. The CRS demonstrated robust predictive capacity in IMvigor210, UNC-108, and BCAN/HCRN datasets and was associated with higher tumor mutational burden (TMB), PD-L1 expression, and unique genomic features. Notably, RBM17 was not linked to the clinical outcomes of BLCA patients but positively correlated with BLCA cell proliferation in vitro. In the meantime, RBM17 was correlated with higher activity in core biological pathways, including antigen processing machinery, CD8 + T effector cells, cell cycle, DNA damage repair, epithelial-mesenchymal transition, histone regulation, and immune checkpoints. Moreover, the high-RBM17 group showed enrichment of LumU/Ba/sq subtypes but fewer FGFR3 alterations. Lastly, RBM17 significantly upregulated ASEs in BLCA samples, leading to higher neoantigen levels, a more inflamed tumor microenvironment, and improved CPI response. RBM17 is associated with higher ASEs and neoantigen levels, thereby potentiating the efficacy of CPI in BLCA. The established predictive signature, utilizing only two genes, has the potential to streamline clinical applications, providing a cost-effective alternative to expensive genomic, transcriptomic, and biological feature tests.

Immunoglobin attenuates fulminant myocarditis by inhibiting overactivated innate immune response.

Fulminant myocarditis (FM) is a myocardial inflammatory disease that can result from either viral diseases or autoimmune diseases. In this study, we have determined the treatment effects of immunomodulatory drugs on FM. FM was induced in A/JGpt mice by intraperitoneal administration of coxsackievirus B3, after which immunoglobins were administered daily by intraperitoneal injection. On the seventh day, the cardiac structure and function were determined using echocardiography and cardiac catheterisation. Single-cell RNA sequencing (scRNA-seq) was performed to evaluate CD45+ cells in the heart. Immunoglobin, a typical immunomodulatory drug, dramatically reduced mortality and significantly improved cardiac function in mice with FM. ScRNA-seq revealed that immunoglobin treatment effectively modulated cardiac immune homeostasis, particularly by attenuating overactivated innate immune responses. At the cellular level, immunoglobin predominantly targeted Plac8+ monocytes and S100a8+ neutrophils, suppressing their proinflammatory activities, and enhancing antigen processing and presentation capabilities, thereby amplifying the efficiency and potency of the immune response against the virus. Immunoglobin benefits are mediated by the modulation of multiple signalling pathways, including relevant receptors on immune cells, direction of inflammatory cell chemotaxis, antigen presentation and anti-viral effects. Subsequently, Bst2-ILT7 ligand-receptor-mediated cellular interactions manipulated by immunoglobin were further confirmed in vivo. Immunoglobin treatment significantly attenuated FM-induced cardiac inflammation and improved cardiac function by inhibiting overactivated innate immune responses.

Abstract A037: Enhanced anti-tumor activity through targeted immunotherapy combined with mutant KRAS inhibition in pancreatic cancer

Abstract Constitutively-active KRASG12D has become targetable via clinical-stage KRASG12D-selective small molecule inhibitors. Prior preclinical research has demonstrated that KRASG12D inhibition makes pancreatic ductal adenocarcinoma (PDAC) more amenable to immunotherapy. However, the impact of such inhibition on antigen presentation by tumor cells remains unclear. To elucidate this phenomenon, we employed a multi-omic profiling workflow to investigate alterations in the proteome and peptide MHC ligandome (immunopeptidome) following treatment of HPAC human cancer cells with a RAS(ON) G12D-selective inhibitor RM-044 (representative of investigational agent RMC-9805) and/or IFNɣ in vitro. Multi-omic profiling revealed significant changes in antigen presentation following KRASG12D inhibition. Pairwise comparisons of differentially expressed proteins in treated vs. untreated conditions showed increased expression of proteins associated with interferon signaling and replication stress. Notably, antigen processing and presentation proteins such as HLA-B and -C alpha chains showed some of the highest expression levels. Immunopeptidomic analysis revealed a 2-fold increase in ligand diversity and abundance in treated vs. untreated conditions. Sequence motif enrichment analysis depicted motifs consistent with HPAC’s HLA-B and -C but not -A alleles, aligning with proteomic findings and highlighting how the integration of these two data layers informs the shaping of the immunopeptidomic landscape. Building on these findings, we hypothesized that KRASG12D signaling inhibition in preclinical models could augment immune responses initiated by immunization targeting tumor antigens in vivo. Our hypothesis was that the release of antigens from KRASG12D-induced cell death, coupled with increased MHC-I expression in remaining tumor cells, would enhance interactions with T cells activated by immunization. To test this, we orthotopically inoculated C57Bl/6 mice with a murine PDAC-KRASG12D cell line engineered to express the model self/tumor-associated antigen gp100. Mice were immunized with either empty ionizable lipid nanoparticles (e-iLNPs) or iLNPs packaged with mRNA encoding full-length gp100 (gp100-iLNP). Following a priming and boost series, mice were treated with either KRASG12D inhibitior MRTX1133 or vehicle for two weeks. Remarkably, mice treated with the gp100 mRNA-iLNP immunization followed by KRASG12D inhibition experienced significant tumor regression compared to mice that received KRASG12D inhibition alone. These preclinical findings underscore the dynamic nature by which PDAC antigen presentation can be modulated by KRAS signaling inhibition and IFNɣ. The combination of allele-specific KRAS inhibition with tumor antigen immunization resulted in significant tumor regression in a stringent in vivo PDAC preclinical model, compared to either treatment modality alone. This rationalizes the combination of both approaches for enhanced anti-tumor activity, offering a strategy that is worth exploring clinically for improving outcomes in pancreatic cancer treatment. Citation Format: Amanda Creech, Hailey Lee, Khalid Rashid, Thuc Le, Alykhan Premji, Tony Luu, Ahmad Kassem, Weihang Zhao, Luyi Li, Nanping Wu, Norbert Pardi, James Wohlschlegel, Timothy Donahue, Caius Radu. Enhanced anti-tumor activity through targeted immunotherapy combined with mutant KRAS inhibition in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr A037.

Decoding the Genetic Basis of Mast Cell Hypersensitivity and Infection Risk in Hypermobile Ehlers-Danlos Syndrome.

Hypermobile Ehlers-Danlos syndrome (hEDS) is a connective tissue disorder marked by joint hypermobility, skin hyperextensibility, and tissue fragility. Recent studies have linked hEDS with mast cell activation syndrome (MCAS), suggesting a genetic interplay affecting immune regulation and infection susceptibility. This study aims to decode the genetic basis of mast cell hypersensitivity and increased infection risk in hEDS by identifying specific genetic variants associated with these conditions. We conducted whole-genome sequencing (WGS) on 18 hEDS participants and 7 first-degree relatives as controls, focusing on identifying genetic variants associated with mast cell dysregulation. Participants underwent clinical assessments to document hEDS symptoms and mast cell hypersensitivity, with particular attention to past infections and antihistamine response. Our analysis identified specific genetic variants in MT-CYB, HTT, MUC3A, HLA-B and HLA-DRB1, which are implicated in hEDS and MCAS. Protein-protein interaction (PPI) network analysis revealed significant interactions among identified variants, highlighting their involvement in pathways related to antigen processing, mucosal protection, and collagen synthesis. Notably, 61.1% of the hEDS cohort reported recurrent infections compared to 28.5% in controls, and 72.2% had documented mast cell hypersensitivity versus 14.2% in controls. These findings provide a plausible explanation for the complex interplay between connective tissue abnormalities and immune dysregulation in hEDS. The identified genetic variants offer insights into potential therapeutic targets for modulating mast cell activity and improving patient outcomes. Future research should validate these findings in larger cohorts and explore the functional implications of these variants to develop effective treatment strategies for hEDS and related mast cell disorders.