B-cell Activation Research Articles

Discovery of a Novel Benzodiazepine Series of Cbl-b Inhibitors for the Enhancement of Antitumor Immunity.

Casitas B-lineage lymphoma proto-oncogene-b (Cbl-b) is a RING finger E3 ligase that is responsible for repressing T-cell, natural killer (NK) cell, and B-cell activation. The robust antitumor activity observed in Cbl-b deficient mice arising from elevated T-cell and NK-cell activity justified our discovery effort toward Cbl-b inhibitors that might show therapeutic promise in immuno-oncology, where activation of the immune system can drive the recognition and killing of cancer cells. We undertook a high-throughput screening campaign followed by structure-enabled optimization to develop a novel benzodiazepine series of potent Cbl-b inhibitors. This series displayed nanomolar levels of biochemical potency, as well as potent T-cell activation. The functional activity of this class of Cbl-b inhibitors was further corroborated with ubiquitin-based cellular assays.

Unraveling the transcriptomic signatures of Parkinson's disease and major depression using single-cell and bulk data.

Motor symptoms are well-characterized in Parkinson's disease (PD). However, non-motor symptoms, such as depression, are commonly observed and can appear up to 10 years before motor features, resulting in one-third of individuals being misdiagnosed with a neuropsychiatric disorder. Thus, identifying diagnostic biomarkers is crucial for accurate PD diagnosis during its prodromal or early stages. We employed an integrative approach, combining single nucleus RNA and bulk mRNA transcriptomics to perform comparative molecular signatures analysis between PD and major depressive disorder (MDD). We examined 39,834 nuclei from PD (GSE202210) and 32,707 nuclei from MDD (GSE144136) in the dorsolateral prefrontal cortex (dlPFC) of Brodmann area 9. Additionally, we analyzed bulk mRNA peripheral blood samples from PD compared to controls (GSE49126, GSE72267), as well as MDD compared to controls (GSE39653). Our findings show a higher proportion of astrocytes, and oligodendrocyte cells in the dlPFC of individuals with PD vs. MDD. The excitatory to inhibitory neurons (E/I) ratio analysis indicates that MDD has a ratio close to normal 80/20, while PD has a ratio of 62/38, indicating increased inhibition in the dlPFC. Microglia displayed the most pronounced differences in gene expression profiles between the two conditions. In PD, microglia display a pro-inflammatory phenotype, while in MDD, they regulate synaptic transmission through oligodendrocyte-microglia crosstalk. Analysis of bulk mRNA blood samples revealed that the COL5A, MID1, ZNF148, and CD22 genes were highly expressed in PD, whereas the DENR and RNU1G2 genes were highly expressed in MDD. CD22 is involved in B-cell activation and the negative regulation of B-cell receptor signaling. Additionally, CD86, which provides co-stimulatory signals for T-cell activation and survival, was found to be a commonly differentially expressed gene in both conditions. Pathway analysis revealed several immune-related pathways common in both conditions, including the complement and coagulation cascade, and B-cell receptor signaling. This study demonstrates that bulk peripheral immune cells play a role in both conditions, but neuroinflammation in the dlPFC specifically manifests in PD as evidenced by the analysis of single nucleus dlPFC datasets. Integrating these two omics levels offers a better understanding of the shared and distinct molecular pathophysiology of PD and MDD in both the periphery and the brain. These findings could lead to potential diagnostic biomarkers, improving accuracy and guiding pharmacological treatments.

Multi-Omic Insights into the Mutational Landscape and Dysregulated Transcriptional Programs of Autoimmune B-Cells in Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is an autoimmune disease with diverse manifestations, from mild and sporadic to severe and life-threatening. SLE heterogeneity arises from various factors, including genetic, epigenetic, and immune niche-related features (Kaul et al., 2016; Jenks et al., 2018). However, the exact interactions and hierarchy between these features remain unclear. Recent studies have found somatic mutations in genes typically mutated in B-cell lymphomas, in subsets of B-cells that are associated with SLE pathogenesis (Piotrowski et al., 2015; Pullabhatla et al., 2018; Singh et al., 2020; Brown et al., 2022). These mutations may support B-cell clonal bursts, but direct information from clinical specimens on the impact of these mutations on B-cell lineages and their influence on SLE progression or malignant transformation is missing. To define the somatic mutational landscape of B-cells in SLE, we first profiled peripheral blood mononuclear cells obtained from a pilot cohort of four SLE patients using whole-exome sequencing (WES; 200X depth). Following GATK best practices (Van der Auwera and O'Connor, 2020), we identified somatic alterations in DDX11 [variant allele frequency (VAF): 10.2%], DNMT3A [VAF: 3.4%]; PMS2 [VAF: 47.9%], and BICD1 [VAF: 47.3%]; these genes have been linked to lymphoid malignancies and SLE pathogenesis (Piotrowski et al., 2015; Pullabhatla et al., 2018; Niroula et al., 2021; Saeed et al., 2021). We validated the presence of the top-identified mutations using droplet digital PCR technology on sorted B-cell subsets (naïve, memory, and double-negative [DN; CD19 hiIgD loCD27 lo]) from these SLE patients. DN cells are a heterogeneous subtype of autoreactive memory B-cells that play a crucial role in SLE pathogenesis being the precursors of autoantibody producing plasma cells (Wei et al., 2007; Jenks et al., 2018). To investigate the transcriptional and epigenetic alterations in the mutation-harboring B-cells, we then conducted single-cell multi-omic sequencing. We profiled sorted activated B-cells (CD19 hiIgD lo) from the four SLE cases, to largely exclude non-autoreactive naïve B-cells. To maintain a comparison with naïve B cells, we included a small proportion of these cells in the input. In total, we analyzed 35,339 cells, and identified different B-cell subsets with distinct gene expression patterns, including DN cells ( n = 1,437 cells; ZEB2 hiTRAF5 lo, Jenks et al., 2018). To uncover, in an unbiased way, transcriptional differences between B-cell subsets, we catalogued variation in transcriptomic signatures derived from the scRNA data using consensus non-negative matrix factorization. We found a unique gene expression program exclusively present in DN cells ( Panel A), which includes key genes implicated in immune regulation and the development of autoimmunity, such as PTPN22 (Chung & Criswell, 2007; Tizaoui et al., 2021) . Pathway analysis of the DN-specific program revealed an enrichment of complement system genes (FDR = 0.074; Hallmark), which are crucial for immune regulation and tolerance, such as CBLB (Tang et al., 2019). Notably, in DN cells from one of the SLE samples carrying lymphoma/SLE-associated mutations in BICD1, PMS2, DDX11, we observed an altered expression of this gene program compared to DN cells from other samples ( P-value = 3.6x10 -11; Panel A, inset), suggesting that a malfunctioning complement system in DN cells may lead to an overly active immune response (Weinstein et al., 2021). In line with this notion, using chromatin accessibility profiles as a measure of transcription factor (TF) regulatory activities, we showed increased activity of TFs involved in interferon-dependent innate immune response and in B-cell activation and differentiation (RFX and OCT-1, respectively; FDR < 0.05), in the DN B-cells of this sample ( Panel B). In summary, we uncovered a unique transcriptional program associated with autoimmune DN B-cells. This program showed enrichment in key genes and pathways involved in immune response regulation. The disruption of this program, accompanied by the somatic SLE-associated mutations, may lead to overactivation of DN B cells, ultimately contributing to autoimmunity. Further analyses involving a larger cohort of clinical specimens are needed to directly link B-cell genotypes with their transcriptional and epigenetic programs and to elucidate the role of the identified mutations in SLE pathobiology.

Characterization and Preclinical Evaluation of AS-1763, an Oral, Potent and Selective Noncovalent BTK Inhibitor, in Chronic Lymphocytic Leukemia

Background: Covalent Bruton's tyrosine kinase (BTK) inhibitors (cBTKi) have transformed treatment landscape of chronic lymphocytic leukemia (CLL). These inhibitors bind to C481 residue in the kinase domain of BTK. This is also the site for the most common mutations rendering cells resistant to cBTKi. To circumvent this limitation of the cBTKi, non-covalent BTKi (ncBTKi) such as pirtobrutinib have been developed. Recently, non-C481 BTK mutations have been reported in patients with CLL at the time of disease progression during pirtobrutinib treatment. These observations underscore the need for ncBTKi that can target C481 as well as non-C481 mutations of BTK. AS-1763 is a potent, highly selective, orally available, and ncBTKi, equipotent against both wild-type and C481S-mutated BTK when tested in biochemical assays. In vivo, AS-1763 demonstrated significant antitumor effects in OCI-LY10 tumor xenograft models harboring wild-type or C481S mutant BTK (Kawahata et al. J Med Chem 64:14129, 2021). Study Design and Methods: In the present project, first we used cell free assay systems to evaluate selectivity and potency of AS-1763 by a kinome-wide profiling and inhibitory effect of AS-1763 in enzyme assays using recombinant mutant BTK. Second, we examined dose- and time-dependent inhibition of mutant BTK that is expressed in HEK293 cell line. Third, we tested biological, biochemical, and molecular impact of AS-1763 in primary CLL cells. Fourth, we determined sensitivity of CLL cells to AS-1763 when combined with other targeted agents. Results: AS-1763 showed a highly selective profile for BTK in a panel of 291 kinase assays with >260-fold selectivity except 3 Tec family kinases (BMX, ITK, and TEC). We have generated a total of 17 recombinant BTK mutant proteins (C481, T474, L528 variants and other BTK mutants; Table 1) reported in the literature or predicted by single nucleotide change in the codon, and established assay methods to measure inhibitory potency of BTKi for those BTK mutants (Table 1). AS-1763 showed potent inhibitory activities for those BTK mutants while inhibitory potencies of other cBTKi and ncBTKi were diminished against some BTK mutants such as T474 and/or L528 mutations. AS-1763 exhibited dose-dependent and slow-off rate inhibitions of BTK autophosphorylation (pY223) in HEK293 cells transfected with various BTK mutants. Furthermore, the observed inhibitory effects of AS-1763 on the BTK autophosphorylation (pY223) in HEK293 cells were continued up to 24 h after washing out of AS-1763. In primary CLL samples, AS-1763, pirtobrutinib or ibrutinib induced a modest apoptosis. AS-1763 effectively inhibited the BCR signaling pathway in a dose dependent manner as evidenced by downregulation of pY223-BTK expression which was also observed in cBTKi and ncBTKi relapsed/refractory CLL samples. In vitro incubations with AS-1763 inhibited CLL cell spontaneous migration, decreased CCL3/CCL4 levels in culture supernatant and was accompanied with the inhibition of intracellular calcium release and B-cell activation, as measured by surface CD86 expression. Besides, AS-1763 incubation for 24 hours was shown to modulate the expression of BCL-2 family proteins with the downregulation of MCL-1 and BCL-xl. Interestingly, in vitro treatment of CLL patient samples with AS-1763 demonstrated a notable elevation in cellular ROS and mitochondrial superoxide levels starting at 1 µM, concurrently impacting SOD1 expression in CLL patient samples. Evaluation of drug interaction models utilizing Compusyn and Synergy Finder applications predominantly indicated additive effects between AS-1763 with BCL-2 inhibitor, venetoclax as well as p53 activator APR-246. Consistent with this data, AS-1763 and venetoclax combinations showed high-rates of apoptosis in samples that were relapsed/refractory to cBTKi and ncBTKi. Conclusions: AS-1763 is a selective ncBTKi that inhibits both wild-type and mutant BTKs listed in Table 1. In CLL cells, AS-1763 was effective in inhibiting BCR pathway signaling and sensitized cells to other agents such as venetoclax. Based on these encouraging data we have initiated a clinical trial to test AS-1763 in patients with CLL and other B cell malignancies who have failed or are intolerant to at least two prior lines of systemic therapy, including cBTKi (NCT05602363 Clinical Trials.gov).

VAYHIT3: An Open-Label, Single-Arm, Phase II Trial to Evaluate the Efficacy and Safety of Ianalumab in Patients with Primary Immune Thrombocytopenia (ITP) Previously Treated with at Least 1 Corticosteroid and 1 Thrombopoietin Receptor Agonist (TPO-RA)

Background: In patients with ITP, autoreactive B cells mediate the production of autoantibodies that target platelets and megakaryocytes, resulting in an increased rate of platelet destruction and decreased platelet production. B-cell activating factor (BAFF) regulates the differentiation, proliferation and survival of B cells via interactions with the BAFF receptor (BAFF-R). Patients with ITP have elevated serum BAFF levels, which positively correlate with increased disease activity. Ianalumab is a novel, fully human immunoglobulin G1 monoclonal antibody that targets BAFF-R and has a unique dual mechanism of action: direct B-cell depletion mediated by antibody-dependent cellular cytotoxicity and inhibition of B-cell differentiation, proliferation and survival via blockade of BAFF-R-mediated signaling. Following first-line corticosteroids, TPO-RAs are a standard second-line treatment for ITP; however, patients often require chronic TPO-RA treatment and endure potential side effects with increased costs. For patients who previously received corticosteroids and a TPO-RA, the choice of subsequent therapy (eg a different TPO-RA, rituximab, fostamatinib, mycophenolate mofetil, splenectomy) is not well defined. Thus, in patients with ITP requiring additional lines of therapy, there is an unmet need for new, well-tolerated therapies with disease-modifying potential that can safely induce high response rates after a short therapeutic course and maintain durable responses after treatment discontinuation. Trial design: VAYHIT3 (NCT05885555) is a multicenter, open-label, single-arm, Phase II trial enrolling approximately 40 adult patients with primary ITP who have previously received at least 1 corticosteroid and 1 TPO-RA. Additional prior therapies are allowed. Eligible patients must have lost response, had an insufficient response, had no response or been intolerant to their last ITP therapy. Along with a platelet count of <30 G/L, patients must be assessed by the investigator as needing treatment. Exclusion criteria include a neutrophil count of <1000/mm 3 and prior splenectomy. All patients will receive intravenous ianalumab every 4 weeks (Figure). Patients may receive concomitant therapy with a corticosteroid or TPO-RA if clinically indicated, which may be tapered. The primary efficacy analysis will occur after all patients have been followed up until Week 25 Day 1 or discontinued the study earlier. All patients with a platelet count of ≥30 G/L in the absence of a rescue therapy in the last 4 weeks or new ITP therapy at Week 25 Day 1 visit will continue efficacy monitoring until they have a platelet count of <30 G/L, start a new ITP therapy or require a rescue therapy. Safety will be monitored in all patients for up to 2 years after the last dose of ianalumab. Endpoints: The primary endpoint is confirmed response, defined as a platelet count of ≥50 G/L for 2 or more consecutive assessments at least 7 days apart between Week 1 Day 1 and Week 25 Day 1 visits and in the absence of both a rescue therapy for ≥4 weeks prior to the assessment of platelet count and the receipt of a new ITP therapy. Secondary endpoints include time to confirmed response, time to loss of response, quality and stability of response, proportions of patients experiencing bleeding events and requiring rescue therapies, changes in B cell and immunoglobulin levels, and pharmacokinetics, immunogenicity and safety of ianalumab. Exploratory biomarker assessments are also included to expand upon the understanding of ianalumab pharmacodynamics and exposure-response in patients with ITP. Conclusions: VAYHIT3 will evaluate the ability of a short therapeutic course of ianalumab to induce durable responses in patients who have received 2 or more prior lines of therapy, including at least 1 corticosteroid and 1 TPO-RA, for whom significant unmet needs exist. Current status: VAYHIT3 is recruiting. Ianalumab is also being investigated in 2 ongoing, randomized, double-blind, Phase III ITP trials: VAYHIT1 (NCT05653349) is assessing ianalumab versus placebo in addition to first-line corticosteroids, and VAYHIT2 (NCT05653219) is assessing ianalumab versus placebo in addition to eltrombopag in patients who failed first-line corticosteroid treatment.

B cell-targeted polylactic acidnanoparticles as platform for encapsulating jakinibs: potential therapeutic strategy for systemic lupus erythematosus.

Background: B cells are pivotal in systemic lupus erythematosus and autoimmune disease pathogenesis. Materials & methods: To address this, Nile Red-labeled polylactic acid nanoparticles (NR-PLA NPs) loaded with the JAK inhibitor baricitinib (BARI), specifically targeting JAK1 and JAK2 in B cells, were developed. Results: Physicochemical characterization confirmed NP stability over 30days. NR-PLA NPs were selectively bound and internalized by CD19+ B cells, sparing other leukocytes. In contrast to NR-PLA NPs, BARI-NR-PLA NPs significantly dampened B-cell activation, proliferationand plasma cell differentiation in healthy controls. They also inhibited key cytokine production. These effects often surpassed those of equimolar-free BARI. Conclusion: This study underscores thepotential ofPLA NPsto regulate autoreactive B cells, offering a novel therapeutic avenue for autoimmune diseases.

Effect of Antigen Valency on Autoreactive B-Cell Targeting.

Many autoimmune diseases are characterized by B cells that mistakenly recognize autoantigens and produce antibodies toward self-proteins. Current therapies aim to suppress the immune system, which is associated with adverse effects. An attractive and more specific approach is to target the autoreactive B cells selectively through their unique B-cell receptor (BCR) using an autoantigen coupled to an effector molecule able to modulate the B-cell activity. The cellular response upon antigen binding, such as receptor internalization, impacts the choice of effector molecule. In this study, we systematically investigated how a panel of well-defined mono-, di-, tetra-, and octavalent peptide antigens affects the binding, activation, and internalization of the BCR. To test our constructs, we used a B-cell line expressing a BCR against citrullinated antigens, the main autoimmune epitope in rheumatoid arthritis. We found that the dimeric antigen construct has superior targeting properties compared to those of its monomeric and multimeric counterparts, indicating that it can serve as a basis for future antigen-specific targeting studies for the treatment of RA.

Lupus and recurrent pregnancy loss: the role of female sex hormones and B cells.

Systemic lupus erythematosus is a debilitating autoimmune disease characterized by uncontrolled activation of adaptive immunity, particularly B cells, which predominantly affects women in a 9 to 1 ratio compared to men. This stark sex disparity strongly suggests a role for female sex hormones in the disease's onset and progression. Indeed, it is widely recognized that estradiol not only enhances the survival of autoreactive B cells but also stimulates the production of autoantibodies associated with systemic lupus erythematosus, such as anti-nuclear antibodies and anti-dsDNA antibodies. Clinical manifestations of systemic lupus erythematosus typically emerge after puberty and persist throughout reproductive life. Furthermore, symptoms often exacerbate during the premenstrual period and pregnancy, as increased levels of estradiol can contribute to disease flares. Despite being fertile, women with lupus face a heightened risk of pregnancy-related complications, including pregnancy loss and stillbirth, which significantly surpass the rates observed in the healthy population. Therefore, this review aims to summarize and discuss the existing literature on the influence of female sex hormones on B-cell activation in patients with systemic lupus erythematosus, with a particular emphasis on their impact on pregnancy loss.

Self-Immolative Carbamate Linkers for CD19-Budesonide Antibody-Drug Conjugates.

Antibody-drug conjugates consist of potent small-molecule payloads linked to a targeting antibody. Payloads must possess a viable functional group by which a linker for conjugation can be attached. Linker-attachment options remain limited for the connection to payloads via hydroxyl groups. A releasing group based on 2-aminopyridine was developed to enable stable attachment of para-aminobenzyl carbamate (PABC) linkers to the C21-hydroxyl group of budesonide, a glucocorticoid receptor agonist. Payload release involves a cascade of two self-immolative events that are initiated by the protease-mediated cleavage of the dipeptide-PABC bond. Budesonide release rates were determined for a series of payload-linker intermediates in buffered solution at pH 7.4 and 5.4, leading to the identification of 2-aminopyridine as the preferred releasing group. Addition of a poly(ethylene glycol) group improved linker hydrophilicity, thereby providing CD19-budesonide ADCs with suitable properties. ADC23 demonstrated targeted delivery of budesonide to CD19-expressing cells and inhibited B-cell activation in mice.

BAFF as a predictive marker for treatment response in immune thrombocytopenia patients

Abstract Background Immune thrombocytopenic purpura (ITP) is a hematological autoimmune bleeding disorder that characterized by isolated thrombocytopenia (platelet count <100 × 109/L) with unclear pathophysiology due to contribution of many cytokines, one of them is B-cell activating factor (BAFF) which affect both B-cell and T-cell activation and survival. Objectives This work aimed to study serum BAFF levels in the Egyptian ITP patients, and the relation between its level and response to steroid therapy, as well its value as a predictive marker for steroid response in ITP patients. Patients and methods 90 subjects were recruited, and divided into 45 patients with primary ITP, and 45 healthy subjects. Serum BAFF was estimated using the ELISA technique. Results BAFF level was significantly higher in the ITP patients than in the control group. Serum BAFF level was significantly higher in newly diagnosed ITP cases and steroids-resistant ITP cases. BAFF was negatively correlated with platelet count, while MPV, PDW, and LDH were positively correlated, BAFF level at a cut-off 201.01 pg/ml is a good predictive for steroid resistance in ITP cases. Conclusion BAFF could be a good inexpensive helper to determine the response to steroid treatment in ITP cases.

EXPLORING THE DEVELOPMENT OF DENDRITIC CELL-BASED CANCER VACCINES WITH A FOCUS ON CANCER RESEARCH

The fundamental premise behind clinical approaches for dendritic cell mediated immunization in cancer is that the limiting defect in natural antitumor immunity is at the level of antigen presentation. In contrast to vaccines for the prevention of infections, cancer vaccines are administered in a therapeutic mode, to eradicate antigen-bearing tumor cells already present in the host. Over decades, the identification of antigens that can serve as targets for immune effectors have resulted in a profusion of strategies for activating tumor antigen-specific immune responses. Therapeutic vaccines, unlike prophylactic vaccines for the prevention of infections, all share some basic attributes, the presence of target antigens, and a method for delivering the antigen into the antigen-presentation machinery in conjunction with other molecules required to provide T- and/or B-cell activation.

NOP2/Sun RNA methyltransferase 2 is a potential pan-cancer prognostic biomarker and is related to immunity.

NOP2/Sun RNA methyltransferase 2 (NSUN2), an important methyltransferase of m5C, has been poorly studied in cancers, and the relationship between NSUN2 and immunity remains largely unclear. Therefore, the purpose of this study was to explore the expression and prognostic value of NSUN2 and the role of NSUN2 in immunity in cancers. The TIMER, CPTAC and other databases were used to analyze the expression of NSUN2, its correlation with clinical stage and its prognostic value across cancers. Moreover, the TISIDB, TIMER2.0 and Sangerbox platform were used to depict the relationships between NSUN2 and immune molecular subtypes, tumor-infiltrating lymphocytes (TILs), immune checkpoints (ICPs) and immunoregulatory genes. Furthermore, the NSUN2-interacting proteins and related genes as well as the coexpression networks of NSUN2 in LIHC, LUAD and HNSC were explored with the STRING, DAVID, GEPIA2 and LinkedOmics databases. Finally, the subcellular location and function of NSUN2 in HepG2, A549 and 5-8F cells were investigated by performing immunofluorescence, CCK-8 and wound healing assays. Overall, NSUN2 was highly expressed and related to a poor prognosis in most types of cancers and was also significantly associated with immune molecular subtypes in some cancer types. Furthermore, NSUN2 was significantly associated with the levels of ICPs and immunoregulatory genes. In addition, NSUN2 was found to be involved in a series of immune-related biological processes, such as the humoral immune response in LIHC and LUAD and T-cell activation and B-cell activation in HNSC. Immunofluorescence and CCK-8 assays also confirmed that NSUN2 was widely expressed in the nucleus and cytoplasm, and overexpression of NSUN2 promoted the proliferation and migration of HepG2, A549 and 5-8F cells. NSUN2 was also confirmed to positively regulate the expression of PD-L1. NSUN2 serves as a pan-cancer prognostic biomarker and is correlated with the immune infiltration of tumors.

ICOSLG-associated immunological landscape and diagnostic value in oral squamous cell carcinoma: a prospective cohort study.

Background: We previously reported that stroma cells regulate constitutive and inductive PD-L1 (B7-H1) expression and immune escape of oral squamous cell carcinoma. ICOSLG (B7-H2), belongs to the B7 protein family, also participates in regulating T cells activation for tissue homeostasis via binding to ICOS and inducing ICOS+ T cell differentiation as well as stimulate B-cell activation, while it appears to be abnormally expressed during carcinogenesis. Clarifying its heterogeneous clinical expression pattern and its immune landscape is a prerequisite for the maximum response rate of ICOSLG-based immunotherapy in a specific population. Methods: This retrospective study included OSCC tissue samples (n = 105) to analyze the spatial distribution of ICOSLG. Preoperative peripheral blood samples (n = 104) and independent tissue samples (n = 10) of OSCC were collected to analyze the changes of immunocytes (T cells, B cells, NK cells and macrophages) according to ICOSLG level in different cellular contents. Results: ICOSLG is ubiquitous in tumor cells (TCs), cancer-associated fibroblasts (CAFs) and tumor infiltrating lymphocytes (TILs). Patients with high ICOSLGTCs or TILs showed high TNM stage and lymph node metastasis, which predicted a decreased overall or metastasis-free survival. This sub-cohort was featured with diminished CD4+ T cells and increased Foxp3+ cells in invasive Frontier in situ, and increased absolute numbers of CD3+CD4+ and CD8+ T cells in peripheral blood. ICOSLG also positively correlated with other immune checkpoint molecules (PD-L1, CSF1R, CTLA4, IDO1, IL10, PD1). Conclusion: Tumor cell-derived ICOSLG could be an efficient marker of OSCC patient stratification for precision immunotherapy.

PLCG2-associated immune dysregulation (PLAID) comprises broad and distinct clinical presentations related to functional classes of genetic variants

Pathogenic variants of phospholipase C gamma 2 (PLCG2) cause 2 related forms of autosomal-dominant immune dysregulation (ID), PLCγ2-associated antibody deficiency and immune dysregulation (PLAID) and autoinflammatory PLAID (APLAID). Since describing these conditions, many PLCG2 variants of uncertain significance have been identified by clinical sequencing of patients with diverse features of ID. We sought to functionally classify PLCG2 variants and explore known and novel genotype-function-phenotype relationships. Clinical data from patients with PLCG2 variants were obtained via standardized questionnaire. PLCG2 variants were generated by mutagenesis of enhanced green fluorescent protein (EGFP)-PLCG2 plasmid, which was overexpressed in Plcg2-deficient DT-40 B cells. B-cell receptor-induced calcium flux and extracellular signal-regulated kinase phosphorylation were assayed by flow cytometry. In some cases, stimulation-induced calcium flux was also measured in primary patient cells. Three-fourths of PLCG2 variants produced functional alteration of B-cell activation, invitro. Thirteen variants led to gain of function (GOF); however, most functional variants defined a new class of PLCG2 mutation, monoallelic loss of function (LOF). Susceptibility to infection and autoinflammation were common with both GOF and LOF variants, whereas a new phenotypic cluster consisting of humoral immune deficiency, autoinflammation, susceptibility to herpesvirus infection, and natural killer cell dysfunction was observed in association with multiple heterozygous LOF variants detected in both familial and sporadic cases. In some cases, PLCG2 variants produced greater effects in natural killer cells than in B cells. This work expands the genotypic and phenotypic associations with functional variation in PLCG2, including a novel form of ID in carriers of heterozygous loss of PLCG2 function. It also demonstrates the need for more diverse assays for assessing the impact of PLCG2 variants on human disease.

Extracellular vesicles as biomarkers for AIDS-associated non-Hodgkin lymphoma risk.

Extracellular vesicles are membrane-bound structures secreted into the extracellular milieu by cells and can carry bioactive molecules. There is emerging evidence suggesting that EVs play a role in the diagnosis, treatment, and prognosis of certain cancers. In this study, we investigate the association of EVs bearing PD-L1 and molecules important in B-cell activation and differentiation with AIDS-NHL risk. EVs were isolated from archived serum collected prior to the diagnosis of AIDS-NHL in cases (N = 51) and matched HIV+ controls (N = 52) who were men enrolled in the Los Angeles site of the MACS/WIHS Combined Cohort Study (MWCCS). Serum specimens of AIDS-NHL cases were collected at a mean time of 1.25 years (range of 2 to 36 months) prior to an AIDS-NHL diagnosis. The expression of PD-L1 and other molecules on EVs (CD40, CD40L, TNF-RII, IL-6Rα, B7-H3, ICAM-1, and FasL) were quantified by Luminex multiplex assay. We observed significantly higher levels of EVs bearing PD-L1, CD40, TNF-RII and/or IL-6Rα in AIDS-NHL cases compared with controls. Using multivariate conditional logistic regression models adjusted for age and CD4+ T-cell count, we found that EVs bearing PD-L1 (OR = 1.93; 95% CI: 1.10 - 3.38), CD40 (OR = 1.97, 95% CI: 1.09 - 3.58), TNF-RII (OR = 5.06; 95% CI: 1.99 - 12.85) and/or IL-6Rα (OR = 4.67; 95% CI: 1.40 - 15.53) were significantly and positively associated with AIDS-NHL risk. In addition, EVs bearing these molecules were significantly and positively associated with non-CNS lymphoma: PD-L1 (OR = 1.94; 95% CI: 1.01 - 3.72); CD40 (OR = 2.66; 95% CI: 1.12 - 6.35); TNF-RII (OR = 9.64; 95% CI: 2.52 - 36.86); IL-6Rα (OR = 8.34; 95% CI: 1.73 - 40.15). These findings suggest that EVs bearing PD-L1, CD40, TNF-RII and/or IL-6Rα could serve as biomarkers for the early detection of NHL in PLWH.

Tumor-Infiltrating Normal B Cells Revealed by Immunoglobulin Repertoire Clonotype Analysis Are Highly Prognostic and Crucial for Antitumor Immune Responses in DLBCL.

Tumor-infiltrating B lymphocytes (TIL-B) have demonstrated prognostic and predictive significance in solid cancers. In this study, we aimed to distinguish TIL-Bs from malignant B-cells in diffuse large B-cell lymphoma (DLBCL) and determine the clinical and biological significance. A total of 269 patients with de novo DLBCL from the International DLBCL R-CHOP Consortium Program were studied. Ultra-deep sequencing of the immunoglobulin genes was performed to determine B-cell clonotypes. The frequencies and numbers of TIL-B clonotypes in individual repertoires were correlated with patient survival, gene expression profiling (GEP) data, and frequencies of DLBCL-infiltrating immune cells quantified by fluorescent multiplex IHC at single-cell resolution. TIL-B abundance, evaluated by frequencies of normal B-cell clonotypes in the immunoglobulin repertoires, remarkably showed positive associations with significantly better survival of patients in our sequenced cohorts. DLBCLs with high versus low TIL-B abundance displayed distinct GEP signatures, increased pre-memory B-cell state and naïve CD4 T-cell state fractions, and higher CD4+ T-cell infiltration. TIL-B frequency, as a new biomarker in DLBCL, outperformed the germinal center (GC) B-cell-like/activated B-cell-like classification and TIL-T frequency. The identified TIL-B-high GEP signature, including genes upregulated during T-dependent B-cell activation and those highly expressed in normal GC B cells and T cells, showed significant favorable prognostic effects in several external validation cohorts. TIL-B frequency is a significant prognostic factor in DLBCL and plays a crucial role in antitumor immune responses. This study provides novel insights into the prognostic determinants in DLBCL and TIL-B functions with important therapeutic implications.

Mining Autoimmune-Disorder-Linked Molecular-Mimicry Candidates in Clostridioides difficile and Prospects of Mimic-Based Vaccine Design: An In Silico Approach.

Molecular mimicry, a phenomenon in which microbial or environmental antigens resemble host antigens, has been proposed as a potential trigger for autoimmune responses. In this study, we employed a bioinformatics approach to investigate the role of molecular mimicry in Clostridioides difficile-caused infections and the induction of autoimmune disorders due to this phenomenon. Comparing proteomes of host and pathogen, we identified 23 proteins that exhibited significant sequence homology and were linked to autoimmune disorders. The disorders included rheumatoid arthritis, psoriasis, Alzheimer's disease, etc., while infections included viral and bacterial infections like HIV, HCV, and tuberculosis. The structure of the homologous proteins was superposed, and RMSD was calculated to find the maximum deviation, while accounting for rigid and flexible regions. Two sequence mimics (antigenic, non-allergenic, and immunogenic) of ≥10 amino acids from these proteins were used to design a vaccine construct to explore the possibility of eliciting an immune response. Docking analysis of the top vaccine construct C2 showed favorable interactions with HLA and TLR-4 receptor, indicating potential efficacy. The B-cell and T-helper cell activity was also simulated, showing promising results for effective immunization against C. difficile infections. This study highlights the potential of C. difficile to trigger autoimmunity through molecular mimicry and vaccine design based on sequence mimics that trigger a defensive response.

Cross-talk between B cells, microglia and macrophages, and implications to central nervous system compartmentalized inflammation and progressive multiple sclerosis

B cells can be enriched within meningeal immune-cell aggregates of multiple sclerosis (MS) patients, adjacent to subpial cortical demyelinating lesions now recognized as important contributors to progressive disease. This subpial demyelination is notable for a 'surface-in' gradient of neuronal loss and microglial activation, potentially reflecting the effects of soluble factors secreted into the CSF. We previously demonstrated that MS B-cell secreted products are toxic to oligodendrocytes and neurons. The potential for B-cell-myeloid cell interactions to propagate progressive MS is of considerable interest. Secreted products of MS-implicated pro-inflammatory effector B cells or IL-10-expressing B cells with regulatory potential were applied to human brain-derived microglia or monocyte-derived macrophages, with subsequent assessment of myeloid phenotype and function through measurement of their expression of pro-inflammatory, anti-inflammatory and homeostatic/quiescent molecules, and phagocytosis (using flow cytometry, ELISA and fluorescently-labeled myelin). Effects of secreted products of differentially activated microglia on B-cell survival and activation were further studied. Secreted products of MS-implicated pro-inflammatory B cells (but not IL-10 expressing B cells) substantially induce pro-inflammatory cytokine (IL-12, IL-6, TNFα) expression by both human microglia and macrophage (in a GM-CSF dependent manner), while down-regulating their expression of IL-10 and of quiescence-associated molecules, and suppressing their myelin phagocytosis. In contrast, secreted products of IL-10 expressing B cells upregulate both human microglia and macrophage expression of quiescence-associated molecules and enhance their myelin phagocytosis. Secreted factors from pro-inflammatory microglia enhance B-cell activation. Potential cross-talk between disease-relevant human B-cell subsets and both resident CNS microglia and infiltrating macrophages may propagate CNS-compartmentalized inflammation and injury associated with MS disease progression. These interaction represents an attractive therapeutic target for agents such as Bruton's tyrosine kinase inhibitors (BTKi) that modulate responses of both B cells and myeloid cells. Stated in Acknowledgments section of manuscript.

Alternative splicing of its 5′-UTR limits CD20 mRNA translation and enables resistance to CD20-directed immunotherapies

AbstractAberrant skipping of coding exons in CD19 and CD22 compromises the response to immunotherapy in B-cell malignancies. Here, we showed that the MS4A1 gene encoding human CD20 also produces several messenger RNA (mRNA) isoforms with distinct 5′ untranslated regions. Four variants (V1-4) were detected using RNA sequencing (RNA-seq) at distinct stages of normal B-cell differentiation and B-lymphoid malignancies, with V1 and V3 being the most abundant. During B-cell activation and Epstein-Barr virus infection, redirection of splicing from V1 to V3 coincided with increased CD20 positivity. Similarly, in diffuse large B-cell lymphoma, only V3, but not V1, correlated with CD20 protein levels, suggesting that V1 might be translation-deficient. Indeed, the longer V1 isoform contained upstream open reading frames and a stem-loop structure, which cooperatively inhibited polysome recruitment. By modulating CD20 isoforms with splice-switching morpholino oligomers, we enhanced CD20 expression and anti-CD20 antibody rituximab-mediated cytotoxicity in a panel of B-cell lines. Furthermore, reconstitution of CD20-knockout cells with V3 mRNA led to the recovery of CD20 positivity, whereas V1-reconstituted cells had undetectable levels of CD20 protein. Surprisingly, in vitro CD20-directed chimeric antigen receptor T cells were able to kill both V3- and V1-expressing cells, but the bispecific T-cell engager mosunetuzumab was only effective against V3-expressing cells. To determine whether CD20 splicing is involved in immunotherapy resistance, we performed RNA-seq on 4 postmosunetuzumab follicular lymphoma relapses and discovered that in 2 of them, the downregulation of CD20 was accompanied by a V3-to-V1 shift. Thus, splicing-mediated mechanisms of epitope loss extend to CD20-directed immunotherapies.

Development and application of an in vitro assay to assess target-independent B-cell activation by targeted TLR7 immune agonists

Targeted immune agonist (TIA) comprising a TLR7 agonist conjugated to tumor-targeting antibodies have been shown to induce potent anti-tumor responses in various preclinical models. However, the clinical proof-of-concept of a TIA has been hampered by systemic dose-limiting immune-related toxicities, including rapid induction of anti-drug antibodies in patients. We have developed ELISPOT-based assay to measure activation of antibody-secreting cells (ASCs), intended to simulate the interaction between TIA and peripheral B cells as a tool to pre-clinically de-risk tumor target-independent peripheral B-cell activation by TIA. This method has proven to be robust and has fast turn-around time to evaluate the induction of spontaneous B-cell activation by TIA in a tumor target- and FcγR-independent manner. This novel ASC assay platform may serve as a preclinical tool to de-risk TIAs that can potentially induce immune-related adverse effects in the clinic.