A Proliferation-inducing Ligand Levels Research Articles

A proliferation-inducing ligand (APRIL) level among risk factors of ocular involvement in patients with Behçet’s disease

IntroductionOcular involvement is quite common in Behçet’s disease (BD) and may cause crucial functional complications. Even though the mechanisms of BD remain unclear, advances in gene­tic and immunological fields have improved our understanding of the immunopathogenesis of BD ocular involvement. Little is known about the expression of a proliferation-inducing ligand (APRIL) in terms of ocular involvement in BD. The objective of this study was to determine whether serum APRIL concentrations are associated with ocular involvement in patients with BD.Material and methodsThe study included 60 patients diagnosed with BD matched by age and sex to 30 healthy individuals. Every patient underwent a clinical evaluation, and the Behçet’s Disease Current Activity Form (BDCAF) was utilized to quantify disease activity. All patients underwent a comprehensive ophthalmological assessment. Serum APRIL was assessed for patients as well as controls.ResultsOne or more ocular manifestations were found in 42 BD patients (70%), while 18 patients (30%) had no ocular involvement. The mean level of serum APRIL levels was markedly elevated in BD patients, particularly those with ocular involvement, compared to both BD patients without ocular involvement and healthy individuals. A statistically significant association was determined between high APRIL concentration and development of uveitis, cataract, and hypopyon. Cutaneous lesions and arthritis were strong independent predictors for ocular involvement in BD patients.ConclusionsOverexpression of APRIL in patients with BD, particularly in terms of uveitis, cataract, and hypopyon, lends credence to the idea that B cell activating factors have an important function in BD. These findings may indicate that serum APRIL concentrations can differentiate a clinical subgroup of BD patients with ocular disease. As a result, finding a new therapeutic strategy targeting the APRIL pathway might be beneficial in BD patients suffering from ocular involvement.

Patients with IgA Nephropathy Show Abnormal Frequencies of B cell Subsets and Unconventional T Cells and High Levels of Gd-IgA1 Coated Gut Bacteria

BackgroundMucosal inflammation is involved in the pathophysiology of Immunoglobulin-A nephropathy (IgAN), but peripheral immune phenotype analyses of IgAN patients often do not include unconventional T cells, the major subset in mucosal immunity. MethodsWe measured serum total IgA, gd-IgA1, secretory IgA, B cell activating factor (BAFF), and A proliferation-inducing ligand (APRIL) in 66 IgAN patients and 30 healthy controls (HC). We also quantified total IgA and gd-IgA1 in stool supernatant and coated on bacteria. In 35 patients and 14 controls, we performed extensive phenotyping (CyTOF) of circulating immune cells, including unconventional T cells [mucosal associated invariant T (MAIT) cells, γδ T, and NK T cells]. The results were validated using RNAseq data from a larger cohort of 179 patients with IgAN, 140 patients with minimal change disease (MCD), and 91 HC. ResultsIgAN patients had higher circulating levels of total IgA, gd-IgA1, and APRIL and higher IgA- and gd-IgA1-coated gut bacteria than controls, while serum levels of secretory IgA and BAFF did not differ between groups. IgAN patients showed more class switched memory and double negative B cells than controls. MAIT cells and γδ T cells were significantly lower, and CD4- CD8- NK T cells significantly higher in IgAN patients than in HC. We validated the significant decrease in MAIT cells in an independent cohort of patients with IgAN. ConclusionThe data indicate that patients with IgAN have increased circulating class switched memory and double negative B cells associated with abnormal T cell immunity, involving defects in unconventional T cell frequency. This may suggest putative alterations at mucosal sites due to cell migration leading to altered IgA production.

Serum BAFF (B-cell activating factor) and APRIL (a proliferation-inducing ligand) levels in the first trimester may predict the future development of gestational diabetes mellitus

BackgroundGestational diabetes mellitus (GDM) is a prevalent condition with an unclear pathogenesis. B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are potential key players in GDM. Participants, materials, and methodsIn a longitudinal observational study, we monitored women from the first trimester through 24–28 weeks of gestation, focusing on the development of GDM. Serum levels of BAFF and APRIL, as well as their mRNA expression, were evaluated in both the first and third trimesters. Furthermore, we assessed cytokines, adipokines, and placental hormones in the serum. ResultsIn the first trimester, participants who later developed GDM exhibited elevated serum BAFF and reduced serum APRIL levels, although the mRNA expression of these molecules was similar to controls. Serum BAFF exhibited significant positive correlations with metabolic markers and placental hormones. Conversely, serum APRIL was negatively correlated with insulin resistance and inflammatory markers but positively correlated with adiponectin. In the early third trimester, GDM participants continued to display higher serum BAFF levels and lower serum APRIL levels than controls. There was no significant difference in mRNA expression of BAFF between GDM and control groups. Conversely, APRIL mRNA expression was significantly lower in the GDM group. The predictive potential of first-trimester BAFF and APRIL levels for future GDM development was explored, with both molecules demonstrating strong predictive capability. Discussion and conclusionThis study suggests that elevated serum BAFF and reduced serum APRIL levels during pregnancy may be associated with the development of GDM. These biomarkers can serve as potential early predictors for GDM.

The role of BAFF and APRIL in IgA nephropathy: pathogenic mechanisms and targeted therapies.

Immunoglobulin A nephropathy (IgAN), characterized by mesangial deposition of galactose-deficient-IgA1 (Gd-IgA1), is the most common biopsy-proven primary glomerulonephritis worldwide. Recently, an improved understanding of its underlying pathogenesis and the substantial risk of progression to kidney failure has emerged. The "four-hit hypothesis" of IgAN pathogenesis outlines a process that begins with elevated circulating levels of Gd-IgA1 that trigger autoantibody production. This results in the formation and deposition of immune complexes in the mesangium, leading to inflammation and kidney injury. Key mediators of the production of Gd-IgA1 and its corresponding autoantibodies are B-cell activating factor (BAFF), and A proliferation-inducing ligand (APRIL), each playing essential roles in the survival and maintenance of B cells and humoral immunity. Elevated serum levels of both BAFF and APRIL are observed in patients with IgAN and correlate with disease severity. This review explores the complex pathogenesis of IgAN, highlighting the pivotal roles of BAFF and APRIL in the interplay between mucosal hyper-responsiveness, B-cell activation, and the consequent overproduction of Gd-IgA1 and its autoantibodies that are key features in this disease. Finally, the potential therapeutic benefits of inhibiting BAFF and APRIL in IgAN, and a summary of recent clinical trial data, will be discussed.

B cell activating factor levels are linked to distinct B cell markers in multiple sclerosis and following B cell depletion and repopulation

Recent studies have highlighted the important role of B cells in the pathogenesis of multiple sclerosis (MS). B cell activating factor (BAFF) and A proliferation inducing ligand (APRIL) play a major role in B cell survival and homeostasis. Here, we studied the association of BAFF and APRIL with B cell immune markers in MS and following B cell depletion and repopulation. We found that BAFF but not APRIL was significantly higher in plasma in untreated MS compared to controls. BAFF increased after rituximab treatment and decreased again during repopulation displaying an inverse correlation with B cell numbers, and more specifically switched memory B cell numbers. Cerebrospinal fluid BAFF inversely correlated with IgG index. BAFF displayed an inverse association to anti-EBV-CA antibodies. In summary, our study identified immune cells and factors that might regulate or be regulated by BAFF and APRIL levels in MS, and during B cell depletion and repopulation.

Human gingival fibroblasts are a source of B cell-activating factor during periodontal inflammation.

Host-modulating therapy is a possible treatment for individuals that respond poorly to conventional periodontal therapy. B cells, abundant in periodontitis lesions, require the cytokines B cell-activating factor (BAFF) and A proliferation-inducing ligand (APRIL) for survival and maturation. Although mRNA levels of BAFF and APRIL are increased in tissue from periodontitis lesions, it is unknown if periodontal resident cells express BAFF and/or APRIL during periodontal inflammation. In this study, we aim to analyze the expression of BAFF and APRIL in human gingival fibroblasts after stimulation with proinflammatory cytokines. Furthermore, we perform protein analysis in tissues and serum from periodontitis patients and healthy controls. Human gingival fibroblasts were cultured and stimulated with the proinflammatory cytokines' tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). The mRNA expression of BAFF and APRIL was analyzed by real-time quantitative polymerase chain reaction (qPCR), and the protein was detected in tissue sections using immune staining. Serum levels of BAFF were analyzed with enzyme-linked immunosorbent assay (ELISA). In gingival fibroblasts, TNF-α upregulated BAFF mRNA, but APRIL was unaffected. IL-1β affected neither BAFF nor APRIL expression. BAFF protein was detected in the oral epithelium and in cells of the underlying connective tissue in periodontitis tissue, and BAFF protein was increased in the serum of periodontitis patients. Periodontal resident cells express BAFF during periodontal inflammation and participate in providing a favorable milieu for the survival and action of B cells.

The contribution of a proliferation-inducing ligand (APRIL) and other TNF superfamily members in pathogenesis and progression of IgA nephropathy.

Advances in our understanding of the pathogenesis of immunoglobulin A nephropathy (IgAN) have led to the identification of novel therapeutic targets and potential disease-specific treatments. Specifically, a proliferation-inducing ligand (APRIL) has been implicated in the pathogenesis of IgAN, mediating B-cell dysregulation and overproduction of pathogenic galactose-deficient IgA1 (Gd-IgA1). Animal and clinical studies support the involvement of APRIL in the pathogenesis and progression of IgAN. An elevated level of APRIL is found in IgAN when compared with controls, which correlates with the level of Gd-IgA1 and associates with more severe disease presentation and worse outcomes. Conversely, anti-APRIL therapy reduces pathogenic Gd-IgA1 and IgA immune complex formation and ameliorates the severity of kidney inflammation and injury. Genome-wide association studies in IgAN have identified TNFSF13 and TNFRSF13B, a cytokine ligand-receptor gene pair encoding APRIL and its receptor, respectively, as risk susceptibility loci in IgAN, further supporting the causal role of the APRIL signalling pathway in IgAN. Several novel experimental agents targeting APRIL, including atacicept, telitacicept, zigakibart and sibeprenlimab, are currently under investigation as potential therapies in IgAN. Preliminary results suggest that these agents are well-tolerated, and reduce levels of Gd-IgA1, with corresponding improvement in proteinuria. Further studies are ongoing to confirm the safety and efficacy of anti-APRIL approaches as an effective therapeutic strategy in IgAN.

Bone Marrow CD8 + Tissue-Resident Memory T Cell Promote B Cell Differentiation and Inhibit Platelet Production in Patients with Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is a prevalent autoimmune disease in which enhanced anti-platelet T cell activity and dysfunction of CD8 + T cells are involved(Audia et al., 2013; Semple & Freedman, 1991). Persistent secretion of antibodies by long-lived plasma cells and memory B cells in the bone marrow contributes to ITP pathogenesis (Roeser, Lazarus, & Mahevas, 2023). However, the role of memory T cells, especially tissue-resident memory T cells (TRM), in ITP remains underexplored. TRM develop in specific tissues and play crucial role in local immunity. TRM exert their effects through mechanisms including the induction of local humoral responses, contributing to autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis (Chang et al., 2021; Gu, Song, Roh, Jung, & Kim, 2021). Bone marrow contains one of the largest pools of memory CD8 + T cells. However, the involvement of bone marrow TRM in ITP pathogenesis remains poorly understood. In this study, we observed a significantly higher proportion of CD8 + TRM (CD8 +CD45RA -CD45RO +CD69 +) in the bone marrow of ITP patients compared to healthy controls. However, no significant differences were observed in CD4 + TRM, CD8 + TCM and CD8 + TEM between the two groups. CD8 + TRM from ITP patients exhibited increased levels of IFN-γ, NLRP3, IL-1β, TNF-α, and decreased levels of IL-10 compared to those from healthy controls. Furthermore, CD8 + TRM proportions were significantly higher in glucocorticoid responders than non-responders, suggesting a potential role of CD8 + TRMs in mediating glucocorticoid therapeutic effects. Transcriptome sequencing revealed upregulated genes, including IGLC2, ASAP2, HIST2H2AA4, IGLV2-11, C1QA, ATP5MC1, IL5RA, and CYC1, and downregulated genes, including CCR9, HSPE1P18, RGCC, and ITGAE, in TRM cells from ITP patients compared to controls. GO/KEGG analysis of the top 500 upregulated genes highlighted pathways associated with B cell-associated immunity. To explore the effect of TRM on B cells, bone marrow CD19 + B cells were co-cultured with autologous TRM or memory T cells without TRM (TM) in the presence of IgM, and the proportion of memory B cells (CD19 +CD27 +CD38 -) and plasma cells (CD19 -CD24 -CD38 +) were measured by flow cytometry. The supernatants were collected, and cytokines and IgG level were tested by ELISA. Results showed that TRMs from ITP patients promoted the differentiation of memory B cells and IgG antibody production compared with those from healthy controls. However, no significant difference was observed in the proportion of naive B cells and plasma cells between the two groups. TRM, but not TM augmented B cell differentiation into memory B cells or plasma cells both in ITP patients and healthy controls. Additionally, TRM-primed B cells showed a stronger effect on antibody production and resulted in a higher level of IgG in supernatant compared with TM primed B cells. In line with these findings, the levels of B cell activating factor (BAFF), a proliferation inducing ligand (APRIL), and sCD40L, which were critical cytokines for B cell survival and differentiation, were significantly higher in supernatants from ITP patients than those from healthy controls. Moreover, the levels of BAFF, APRIL and CD40L in co-culture system with TRM were significantly increased compared to the system with TM, providing insights into the impact of TRM on B cell differentiation and function. To further investigate the role of TRM in regulating platelet production in ITP patients, we cocultured TRM with CD34 +cells in the presence of thrombopoietin (TPO), stem cell factor (SCF) and interleukin (IL)-3. Results showed that TRM did not suppress the production of CD41 + megakaryocytes from CD34 + cells, but reduced megakaryocyte apoptosis and increased the percentage of polyploidy (≥4N) megakaryocytes compared with TM. Additionally, TRM inhibited reticulated platelet formation and platelet production. Notably, dexamethasone (DXM) modulation alleviated certain suppressive effects on platelet production. In summary, our findings reveal the involvement of impaired bone marrow CD8 + TRM in the pathogenesis of ITP through the promotion of B cell differentiation and inhibition of platelet production. These results shed new light on the potential of immune therapy targeting TRM in the management of ITP.

Povetacicept (ALPN-303), a Potent Dual BAFF/APRIL Antagonist in Development for the Treatment of Autoimmune Cytopenias, Suppresses Disease in a Mouse Model of Autoimmune Hemolytic Anemia

Introduction: B cell activating factor (BAFF) and a proliferation inducing ligand (APRIL) play key roles in B cell development, survival, and differentiation into antibody-secreting cells (ASC). Given their importance in ASC survival and antibody production, inhibition of BAFF and/or APRIL (particularly in combination) is a promising approach for the treatment of a variety of autoimmune or autoantibody-related diseases including autoimmune cytopenias like warm autoimmune hemolytic anemia (wAIHA), immune thrombocytopenia (ITP), and cold agglutinin disease (CAD). Significantly higher levels of both BAFF and APRIL have been observed in the serum of patients with AIHA and ITP compared to healthy subjects, and polymorphisms in BAFF and TACI have been associated with ITP [Abdel-Hamid et al., Am J Med, 2011; Xu et al., Int J Hematol., 2015; Emmerich, et al., Br J Haematol, 2007; Peng, et al., J Thromb Haemost, 2017; Yu, et al., Blood Adv, 2021]. Belimumab, an anti-BAFF antibody, has demonstrated encouraging efficacy in the treatment of ITP associated with systemic lupus erythematosus [De Marchi, et al., Clin Exp Rheumatol, 2017] and in combination with rituximab in patients with ITP [Mahévas, et al., Haematologica, 2021]. Currently, there are no BAFF and/or APRIL inhibitors approved to treat AIHA or ITP. Povetacicept (ALPN-303) is an engineered, potent dual BAFF/APRIL antagonist. We previously evaluated the impact of BAFF/APRIL co-inhibition preclinically in the accelerated HODxOTII transgenic mouse model of AIHA, in which povetacicept treatment significantly suppressed plasma cells in the spleen and bone marrow, reduced pathogenic anti-RBC autoantibodies, and significantly increased hematocrit [Dillon et al., ASH 2022 abstract #3763]. Here, we have evaluated povetacicept in a second preclinical model of AIHA, a rat red blood cell (RRBC)-to-mouse model of erythrocyte autoimmunity. Methods: In the RRBC model, C57BL/6NJ mice were immunized weekly with 2 x 10 8 Wistar rat RBC for 10 weeks, leading to development of anti-mouse RBC autoantibodies. Groups of mice were treated twice weekly via intraperitoneal injection with povetacicept or a matched Fc isotype control. Analyses included anti-RRBC alloantibodies and autoantibodies bound to mouse erythrocytes (measured via direct anti-globulin test [DAT]). While significant anemia does not occur in this model, serum lactate dehydrogenase (LDH) was also measured as an index measure of subclinical hemolysis. Immune cell subset analysis of splenocytes by flow cytometry was also performed. Results: As compared to Fc control, povetacicept treatment significantly reduced levels of anti-RRBC and DAT of IgM and IgG isotypes and significantly limited serum LDH elevations at various timepoints during the study ( Figure 1). Furthermore, at 10 weeks, numbers of T follicular helper (Tfh) cells, total B cells, germinal center (GC) B cells, and plasma cells were significantly lower in spleens of povetacicept-treated mice ( Figure 2). Conclusions: Povetacicept effectively reduced pathogenic autoantibodies and key B cell populations (e.g., ASC) and limited serum LDH elevations in this mouse model of erythrocyte autoimmunity. These data suggest that povetacicept may reduce multiple pathogenic inflammatory processes including autoantibody production and may be an effective treatment for AIHA and other autoimmune cytopenias. Povetacicept is currently being evaluated in an open-label study (RUBY-4; NCT05757570) of adults with autoimmune cytopenias (ITP, AIHA, and CAD).

#4337 UPDATED INTERIM RESULTS OF A PHASE 1/2 STUDY OF BION-1301 IN PATIENTS WITH IGA NEPHROPATHY

Abstract Background and Aims Immunoglobulin A nephropathy (IgAN) is the leading cause of primary glomerulonephritis worldwide with limited treatment options, especially for high-risk patients. Approximately 30-45% of IgAN patients progress to end-stage kidney disease over a period of 20-25 years and proteinuria is the strongest predictor of disease progression [1]. BION-1301 is a novel humanized monoclonal antibody that blocks a proliferation-inducing ligand (APRIL), a cytokine that is elevated in patients with IgAN. APRIL promotes the production of pathogenic galactose-deficient IgA1 (Gd-IgA1), leading to immune complex deposition and subsequent kidney injury. Blocking APRIL with BION-1301 is a potential disease-modifying approach to directly target the pathogenesis of IgAN. In a Phase 1/2 study (NCT 03945318) in healthy volunteers and patients with IgAN, BION-1301 was well-tolerated with no serious adverse events (SAEs) and durably reduced free APRIL, IgA, Gd-IgA1, IgM and to a lesser extent, IgG [2]. Method For the ongoing phase 1/2 open-label, multicohort trial, eligibility criteria include adults with biopsy-proven IgAN, eGFR ≥30 mL/min per 1.73 m2, baseline urine protein excretion ≥0.5 g/24 hrs or UPCR ≥0.5 g/g, and on stable/optimized RASi (or intolerant). Cohort 1 received 450 mg of BION-1301 administered IV every 2 weeks, transitioning to SC at 600 mg every 2 weeks after at least 24 weeks. Cohort 2 receives 600 mg of BION-1301 SC every 2 weeks. Results In both Cohorts 1 and 2, BION-1301 was generally well-tolerated, with no SAEs or terminations due to AEs as of the last reported interim analysis (November 2022) [2]. Durable reductions in serum levels of free APRIL and immunoglobulins were observed in both cohorts. No anti-drug antibodies have been observed in patients with IgAN to date. In Cohort 1, clinically meaningful reductions in proteinuria were seen as early as 12 weeks (30.4% geometric mean UPCR reduction, n = 7), and were sustained through 24 weeks (48.8% geometric mean UPCR reduction, n = 8) and 52 weeks (66.9% geometric mean UPCR reduction, n = 8). Reductions in proteinuria were consistent in Cohort 2 (53.8% geometric mean UPCR reduction, n = 9) at 24 weeks. Significant and durable reductions in serum Gd-IgA1 concentrations were observed and were consistent across both cohorts. Updated data will be reported at the time of presentation. Conclusion BION-1301 offers disease-modifying potential by directly targeting the initiating pathogenesis of IgAN. Interim biomarker and clinical activity responses support advancement of BION-1301 into later-stage development for patients with IgAN.

#5639 TARGETING BAFF AND APRIL IN IGA-NEPHROPATHY

Abstract Background and Aims B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are critical factors in the differentiation and longevity maintenance of the B-cells pool thereby mediating humoral immunity. BAFF and APRIL are involved in initiating B-cells to become self-reactive and elevated levels of these cytokines are detected in the sera of patients with systemic autoimmune diseases. The aim of the study was to estimate role of APRIL and BAFF in IgA-nephropathy (IgAN) patients and to determine the appropriate IgAN treatment based on the assessment of BAFF and APRIL dynamics in IgAN patients’ sera after 6 months of different treatments. Method The 52 IgAN patients aged 32,0 (27,0; 36,0) y.o., male/female ratio as 34/18 despite using of renin-angiotensin-aldosterone system inhibitors (RAASIs) for 6 months with PU 1,8 (1,0; 1,9) g/day and estimated glomerular filtration rate (eGFR) 78 (61; 103) ml/min were divided into 3 treatment groups: 1 group (n = 20) – 200 mg hydroxychloroquine (HCQ) twice a day, 2 group (n = 20) – received glucocorticoids (GC) regimen Pozzi protocol, 3 group (n = 12) – received (RAASIs) in maximal tolerated dose. The control group included age- and sex-matched healthy donors (n = 10). The number of B-cells in peripheral blood was identified by flow cytometry method. The concentrations of total IgM, IgG, IgA, IgE, APRIL and BAFF were determined by ELISA method using commercial kits. Statistical analysis was done using Statistica 10.0. Results Despite the absence of statistically significant differences in the number of B-lymphocytes the increased levels of total IgM, IgA and IgE (p = 0,001) as well as APRIL (5336 (3574; 5965) pg/ml vs 4543 (4518 ÷ 4755) pg/ml (p = 0,05) and BAFF 378 (191; 541) vs 336 (257; 424) pg/ml (p = 0,07) were established in sera of IgAN patients as compared to control group, respectively. The initial APRIL level was correlated with the degree of tubular atrophy with interstitial fibrosis (R = 0,40, p = 0,05) and serum IgG level (R = 0,35, p = 0,05) in IgAN patients. After 6 months of treatment proteinuria was significantly reduced in HCQ (p = 0,03) and GC (p = 0,02) groups while kidney function was stable in all patients. The dynamic of immunological parameters is presented in the Table 1. It was established that HCQ treatment in IgAN patients decreased the production of IgM (p = 0,01) and IgG (p = 0,02) as well as serum concentration of the APRIL factor (p = 0,05) what correlated with the tendency to eGFR increase (R = –0,46, p = 0,06) as well as with clinical effect of therapy improvement of (R = –0,45, p = 0,04). There were no statistical changes in the level of the BAFF factor in patients with HCQ. After GC treatment a decrease in the synthesis of serum IgA (p = 0,01) as well as trend to decline of B-cells number (p = 0,07) were determined, while in patients treated with RAASIs a significant increase in IgE production (p = 0,05) and tendency in elevation in BAFF levels (p = 0,06) were observed. Conclusion Immunological changes may be the determining factors in the choice of treatment in IgAN patients.

Features of BAFF and APRIL receptors on circulating B cells in antineutrophil cytoplasmic antibody-associated vasculitis.

To investigate the features of circulating B cells, their expressing receptors, serum levels of B-cell activation factor of the TNF family (BAFF), and a proliferation-inducing ligand (APRIL) in antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Blood samples from 24 patients with active AAV (a-AAV), 13 with inactive AAV (i-AAV), and 19 healthy controls (HC) were included in this study. The proportion of B cells and their expressing BAFF receptor (BAFF-R), transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI), and B-cell maturation antigen were analyzed via flow cytometry. Serum levels of BAFF, APRIL, and interleukin (IL)-4, IL-6, IL-10, and IL-13 were also evaluated using an enzyme-linked immunosorbent assay. The proportion of plasmablasts (PB)/plasma cells (PC) and serum levels of BAFF, APRIL, IL-4, and IL-6 were significantly higher in a-AAV than in HC. Higher serum levels of BAFF, APRIL, and IL-4 were observed in i-AAV than in HC. Lower expression of BAFF-R on memory B cells and higher expression of TACI on CD19+ cells, immature B cells, and PB/PC were demonstrated in a-AAV and i-AAV than in HC. The population of memory B cells was positively associated with serum APRIL levels and BAFF-R expression in a-AAV. In conclusion, decreased expression of BAFF-R on memory B cells and increased expression of TACI on CD19+ cells, immature B cells, and PB/PC, as well as increased serum levels of BAFF and APRIL, were sustained even in the remission phase of AAV. Persistent aberrant signaling of BAFF/APRIL may contribute to disease relapse.

A Randomized, Placebo-Controlled, Phase 1 Study in Healthy Adult Volunteers of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of ALPN303, a Potent Dual BAFF/APRIL Antagonist for the Treatment of Autoimmune Cytopenias

Background B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are tumor necrosis factor superfamily (TNFSF) members that bind transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI), B-cell maturation antigen, and/or BAFF receptor (BAFF-R) on B cells and together support B-cell development, survival, and differentiation into antibody-secreting cells (ASC). In preclinical studies, co-neutralization of BAFF and APRIL can directly suppress ASC and reduce circulating immunoglobulins. Autoimmune hemolytic anemia (AIHA) and immune thrombocytopenic purpura (ITP) are diseases characterized by autoantibodies directed against red blood cells and platelets, respectively. Significantly higher levels of both BAFF and APRIL have been observed in the serum of patients with AIHA and ITP compared to healthy subjects, and polymorphisms in BAFF and TACI have been associated with ITP [Abdel-Hamid, et al., Am J Med, 2011; Emmerich, et al., Br J Haematol, 2007; Peng, et al., J Thromb Haemost, 2017; Yu, et al., Blood Adv, 2021]. Currently, there are no B cell targeting agents approved to treat AIHA or ITP. Rituximab, an anti-CD20 therapeutic which depletes CD20+ B cells, and thereby only indirectly reduces autoantibody production, has demonstrated some efficacy in both ITP [Neunert, et al., Blood, 2019] and AIHA [Jäger, et al., Blood Rev, 2019], though it is not approved for use in either indication. Belimumab, an anti-BAFF neutralizing antibody (Ab), has demonstrated encouraging efficacy in the treatment of ITP associated with systemic lupus erythematosus (SLE) [De Marchi, et al., Clin Exp Rheumatol, 2017] and also in combination with rituximab in patients with ITP [Mahévas, et al., Haematologica, 2021], but only had a modest impact on hematological manifestations in SLE patients [Manzi, et al., Ann Rheum Dis, 2012]. To address the shortcomings of existing B-cell-targeting agents, we have developed ALPN-303, an Fc fusion of an engineered TACI variant TNFRSF domain, which substantially improves upon the ligand affinity liabilities of wild type (WT) TACI, resulting in highly potent dual BAFF/APRIL inhibition superior to WT TACI-Fc, or to BAFF- or APRIL-specific monoclonal Abs. In preclinical studies, ALPN-303 demonstrates enhanced pharmacokinetic (PK) and immunomodulatory properties vs. WT TACI-Fc, which may translate to lower and/or less frequent doses in humans. ALPN-303 also suppresses autoantibodies and nephritis in mouse models of lupus. Taken together, these observations suggest that a potent dual BAFF/APRIL antagonist such as ALPN-303, by lowering pathogenic autoantibody levels, may be particularly beneficial in the treatment of antibody-related hematologic diseases, such as autoimmune cytopenias. Methods In this first-in-human study (NCT05034484), healthy adult volunteers have been enrolled in single ascending dose cohorts of intravenously (IV) or subcutaneously (SC) administered ALPN-303. For each IV cohort, the first 2 sentinel subjects are randomized 1:1 to receive ALPN-303 or placebo, followed by the remaining 4 subjects randomized 3:1 to receive ALPN-303 or placebo. SC cohorts are randomized 4:2 to receive a single SC dose of ALPN-303 or placebo. All subjects are followed to assess safety, PK, and pharmacodynamic (PD) effects including impacts on circulating immunoglobulins (Ig), and peripheral B-cell populations. Results ALPN-303 has been well tolerated in all cohorts evaluated to date and exhibits dose-dependent PK and expected PD effects, including dose-dependent reductions in circulating CD38+ (CD19+CD27+IgD-) ASC (Figure 1) and in serum Ig (Figure 2). To date, there have been no serious adverse events, and no events of cytokine release syndrome. Dose escalation will be complete by the time of the meeting; the presentation will include all available safety, PK, and PD data. Conclusions In this phase 1 study, ALPN-303 demonstrates acceptable preliminary safety and tolerability and exhibits dose-dependent PK and expected PD effects on circulating Ig and B-cell populations. These findings support future clinical development of ALPN-303 in patients with antibody-related diseases, including autoimmune cytopenias. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

B cell-activating factor is involved in thrombocytopenia in patients with liver cirrhosis

Liver cirrhosis (LC) involves B cells that produce anti-glycoprotein (GP) IIb/IIIa antibodies, found in primary immune thrombocytopenia (ITP). The role of autoimmunity in the pathology of thrombocytopenia in LC was investigated using 25 LC patients with thrombocytopenia, 18 ITP patients, and 30 healthy controls. Anti-GPIIb/IIIa antibody-producing B cells were quantified using enzyme-linked immunospot assay. Platelet-associated and plasma anti-GPIIb/IIIa antibody, plasma B cell-activating factor (BAFF), and a proliferation-inducing ligand (APRIL) levels were measured using enzyme-linked immunosorbent assay. B cell subset fractions and regulatory T cells (Tregs) were quantified using flow cytometry.The number of anti-GPIIb/IIIa antibody-producing B cells was significantly higher in LC patients than in ITP patients and healthy controls (both p < 0.001). Platelet-associated anti-GPIIb/IIIa antibodies were significantly higher in LC patients than in ITP patients and healthy controls (p = 0.002, p < 0.001, respectively). BAFF levels were significantly higher in LC patients than in ITP patients and healthy controls (p = 0.001 and p < 0.001, respectively), and APRIL levels were significantly higher in LC patients than in healthy controls (p < 0.001). Anti-GPIIb/IIIa antibody-producing B cells and platelet-associated anti-GPIIb/IIIa antibodies were positively correlated with BAFF levels in LC patients. LC patients had more naïve B cells and plasmablasts than healthy controls (p = 0.005, p = 0.03, respectively); plasmablasts were positively correlated with BAFF levels. LC patients had similar Tregs levels as ITP patients and healthy controls. Therefore, excessive BAFF production in LC patients with thrombocytopenia is likely associated with autoimmune B cell response, inducing anti-GPIIb/IIIa antibody production.

A Proliferation-Inducing Ligand and B-Cell Activating Factor Are Upregulated in Patients with Essential Thrombocythemia.

A proliferation-inducing ligand (APRIL) and B-cell activating factor (BAFF) are cytokines belonging to the tumor necrosis factor family which play an essential role in B-cell maturation, differentiation, and survival. Recent evidence indicates their importance in hematological disorders; however, their function in essential thrombocytosis (ET) pathogenesis remains elusive. Therefore, we aimed to analyze the role of APRIL and BAFF in megakaryocytopoiesis in ET patients. We observed elevated levels of APRIL and BAFF in the plasma of ET patients compared with healthy controls, while no differences were found among patients with different JAK2(V617F) statuses. In addition, APRIL levels were positively associated with the number of platelets and WBC count. In the bone marrow, APRIL but not BAFF levels were higher in ET patients with the JAK2(V617F) mutation; however, JAK2(V617F)-negative patients showed slightly reduced levels of BAFF. In ET patients, we showed that the differentiation of CD34+ progenitor cells towards megakaryocytes induces the expression of both APRIL and BAFF. More importantly, APRIL neutralization significantly reduced platelet production. In conclusion, our data provide evidence that blocking APRIL signaling, which acts as an autocrine growth factor for terminal megakaryocytopoiesis, inhibits platelet production in ET patients, regardless of the status of JAK2(V617F) mutation.

Elevated serum level of B-cell activating factor (BAFF) after rituximab therapy in pemphigus vulgaris patients suggests a possible therapeutic efficacy of B-cell depletion therapies combined with anti-BAFF agents.

Rituximab is widely used for treatment of pemphigus patients. B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) play key roles in B cell survival, maturation, and differentiation. Here, the effect of rituximab on BAFF and APRIL in patients with pemphigus vulgaris (PV) was studied. Fifty PV cases and 56 healthy individuals were recruited. Patients received rituximab for a period of 6 months. The levels of BAFF and APRIL were measured in the serum samples. The frequency of CD19+ B cells was measured by flow cytometry. The level of BAFF was significantly higher in the patients at the baseline level than controls (P = 0.0005). The level of BAFF was significantly higher at the 3rd month follow-up compared to the baseline (P = 0.033). There was a significant increase in the BAFF level at the 6th month follow-up compared to baseline (P = 0.0134). There was no significant difference in the CD19+ B cells/total lymphocytes ratio in the PV patients between the 3rd and 6th month follow-ups. Elevated BAFF in the sera could be associated with PV immunopathogenesis. Inhibition of BAFF after rituximab therapy might interfere with repopulation of B cells and confer a therapeutic approach in PV.

APRIL and BAFF play a key role in differentiating vitreoretinal lymphoma from uveitis

BackgroundEarly diagnosis of vitreoretinal lymphoma (VRL) is critical for the successful treatment of this rare intraocular malignancy. However, fast and reliable diagnosis of VRL in patients presenting with intermediate or posterior non-infectious uveitis remains a challenge. A proliferation-inducing ligand (APRIL) and B-cell activating factor (BAFF) are vital factors in the pathophysiology, diagnosis, and prognosis of primary central nervous system lymphoma (PCNSL) and systemic autoimmune diseases. However, their utility as biomarkers for the diagnosis of VRL and uveitis remains unclear. MethodsIn this retrospective study, we analyzed APRIL and BAFF levels in the aqueous humor (AH) of 43 eyes of 40 patients, including 23 eyes of 20 patients with VRL, eight eyes of eight patients with uveitis, and 12 eyes of 12 patients with other ocular diseases (OODs). Additionally, we measured their levels after induction of chemotherapy in five eyes of five patients with VRL. ResultsAH levels of APRIL reliably distinguished VRL from uveitis, with a specificity of 78.3% and sensitivity of 75%. BAFF also showed similar potential. Serial AH analysis of patients with VRL during chemotherapy demonstrated a corresponding decline in AH levels of APRIL and BAFF. ConclusionThis study extends the spectrum of valuable diagnostic biomarkers for VRL and uveitis. In patients with uveitis, the assessment of AH APRIL may help accelerate the diagnosis of VRL. Moreover, our results underline the important role of APRIL and BAFF in therapeutic monitoring of VRL.

Serum Cytokine Levels of Systemic Lupus Erythematosus Patients in the Presence of Concomitant Cardiovascular Diseases.

Systemic lupus erythematosus (SLE) is known to be associated with an increased risk of cardiovascular diseases (CVD). SLE patients suffer from CVD 3.5 times more often than healthy people. Cytokine-mediated inflammation is actively involved in the development of cardiovascular pathology. Here, we analyzed serum levels of nine cytokines of steroids-treated SLE patients depending on the presence of concomitant CVD. The levels of interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-10, IL-21, tumor necrosis factor α (TNFα), B-cell activating factor (BAFF), and a proliferation-inducing ligand (APRIL) were analyzed using multiplex immunoassay. In the total group of SLE patients (n=29), the concentrations of IL-6 and IL-10 were higher, and the APRIL level decreased compared to healthy donors (n=39, p<0.05). The same changes were observed in the group of patients without CVD (n=15); the levels of IL-6 and IL- 10 were found to be increased, and the level of APRIL was lower than in healthy individuals (p<0.05). In the group of SLE patients with CVD (n=14), the concentrations of IL-4, IL-6, IL- 10, and TNFα were found to be increased (p<0.05). Interestingly, the levels of TNFα and BAFF in SLE patients with CVD were higher than in patients without cardiovascular pathology. Thus, TNFα and BAFF levels were significantly altered in SLE with concomitant CVD compared to SLE without CVD. These findings suggest that cytokine profiles in SLE with concomitant CVD and SLE without CVD are different, which should be considered in further research with large samples.

The relationship between serum A proliferation-inducing ligand and B-cell activating factor levels with disease activity and organ involvement in systemic lupus erythematosus.

We aim to investigate the association between serum B-cell activating factor (BAFF) and A proliferation-inducing ligand (APRIL) levels with disease activity and clinical findings in SLE patients. Seventy-nine patients with SLE and 27 healthy controls were included into the study. Serum BAFF and APRIL levels were measured by using ELISA. In 19 patients with active disease at the time of the assessment, BAFF/APRIL levels were reassessed after 6months of follow-up and disease activity was evaluated by using SLEDAI-2K. The relationship between renal histopathology index scores and lupus nephritis (LN) classes with serum BAFF/APRIL levels was examined in 16 patients who had recent renal involvement and underwent biopsy during the study. Although both BAFF/APRIL levels were higher in patients with SLE compared to the control group (p < 0.001), no correlation was found between BAFF/APRIL levels and SLEDAI scores. Serum BAFF levels were higher in patients with renal disease activity (p = 0.01), and there was a significant correlation between APRIL levels and proteinuria (r = 0.42, p = 0.02). A weak inverse correlation was observed between BAFF and C3 levels (r = 0.25, p = 0.02). No correlation was found between BAFF/APRIL levels and renal SLEDAI scores, renal histopathology, activity, and chronicity index scores. In the active disease group after treatment, there was no significant change in serum BAFF levels, but a significant increase in serum APRIL levels was observed. These results suggest that both cytokines are involved in the pathogenesis of SLE and that serum BAFF can be valuable as a biomarker in SLE especially in patients with renal activity.

POS-109 INTERIM RESULTS OF PHASE 1 AND 2 TRIALS TO INVESTIGATE THE SAFETY, TOLERABILITY, PHARMACOKINETICS, PHARMACODYNAMICS, AND CLINICAL ACTIVITY OF BION-1301 IN PATIENTS WITH IgA NEPHROPATHY

IgA nephropathy (IgAN) is an autoimmune disease with no approved treatments. A critical step in IgAN pathogenesis is the production of galactose-deficient IgA1 (Gd-IgA1) leading to the generation of anti-Gd-IgA1 autoantibodies and the formation of immune complexes that result in kidney inflammation and damage. A Proliferation-Inducing Ligand (APRIL), a soluble factor that regulates B cell differentiation, proliferation and survival of plasma cells, and IgA class-switching is elevated in patients with IgAN. IgAN patients with high plasma APRIL levels are reported as having higher levels of Gd-IgA1 and proteinuria and lower estimated glomerular filtration rates compared to those with lower plasma APRIL levels. BION-1301 is a novel humanized blocking antibody targeting APRIL that has been evaluated in a Phase 1 study of healthy volunteers (HV). In that study, BION-1301 was well-tolerated with no serious adverse events (SAEs), a pharmacokinetic (PK) half life >30 days and demonstrated dose-dependent pharmacodynamic (PD) effects characterized by durable reductions in serum levels of free April (fAPRIL), IgA and Gd-IgA1, IgM, and to a lesser extent IgG. Here we present interim results from Part 3 of the Phase 1 and the Phase 2 Open-Label Extension (OLE) trials that characterize the safety, PK and PD profile, and preliminary efficacy of BION-1301 in patients with IgAN. The Phase 1 study (NCT03945318) comprises 3 parts. Parts 1 and 2 assessed single- and multiple ascending doses of BION-1301 in HV from 10mg to 1350mg and 50mg to 450mg once every 2 weeks for one month, respectively. Part 3 is an ongoing, open-label, two cohort design in approximately 20 IgAN patients with BION-1301 at 450mg once every 2 weeks for a total of 12 weeks. Key eligibility criteria for Part 3 include: (1) biopsy-verified diagnosis of IgAN within the past 10 years,(2) urine protein ≥0.5 g/24h or baseline UPCR ≥0.5 g/g, and (3) stable/optimized dose of ACE-I/ARB (or intolerant). Patients completing Part 3 are eligible to enroll in the Phase 2 OLE study (NCT04684745) to receive BION-1301 for an additional 2 years. To evaluate PK and PD effects of BION-1301, serum levels of BION-1301, fAPRIL, antidrug antibodies (ADA), neutralizing antibodies (NAbs), and Gd-IgA1 were quantitated using ELISA-based immunoassays. Serum levels of IgA, IgG, and IgM were measured by immunoturbidimetry. UPCR was assessed from 24-hour urine collections. BION-1301 has been well tolerated in IgAN patients receiving a 450mg IV dose every two weeks for 12+ weeks with no SAEs or treatment related AE’s. Consistent with PD responses reported in HVs, durable reductions in serum levels of fAPRIL and immunoglobulins were observed in IgAN patients. Clinically meaningful reductions in proteinuria were seen as early as 12 weeks and were associated with the reduction in Gd-IgA1 levels. Additional data from patients receiving long-term treatment will be updated. This abstract was also submitted for the 58thERA-EDTA Congress. BION-1301 offers disease modifying potential by directly targeting the underlying multi-hit immune pathogenesis of IgAN, which is not addressed with the current standard of care treatment. Promising early biomarker and clinical activity responses support the continued development of BION-1301 in IgAN.