Cyclophilin Ligand Interactor Research Articles

#2042 Efficacy and safety of telitacicept in IgA nephropathy: a retrospective study

Abstract Background and Aims Telitacicept is a novel fusion protein composed of a recombinant transmembrane activator, calcium modulator, and cyclophilin ligand interactor (TACI) receptor fused with the fragment crystallizable (Fc) region of human immunoglobulin G (IgG). Telitacicept inhibits the differentiation of immature B cell and survival of long-lived plasma cells by neutralizing the activity of B Lymphocyte Stimulator (BlyS) and A Proliferation-Inducing Ligand (APRIL). It was approved for the treatment of patients with Systemic Lupus Erythematosus (SLE) in China in March 2021. Given that BlyS/APRIL overexpression has also been identified in IgA nephropathy (IgAN), telitacicept is in clinical trials for the treatment in IgAN. In this study, we aim to retrospectively evaluate the efficacy and safety of telitacicept in patients with IgAN. Method In this retrospective study, 27 patients with primary IgAN were enrolled from Nephrology Department of Renmin hospital of Wuhan university in China from February 2022 to March 2023. Patients were administered 160 mg telitacicept by subcutaneous injection based on the previous treatment once a week at least 4 weeks, and were followed up. Adults 20–75 years of age who met the following criteria were included: biopsy-proven primary IgAN and 24-hour proteinuria >0.75 g. Patients were excluded if they had secondary causes of IgAN, 24 h proteinuria <0.75 g or immunocompromised state. Changes in proteinuria, serum creatinine, estimated glomerular filtration rate (eGFR), serum immunoglobulins, complement protein (in blood serum), albumin, urine erythrocyte, blood leukocyte and hemoglobin were analyzed during treatment. Key assessment time points were at 2, 4, 8, 12, 16 and 24 weeks after the first administration. Results In this study, duration of telitacicept exposure ranged from 4 weeks to 32 weeks, the median of which was 16 weeks. After administration of telitacicept, baseline 24 h proteinuria of 3.37 g/d decreased to 1.05 g/d at the Week 24 (z = −4.46, p < 0.05), with reductions statistically significant by Week 4. During telitacicept treatment, the median eGFR showed stable trend without sudden decline. Compared to the baseline eGFR of 68.34 ml/(min 1.73 m2), the eGFR at Week 24 was 72 ml/(min 1.73 m2). Changes in immunoglobulin A (IgA), immunoglobulin G (IgG) and immunoglobulin M (IgM) all showed downward trend while complement protein 3 (C3) and complement protein 4 (C4) maintained stable trend. Specifically, IgA decreased from 2.51 g/L at baseline to 1.41 g/L at Week 24, there was a significant reduction by Week 4 (P = 0.001). The median of IgG decreased from 8.31 g/L at baseline to 6.71 g/L at Week 24, with reductions statistically significant by Week 4 (P = 0.008). IgM decreased significantly at Week 2 from baseline of 1.13 g/L to 1.05 g/L (P = 0.017) and was 0.64 g/L at Week 24. The median C3 was stable from baseline to Week 24 (0.92 g/L, 0.87 g/L, respectively), and C4 were 0.22 g/L and 0.23 g/L, in order. Patients had a significant increase in albumin from baseline to Week 2 (P = 0.009) and the Week 24. (36.7 g/L, 37.1 g/L and 41.8 g/L, respectively). Conversely, there was a continuous reduction in urine erythrocyte, from baseline of 62.46/μL to 7.68/μL at Week 24. There remained stable in blood leukocyte from baseline to Week 24 (8.48 × 109/L, 8.67 × 109/L, respectively), with no significant changes. By the end of the study, 10/27 patients was in complete remission (CR) and 8/27 patients had achieved partial remission (PR). The overall remission rate of primary IgAN with telitacicept treatment reached 67%. Telitacicept was generally well tolerated in patients with IgAN in this study. No treatment-emergent adverse events (AEs) occurred in all 27 patients, such as respiratory tract infection, urinary tract infections and injection site allergic. Conclusion In conclusion, based on the retrospective analysis with a small sample, telitacicept, a novel BLyS/APRIL dual inhibitor, effectively decreases proteinuria in IgAN with stable renal function. In addition, it demonstrates a favorable safety profile in patients. The data are supportive of further study with telitacicept in IgAN.

#2043 Telitacicept in patients with IgA nephropathy

Abstract Background and Aims IgA nephropathy (IgAN) is typified by the renal deposition of IgA immune complexes. Advancements in understanding the pathogenesis of this disease have paved the way for innovative therapeutic approaches. Telitacicept is a fusion protein composed of transmembrane activator and calcium-modulating cyclophilin ligand interactor and fragment crystallizable portion of immunoglobulin G (IgG), which neutralizes the B lymphocyte stimulator and a proliferation-inducing ligand. We presented our single-center experience of treating IgAN with Telitacicept. Method Six patients with IgAN who received Telitacicept at the First affiliated hospital of Xi'an Jiaotong university between January 2023 and July 2023 were included in this retrospective study. All the patients had proteinuria ≥ 1.0 g/d despite optimal supportive therapy and received subcutaneous telitacicept 160 mg weekly. Clinical and laboratory parameters were evaluated before and after telitacicept treatment. Results Of all patients, there were 4 men and mean age was 35.2 ± 7.9 years. Table 1 shows baseline demographic characteristics of these patients. Before telitacicept administration, the mean serum creatinine was 133.2 ± 40.6 umol/L, median protein excretion was 2.23 (IQR, 2.05–3.54) g/d, and MAP was 97.9 ± 17.5 mmHg. After a median follow-up of 151 ± 91 days after telitacicept therapy, the mean proteinuria reduction percentage was 51.1% from baseline. The eGFR remained stable over time. The detailed laboratory parameters were shown in Table 2. No adverse events were observed during the follow-up. Conclusion Telitacicept treatment led to a clinically meaningful reduction in proteinuria in patients with IgAN. Larger prospective studies are needed to confirm these findings.

#1170 Efficacy and safety of telitacicept in IgA nephropathy: a real-world study

Abstract Background and Aims IgA nephropathy (IgAN) is the most common primary glomerular disease in the world, and the specific therapeutic methods are limited in IgAN. Telitacicept is a humanized fusion protein composed of a transmembrane activator and calcium-modulating cyclophilin ligand interactor receptor and human IgG. This study was designed to evaluate the efficacy and safety of telitacicept in adult patients with IgAN in a real-world study. Method Biopsy-proven IgAN patients with 24-hour proteinuria greater than 0.5 g/day who received telitacicept 240 mg once a week were recruited in this study and 1:1 matched with patients who received supportive treatment only or immunosuppressive treatment by propensity score matching. The primary outcome was the change from baseline in 24-hour proteinuria over the 3-month follow-up. Results Twenty-one patients in each group were enrolled. The mean eGFR was 80.1 ml/min/1.73 m2, and the median 24-hour urine protein level was 1.48 g/day. At the end of the 3-month follow-up period, telitacicept reduced median proteinuria by 0.72 g/d (54.6%) from baseline, compared with a reduction of 0.18 g/d (20%) in the supportive treatment group (P < 0.001), and 1.12 g/d (72.1%) in the immunosuppressive treatment group (P = 0.814). Preserved eGFR levels were observed in the telitacicept group (1.9 ml/min/1.73 m2 [4.3%]), while the eGFR level declined in the supportive treatment group (- 2.9 ml/min/1.73 m2 [- 5.8%]) and immunosuppression group (- 6.1 ml/min/1.73 m2 [- 8.4%]). No serious adverse events were observed in the telitacicept treatment group. Injection site reactions were more prevalent in the telitacicept group (8/21 [38.1%]), meanwhile immunosuppression group had more respiratory tract infections (7/21, [33.3%]). Conclusion Telitacicept can reduce proteinuria in patients with IgAN and showed a favourable safety profile in patients with IgAN.

#2631 Efficacy and safety of Telitacicept combined with low-dose mycophenolate mofetil in IgA nephropathy

Abstract Background and Aims Currently, there is no specific agent blocking for IgA nephropathy. The KDIGO guideline recommends basic treatment with renin-angiotensin-aldosterone system (RAAS) antagonists. MMF can be used for Chinese patients. Telitacicept is a fusion protein composed of transmembrane activator and calcium modulating cyclophilin ligand interactor and fragment crystallizable portion of immunoglobulin G (IgG), which neutralizes the B lymphocyte stimulator and a proliferation-inducing ligand. Telitacicept (240 mg qw ih) treatment led to a clinically meaningful reduction in proteinuria in patients with IgAN in the present phase 2 clinical trial. This study intends to observe the efficacy of Telitacicept (160 mg qw ih) combined with low-dose MMF in the treatment of IgA nephropathy. Method Retrospective analysis involving all biopsy proven IgA nephropathy patients with complete clinical data in our department. After RAAS inhibitor treatment for 3 months, the patient's urinary protein more than 0.75 g/24 h, he or she was given Telitacicept (160 mg qw) combined with Mycophenolate mofetil (1 g, twice a day) was treated for 6 months, and follow-up for 6-12 months. The quantification of 24-hour urinary protein and immunity functional, renal function was observed. Results 25 patients with IgA nephropathy confirmed by renal biopsy were enrolled, 14 males and 11 females, aged 34.32 ± 9.68 years’ old, 3 patients with Lee's grade II, Grade III 17 patients, Grade IV 3 patients, and Grade V 2 patients. For Oxford classification, there were 3 cases with M0, 22 cases with M1 lesions, 20 cases with E0, 5 cases with E1 lesions, 1 case with S0, 24 cases with S1 lesions, 10 cases with T0, 15 cases with T1 lesions, and 17 cases with C0, 8 cases with C1 lesions. The patient's urine protein quantification was 2.52 ± 1.82 g before treatment, after Telitacicept and MMF treatment for 2 months, the proteinuria was 1.05 ± 0.55 g (compared with that before treatment, P = 0.0004), and at 4 months, it was 0.71 ± 0.39 g (compared with that before treatment, P < 0.0001), 0.53 ± 0.31 g at 6 months (compared with than before treatment, P < 0.0001). And the 24-hour urine protein quantification of 13 patients was all lower than 0.5 g/24 hours. The renal function of all patients was stable during the observation period. The serum creatinine before treatment was 83.16 ± 21.85 μmol/L and it was 81.88 ± 19.48 μmol/L (P = 0.83) after 6 months. There were no patients with worsening renal function after treatment. Among them, the renal function of 3 patients was better than that after treatment. During follow-up period for 6- to 12-month, the patient did not develop any pulmonary infection requiring for hospitalization or other infections. Some patients experienced adverse reactions such as pain at the site of injection, but no patient discontinued treatment due to adverse reactions. Conclusion Telitacicept combined with low-dose mycophenolate mofetil is a alternative method for the treatment of IgA nephropathy. It is more effective than mycophenolate mofetil or Telitacicept use alone, and with fewer adverse reactions, especially with S or C lesions of Oxford classification. This is an observational retrospective study with a few cases, it's worthy further randomized clinical study to prove.

Effect of Telitacicept on Circulating Gd-IgA1 and IgA-Containing Immune Complexes in IgA Nephropathy

IntroductionTelitacicept, a transmembrane activator and cyclophilin ligand (CAML) interactor (TACI) fusion protein targeting B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL), has proven efficacy in treating Immunoglobulin A (IgA) nephropathy. However, serum biomarkers that could predict the clinical response during the treatment remain unclear. MethodsPlasma samples from 24 participants in the Phase 2 clinical trial were collected at baseline and after 4, 12, and 24 weeks, and 8 participants in the placebo group, 9 in the 160 mg group, and 7 in the 240 mg group. We measured the levels of Galactose deficient-IgA1(Gd-IgA1) , IgA-containing immune complexes, C3a, C5a, and sC5b-9. The association between the changes in these markers and proteinuria reduction was analyzed. ResultsAfter 24 weeks of treatment, Gd-IgA1 decreased by 43.9% (95% CI: 29.8%, 55.1%), IgG-IgA immune complex by 31.7% (14.4%, 45.5%), and poly-IgA immune complex by 41.3% (6.5%, 63.1%) in the 160 mg group; Gd-IgA1 decreased by 50.4% (38.6%, 59.9%), IgG-IgA immune complex decreased by 42.7% (29.5%, 53.4%), and poly-IgA immune complex decreased by 67.2% (48.5%,79.1%) in the 240 mg group. There were no significant changes in the circulatory C3a, C5a, or sC5b-9 levels during telitacicept treatment. Decreases in both plasma Gd-IgA1 and IgG-IgA or poly-IgA immune complexes were associated with proteinuria reduction. In turn, IgG-IgA or poly-IgA immune complexes showed a dose-dependent effect, consistent with proteinuria reduction during telitacicept treatment1. ConclusionTelitacicept lowered both circulating Gd-IgA1 and IgA-containing immune complexes, while IgA immune complex levels were more consistent with decreased proteinuria.

BAFF system expression in double negative 2, activated naïve and activated memory B cells in systemic lupus erythematosus.

B cell activating factor (BAFF) has an important role in normal B cell development. The aberrant expression of BAFF is related with the autoimmune diseases development like Systemic Lupus Erythematosus (SLE) for promoting self-reactive B cells survival. BAFF functions are exerted through its receptors BAFF-R (BR3), transmembrane activator calcium modulator and cyclophilin ligand interactor (TACI) and B cell maturation antigen (BCMA) that are reported to have differential expression on B cells in SLE. Recently, atypical B cells that express CD11c have been associated with SLE because they are prone to develop into antibody-secreting cells, however the relationship with BAFF remains unclear. This study aims to analyze the BAFF system expression on CXCR5- CD11c+ atypical B cell subsets double negative 2 (DN2), activated naïve (aNAV), switched memory (SWM) and unswitched memory (USM) B cells. Forty-five SLE patients and 15 healthy subjects (HS) were included. Flow cytometry was used to evaluate the expression of the receptors in the B cell subpopulations. Enzyme-linked immunosorbent assay (ELISA) was performed to quantify the soluble levels of BAFF (sBAFF) and IL-21. We found increased frequency of CXCR5- CD11c+ atypical B cell subpopulations DN2, aNAV, SWM and USM B cells in SLE patients compared to HS. SLE patients had increased expression of membrane BAFF (mBAFF) and BCMA receptor in classic B cell subsets (DN, NAV, SWM and USM). Also, the CXCR5+ CD11c- DN1, resting naïve (rNAV), SWM and USM B cell subsets showed higher mBAFF expression in SLE. CXCR5- CD11c+ atypical B cell subpopulations DN2, SWM and USM B cells showed strong correlations with the expression of BAFF receptors. The atypical B cells DN2 in SLE showed significant decreased expression of TACI, which correlated with higher IL-21 levels. Also, lower expression of TACI in atypical B cell DN2 was associated with high disease activity. These results suggest a participation of the BAFF system in CXCR5- CD11c+ atypical B cell subsets in SLE patients. Decreased TACI expression on atypical B cells DN2 correlated with high disease activity in SLE patients supporting the immunoregulatory role of TACI in autoimmunity.

Early Cytomegalovirus Reactivation in Renal Recipients Is Associated with High Levels of B Cell Maturation Antigen Transcript Expression Prior to Transplantation.

Cytomegalovirus (CMV) infection is the most frequent infection episode in kidney transplant (KT) recipients. Reactivation usually occurs in the first three months after transplantation and is associated with higher cellular and/or antibody-mediated rejection rates and poorer graft performance. CMV induces the expression of BAFF (B-cell-activating factor, a cytokine involved in the homeostasis of B cells), which communicates signals for survival and growth to B cells and virus-specific plasma cells via the R-BAFF (BAFF receptor), TACI (the calcium modulator, the cyclophilin ligand interactor), and BCMA (B cell maturation antigen) receptors. These molecules of the BAFF system have also been suggested as biomarkers for the development of alloantibodies and graft dysfunction. This prospective study included 30 CMV-IgG seropositive KT recipients. The expression levels of the genes BAFF-R, transmembrane activator and CAML interactor (TACI), and B cell maturation antigen (BCMA) in peripheral blood leukocytes (PBL) pre-KT were determined using qPCR. qPCR was also used to monitor CMV reactivation in the first three months following KT. The remainder of the KT recipients were classified as CMV- reactivation, and those with more than 500 copies/mL in at least one sample were classified as CMV+ reactivation. There were no discernible variations in the BAFF-R and TACI transcript expression levels. In the CMV+ group, we examined the relationship between the transcript levels and peak viremia. Peak viremia levels and BCMA transcript levels showed a strong correlation. BAFF-R and TACI expressions showed no measurable differences. In patients with early CMV reactivation, high BCMA receptor expression was associated with increased plasmablast, lymphocyte B cell class-switched levels (LBCS), and viral load. Our findings demonstrate that pre-KT BCMA transcript levels increased in KT recipients with early CMV reactivation. These transcript levels positively correlate with peak viremia and weakly with plasmablast and LBCS levels in PBLs.

An uncommon presentation of primary sclerosing cholangitis leading to the diagnosis of B cell lymphoma and common variable immunodeficiency

Abstract Common Variable Immunodeficiency (CVID) is a disorder of B cells, with hypogammaglobulinemia and an impaired immune response leading to increased risk of infection, autoimmune complications, and risk of malignancy. A 17-year-old, previously healthy male presented with three months of pruritus, jaundice and transaminitis. Imaging and biopsy showed liver heterogeneity without evidence of cholestasis or ductal dilation. Over time, imaging was consistent with primary sclerosing cholangitis (PSC). The patient eventually required liver transplant after several complications, despite stent therapy. Explant liver pathology revealed diffuse large B cell and follicular lymphoma, grade 3A with mature monoclonal B cells follicular in origin, negative for MYC rearrangement and MUM1. PCR detected IgH and IgK B cell clonality. He received chemotherapy without complication, for primary hepatic non-Hodgkin's lymphoma. Continued flatulence and diarrhea prompted endoscopy, revealing eosinophilic esophagitis. Due to his variable pathology, he was evaluated for a primary immunodeficiency. His labs demonstrated globally diminished immunoglobulins, a low Hib titer and one pathogenic mutation in TNFRSF13B (c.542C>A; p.Ala181Glu), a transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI). Thus, the patient was diagnosed with CVID. This case highlights a unique presentation of CVID from demonstration of PSC and primary hepatic diffuse large B cell lymphoma. Consideration of immunodeficiencies early on in challenging cases of autoimmune and unique oncologic diagnoses may lead to earlier treatment of underlying conditions and prevention of future complications.

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.

The Rapidly Expanding Genetic Spectrum of Common Variable Immunodeficiency–Like Disorders

The understanding of common variable immunodeficiency disorders (CVID) is in evolution. CVID was previously a diagnosis of exclusion. New diagnostic criteria have allowed the disorder to be identified with greater precision. With the advent of next-generation sequencing (NGS), it has become apparent that an increasing number of patients with a CVID phenotype have a causative genetic variant. If a pathogenic variant is identified, these patients are removed from the overarching diagnosis of CVID and are deemed to have a CVID-like disorder. In populations where consanguinity is more prevalent, the majority of patients with severe primary hypogammaglobulinemia will have an underlying inborn error of immunity, usually an early-onset autosomal recessive disorder. In nonconsanguineous societies, pathogenic variants are identified in approximately 20% to 30% of patients. These are often autosomal dominant mutations with variable penetrance and expressivity. To add to the complexity of CVID and CVID-like disorders, some genetic variants such as those in TNFSF13B (transmembrane activator calcium modulator cyclophilin ligand interactor) predispose to, or enhance, disease severity. These variants are not causative but can have epistatic (synergistic) interactions with more deleterious mutations to worsen disease severity. This review is a description of the current understanding of genes associated with CVID and CVID-like disorders. This information will assist clinicians in interpreting NGS reports when investigating the genetic basis of disease in patients with a CVID phenotype.

Ocrelizumab Treatment Modulates B-Cell Regulating Factors in Multiple Sclerosis.

Antibodies to CD20 efficiently reduce new relapses in multiple sclerosis (MS), and ocrelizumab has been shown to be effective also in primary progressive MS. Although anti-CD20 treatments efficiently deplete B cells in blood, some B cells and CD20- plasma cells persist in lymphatic organs and the inflamed CNS; their survival is regulated by the B cell-activating factor (BAFF)/A proliferation-inducing ligand (APRIL) system. The administration of a soluble receptor for BAFF and APRIL, atacicept, unexpectedly worsened MS. Here, we explored the long-term effects of ocrelizumab on immune cell subsets as well as on cytokines and endogenous soluble receptors comprising the BAFF-APRIL system. We analyzed immune cell subsets and B cell-regulating factors longitudinally for up to 2.5 years in patients with MS treated with ocrelizumab. In a second cohort, we determined B-cell regulatory factors in the CSF before and after ocrelizumab. We quantified the cytokines BAFF and APRIL along with their endogenous soluble receptors soluble B-cell maturation antigen (sBCMA) and soluble transmembrane activator and calcium-modulator and cyclophilin ligand (CAML) interactor (sTACI) using enzyme-linked immunosorbent assays (ELISAs). In addition, we established an in-house ELISA to measure sTACI-BAFF complexes. Ocrelizumab treatment of people with MS persistently depleted B cells and CD20+ T cells. This treatment enhanced BAFF and reduced the free endogenous soluble receptor and decoy sTACI in both serum and CSF. Levels of sTACI negatively correlated with BAFF levels. Reduction of sTACI was associated with formation of sTACI-BAFF complexes. We describe a novel effect of anti-CD20 therapy on the BAFF-APRIL system, namely reduction of sTACI. Because sTACI is a decoy for APRIL, its reduction may enhance local APRIL activity, thereby promoting regulatory IgA+ plasma cells and astrocytic interleukin (IL)-10 production. Thus, reducing sTACI might contribute to the beneficial effect of anti-CD20 as exogenous sTACI (atacicept) worsened MS. This study provides Class IV evidence that endogenous sTACI in blood and CSF is decreased after ocrelizumab treatment.

PS-P13-6: DEFINING THE RELATIONSHIP BETWEEN IMMUNE TRAITS AND LIPIDS IN TWINSUK

Objective: The primary aim of this work was to evaluate associations of distinct immune cell subtypes and circulating lipids in a general population setting. Methods: The associations between 3,855 immune traits and lipids (HDL-C, LDL-C, TC, TG, non-HDL-C) were examined in 1,491 individuals from the TwinsUK cohort. Immune traits were defined by high-dimensional flow-cytometry which enabled in-depth assessment of all major lymphocyte and myeloid subsets in peripheral blood. Information on immune cell subset frequency (FREQ) and mean fluorescence intensity (MFI) was available. A linear mixed model regression analysis adjusted for family structure, gender, age, BMI and batch effect was used to examine the associations between immune traits and lipids. A sub-analysis in 441 individuals and 122 lipid metabolites quantified using nuclear magnetic resonance spectroscopy was undertaken to investigate the associations of 40 significant immune traits and lipoprotein particles. Secondary analyses explored the associations of lipids and immune traits with pulse wave velocity (PWV). A mediation model was constructed to test mediation effects of an immune marker on the total effect of lipids on PWV. Results: Significant associations were observed between 46 MFI and 6 FREQ immune traits and lipids (Bonferroni P < 2.45x10–5). These included associations between circulating lipids and different myeloid or lymphoid subsets including monocytes, NK cells and T cells. The top associations involved the expression of transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) cytokine on classical (cM) and intermediate (iM) monocyte subsets. Decreased levels of non-HDL-C [cMP = 6.98x10–10, iMP = 3.72x10–7], LDL-C (cMP = 3.28x10–7, iMP = 1.75x10–5) and TG [cMP = 1.18x10–9, iMP = 2.97x10–6], and increased levels of HDL-C (cMP = 3.64x10–12, iMP = 1.44x10–10) were associated with higher TACI expression on both cM and iM subsets. Significant associations were identified between TACI expression and 13 lipid metabolites (Bonferroni P < 1.36x10–4). All linked metabolites referred to HDL related measures. Increased apolipoprotein A1 levels, total cholesterol in HDL and HDL2 and large and medium HDL related particles were associated with increased TACI expression on cM and iM subsets. The strongest association found between total cholesterol in HDL2-C and TACI expression levels on cM (P = 3.57x10–6). Mediation analysis showed that TACI expression on monocytes partially mediates the effect (∼10%) of TG on PWV. Conclusions: This study provides the first comprehensive picture of lipid-immune cell associations in the circulatory system. Interesting novel immune cell subset alterations and insights into the relationship between lipids, PWV and immunity have extended our knowledge. Further work is required to dissect the role of immune responses in cardiovascular disease.

Randomized Phase 2 Trial of Telitacicept in Patients With IgA Nephropathy With Persistent Proteinuria

To date, no specific therapies have been approved for immunoglobulin A nephropathy (IgAN) treatment. Telitacicept is a fusion protein composed of transmembrane activator and calcium-modulating cyclophilin ligand interactor and fragment crystallizable portion of immunoglobulin G (IgG), which neutralizes the B lymphocyte stimulator and a proliferation-inducing ligand. This phase 2 randomized placebo-controlled trial aimed to evaluate the efficacy and safety of telitacicept in patients with IgAN. Participants with an estimated glomerular filtration rate (eGFR) >35 ml/min per 1.73 m2 and proteinuria≥0.75 g/d despite optimal supportive therapy, were randomized 1:1:1 to receive subcutaneous telitacicept 160 mg, telitacicept 240 mg, or placebo weekly for 24 weeks. The primary end point was the change in 24-hour proteinuria at week 24 from baseline. Forty-four participants were randomized into placebo (n= 14), telitacicept 160 mg (n= 16), and telitacicept 240 mg (n= 14) groups. Continuous reductions in serum IgA, IgG, and IgM levels were observed in the telitacicept group. Telitacicept 240 mg therapy reduced mean proteinuria by 49% from baseline (change in proteinuria vs. placebo, 0.88; 95% confidence interval,-1.57 to-0.20; P= 0.013), whereas telitacicept 160 mg reduced it by 25% (-0.29; 95% confidence interval,-0.95 to 0.37; P= 0.389). The eGFR remained stable over time. Adverse events (AEs) were similar in all groups. Treatment-emergent AEs were mild or moderate, and no severe AEs were reported. Telitacicept treatment led to a clinically meaningful reduction in proteinuria in patients with IgAN in the present phase 2 clinical trial. This effect is indicative of a reduced risk for future kidney disease progression.

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

Association between early immunophenotypic changes and therapeutic response of belimumab in patients with systemic lupus erythematosus.

Belimumab is a therapeutic medication that inhibits the B-cell-activating factor (BAFF) used for systemic lupus erythematosus (SLE); however, the response sometimes varies among individuals, even when patients are stratified based on general clinical characteristics. Therefore, we focused on immunological phenotypic changes with belimumab, investigated their association with subsequent clinical courses, and sought to identify relevant immunological indicators to stratify patients who would benefit from belimumab. We assessed changes in B and T cell phenotypes, as well as BAFF-related factors, such as levels of BAFF and a proliferation-inducing ligand, and expression of three BAFF receptors: BAFF receptor (BAFF-R), B-cell maturation antigen (BCMA), transmembrane activator and cyclophilin ligand interactor (TACI), in 19 patients with SLE who were treated with belimumab before and 3months after treatment. First, to visualize patterns in complex and diverse data, we summarized B cell changes such as subsets and BAFF receptor expressions into two axes, the first and second principal components (PC1 and PC2), and characterized broad phenotypic changes by cluster analysis. Next, we evaluated whether the B cell changes represented by PC1 and PC2 were associated with other concurrent phenotypic changes, baseline factors, and treatment response at 6months. We found that lower PC2, indicating increased BAFF-R expression and decreased percentage of naïve B cells, was associated with a subsequent therapeutic response at 6months (odds ratio 5.3, 95% confidence interval 1.2-24, p = .031). Furthermore, higher percentages of effector memory CD3+CD4+ T cells at baseline were associated with lower PC2 and therapeutic response. Further analysis revealed that increased PC1, as reflected by increased BCMA and TACI expression and an increase in the percentage of class-switched memory B cells, was associated with both T and B cell activation. Although belimumab is a B-cell targeted therapy, it can also influence T-cell phenotypes. Thus, early B cell changes could be used to predict treatment response, and their changes could be predicted from baseline T cell phenotypes, indicating the importance of B and T cell interactions.

The impact of Epstein-Barr virus latent membrane protein 2A on the production of B cell activating factor of the tumor necrosis factor family (BAFF), APRIL and their receptors.

IntroductionEpstein‐Barr virus (EBV) establishes a lifelong infection in human B cells where the virus consistently expresses Latent Membrane Protein 2A (LMP2A) to promote B cell survival. A prior study indicates that LMP2A may increase the production of the pro‐survival factor, B cell Activating Factor of the tumor necrosis factor family (BAFF), which could also indirectly increase B cell survival. The current study sought to extend these findings and determine if LMP2A increased BAFF production and/or the responsiveness of LMP2A‐expressing cells to this cytokine.MethodsFour independently derived LMP2A‐negative and ‐positive B cell lymphoma cell lines were analyzed for BAFF and APRIL levels by both ELISA and Western Blot analysis. Additionally, flow cytometric analysis measured any LMP2A‐dependent changes in the receptors for BAFF and APRIL (BAFF‐R, transmembrane activator and calcium‐modulator and cyclophilin ligand interactor [TACI], B cell maturation antigen [BCMA]) in both LMP2A‐negative and ‐positive B cell lymphoma cell lines.ResultsIn contrast to previous reports, our data indicate that LMP2A does not increase the expression of BAFF or APRIL by Western blot analysis or ELISA. Additionally, flow cytometric analysis indicates that LMP2A does not influence the expression of the receptors for BAFF and APRIL: TACI, BAFF‐R, and BCMA.ConclusionTherefore, these data suggest that while EBV utilizes other latency proteins to regulate BAFF production, EBV does not appear to use LMP2A to enhance BAFF‐or APRIL‐dependent survival to promote EBV latency.

The effects of B-cell-activating factor on the population size, maturation and function of murine natural killer cells.

The role of B-cell-activating factor (BAFF) in B-lymphocyte biology has been comprehensively studied, but its contributions to innate immunity remain unclear. Natural killer (NK) cells form the first line of defense against viruses and tumors, and have been shown to be defective in patients with systemic lupus erythematosus (SLE). The link between BAFF and NK cells in the development and progression of SLE remains unstudied. By assessing NK cell numbers in wild-type (WT), BAFF-/- (BAFF deficient), BAFF-R-/- (BAFF receptor deficient), TACI-/- (transmembrane activator and calcium modulator and cyclophilin ligand interactor deficient), BCMA-/- (B-cell maturation antigen deficient) and BAFF transgenic (Tg) mice, we observed that BAFF signaling through BAFF-R was essential for sustaining NK cell numbers in the spleen. However, according to the cell surface expression of CD27 and CD11b on NK cells, we found that BAFF was dispensable for NK cell maturation. Ex vivo and in vivo models showed that NK cells from BAFF-/- and BAFF Tg mice produced interferon-γ and killed tumor cells at a level similar to that in WT mice. Finally, we established that NK cells do not express receptors that interact with BAFF in the steady state or in the BAFF Tg mouse model of SLE. Our findings demonstrate that BAFF has an indirect effect on NK cell homeostasis and no effect on NK cell function.

Ligation of TLR Homologue CD180 of B Cells Activates the PI3K/Akt/mTOR Pathway in Systemic Sclerosis and Induces a Pathological Shift in the Expression of BAFF Receptors.

The phosphatidylinositol-3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) pathways are known to play a key role in B-cell activation and fibrosis in systemic sclerosis (SSc). Receptors of B-cell activator factor (BAFF) utilize these pathways, which can be influenced by Toll-like receptors (TLRs), as TLRs can alter the expression of BAFF-binding receptors. Our results show that B-cell stimulation via TLR homologue CD180 phosphorylates Akt in diffuse cutaneous SSc (dcSSc) to a lower extent than in healthy controls (HCs). We found basal downregulated BAFF receptor (BAFF-R) and enhanced transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) expression in dcSSc B cells, which might enhance the formation of autoantibody-secreting plasma cells. Moreover, this pathological shift was observed in naive B cells, emphasizing the importance of their increase in SSc. Additionally, we measured higher serum levels of autoantibodies to BAFF in dcSSc patients, suggesting that an imbalance in the complex system of BAFF/anti-BAFF autoantibodies/BAFF-binding receptors may contribute to the development of SSc. Anti-CD180 antibody treatment had opposite effects on the expression of BAFF-R and TACI in HC B cells, resulting in similar levels as observed in SSc B cells without stimulation, which argues against the usefulness of such therapy in SSc.

AB0030 THE BIOLOGICAL FUNCTION AND MECHANISM EXPLORATION OF TACI IN SJOGREN’S SYNDROME

Backgroundprimary Sjogren’s syndrome (pSS) is a chronic autoimmune disease that affects the lacrimal, salivary and other exocrine glands. More and more studies have shown that B cells play a central role in the pathogenesis of SS.ObjectivesWe intended to explore the expression of the transmembrane activator, calcium modulator and cyclophilin ligand interactor (TACI) on the B cells, its role in pSS, and possible signal transduction pathways.MethodsWe included 34 naive pSS patients who visited the rheumatology department of Peking University First Hospital, and 37 gender- and age-distribution matched healthy controls (HCs). (1) To compare the B cell subsets, expression of TACI and relevant receptors in pSS patients, peripheral blood mononuclear cells were separated to analyze the ratio of B subsets, TACI, and BAFF-R by flow cytometry; ELISA was applied to detect the serum BAFF and soluble TACI (sTACI) concentration. (2) As for functional research of TACI, CD19+ B cells separated by magnetic sorting were treated under in vitro culture circumstances with raw TACI, TACI knocked down by siRNA, and sTACI analog (telitacicept) intervention with varing doses. The apoptosis, proliferation, differentiation and regulatory capacity on T cells were analyzed by flow cytometry, inflammatory cytokines and immunoglobulin levels in the culture supernatants were detected by CBA. (3) As for TACI-associated signaling pathway exploration, based on our previous miRNA data and relevant report of high quality, miRNA associated with TACI with significantly biased expression was confirmed by RT-qPCR. Screening the target gene of the candidate miRNA, and miRNA overexpression and inhibition experiments were conducted to validate the targeted relationship in B cells. And TACI-associated signaling pathway was explored via overexpressing and inhibiting the target gene.Results(1) Compared to HC, peripheral blood B subsets of pSS patients exhibited a significant bias, manifesting as increased proportion of CD19+CD24hiCD38hi Breg and decreased ratio of CD19+CD24+CD38- memory B cells. The expression of TACI in all B subsets was down-regulated, while that of BAFF-R was up-regulated. Both the serum concentration of BAFF and sTACI in pSS patients increased significantly. (2) As for functional research of TACI, in the setting of raw TACI, B cells in the pSS group showed higher apoptosis rate than HC under culture in vitro, where the ligand of TACI (APRIL or BAFF) addition turned the rate comparable; more active proliferation, and impaired capacity of inducing Treg cells to secrete IL-10. When TACI was knocked down by 50%, B cells performed less late apoptosis, significantly increased proliferation, impaired differentiation, significant dysfunction of Breg itself and impaired induction of Treg cells to secrete IL-10. While telitacicept intervention increased early apoptosis rate of B cells, significantly inhibited proliferation in 500ng/mL group and impaired ability of Breg and Treg cells to secrete IL-10. Besides, increased TACI on B cells treated with telitacicept, decreased IgG and increased IgA in the culture supernatants were observed. (3) As for TACI-associated signaling pathway exploration, hsa-miR-30b-5p showed satisfactory correlation between both transmembrane and sTACI. Besides, the expression of hsa-miR-30b-5p was significantly down-regulated, and inhibition its expression in vitro could lead to differentiation retard, impaired secretion of IL-10 by Breg cells. SMAD1 was screened based on database and validated as its target gene by overexpressing and inhibiting hsa-miR-30b-5p in B cell. After targeted up- or down-regulating the transcription of SMAD1 further, the transcription of ID2 downstream the TGF-β/Hippo signaling pathway changed accordingly.ConclusionThe expression of TACI on peripheral blood B cells was deficient in pSS patients. TACI deficiency was closely associated with the downregulation of hsa-miR-30b-5p, activating TGF-β/Hippo pathway mediated by its target gene SMAD1 and taking part in the pathogenesis of pSS.Disclosure of InterestsNone declared

A nasal double DNA adjuvant system induces atheroprotective IgM antibodies via dendritic cell-B-1a B cell interactions

We previously demonstrated that the dendritic cell (DC)-targeting nasal double DNA adjuvant system, which consists of a DNA plasmid expressing Flt3 ligand (pFL) and CpG oligodeoxynucleotide 1826 (CpG ODN), elicits specific immune responses to various antigens in the mucosal and systemic compartments. Here, we investigated, using phosphorylcholine (PC)-conjugated keyhole limpet hemocyanin (PC-KLH) as an antigen, whether the nasal double DNA adjuvant system induces protective immunity to atherosclerosis in apolipoprotein E-deficient (ApoE KO) mice. Further, we assessed the molecular and cellular mechanisms in the induction of anti-PC-specific immune responses. Nasal immunization with PC-KLH plus pFL and CpG ODN enhanced induction of PC-specific IgM in plasma, peritoneal fluids, and nasal washes when compared with mice administered PC-KLH alone. Of importance, these antibodies exhibited highly specific binding to the PC molecule, and dose-dependent binding to anti-T15 idiotype (AB1-2). Twelve weeks after the last immunization, the nasal double DNA adjuvant system with PC-KLH resulted in a reduction of atherogenesis in the aortic arch of ApoE KO mice. Therefore, we next assessed immunocytological mechanism to induce these antibodies. The nasal double DNA adjuvant system with PC-KLH resulted not only in significantly increased frequencies of CD11c+ DCs in the spleen, peritoneal cavity (PEC), and nasopharyngeal-associated lymphoid tissues (NALT), but also significantly increased expression of a proliferation-inducing ligand and B-cell-activating factor by CD11c+ DCs. In addition, the double DNA adjuvant system induced significantly increased numbers of B-1 B cells in the spleen, PEC, and NALT, and increased expression of transmembrane activator and calcium modulator and cyclophilin ligand interactor on CD5+ B220+ (B-1a) B cells. These findings demonstrated that the nasal double DNA adjuvant system with PC-KLH resulted in the induction of T15-like antibodies in the mucosal and systemic lymphoid tissues through interaction between DCs and B-1a B cells, and inhibited the progression of atherogenesis.