Cell Activating Factor Research Articles

Enhanced alloresponse to platelet transfusion due to immune dysregulation following ablative chemotherapy in mice.

Alloimmunization is common following platelet transfusion and can result in negative outcomes for recipients such as refractoriness to subsequent transfusions and rejection of transplants. Healthy people do not receive blood transfusions, and the diseases and therapies that result in a need to transfuse have significant impacts on the immunological environment to which these alloantigens are introduced. Ablative chemotherapies are common among platelet recipients and have potent immunological effects. In this study, we modeled the impact of chemotherapy on the alloresponse to platelet transfusion. As chemotherapies are generally regarded as immunosuppressive, we hypothesized that that they would result in a diminished alloresponse. Mice were given a combination chemotherapeutic treatment of cytarabine and doxorubicin followed by transfusion of allogeneic platelets, and compared to controls given no treatment, chemotherapy alone, or transfusion alone. Alloantibody responses were measured 2 weeks after transfusion, and cellular responses and growth factors were monitored over time. Contrary to our hypothesis, we found that chemotherapy led to increased alloantibody responses to allogeneic platelet transfusion. This enhanced response was antigen-specific and was associated with increased CD4+ and CD8+ T cell responses. Chemotherapy led to rapid lymphocyte depletion followed by reconstitution, non-specific activation of transitional B cells with the highest levels of activation in the least mature subsets, and increased serum levels of B cell activating factor (BAFF). These data suggest that ablative chemotherapy can increase the risk of alloimmunization and, if confirmed clinically, that additional measures to protect these patient populations may be warranted.

B-cell activating factor gene variants in multiple sclerosis: Possible associations with disease susceptibility among females

Although B cells and B cell activating factor (BAFF) have been previously implicated in MS pathogenesis, data regarding the genetic influence of BAFF polymorphisms on MS susceptibility are limited. Here we aim to explore whether BAFF polymorphisms could contribute to MS susceptibility.156 RRMS patients fulfilling the revised McDonald criteria for MS diagnosis and 220 HCs were enrolled. Clinical, laboratory, and imaging characteristics were recorded. BAFF rs9514827, rs1041569, and rs9514828 polymorphisms were assessed by RFLP-PCR in DNA samples extracted from whole peripheral blood.The BAFF rs1041569 TT genotype along with the CTT and TTC haplotypes were associated with significantly increased risk for MS development in female MS patients compared to healthy female counterparts. These findings were not confirmed in males. The rs1041569 BAFF variant together with the CTT and TTC BAFF haplotypes derived from the BAFF rs9514827, rs1041569, and rs9514828 polymorphisms may represent novel genetic contributors to the development of MS in females.

T helper-1 activation via interleukin-16 is a key phenomenon in the acute phase of severe, first-episode major depressive disorder and suicidal behaviors

BackgroundImmune-inflammatory pathways in major depressive disorder are confined to the major dysmood disorder (MDMD) phenotype (Maes et al., 2022). No studies have addressed the immune profile of first episode MDMD (FE-MDMD). MethodsThis study investigated the immune profiles of 71 patients with the acute phase of first-episode major depressive disorder (FE-MDMD) and 40 healthy controls. We measured 48 cytokines/chemokines/growth factors, classical M1, alternative M2, T helper (Th)-1, Th-2, and Th-17 phenotypes, immune-inflammatory response system (IRS), compensatory immunoregulatory system (CIRS), and neuro-immunotoxicity profiles. ResultsFE-MDMD patients show significantly activated M1, M2, Th-1, IRS, CIRS, and neurotoxicity, but not Th-2 or Th-17, profiles compared to controls. FE-MDMD is accompanied by Th-1 polarization, while there are no changes in M1/M2 or IRS/CIRS ratios. The top single indicator of FE-MDMD was by far interleukin (IL)-16, followed at a distance by TRAIL, IL-2R, tumor necrosis factor (TNF)-β. The severity of depression and anxiety was strongly associated with IRS (positively) and Th-2 (inversely) profiles, whereas suicidal behavior was associated with M1 activation. Around 56–60% of the variance in depression, anxiety, and suicidal behavior scores was explained by IL-16, platelet-derived growth factor (PDGF) (both positively), and IL-1 receptor antagonist (inversely). Increased neurotoxicity is mainly driven by IL-16, TNF-α, TRAIL, IL-6, and chemokine (CCL2, CCL11, CXCL1, CXCL10) signaling. Antidepressant-treated patients show an increased IRS/CIRS ratio as compared with drug-naïve FE-MDMD patients. ConclusionsFE-MDMD is accompanied by positive regulation of the IRS mainly driven by Th-1 polarization and T cell activation (via binding of IL-16 to CD4), and TNF, chemokine, and growth factor signaling.

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).

Readministration of high-dose adeno-associated virus gene therapy vectors enabled by ImmTOR nanoparticles combined with B cell-targeted agents.

Tolerogenic ImmTOR nanoparticles encapsulating rapamycin have been demonstrated to mitigate immunogenicity of adeno-associated virus (AAV) gene therapy vectors, enhance levels of transgene expression, and enable redosing of AAV at moderate vector doses of 2 to 5E12 vg/kg. However, recent clinical trials have often pushed AAV vector doses 10-fold to 50-fold higher, with serious adverse events observed at the upper range. Here, we assessed combination therapy of ImmTOR with B cell-targeting drugs for the ability to increase the efficiency of redosing at high vector doses. The combination of ImmTOR with a monoclonal antibody against B cell activation factor (aBAFF) exhibited strong synergy leading to more than a 5-fold to 10-fold reduction of splenic mature B cells and plasmablasts while increasing the fraction of pre-/pro-B cells. In addition, this combination dramatically reduced anti-AAV IgM and IgG antibodies, thus enabling four successive AAV administrations at doses up to 5E12 vg/kg and at least two AAV doses at 5E13 vg/kg, with the transgene expression level in the latter case being equal to that observed in control animals receiving a single vector dose of 1E14 vg/kg. Similar synergistic effects were seen with a combination of ImmTOR and a Bruton's tyrosine kinase inhibitor, ibrutinib. These results suggest that ImmTOR could be combined with B cell-targeting agents to enable repeated vector administrations as a potential strategy to avoid toxicities associated with vector doses above 1E14 vg/kg.

In ovo feeding of probiotic lactobacilli differentially alters expression of genes involved in the development and immunological maturation of bursa of Fabricius in pre-hatched chicks

Compelling evidence indicates that immunological maturation of the gut-associated lymphoid tissues, including the bursa of Fabricius, is dependent upon antigenic stimulation post-hatch. In view of these data, the present study investigated the impact of exposing the immune system of chick embryos to antigenic stimuli, via in ovo delivery of poultry-specific lactobacilli, on the expression of genes associated with early bursal development and maturation. Broiler line embryonated eggs were inoculated with 106 and 107 colony-forming units (CFUs) of an individual or a mixture of Lactobacillus species, including L. crispatus (C25), L. animalis (P38), L. acidophilus (P42), and L. reuteri (P43), at embryonic day 18 (ED18). The bursa of Fabricius was collected from pre-hatched chicks (ED20) to measure the expression levels of various immune system genes. The results revealed that L. acidophilus and the mixture of Lactobacillus species at the dose of 106 CFU consistently elicited higher expression of genes responsible for B cell development, differentiation, and survival (B cell activating factor (BAFF), BAFF-receptor (BAFF-R)), and antibody production (interleukin (IL)-10) and diversification (TGF-β). Similar expression patterns were also noted in T helper (Th) cell-associated cytokine genes, including Th1-type cytokines (interferon (IFN)-γ and IL-12p40), Th2-type cytokines (IL-4 and IL-13) and Th17 cytokine (IL-17). Overall, these results suggest that the supplementation of poultry-specific lactobacilli to chick embryos might be beneficial for accelerating the development and immunological maturation of the bursa of Fabricius. However, further studies are required to determine if the changes in gene expression are associated with the developmental trajectory and phenotypes of bursal cells.

Excessive MALAT1 promotes the immunologic process of neuromyelitis optica spectrum disorder by upregulating BAFF expression.

Increased B cell activating factor (BAFF) expression in patients with neuromyelitis optica spectrum disorder (NMOSD) is associated with B cell overstimulation, but the underlying mechanism remains unclear. This study aimed to reveal the emerging mechanisms that regulate BAFF expression in the inflammatory process of NMOSD. The results showed that the expression of miR-30b-5p was significantly decreased in NMOSD CD14+ monocytes compared with the normal control. Furthermore, we confirmed that metastasis-associated lung adenocarcinoma transcription 1 (MALAT1) is an upstream target of miR-30b-5p, and it could act as a ceRNA and absorb miR-30b-5p with reduced expression of miR-30b-5p. The low expression of miR-30b-5p could not bind to BAFF messenger RNA (mRNA), which resulted in the overexpression of both BAFF mRNA and protein expression. Overexpression of BAFF could bind to the corresponding receptors on B cells, which may initiate activation and proliferation of B cells and increase their production of autoantibodies. Therefore, these findings interpreted that excessive MALAT1 expression in NMOSD mononuclear macrophages led to increased BAFF expression by targeting miR-30b-5p, which caused B cell autoimmune reaction and autoantibodies production, aggravated the disease progression of NMOSD.

BAFF blockade in experimental autoimmune encephalomyelitis reduces inflammation in the meninges and synaptic and neuronal loss in adjacent brain regions

Multiple sclerosis (MS) has traditionally been viewed as a chronic inflammatory disease affecting the white matter of the central nervous system. However, over the past two decades, increasing evidence has highlighted the role of gray matter pathology in MS-related disability. Numerous studies have linked the presence of leptomeningeal inflammation to a more severe disease course, underscoring its potential importance as a driver of gray matter pathology in MS. The major components of leptomeningeal inflammation include T cells, B cells, macrophages, follicular dendritic cells, and plasma cells. Since BAFF [B cell-activating factor of the tumor necrosis factor (TNF) family] promotes B cell survival and maturation and is a co-stimulator of T cells, we used anti-BAFF antibody 10F4 as a BAFF antagonist to study its effect on meningeal inflammation and adjacent brain regions in a relapsing–remitting PLP-EAE (rr-EAE) model of multiple sclerosis in SJL/J mice. rr-EAE mice were treated either with anti-BAFF antibody 10F4 or with IgG control antibody. We performed ultra-high field (11.7 T) MRI to identify areas of meningeal inflammation and track them over time in both treatment groups. We also performed histopathological analysis in brain sections of these mice to study the effects of the BAFF antagonist on leptomeningeal inflammation, and hippocampal and cortical neurons and synapses. We observed that BAFF antagonist treatment reduced B cells, T cells, and myeloid cells in regions of meningeal inflammation. Additionally, we noted that BAFF treatment protected against EAE-induced synaptic and neuronal loss in the adjacent cortex and in the CA1, CA3, and dentate gyrus regions of the hippocampus likely due to its effects on meningeal inflammation.

Target Therapy in Systemic Lupus Erythematosus: A Narrative Literature Review

Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by the presence of autoantibodies against cells and involves many organ systems in the body. The Lupus Foundation of America estimates that around 1.5 million cases occur in America and at least 5 million cases occur worldwide. Every year it is estimated that there are around 16 thousand new cases of SLE. Various pro- and anti-inflammatory cytokines such as transforming growth factor (TGF), interleukin-10, B cell activating factor (BAFF), interferon-α, interleukin-17, and interleukin-23 play an important pathogenic role. Disruption of apoptotic cells and immune complexes is an important contributor to the development of this disease. Loss of immune tolerance increases antigenic load, excessive role of T cells, impaired B cell suppression and impaired transition of the immune response from T helper 1 (Th1) to Th2 which causes hyperactivity of B cells and produces pathogenic autoantibodies. The management of cases of severe or refractory SLE to conventional therapy has attracted a lot of attention in recent years, so that many researchers have developed several targeted therapies that have been tested on SLE, such as anti-CD 20 and CD 22 antibodies and BAFF inhibitors found in B lymphocyte cells. The Rituximab anti-CD 20 antibody target has been clinically proven to be able to improve the severity of SLE, while the effectiveness of other targeted therapies is still under research.

Length-Dependent Modulation of B Cell Activating Factor Transcripts in Chicken Macrophage by Viral Double-Stranded RNA.

Viral double-stranded RNA (dsRNA) interacts with Retinoic-acid-inducible-gene-1 (RIG-1)-like receptors (RLRs) to induce type 1 interferons. Melanoma-derived-antigen-5 (MDA-5), an RLR, but not RIG-1, is found in chickens. Ducks express both RIG-1 and MDA-5, a possible cause of differences in susceptibility to influenza virus infection between chickens and ducks. Using the HD11 chicken macrophage cell line and an RT2 Profiler PCR-array system, we showed that high-molecular-weight poly(I:C), HMW-poly(I:C), upregulates CCL4, interferon-gamma, interleukin-1, and interleukin-6 mRNA transcripts. HMW-poly(I:C), an in vitro surrogate of long dsRNA species, also induces the upregulation of IL-12B and B cell activating factor (BAFF). Conversely, low-molecular-weight poly(I:C), LMW-poly(I:C) did not induce a distinct cytokine expression pattern. Nonetheless, co-transfection of LMW and HMW-poly(I:C) significantly reduced the upregulation of IL12B and BAFF by HMW-poly(I:C). These findings support previous studies that found no expression of RIG-1, a receptor for short dsRNA species, in chicken cells. Surprisingly, however, our data suggested that in the absence of RIG-1 in chicken macrophages, short dsRNA species may inhibit macrophage-mediated B cell development and survival by modulating the expression of BAFF without significantly reducing type 1 interferon response.

Determination of plasma concentration of Belimumab by LC-MS/MS: Method development, validation, and clinical application

IntroductionBelimumab is a monoclonal antibody against B cell activating factor (BLyS). This monoclonal antibody (mAb) has been shown to be effective in reducing disease activity in patients with systemic lupus erythematosus (SLE). Belimumab is available in two forms as a lyophilized powder for intravenous (IV) use, or single-dose syringe for subcutaneous (SC) use. The aim of this study was to develop and validate a liquid chromatography-tandem mass spectrometry (LC–MS/MS) method for quantitation of belimumab in human serum. Material and methodsAll analyses relied on nano-surface and molecular-orientation limited (nSMOL) proteolysis coupled with LC-MS/MS. Quantifications was performed in multiple reactions monitoring (MRM) mode, and electrospray ionization was conducted in positive mode. ResultsBelimumab was quantified with signature peptide QAPGQGLEWMGGIPFGTAK and normalized using P14R. The total run time per assay was 10 min. Linearity was measured from 5 to 800 μg/mL (r² > 0.995). Accuracy and precision based on three quality control levels range from 11.2 – 9.51 % and 1.24 – 13.12 % respectively. The carryover was less than 7 %. In all, 87 patient samples were processed (65, IV; 22, SC). Mean concentration of belimumab was significantly higher for SC (93.0 ± 74.0 µg/mL) than for IV (67.4 ± 38.9 µg/mL) administration. ConclusionWe have developed the first method of belimumab quantification combining LC-MS/MS and nSMOL proteolysis. It can be used for future clinical pharmacokinetic studies of belimumab and for investigating the relationship between belimumab concentration, efficacy, and toxicity in SLE patients.

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.

Tertiary Lymphoid Tissues Are Microenvironments with Intensive Interactions between Immune Cells and Proinflammatory Parenchymal Cells in Aged Kidneys.

Ectopic lymphoid structures called tertiary lymphoid tissues (TLTs) develop in several kidney diseases and are associated with poor renal prognosis. However, the mechanisms underlying TLT expansion and their effect on renal regeneration remain unclear. The authors report that single-nucleus RNA sequencing and validation experiments demonstrate that TLTs potentially amplify inflammation in aged injured kidneys. Lymphocytes within TLTs promote proinflammatory phenotypes of the surrounding proximal tubules and fibroblasts within the TLTs via proinflammatory cytokine production. These proinflammatory parenchymal cells then interact with immune cells by chemokine or cytokine production. Such cell-cell interactions potentially increase inflammation, expand TLTs, and exacerbate kidney injury. These findings help illuminate renal TLT pathology and suggest potential therapeutic targets. Ectopic lymphoid structures called tertiary lymphoid tissues (TLTs) develop in several kidney diseases and are associated with poor renal prognosis. However, the mechanisms that expand TLTs and underlie exacerbation of kidney injury remain unclear. We performed single-nucleus RNA sequencing (snRNA-seq) on aged mouse kidneys with TLTs after ischemia-reperfusion injury. The results were validated using immunostaining, in situ hybridization of murine and human kidneys, and in vitro experiments. Using snRNA-seq, we identified proinflammatory and profibrotic Vcam1+ injured proximal tubules (PTs) with NF κ B and IFN-inducible transcription factor activation. VCAM1 + PTs were preferentially localized around TLTs and drove inflammation and fibrosis via the production of multiple chemokines or cytokines. Lymphocytes within TLTs expressed Tnf and Ifng at high levels, which synergistically upregulated VCAM1 and chemokine expression in cultured PT cells. In addition, snRNA-seq also identified proinflammatory and profibrotic fibroblasts, which resided within and outside TLTs, respectively. Proinflammatory fibroblasts exhibited STAT1 activation and various chemokine or cytokine production, including CXCL9/CXCL10 and B cell-activating factor, contributing to lymphocyte recruitment and survival. IFN γ upregulated the expression of these molecules in cultured fibroblasts in a STAT1-dependent manner, indicating potential bidirectional interactions between IFN γ -producing CXCR3 + T cells and proinflammatory fibroblasts within TLTs. The cellular and molecular components described in this study were confirmed in human kidneys with TLTs. These findings suggest that TLTs potentially amplify inflammation by providing a microenvironment that allows intense interactions between renal parenchymal and immune cells. These interactions may serve as novel therapeutic targets in kidney diseases involving TLT formation.

BAFFR expression in circulating T follicular helper (CD4+CXCR5+PD-1+) and T peripheral helper (CD4+CXCR5-PD-1+) cells in systemic lupus erythematosus.

Circulating T follicular helper (cTfh) and T peripheral helper (Tph) subpopulations are shown to be higher in systemic lupus erythematosus (SLE) patients and have been involved in promoting extrafollicular B cell responses. However, a possible association with the B cell activating factor (BAFF), a cytokine mainly related to B cell responses and disease activity in SLE, has not been investigated. Therefore, this study aimed to evaluate the association of cTfh and Tph subpopulations with the BAFF system expression and clinical activity in SLE patients. This study included 43 SLE patients and 12 healthy subjects (HS). The identification of cTfh (CD4+CXCR5+PD-1+), Tph (CD4+CXCR5-PD-1+) cells, expression of membrane-bound BAFF (mBAFF), BAFFR, TACI, BCMA, and intracellular IL-21 was performed by flow cytometry. Serum levels of IL-21, CXCL13, and BAFF were analyzed using ELISA. The SLEDAI-2K score was used to evaluate disease activity in SLE patients. Compared with HS, SLE patients showed a significantly increased percentage of cTfh and Tph cells, higher in patients with clearly active disease. SLE patients had markedly higher IL-21-producing cTfh and Tph cells than HS. Both subpopulations were positively correlated with the disease activity in SLE patients. Tph cells were negatively correlated with CD19+CXCR5+ B cells and positively correlated with CD19+CXCR5- B cells. A low expression of mBAFF and their receptors TACI and BCMA was found on cTfh and Tph cells in SLE patients and HS. However, SLE patients with clearly active disease showed decreased expression of BAFFR on cTfh and Tph subpopulations than patients with mildly active/nonactive disease. Serum IL-21, CXCL13, and BAFF levels were higher in SLE patients than in HS. Levels of CXCL13 were correlated with disease activity. Non-significant correlations were observed among T cell subpopulations and IL-21, CXCL13, and BAFF levels. This study emphasizes the importance of cTfh and Tph cells in SLE pathogenesis. Besides the importance of IL-21, our results suggest that BAFFR could play a role in cTfh and Tph subpopulations in the autoimmunity context.

Physiological Effects of Calprotectin and B Cell Activating Factor in COVID-19 Patients

Objectives: This study set out to determine how Calprotectin and B cell activating factor contributes to early COVID-19 patient severity prediction.
 Methods: The study included 25 healthy controls and 52 patients with SARS-COV2 infection who were clinically diagnosed with COVID-19 illness and were between the ages of 23 and 35. The serum levels of CALP and BAFF were measured using the ELISA method. To gauge CRP levels, an immunoturbidometric assay was performed.
 Results: Variations in serum levels of CALP and BAFF were found to be statistically insignificant in the study (P=0.7109 & P=0.7575, respectively). When compared to the control group (103.95±36.67 ng/mL; 403.03±1.03), COVID-19 patients had non-significantly raised levels of CALP and BAFF (106.5±4.67 ng/mL; 436.9±12.77 pg/mL, respectively). According to ROC curve analysis, the area under the receiver operating characteristics curve (AUC) for CALP and BAFF was (0.5170) and (0.5259), respectively. (r=0.6923; P=0.0001). There was a significant positive correlation between serum CALP and BAFF levels. The connection between serum CRP levels and CALP (r=0.3010; P=0.1271) and BAFF levels (r=0.2912; P=0.1406) was insignificantly positive.
 Conclusion: The current study's findings suggested that serum CALP and BAFF concentrations were increased in COVID-19 patients, suggesting that these inflammatory markers may be helpful indicators of the severity of COVID-19.

The Safety and Efficacy of Rituximab and Belimumab in Systemic Lupus Erythematosus: A Systematic Review.

There is a vital role of B cells in the pathogenesis of Systemic Lupus Erythematosus (SLE). Belimumab (Bel), an inhibitor of B cell activating factor (BAFF), and Rituximab (RTX), a monoclonal antibody targeting Cd20 antigen, have been used to manage systemic lupus. Several randomized controlled trials (RCTs) have evaluated these two agents' clinical efficacy and safety in different manifestations of SLE.This study aims to review the randomized control trials involving these two agents systematically and to explain if any disparity is noticed in the primary and secondary outcomes between these two agents. This study is done according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)guidelines. After applying the inclusion criteria and quality assessment by independent reviewers and co-authors, relevant papers were identified, and data were extracted. The results have shown thatRCTs involving Belimumab achieved primary endpoints; however, targeted endpoints were not achieved in studiesinvolving Rituximab. It is concluded that despite the conflicting results obtained in clinical trials, both are effective in systemic lupus, as indicated in real-world clinical experience. However, better-designed multicenter studies evaluating these B-cell-targeting drugs are needed.

Intrathecal Th17-driven inflammation is associated with prolonged post-treatment convalescence for patients with Lyme neuroborreliosis

Lyme neuroborreliosis (LNB) is associated with increased levels of pro-inflammatory cytokines and chemokines in the cerebrospinal fluid (CSF). Residual symptoms after antibiotic treatment can have deleterious effects on patients and knowledge regarding the pathogenesis linked to prolonged recovery is lacking. In this prospective follow-up study, we investigated the B cell-associated and T helper (Th) cell-associated immune responses in well-characterized patients with LNB and controls. The aims were to assess the kinetics of selected cytokines and chemokines involved in the inflammatory response and to identify potential prognostic markers. We investigated 13 patients with LNB according to a standardized clinical protocol before antibiotic treatment and after 1, 6 and 12 months of follow-up. CSF and blood samples were obtained at baseline and after 1 month. As controls, we used CSF samples from 37 patients who received spinal anesthesia during orthopedic surgery. The CSF samples were analyzed for CXCL10 (Th1-related), CCL22 (Th2-related) and IL-17A, CXCL1 and CCL20 (Th17-related), as well as for the B cell-related cytokines of a proliferation-inducing ligand (APRIL), B cell-activating factor (BAFF) and CXCL13. The CSF levels of all the cytokines and chemokines, with the exception of APRIL, were significantly higher at baseline in patients with LNB compared with controls. All the cytokines and chemokines, except for IL-17A were significantly reduced at 1-month follow-up. Patients with quick recovery (< 1 month, n = 3) had significantly lower levels of CCL20 at baseline and lower levels of IL-17A at 1-month follow-up. Patients with time of recovery > 6 months (n = 7) had significantly higher levels of IL-17A at the one-month follow-up. No other cytokines or chemokines were associated with prolonged recovery. Dominating residual symptoms were fatigue, myalgia, radiculitis and/or arthralgia. In this prospective follow-up study of patients with LNB, we found significantly lower levels of CCL20 in those who recovered rapidly, and increased levels of IL-17A in patients with delayed recovery post-treatment. Our findings indicate persistent Th17-driven inflammation in the CSF, possibly contributing to a longer convalescence, and suggest IL-17A and CCL20 as potential biomarker candidates for patients with LNB.

Association between levels of serum and urinary B cell-activating factor and systemic lupus erythematosus disease activity.

This study investigated the correlation between serum and urinary B cell-activating factor (BAFF) levels and systemic lupus erythematosus (SLE) disease activity. This case-control study was conducted with 87 participants between December 2020 and September 2021. Sixty-two SLE patients who fulfilled the eligibility criteria were enrolled. SLE patients were categorized into active (n=34) and inactive (n=28) groups based on their Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) scores. The control group consisted of 25 healthy subjects. Serum and urine samples were collected for the measurement of BAFF levels. Finally, the relationship between these variables and SLE disease activity was investigated. The mean age of active (SLEDAI-2K >4) and inactive (SLEDAI-2K ≤4) SLE patients and healthy individuals were 32.8±7.8, 32.5±6.8, and 31.7±7.8 years, respectively (p=0.62). The median serum BAFF (s-BAFF) and urinary BAFF (u-BAFF) in active lupus patients (10.4 [2.3] ng/mL and 8.2 [3.7] ng/mL, respectively) were significantly higher than in inactive lupus patients (6 (7.1) ng/mL and 1.7 (4.7) ng/mL, respectively; p<0.001) and the control group (3 (3.7) ng/mL and 1.6 (2.2) ng/mL, respectively; p<0.001). However, s-BAFF (p=0.07) and u-BAFF (p=0.43) did not significantly differ between the inactive group and the control group. A significant positive correlation was observed between s-BAFF (r=0.41 and p=0.001) and u-BAFF (r=0.78 and p<0.001) levels and the SLEDAI-2K score. There is a significant positive correlation between serum and urinary BAFF levels and SLE disease activity. Furthermore, significantly higher levels of s-BAFF and u-BAFF have been observed in patients with active lupus compared to inactive and healthy subjects, indicating a possible role for BAFF in the pathogenesis of SLE disease activity.

#4024 PHASE 1 STUDY OF THE SAFETY, TOLERABILITY, PHARMACOKINETICS, AND PHARMACODYNAMICS OF POVETACICEPT FOR AUTOIMMUNE GLOMERULONEPHRITIDES

Abstract Background and Aims B cell activating factor (BAFF) of the tumor necrosis factor (TNF) family and a proliferation-inducing ligand (APRIL), cytokines which bind and signal through BAFF-R, transmembrane activator and CAML interactor (TACI), and/or B cell maturation antigen (BCMA) on B cells, play overlapping and non-redundant roles in B cell development, proliferation, function, and survival. Therapeutic agents targeting BAFF and/or APRIL have demonstrated promising clinical potential in autoantibody-related glomerulonephritides (GN) such as lupus nephritis (LN), immunoglobulin (Ig) A nephropathy (IgAN), membranous nephropathy, and other B cell-related diseases such as systemic lupus erythematosus (SLE); however, there is still need for more safe and efficacious therapies. Povetacicept (ALPN-303) is an Fc fusion protein of an engineered TACI variant TNFRSF domain (vTD) with enhanced affinity for APRIL and BAFF which mediates more potent inhibitory activity than wild type (WT) TACI-Fc or BAFF- or APRIL-specific antibodies. In preclinical studies, povetacicept demonstrated enhanced pharmacokinetic (PK) and immunomodulatory properties vs. WT TACI-Fc, which may translate to lower and/or less frequent doses in humans. Povetacicept also suppressed autoantibodies, renal IgG deposition, and nephritis in mouse models. Povetacicept may therefore significantly improve clinical outcomes in autoantibody-mediated GNs and other B cell-related diseases. Method In this first-in-human study (NCT05034484), 66 healthy adult volunteers were randomized 4:2 into single ascending dose cohorts of intravenous (IV) or subcutaneous (SC) povetacicept or placebo. Participants were followed to assess safety and PK, circulating Ig, galactose-deficient IgA1 (Gd-IgA1), and circulating leukocyte populations. Results Povetacicept has been well tolerated in all cohorts evaluated as single IV or SC doses of up to 960 mg. Overall, it exhibits dose-related PK and expected pharmacodynamic (PD) effects, including dose-related reductions in serum IgA, IgM, IgG, and Gd-IgA1 (Figure 1), and in circulating antibody-secreting cells (ASC; plasmablasts and plasma cells) (Figure 2). In the same setting, these PD effects appear greater than those reported for WT TACI-Fc molecules and appear to be saturated at doses ≥80 mg. Coverage of free APRIL was maintained for 2-3 weeks with 80 mg and ≥4 weeks with 240 mg, respectively. The most frequent adverse event has been mild headache. To date, there have been no imbalances of infections between placebo and povetacicept groups, no treatment-related reactions other than mild injection site pain, and no adverse trends in safety laboratories. Conclusion To date, povetacicept has demonstrated acceptable safety and tolerability as single IV or SC doses, exhibiting dose-dependent PK and PD that appear to differentiate favorably vs WT TACI-Fc. Based on the magnitude and duration of the observed PD effects, dose regimens of 80-240 mg SC every 4 weeks are anticipated for use in future studies. Overall, the study findings support future clinical development of povetacicept in multiple autoantibody-related GN, as well as other B cell- and/or autoantibody-related diseases such as SLE and autoantibody-associated cytopenias.

Abstract 443: BAFF Neutralization Impairs The Regression Of Insulin Resistance In Diabetic Mice By Modulating The Innate Immune Response

Adults with type 2 diabetes have a two-to-three-fold increased risk of cardiovascular diseases. B cell activating factor (BAFF), a tumor necrosis factor superfamily member, is implicated both in diabetes and cardiovascular diseases, and hence a therapeutic target of interest. High levels of BAFF are known to promote autoantibody synthesis and autoimmune diseases. We examined if BAFF neutralization with an anti-BAFF antibody improves glucose intolerance in a model of regression of insulin resistance in diabetic mice. Male C57BL/6J mice were fed a high-fat diet (HFD) for 12 weeks and segregated into two groups based on their glucose intolerance determined by a glucose tolerance test. Each group was simultaneously switched from HFD to a normal chow diet and received injections of anti-BAFF or an isotype control antibody every 2 nd week for a total of 6 weeks. As expected, body weights decreased in both groups parallel with the increase in insulin sensitivity. Unexpectedly, the BAFF-neutralized mice had impaired regression of insulin resistance compared to the control mice. Extensive cellular phenotyping of immune cells indicated systemic depletion of only the B2 cells and lower levels of circulating autoantibodies in the BAFF-neutralized mice. Gonadal white adipose tissue (gWAT) was the primary source of BAFF, and no differences in the M1 and M2 macrophages, eosinophils, natural killer cells, helper T cells, and cytotoxic T cell populations were found. RNA sequencing analysis of stromal vascular fraction from gWAT revealed impaired B cell receptor signaling, immunoglobulin production, complement activation, and phagocytosis pathways in the BAFF-neutralized mice. In this line, (i) an increased number of dead adipocytes, (ii) decreased levels of IgG2b and IgM, (iii) increased citrullinated histone H3, neutrophils, and DNA extracellular traps were found in the gWAT of BAFF-neutralized mice. These results suggest attenuated humoral response and a dominant and harmful role of innate response in the gWAT following BAFF neutralization in late-stage obesity. Since anti-BAFF biologics are approved for the treatment of lupus patients, our results highlight the need for further studies on the role of BAFF in late-stage obesity and diabetes.