A Proliferation-inducing Ligand Research Articles

Antibiotic therapy-induced collateral damage: IgA takes center stage in pulmonary host defense.

The use of broad-spectrum antibiotics in empirical antimicrobial therapy is a lifesaving strategy for patients in intensive care. At the same time, antibiotics dramatically increase the risk for nosocomial infections, such as hospital‑acquired pneumonia caused by Pseudomonas aeruginosa, and other antibiotic-resistant bacteria. In this issue of the JCI, Robak and colleagues identified a mechanism by which depletion of resident gut and lung microbiota by antibiotic treatment results in secondary IgA deficiency and impaired anti-P. aeruginosa host defense. Impaired defenses could be improved by substitution of polyclonal IgA via the intranasal route in a mouse model of pneumonia. Importantly, antibiotic treatment caused lung IgA deficiency that involved reduced TLR-dependent production of a proliferation-inducing ligand (APRIL) and B cell-activating factor (BAFF) in intensive care unit patients. These patients might therefore benefit from future strategies to increase pulmonary IgA levels.

Antibiotic treatment-induced secondary IgA deficiency enhances susceptibility to Pseudomonas aeruginosa pneumonia.

Broad-spectrum antibiotics are widely used with patients in intensive care units (ICUs), many of whom develop hospital-acquired infections with Pseudomonas aeruginosa. Although preceding antimicrobial therapy is known as a major risk factor for P. aeruginosa-induced pneumonia, the underlying mechanisms remain incompletely understood. Here we demonstrate that depletion of the resident microbiota by broad-spectrum antibiotic treatment inhibited TLR-dependent production of a proliferation-inducing ligand (APRIL), resulting in a secondary IgA deficiency in the lung in mice and human ICU patients. Microbiota-dependent local IgA contributed to early antibacterial defense against P. aeruginosa. Consequently, P. aeruginosa-binding IgA purified from lamina propria culture or IgA hybridomas enhanced resistance of antibiotic-treated mice to P. aeruginosa infection after transnasal substitute. Our study provides a mechanistic explanation for the well-documented risk of P. aeruginosa infection following antimicrobial therapy, and we propose local administration of IgA as a novel prophylactic strategy.

Differential Roles of Tumor Necrosis Factor Ligand Superfamily Members as Biomarkers in Pancreatic Cancer.

The tumor necrosis factor–related weak inducer of apoptosis (TWEAK) belongs to the tumor necrosis factor ligand superfamily, which was shown to play an important role in inflammatory and malignant gastrointestinal diseases, including colitis or colorectal cancer. However, in contrast to other members of the TNF ligand superfamily, its role as a biomarker in pancreatic cancer is currently unknown. We analyzed serum levels of A proliferation-inducing ligand (APRIL) and TWEAK in 134 patients with pancreatic cancer. Results were compared with 50 healthy controls and correlated with clinical data. Intratumoral expression of APRIL and TWEAK in pancreatic cancer was analysed using the datasets made available by the TCGA-LIHC project. APRIL serum levels were significantly elevated in patients with pancreatic cancer compared to healthy controls, which is in line with previous findings. Notably, the diagnostic accuracy of circulating APRIL levels was similar to CA19-9, an established tumor marker for pancreatic cancer. In contrast, serum concentrations of TWEAK were decreased in pancreatic cancer patients. Interestingly, no differences in TWEAK concentrations became apparent between different clinical subgroups of pancreatic cancer. Moreover, within our cohort of patients, TWEAK levels did not correlate with the patients’ prognosis and the diagnostic as well as prognostic potential of TWEAK was lower than CA 19-9, when analyzed in this setting. Finally, using data from the TCGA-LIHC project, we demonstrate that expression levels of TWEAK and APRIL represent prognostic markers for patients’ survival according to Kaplan-Meier curve analyses. TWEAK and APRIL serum concentrations are regulated differently in patients with pancreatic cancer, highlighting diverse roles of variant TNF ligands in this type of cancer.

Serum BAFF and APRIL levels in Indian patients with Takayasu arteritis.

Despite many studies focused on involvement of T cell in pathogenesis of Takayasu arteritis (TaK), very few have explored the role of B cells. Hence, we sought evidence of B cell involvement in a large cohort of TaK by measuring serum levels of B cell survival factors activation factor (BAFF) and A proliferation inducing ligand (APRIL). Serum BAFF and APRIL levels were measured by ELISA in 50 patients and 48 healthy individuals, and further assessed for correlation with outcome measures, such as Indian Takayasu Clinical Activity Score-ESR (ITAS-ESR) and Takayasu arteritis Damage score (TADS). Forty women and ten men of median age 26 (11-52) and disease duration of 3years (0.1-22) were studied. Type V disease was the most common subset (n = 31), while type I, II, III, and IV was seen in ten, four, three, and two patients respectively. Serum APRIL levels were raised in patients as compared to healthy controls [2087.5pg/ml (1480.0-2279.0) vs. 1288.64pg/ml, (844.2-1632.9) p = 0.01]. Median serum APRIL level was also raised in patients with active disease (n = 24) as compared to inactive disease (n = 26) 2098.79pg/ml, (1930.75-2768.75) vs. 1802.5pg/ml, (1066.75-2098); p = 0.03). Serum BAFF levels were not raised in patients with TaK when compared to healthy Individuals. Neither BAFF, nor APRIL levels correlated with disease activity (ITAS-ESR) or TADS. Elevated APRIL levels in active TaK suggest probable role of B cells in pathogenesis.

Abstract 1540: Allogeneic chimeric antigen receptor T cells targeting B cell maturation antigen

Abstract B cell maturation antigen (BCMA) is a tumor necrosis factor family cell surface receptor that binds B cell activating factor (BAFF) and a proliferation inducing ligand (APRIL) and is involved in the long-term survival of B cells. BCMA has been shown to be expressed broadly on monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) cells and for this reason has been pursued as a potential antigen for the treatment of MM. Indeed, clinical studies evaluating autologous chimeric antigen receptor T cells (CAR-T cells) targeting BCMA for the treatment of MM have shown promising efficacy with >80% response rates. However, logistical challenges will potentially limit the number of patients that have access to autologous therapies. Using the CRISPR/CAS9 system, we generated allogeneic CAR-T cells targeting BCMA by disrupting the beta-2-microglobulin (B2M) and T cell receptor alpha constant (TRAC) genes and inserting an anti-BCMA CAR into the TRAC locus. This results in allogeneic CAR-T cells lacking the major histocompatibility complex (MHC) and endogenous T cell receptor (TCR) expression while being potently cytotoxic towards cells expressing BCMA. These data show proof-of-concept for an “off the shelf” CAR-T therapy targeting BCMA. Citation Format: Henia Dar, Daniel Henderson, Zinkal Padalia, Ashley Porras, Dakai Mu, Kyungah Maeng, Seshi Police, Demetrios Kalaitzidis, Jonathan Terrett, Jason Sagert. Allogeneic chimeric antigen receptor T cells targeting B cell maturation antigen [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1540.

The role of the BAFF/APRIL system in the T cell-independent specific response to blood stage Plasmodium falciparum hemozoin

BackgroundThe B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are tumor necrosis factor family members that regulate B cell maturation, proliferation, survival and function. We have previously shown that blood-stage Plasmodium falciparum hemozoin (HZ) can act as a T-independent antigen (TI Ag) that induces the production of specific IgG to soluble crude P. falciparum Ag through the BAFF pathway. However, we have not yet clarified whether HZ need APRIL signaling in the TI response. Here, we aimed to clarify whether both BAFF and APRIL signaling pathways play roles in HZ induction of specific antibody production without T-cell help. MethodsNormal monocytes alone or co-cultured with naïve B cells were stimulated by HZ (10 µM) in vitro. Naïve B cell cultures, with HZ alone or with exogenous recombinant BAFF (rBAFF) and recombinant APRIL (rAPRIL) plus recombinant IL-4 (rIL-4) for 6 and 10 days were used as controls to investigate activation of B cells. At various times, the levels of sBAFF, sAPRIL, and HZ-specific IgG in the culture supernatants were assessed by enzyme-linked immunosorbent assay. The BAFF and APRIL expression levels on the HZ-stimulated monocytes and their specific receptors on activated B cells, including the BAFF receptor (BAFF-R), the transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) and the B cell maturation antigen (BCMA), were determined by flow cytometry. mRNA expression levels for the receptors were validated using Real-Time quantitative PCR. ResultsHZ-activated monocytes released sBAFF and sAPRIL during the 72 h stimulation period. Increased mRNA encoding of their cognate receptors, BAFF-R, TACI, and BCMA, and increased HZ-specific IgG levels were also observed in HZ induction within the monocyte and B cell co-culture. The experiments under control conditions revealed that HZ alone could induce B cell culture to produce a small amount of the specific IgG compared with those in medium alone or rBAFF + rAPRIL + rIL-4. ConclusionTaken together, we suggest that in the TI response HZ stimulates monocyte and B cell co-culture to produce specific IgG through BAFF, APRIL and other independent complimentary signaling pathways.

Bone marrow PDGFRα+Sca-1+-enriched mesenchymal stem cells support survival of and antibody production by plasma cells in vitro through IL-6.

Plasma cells (PCs) acquiring long lifespans in the bone marrow (BM) play a pivotal role in the humoral arm of immunological memory. The PCs reside in a special BM niche and produce antibodies against past-encountered pathogens or vaccine components for a long time. In BM, cysteine-X-cysteine (CXC) chemokine receptor type 4 (CXCR4)-expressing PCs and myeloid cells such as dendritic cells are attracted to and held by CXC chemokine ligand 12 (CXCR12)-secreting stromal cells, where survival of the PCs is supported by soluble factors such as IL-6 and APRIL (a proliferation-inducing ligand) produced by neighboring myeloid cells. Although these stromal cells are also supposed to be involved in the support of the survival and antibody production, the full molecular mechanism has not been clarified yet. Here, we show that BM PDGFRα+Sca-1+-enriched mesenchymal stem cells (MSCs), which can contribute as stromal cells for hematopoietic stem cells, also support in vitro survival of and antibody production by BM PCs. IL-6 produced by MSCs was found to be involved in the support. Immunohistochemistry of BM sections suggested a co-localization of a minor population of PCs with PDGFRα+Sca-1+ MSCs in the BM. We also found that the sort-purified MSC preparation was composed of multiple cell groups with different gene expression profiles, as found on single-cell RNA sequencing, to which multiple roles in the in vitro PC support could be attributed.

Correlation of APRIL with production of inflammatory cytokines during acute malaria in the Brazilian Amazon.

IntroductionA proliferation‐inducing ligand (APRIL) and B cell activation factor (BAFF) are known to play a significant role in the pathogenesis of several diseases, including BAFF in malaria. The aim of this study was to investigate whether APRIL and BAFF plasma concentrations could be part of inflammatory responses associated with P. vivax and P. falciparum malaria in patients from the Brazilian Amazon.MethodsBlood samples were obtained from P. vivax and P. falciparum malaria patients (n = 52) resident in Porto Velho before and 15 days after the beginning of treatment and from uninfected individuals (n = 12). We investigated APRIL and BAFF circulating levels and their association with parasitaemia, WBC counts, and cytokine/chemokine plasma levels. The expression levels of transmembrane activator and calcium‐modulating cyclophilin ligand interactor (TACI) on PBMC from a subset of 5 P. vivax‐infected patients were analyzed by flow cytometry.ResultsAPRIL plasma levels were transiently increased during acute P. vivax and P. falciparum infections whereas BAFF levels were only increased during acute P. falciparum malaria. Although P. vivax and P. falciparum malaria patients have similar cytokine profiles during infection, in P. vivax acute phase malaria, APRIL but not BAFF levels correlated positively with IL‐1, IL‐2, IL‐4, IL‐6, and IL‐13 levels. We did not find any association between P. vivax parasitaemia and APRIL levels, while an inverse correlation was found between P. falciparum parasitaemia and APRIL levels. The percentage of TACI positive CD4+ and CD8+ T cells were increased in the acute phase P. vivax malaria.ConclusionThese findings suggest that the APRIL and BAFF inductions reflect different host strategies for controlling infection with each malaria species.

BAFF and APRIL expression as an autoimmune signature of membranous nephropathy.

BackgroundBased on the fact that B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) have a regulatory role in B cell biology, excessive levels of these cytokines can promote autoimmune pathogenesis. However, the expression and implication remain unresolved in cases of membranous nephropathy (MN).ResultsThe plasma BAFF levels of the primary MN patients were higher than those of healthy controls but lower than those of secondary MN patients, whereas the APRIL levels were similar between the MN patients and healthy controls. The BAFF levels were higher in relapse cases, whereas the APRIL levels were higher in the patients who did not experience remission compared with the counterpart patients. The ectopic expression of BAFF and APRIL was observed in the glomeruli or circulating B cells of MN patients, and this high expression trend was similar to that of lupus patients.ConclusionsExpression profile of BAFF and APRIL in MN is similar to that of other autoimmune disease, which affects the kidney outcomes.MethodsPlasma BAFF and APRIL levels were measured upon kidney biopsy in patients with primary (n = 89) and secondary MN (n = 13), and the results were compared with the levels in healthy controls (n = 111). The kidney outcomes (e.g., remission and relapse) were traced for the median of 3 years. Aberrant expression of the cytokines was evaluated in the kidney and circulating B cells using immunohistochemistry and flow cytometry analyses, respectively.

Current and future therapies for SLE: obstacles and recommendations for the development of novel treatments.

SLE is a serious, debilitating autoimmune disease that affects various organs and body systems. Of all the heterogeneous autoimmune diseases, SLE is perhaps the most heterogeneous. Patients with SLE, who are primarily female, have diverse disease manifestations and severity. SLE is characterised by substantial concentrations of autoantibodies against nuclear antigens, which are thought to be caused by immune cell dysregulation. Until recently, several immunosuppressant agents were used to treat this disease. Efforts to develop drugs against targets potentially involved in disease mechanisms have resulted in the identification and use of BAFF (B-cell activating factor)/APRIL (a proliferation-inducing ligand) inhibitors to treat SLE. Drugs in late-stage development that focus on pathways that are dysregulated in SLE include those that target the interferon pathway, T-cell signalling and B-cell signalling. New therapeutic agents are still necessary because of the unmet medical needs associated with this disease, including insufficient disease control, poor health-related quality of life, comorbidities, toxicity of the majority of therapies and diminished survival. Despite the substantial long-term investment of research, clinical activity and resources for identifying new treatments for this disease, only one new therapy, the biological belimumab, has been approved in the past 50 years. Efforts to develop drugs to address these needs are challenged by problems associated with disease heterogeneity, variable disease mechanisms and trial design. This review provides an overview of current and future treatments, discusses challenges in the SLE drug development process and offers recommendations for overcoming these challenges.

APRIL promotes non-small cell lung cancer growth and metastasis by targeting ERK1/2 signaling.

Non-small-cell lung cancer (NSCLC) is the major subtype of lung cancer, which is the most common cause of cancer-related mortality in the world. It is a complex disease involving multiple genetic alterations. As a cytokine belonging to the Tumor Necrosis Factor-α (TNF- α) family, the - a proliferation-inducing ligand (APRIL) expression and its signaling have been studied in many human solid tumor types, but the data on APRIL signaling in NSCLC are lacking. The aim of this study was to evaluate the APRIL expression and investigate its signaling in NSCLC. The expression of APRIL and its receptors, B cell maturation antigen (BCMA) and transmembrane activator and calcium-modulatorand cyclophilin ligand interactor (TACI), was analyzed by using immunohistochemistry in NSCLC samples. Quantitative RT-PCR was performed to evaluate mRNA expression of APRIL, BCMA and TACI in human lung adenocarcinoma cell lines A549, H1299, and H1650. Cell proliferation was measured by using the cell proliferation and cytotoxicity assay kit 8 (CCK8) assay, cell migration by using wound healing assay, and cell invasion by using transwall assay. The protein level of APRIL, BCMA and TAC, and the activation of extracellular regulated protein kinases 1/2 (ERK1/2) signaling, were determined by western blot. Our results indicated, APRIL and its receptors BCMA and TACI, were overexpressed in most of human NSCLC samples and cell lines; APRIL promoted tumor proliferation, migration and metastasis in A549 and H1299 cells via BCMA and TACI. Furthermore, ERK1/2 activation was involved in APRIL signaling through TACI but not BCMA in A549 and H1299 cells. APRIL might serve as a potential prognostic biomarker for NSCLC, and APRIL related signaling pathway could be a therapeutic target for NSCLC.

APRIL gene expression in a cohort of Egyptian acute myeloid leukemia patients: Clinical and prognostic significance

APRIL (A Proliferation Inducing Ligand) is a member of the tumor necrosis factor (TNF) family. It is essential for the survival of normal and malignant B lymphocytes. Increased expression of APRIL is noted in most of hematological malignancies and auto immune diseases. We investigated the expression level of APRIL mRNA in 50 de novo acute myeloid leukemia (AML) patients, together with 20 healthy controls using a Real-Time Quantitative Reverse-Transcriptase Polymerase Chain Reaction (RTQ-PCR) with a specific aim of determining its relation to clinical features and laboratory findings at diagnosis and its impact on the response to therapy. APRIL mRNA expression level was significantly higher in AML patients than in controls (p = < 0.001). APRIL expression level was significantly higher in patients who didn't achieve CR compared to those who achieved CR (p < 0.001). Patients who did not achieve CR also had higher TLC, lower platelets and older age than CR patients. The difference was statistically significant (p < 0.001, p = 0.047, p = 0.019) respectively. APRIL levels showed significant positive correlation with TLC (r = 0.743.p < 0.001), with age (r = 0.296,p = 0.037) and a negative correlation with platelets count (r = -0.443,p = 0.001) and no correlation with gender, Hb level, BM blast, HSM or LNs enlargement. Our study has shown that APRIL is overexpressed in AML patients, its level might serve as an indicator for disease progression. APRIL might be an indicator for poor prognosis and treatment resistance in AML patient; therefore, APRIL antagonists may represent a novel therapeutic approach for the treatment of AML.

The Role of BAFF System Molecules in Host Response to Pathogens.

The two ligands B cell-activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) and the three receptors BAFF receptor (BAFF-R), transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI), and B cell maturation antigen (BCMA) are members of the "BAFF system molecules." BAFF system molecules are primarily involved in B cell homeostasis. The relevance of BAFF system molecules in host responses to microbial assaults has been investigated in clinical studies and in mice deficient for each of these molecules. Many microbial products modulate the expression of these molecules. Data from clinical studies suggest a correlation between increased expression levels of BAFF system molecules and elevated B cell responses. Depending on the pathogen, heightened B cell responses may strengthen the host response or promote susceptibility. Whereas pathogen-mediated increases in the expression levels of the ligands and/or the receptors appear to promote microbial clearance, certain pathogens have evolved to ablate B cell responses by suppressing the expression of TACI and/or BAFF-R on B cells. Other than its well-established role in B cell responses, the TACI-mediated activation of macrophages is also implicated in resistance to intracellular pathogens. An improved understanding of the role that BAFF system molecules play in infection may assist in devising novel strategies for vaccine development.

Increased BAFF and APRIL levels in the cerebrospinal fluid of patients with anti-neutrophil cytoplasmic antibody-related hypertrophic pachymeningitis

Hypertrophic pachymeningitis (HP) is an inflammatory disorder involving intracranial or spinal thickened dura mater. It has been recognized that anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis may lead to HP; however, the immune-mediated pathogenesis of ANCA-related HP (ANCA-HP) remains elusive. In the present study, we analyzed B-cell activation factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) expression in the cerebrospinal fluid (CSF) and serum of patients with ANCA-HP, multiple sclerosis (MS), and non-inflammatory neurological disorders (NIND). BAFF and APRIL levels in the CSF were significantly higher in patients with ANCA-HP than in those with MS and NIND. In addition, a positive correlation between BAFF levels in the CSF and IgG-index was found in patients with ANCA-HP. On the other hand, no correlation was detected between CSF and serum levels of BAFF or APRIL. The results suggest that increased levels of BAFF and APRIL produced in the central nervous system may influence the development of ANCA-HP.

APRIL:TACI axis is dispensable for the immune response to rabies vaccination

There is significant need to develop a single-dose rabies vaccine to replace the current multi-dose rabies vaccine regimen and eliminate the requirement for rabies immune globulin in post-exposure settings. To accomplish this goal, rabies virus (RABV)-based vaccines must rapidly activate B cells to secrete antibodies which neutralize pathogenic RABV before it enters the CNS. Increased understanding of how B cells effectively respond to RABV-based vaccines may improve efforts to simplify post-exposure prophylaxis (PEP) regimens. Several studies have successfully employed the TNF family cytokine a proliferation-inducing ligand (APRIL) as a vaccine adjuvant. APRIL binds to the receptors TACI and B cell maturation antigen (BCMA)–expressed by B cells in various stages of maturation–with high affinity. We discovered that RABV-infected primary murine B cells upregulate APRIL ex vivo. Cytokines present at the time of antigen exposure affect the outcome of vaccination by influencing T and B cell activation and GC formation. Therefore, we hypothesized that the presence of APRIL at the time of RABV-based vaccine antigen exposure would support the generation of protective antibodies against RABV glycoprotein (G). In an effort to improve the response to RABV vaccination, we constructed and characterized a live recombinant RABV-based vaccine vector which expresses murine APRIL (rRABV-APRIL). Immunogenicity testing in mice demonstrated that expressing APRIL from the RABV genome does not impact the primary antibody response against RABV G compared to RABV alone. In order to evaluate the necessity of APRIL for the response to rabies vaccination, we compared the responses of APRIL-deficient and wild-type mice to immunization with rRABV. APRIL deficiency does not affect the primary antibody response to vaccination. Furthermore, APRIL expression by the vaccine did not improve the generation of long-lived antibody-secreting plasma cells (PCs) as serum antibody levels were equivalent in response to rRABV-APRIL and the vector eight weeks after immunization. Moreover, APRIL is dispensable for the long-lived antibody-secreting PC response to rRABV vaccination as anti-RABV G IgG levels were similar in APRIL-deficient and wild-type mice six months after vaccination. Mice lacking the APRIL receptor TACI demonstrated primary anti-RABV G antibody responses similar to wild-type mice following immunization with the vaccine vector indicating that this response is independent of TACI-mediated signals. Collectively, our findings demonstrate that APRIL and associated TACI signaling is dispensable for the immune response to RABV-based vaccination.

TACI-deficient macrophages alleviate metabolic disease symptoms in obese mice

Abstract TACI (transmembrane activator and calcium-modulator and cyclophilin ligand interactor) is one of receptors for the TNF superfamily cytokines BAFF (B cell activating factor) and APRIL (A Proliferation Inducing Ligand). In this study, we investigated the role of TACI in high fat diet induced obesity and metabolic disease. Compared to WT mice, TACI KO mice exhibited less weight gain, decreased body fat, enhanced glucose tolerance and insulin sensitivity. Improved metabolic changes in TACI KO mice were accompanied by significantly less accumulation of CD8+ T cells and F4/80+CD11c+ inflammatory macrophages in visceral fat pad. In addition, TACI KO mouse adipose tissue contained elevated numbers of ILC2, eosinophils and M2 macrophages. Underscoring the protective phenotype of M2-skewed macrophages, the transfer of TACI KO macrophages into obese WT mouse significantly improved insulin sensitivity and glucose tolerance in WT mouse. Interestingly, adoptively transferred TACI KO macrophages into WT mice also increased numbers of the host M2 macrophages and eosinophils in the adipose tissue. We identified IL-10 secreted by TACI KO macrophages was majorly responsible for the improved insulin sensitivity because not only TACI KO macrophage culture media contained high levels of IL-10 but also an IL-10 blocking antibody abolished the enhancement of insulin signaling provided by TACI KO macrophage culture media. These findings indicate that macrophage TACI mediated inflammatory signals promote obesity induced metabolic changes. Consequently, TACI blocking reagents may offer therapeutic benefits to obese patients suffering from metabolic complications.

A mouse model of systemic lupus erythematosus responds better to soluble TACI than to soluble BAFFR, correlating with depletion of plasma cells

The TNF family cytokines B‐cell activating factor (BAFF) and a proliferation‐inducing ligand (APRIL) support plasma cell survival. It is known that inhibitors of BAFF only (BAFFR‐Fc) or BAFF and APRIL (TACI‐Fc) administered early enough in an NZB/NZW F1 mouse model of systemic lupus erythematosus (SLE) ameliorate clinical outcomes, pointing to a pathogenic role of BAFF. In the present study, TACI‐Fc administrated at a later stage of disease, after onset of autoimmunity, decreased the number of bone marrow plasma cells and slowed down further formation of autoantibodies. TACI‐Fc prevented renal damage during a 12‐week treatment period regardless of autoantibody levels, while BAFFR‐Fc did not despite a similar BAFF‐blocking activity in vivo. TACI‐Fc also decreased established plasma cells in a T‐dependent hapten/carrier immunization system better than single inhibitors of BAFF or APRIL, and sometimes better than combined single inhibitors with at least equivalent BAFF and APRIL inhibitory activities. These results indicate that TACI‐Fc can prevent symptoms of renal damage in a mouse model of SLE when BAFFR‐Fc cannot, and point to a plasticity of plasma cells for survival factors. Targeting plasma cells with TACI‐Fc might be beneficial to prevent autoantibody‐mediated damages in SLE.

TACI-dependent APRIL signaling maintains autoreactive B cells in a mouse model of systemic lupus erythematosus.

Autoantibodies contribute to the development of systemic lupus erythematosus (SLE). APRIL (a proliferation-inducing ligand), a member of the TNF superfamily, regulates plasma-cell survival and binds to TACI (transmembrane activator CAML interactor) and BCMA (B-cell maturation antigen). We previously showed that APRIL blockade delayed disease onset in lupus-prone mice. In order to evaluate the role of APRIL receptors in the development of SLE, APRIL, TACI, BCMA, or double TACI.BCMA null mutations were introduced into the Nba2.Yaa (Y-linked autoimmune acceleration) spontaneous lupus mouse model. Mortality as a consequence of glomerulonephritis (GN) was reduced in Nba2.APRIL-/- .Yaa, Nba2.TACI-/- .Yaa and double-KO mice compared with Nba2.Yaa mice and correlated with lower levels of circulating antibodies, while splenic populations remained unchanged. In contrast, the appearance of symptoms was accelerated in BCMA-deficient mice, in which TACI signaling was increased. Finally, lupus-prone mice deficient for the APRIL-TACI axis produced less pathogenic antibodies and developed less GN. Disease reduction was attributed to impaired T-independent type 2 responses when the APRIL-TACI signaling axis was disrupted. Collectively, our results have identified and confirmed APRIL as a new target involved in B-cell activation, in the maintenance of plasma cell survival and subsequent increased autoantibody production that sustains lupus development in mice.

Abstract P1-02-10: Reduced serum B-cell maturation antigen levels predict poor outcome in metastatic breast cancer patients in a phase 3 randomized 2nd-line hormone therapy trial

Abstract Background: B-cell maturation antigen (BCMA) is a member of the tumor necrosis factor receptor family and has two ligands, B-cell activating factor (BAFF) and a proliferation inducing ligand (APRIL). These ligands activate cell proliferation and inhibit apoptosis of normal and malignant B-cells including in multiple myeloma (MM) cell lines. Berenson et al have recently reported that circulating BCMA levels are elevated in B-cell malignancies and can be used to monitor disease and predict PFS and OS for patients with MM, Waldenstroms's macroglobulinemia and chronic lymphocytic leukemia (CLL). On the other hand, recent studies have shown that serum BCMA levels are very low among patients with MM in complete remission with low antibody levels and those with primary immune deficiencies specifically those with combined variable immune deficiency and X-linked agammaglobulinemia. Studies of the potential role of serum BCMA for patients with solid tumors has not been evaluated to date. Methods: The pretreatment serum from 139 patients with hormone receptor-positive metastatic breast cancer who were enrolled in a phase 3 randomized clinical trial of second-line hormone therapy was evaluated using an ELISA for BCMA. The BCMA ELISA was from R&amp;D Systems (Minneapolis, MN). Serum BCMA was correlated with TTP using categorical serum BCMA cutpoints. Results: Pretreatment serum BCMA levels had a median of 55.61 ng/ml, an interquartile range of 34.20 and 78.79 ng/ml, and full range from 3.99 to 1193.26 ng/ml. In univariate analysis for TTP, reduced serum BCMA correlated with shorter TTP at the following dichotomous cutpoints: 15 ng/ml [HR=2.60, p=0.064, n=6 (4.3%) of patients below cutpoint]; 20 ng/ml [HR=2.88, p=0.005, n=10 (7.2%) of patients below cutpoint]; 25 ng/ml [HR=2.16, p=0.023, n=13 (9.4%) of patients below cutpoint]; and 30 ng/ml [HR=1.77, p=0.016, n=27 (19.4%) of patients below the cutpoint]. Conclusions: In a phase 3 randomized clinical trial of second-line hormone therapy among patients with hormone receptor-positive metastatic breast cancer, reduced pretreatment serum BCMA was associated with shorter TTP. This may be due to the association of reduced serum BCMA with immune deficiency; and, thus, lead to shorter TTP among patients with metastatic breast cancer. Evaluation of serum BCMA as a new biomarker to predict outcomes for breast cancer and other solid tumor patients deserves further study. Citation Format: Ali SM, Leitzel K, Li M, Udd K, Wang J, Sanchez E, Chen H, Berenson J, Lipton A. Reduced serum B-cell maturation antigen levels predict poor outcome in metastatic breast cancer patients in a phase 3 randomized 2nd-line hormone therapy trial [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-02-10.

Expression profile of BAFF in peripheral blood from patients of IgA nephropathy: Correlation with clinical features and Streptococcuspyogenes infection.

B cells are critically important for the pathogenesis of IgA nephropathy (IgAN). The present study aimed to investigate the abundance of B cell activating factor (BAFF), which belongs to the tumor necrosis factor superfamily, in the peripheral blood of patients with IgAN. The different forms of BAFF in peripheral blood and its association with clinical features and immunological factors were analyzed. mRNA levels of BAFF and other associated genes in the peripheral blood mononuclear cells (PBMCs) of patients with IgAN and controls were analyzed by quantitative polymerase chain reaction. Cellular BAFF proteins in PBMCs and plasma soluble BAFF proteins were measured by western blot analysis and ELISA, respectively. PBMCs from patients were stimulated with Streptococcuspyogenes (S.pyogenes) exvivo for the BAFF secretion assay. The data demonstrated that, although mRNA levels of BAFF in PBMC were not significantly increased in patients with IgAN, they were positively associated with those of a proliferation inducing ligand (APRIL), Toll‑like receptor (TLR)2, TLR4 and TLR7. The cellular BAFF protein in PBMCs was not upregulated. Plasma BAFF protein levels in patients with IgAN (n=76) were significantly decreased compared with controls. However, plasma BAFF levels were positively associated with serum creatinine, proteinuria, uric acid and group A Streptococcus infection index in patients with IgAN. In patients with IgAN, plasma BAFF concentrations were markedly higher in those with more severe renal tubular atrophy/interstitial fibrosis and global glomerulosclerosis. Furthermore, BAFF production in PBMCs of patients with IgAN was increased following S.pyogenes stimulation exvivo. In conclusion, plasma BAFF levels in patients with IgAN were associated with renal function and disease activity. S.pyogenes infection was closely associated with BAFF production in patients with IgAN.