A Proliferation-inducing Ligand Research Articles

Raised cerebrospinal fluid BAFF and APRIL levels in anti-N-methyl-d-aspartate receptor encephalitis: Correlation with clinical outcome

In this study, we aimed to assess the levels of B cell activating factor from the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) in cerebrospinal fluid (CSF) of patients with anti–N-methyl-d-aspartate receptor (NMDAR) encephalitis and determine their correlation with clinical outcome. BAFF and APRIL concentrations in CSF and serum from 40 patients with anti-NMDAR encephalitis and 20 controls were measured by enzyme-linked immunosorbent assay (ELISA). Compared with controls, the levels of both BAFF and APRIL in CSF were significantly increased in patients with anti-NMDAR encephalitis (p<0.001 and p<0.001). Patients with unfavorable outcome had higher levels of BAFF and APRIL in CSF than those who had favorable outcome (p<0.05 and p<0.05). BAFF and APRIL levels in CSF were elevated and associated with clinical outcome in patients with anti-NMDAR encephalitis, indicating that they may be valuable biomarkers to this disease.

Interleukin-21 Drives Proliferation and Differentiation of Porcine Memory B Cells into Antibody Secreting Cells.

Immunological prevention of infectious disease, especially viral, is based on antigen-specific long-lived memory B cells. To test for cellular proliferation and differentiation factors in swine, an outbred model for humans, CD21+ B cells were activated in vitro with CD40L and stimulated with purported stimulatory cytokines to characterize functional responses. IL-21 induced a 3-fold expansion in total cell numbers with roughly 15% of all B cells differentiating to IgM or IgG antibody secreting cells (ASCs.) However, even with robust proliferation, cellular viability rapidly deteriorated. Therefore, a proliferation inducing ligand (APRIL) and B cell activating factor (BAFF) were evaluated as survival and maintenance factors. BAFF was effective at enhancing the viability of mature B cells as well as ASCs, while APRIL was only effective for ASCs. Both cytokines increased approximately two-fold the amount of IgM and IgG which was secreted by IL-21 differentiated ASCs. Mature B cells from porcine reproductive and respiratory virus (PRRSV) immune and naïve age-matched pigs were activated and treated with IL-21 and then tested for memory cell differentiation using a PRRSV non-structural protein 7 ELISPOT and ELISA. PRRSV immune pigs were positive on both ELISPOT and ELISA while naïve animals were negative on both assays. These results highlight the IL-21-driven expansion and differentiation of memory B cells in vitro without stimulation of the surface immunoglobulin receptor complex, as well as the establishment of a defined memory B cell culture system for characterization of vaccine responses in outbred animals.

Molecular mechanism of the selectivity between BAFF/APRIL and their receptors by molecular simulations

B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) belonging to the tumour necrosis factor (TNF) ligand family can bind three unusual TNF receptors (BCMA, TACI and BR3) with various binding affinities. BAFF and APRIL are regarded as promising therapeutic targets for autoimmune diseases because of their pivotal roles in cell survival and immune regulation. In this work, we carried out molecular dynamics calculations to explore the structural and chemical features responsible for ligand recognition by extracellular functional segments of TNF receptors. We found that the conserved pocket Dcons of BAFF/APRIL contacted the DxL motif of TNF receptors, while the Dspe1–3 sub-domains were responsible for their different affinities, especially Dspe1 and Dspe2. The residues at position II–V of DxL motif were wrapped into the Dcons pocket via salt-bridge and hydrophobic interactions. The hydrophobic residues of strand3 and helix1 in TNF receptors provided remarkable contributions for the affinities to BAFF/APRIL. Additionally, ArgVI of DxL motif played a key role in the binding selectivity via salt-bridge interaction with residue D275B in BAFF. Arg27 in BCMA contributed to the high affinity for APRIL so that BCMA showed a preference for APRIL. Our studies indicated that Arg84 and Gln95 in TACI2 played an important role in the selectivity of two cysteine-rich domain segments in TACI, leading to the higher binding affinities of TACI2 than those of TACI1. The primary cause of the disability to bind APRIL was the space conflict with the rigid conformation of the C-terminus coil of BR3. These thorough understanding of the molecular mechanism for BAFF/APRIL recognition by their receptors provides new insights for guiding inhibitor design.

Orbital fibroblasts of Graves' orbitopathy stimulated with proinflammatory cytokines promote B cell survival by secreting BAFF

The success of rituximab for the treatment of active Graves' orbitopathy (GO) suggests that B cells play a critical role in intraorbital inflammation. B cell activating factor (BAFF) and its homolog a proliferation-inducing ligand (APRIL) are critical for B cell survival. However, the contribution of BAFF/APRIL to GO remains unclear. We sought to determine the role of BAFF/APRIL in the orbits of GO, and found that BAFF was markedly upregulated, while APRIL was not. Additionally, cultured GO orbital fibroblasts (GO-OFs)2 expressing BAFF were induced to produce a large amount of BAFF. In contrast, a weak APRIL expression was detected in the OFs, and they exhibited a slight response to stimulation. Notably, pretreated GO-OFs promoted B cell survival, and this effect was significantly inhibited by a BAFF-R neutralizing antibody. This study indicates that OFs from GO can express BAFF and mediate the intraorbital survival of B cells via BAFF mechanism.

Hepatitis B Virus e Antigen Regulates Monocyte Function and Promotes B Lymphocyte Activation.

Hepatitis B virus (HBV) e (HBe) antigen is a nonstructural virus component with great immune regulation roles. It regulates adaptive immunity response and participates in persistent infection development. However, its roles on monocytes and B lymphocytes were rarely studied. Herein, we studied HBe roles on U937 and Hmy2.CIR by creating HBe stably transfected cells using lentivirus. We detected the motility of HBe-U937 through transwell migration assay. Cytokines that primarily produced by monocytes, including BAFF, B-cell activating factor (BAFF), interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α, and A proliferation inducing ligand (APRIL), were measured in culture supernatants of transfected U937, and serum BAFF, IL-6, and IL-10 were detected in HBe-positive and HBe-negative HBV-infected patients. Among these, BAFF mRNA and membrane-bound BAFF were further detected. Activation and inhibition markers of B lymphocytes on HBe-Hmy2.CIR and proliferation of transfected Hmy2.CIR after coculture with transfected U937 were also detected. We found that U937 migration was inhibited by HBe. BAFF expression was increased in HBe-U937, however, membrane-bound BAFF on HBe-U937 was decreased. In addition, Serum BAFF in HBe-positive patients was higher than in HBe-negative patients. IL-6 and IL-10 were increased in HBe-U937 after being stimulated by lipopolysaccharide (LPS), however, serum IL-6 and IL-10 were not associated with HBe status in patients. Besides, TNF-α and APRIL expression were basically the same in GV166-U937 and HBe-U937. B lymphocyte activation markers CD86 and Tspan33 were raised in HBe-Hmy2.CIR. However, inhibition markers Lyn and CD32b had no differences between HBe-Hmy2.CIR and control. Proliferation of transfected Hmy2.CIR was not affected by coculture with transfected U937, however, HBe transfection itself enhanced Hmy2.CIR proliferation. Altogether, these revealed that HBe can inhibit U937 migration and promote cytokines, including BAFF, IL-6, and IL-10, production in U937. Besides, HBe enhances BAFF release from U937 and increases BAFF concentration in vivo. In addition, HBe antigen facilitates Hmy2.CIR activation and proliferation through direct induction.

Synergisic effect of APRIL knockdown and Jiedu Xiaozheng Yin, a Chinese medicinal recipe, on the inhibition of hepatocellular carcinoma cell proliferation.

It is well documented that A proliferation-inducing ligand (APRIL), a member of the tumor necrosis factor superfamily, plays a crucial role in the occurrence and development of tumors. In the present study, we evaluated the synergistic effect of APRIL knockdown and Jiedu Xiaozheng Yin (JXY), a Traditional Chinese Medicinal recipe, on the inhibition of hepatocellular carcinoma (HCC) cell proliferation and elucidated the underlying mechanism. The results demonstrated that both APRIL knockdown using small interfering RNA (siRNA) and JXY treatment could trigger cell cycle arrest and cell apoptosis, and suppress HCC cell proliferation through an NF-κB-related pathway. Synergism was further demonstrated between APRIL knockdown and JXY treatment. In conclusion, these results indicate that APRIL is a target gene for HCC and combination of siRNA-APRIL and JXY application holds great promise as a novel approach for the treatment of APRIL-positive HCC.

A novel BCMA/CD3 bispecific T-cell engager for the treatment of multiple myeloma induces selective lysis in vitro and in vivo

B-cell maturation antigen (BCMA) is a highly plasma cell-selective protein that is expressed on malignant plasma cells of multiple myeloma (MM) patients and therefore is an ideal target for T-cell redirecting therapies. We developed a bispecific T-cell engager (BiTE) targeting BCMA and CD3ɛ (BI 836909) and studied its therapeutic impacts on MM. BI 836909 induced selective lysis of BCMA-positive MM cells, activation of T cells, release of cytokines and T-cell proliferation; whereas BCMA-negative cells were not affected. Activity of BI 836909 was not influenced by the presence of bone marrow stromal cells, soluble BCMA or a proliferation-inducing ligand (APRIL). In ex vivo assays, BI 836909 induced potent autologous MM cell lysis in both, newly diagnosed and relapsed/refractory patient samples. In mouse xenograft studies, BI 836909 induced tumor cell depletion in a subcutaneous NCI-H929 xenograft model and prolonged survival in an orthotopic L-363 xenograft model. In a cynomolgus monkey study, administration of BI 836909 led to depletion of BCMA-positive plasma cells in the bone marrow. Taken together, these results show that BI 836909 is a highly potent and efficacious approach to selectively deplete BCMA-positive MM cells and represents a novel immunotherapeutic for the treatment of MM.

Urinary B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL): potential biomarkers of active lupus nephritis.

B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) help in B cell activation, maintenance and plasma cell survival. B cell infiltration has been demonstrated in kidneys of patients with lupus nephritis (LN). Serum levels of BAFF and APRIL have shown inconsistent relationships with lupus disease activity. We evaluated urinary levels of BAFF and APRIL as biomarker for LN. Thirty-six patients with proliferative lupus nephritis (AN), 10 with active lupus without nephritis (AL) and 15 healthy controls (HC) were studied. APRIL and BAFF levels were measured in both serum and urine using enzyme-linked immunosorbent assay (ELISA). Urine levels were normalized for urinary creatinine excretion. Urine levels were correlated with conventional disease activity markers and histology. Levels were reassessed in 20 AN patients at 6 months after treatment with cyclophosphamide. Urinary APRIL (uAPRIL) and BAFF (uBAFF) levels were raised significantly in AN. uAPRIL, but not uBAFF, correlated moderately with renal Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) in AN (r = 0·36, P < 0·05). On receiver operator curve (ROC) analysis, uBAFF and uAPRIL showed an area under the curve (AUC) of 0·825 and 0·781, respectively, in differentiating between nephritis and non-nephritis, which performed better than low C3, C4 and raised anti-dsDNA antibodies. There was no correlation of serum levels with uBAFF (r = 0·187, P = 0·261) and uAPRIL (r = 0·114, P = 0·494). uAPRIL levels reduced after treatment (mean 125 pg/mg to 36 pg/mg, P < 0·05). uBAFF levels reduced in 16 responders while two of four non-responders had increase in levels. Thus, uBAFF and uAPRIL are potential biomarkers of proliferative lupus nephritis.

Development of a New BCMAxCD3 Duobody® Antibody for Multiple Myeloma

B-cell maturation antigen (BCMA) is a tumor necrosis factor (TNF) family surface protein predominantly expressed on terminally differentiated B-cells. BCMA signals through P38/NF-κB pathway upon binding to its ligands; a proliferation inducing ligand (APRIL) and B-cell activator of the TNF family (BAFF) and promote anti-apoptotic gene expression. BCMA expression is elevated in plasma blasts, plasma cells from spleen and bone marrow and correlates with disease progression in multiple myeloma (MM). BCMA expression in premalignant MM settings such as monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) also gives an opportunity for early cancer interception. To target cancer cells expressing BCMA, we developed a BCMAxCD3 bispecific antibody using the Genmab DuoBody® technology (Ab-957) to recruit T cells to BCMA-expressing MM cells so that T cells could be activated and induced to kill BCMA+ cancer cells. This antibody can induce cytotoxicity of BCMA+ MM cell lines in vitro (H929 cells: EC50=0.15nM, MM1.R cells: EC50=0.06nM, RPMI8226 cells: EC50=0.45nM) with a concomitant T cell activation (H929 cells: EC50=0.21nM, MM1.R cells: EC50=0.1nM, RPMI8226 cells: EC50=0.28nM). In contrast, this antibody was unable to kill BCMA- cancer cell line (MV4-11), demonstrating the specificity of the cytotoxicity. Ab-957 also inhibited tumor development or growth in two BCMA+ MM murine xenograft models inoculated with human T cells. Furthermore, this antibody could deplete BCMA+ cells in bone marrow samples from MM patient’s in an ex-vivo assay with an average EC50 value of 2.5 nM. Lastly, Ab-957 is well-tolerated in cynomolgus monkey and is being developed for Phase I clinical trial in patients with multiple myeloma. DisclosuresPillarisetti:Janssen: Employment. Baldwin:Janssen: Employment. Babich:Janssen: Employment. Majewski:Janssen: Employment. Barone:Janssen: Employment. Li:Janssen: Employment. Zhang:Janssen: Employment. Chin:Janssen: Employment. Luistro:Janssen: Employment. Mendonça:Janssen: Employment. Nanjunda:Janssen: Employment. Rudnick:Janssen Pharmaceuticals R&D: Employment. Bellew:Janssen: Employment. Elsayed:Janssen: Employment, Other: stock options. Attar:Janssen: Employment. Gaudet:Janssen Pharmaceuticals R&D: Employment, Other: Stock options, Patents & Royalties: pending, not yet issued.

The relationship of A Proliferation-Inducing Ligand expression with the clinical pathology and prognosis in colorectal carcinoma

Objective: To investigate the protein expression of A Proliferation-Inducing Ligand (APRIL) in colorectal cancer (CRC) tissue, and its correlation with clinical pathology and prognosis. Methods: One hundred and twenty cases of CRC tissue and related clinical data were collected from the Department of Pathology of Affiliated Hospital of Nantong University. The specimens were made into tissue microarray. The protein expression of APRIL was detected by Envision immunohistochemistry. The relationship of the protein expression of APRIL with clinicopathological parameters and follow-up data were statistically analyzed. Results: APRIL protein expression positive rate of CRC tissue and cancer adjacent normal mucosal tissue were 83.33% (100/120) and 12.5% (15/120), with a statistical significance (P<0.001). The expression of APRIL was related to TNM staging (χ2=10.222, P=0.006) and the depth of tumor invasion (χ2=5.987, P=0.014). Kaplan-Meier survival curves showed that five years survival rate of high APRIL expression group was lower than that of low APRIL expression group. Univariate survival analysis showed that the expression of APRIL (P<0.001), the degree of tumor differentiation (P=0.033), TNM staging (P<0.001), depth of tumor invasion (P=0.011), lymph node metastasis (P<0.001) and serum CEA (P=0.003) time were associated with postoperative survival. Multivariate COX proportional hazard regression model analysis further revealed the expression of APRIL (P=0.001), the degree of tumor differentiation (P=0.005), TNM staging (P=0.001) and serum CEA (P=0.039) were the independent risk factors for prognosis. Conclusion: The expression of APRIL in CRC tumor tissue is closely related to TNM stage and depth of tumor invasion. The high expression of APRIL prompts bad prognosis. APRIL is one of the independent prognostic factors in patients with CRC, and could be a potential target for the therapy of CRC.

Increased proportions of Tc17 cells and NK cells may be risk factors for disease progression in Hashimoto's thyroiditis

Both cellular and humoral responses play important roles in the pathogenesis of Hashimoto's thyroiditis (HT). However, the immunological differences between euthyroid (mild HT) and hypothyroid (severe HT) patients are unknown. This study aimed to investigate the distribution of lymphocyte subsets and cytokine profiles in HT patients with differences in thyroid function.Peripheral blood was drawn from 18 healthy controls and 54 HT patients (33 patients with mild HT, 21 patients with severe HT). The percentages of B cell subsets, T cell subsets and NK cells were analyzed by flow cytometry. The levels of IL-21 and Bcl-6 mRNA were assessed using real-time PCR. The levels of serum IFN-γ, TNF-α, TGF-β, IL-4, IL-6, IL-10 and a proliferation-inducing ligand (APRIL) were measured by ELISA or cytometric bead array.The percentages of double-negative memory B cells, plasma cells, Tfh cells and Tc17 cells were higher in HT patients than in the healthy controls. The percentages of Tc17 cells and NK cells were higher in the patients with severe HT than in the patients with mild HT. The levels of serum APRIL, IL-6 and IL-10 were higher in the patients with severe HT than in those with mild HT. The percentage of NK cells was positively correlated with TSH levels in the HT patients.Our data indicate that the distribution of lymphocyte subsets and cytokine profiles is aberrant in HT patients, and the increased percentages of Tc17 cells and NK cells and increased cytokine levels might be involved in the progression of HT.

Biotherapies in systemic lupus erythematosus: New targets

Systemic lupus erythematosus (SLE) is an autoimmune disease with a polymorphic presentation. The variability in the clinical expression and severity of SLE makes new treatments both essential and challenging to develop. Several biotherapies targeting different pathophysiological pathways have been developed over the past 15 years. The results of Phase II trials were encouraging but rarely borne out by Phase III trials. Recent data, which are discussed in detail in this review, allowed belimumab – a monoclonal antibody against BLyS (B-lymphocyte stimulator) – to become the first biotherapy approved for use in SLE. Other molecules targeting B cells include the two anti-BLyS antibodies tabalumab and blisibimod; atacicept, which targets both BLyS and APRIL (a proliferation-inducing ligand); and the monoclonal antibody to CD22 epratuzumab. The rekindling of interest in the B-cell pathway has also driven new clinical research into rituximab, a monoclonal antibody targeting CD20 with evaluations of new strategies. A new and promising approach is the use of inhibitors of the type 1 interferon (IFN) pathway, of which the most promising is anifrolumab, a monoclonal antibody targeting the type 1 IFN receptor. In this review, we discuss study findings and their clinical relevance, present the most promising targets, and analyze possible explanations to negative results, such as inappropriate patient selection and treatment response criteria or the erratic use of high-dose glucocorticoid therapy.

APRIL, BCMA and TACI proteins are abnormally expressed in non-small cell lung cancer.

Lung cancer is the leading cause of cancer-associated mortality. Non-small cell lung cancer (NSCLC) accounts for >80% of lung cancers. The overall survival for NSCLC is dismal, with a 5-year survival of <5% for patients. Thus, identifying an effective biomarker for early diagnosis of lung cancer is the first essential step to reduce mortality. It has been recognized that certain inflammatory and immune responses are important in lung cancer development and prevention. The present study demonstrated that, in NSCLC, a proliferation-inducing ligand (APRIL), B-cell maturation antigen (BCMA)and transmembrane activator and CAML interactor (TACI) proteins are abnormally expressed by immunohistochemistry, reverse transcription-quantitative polymerase chain reaction and western blotting. In addition, the expression of APRIL, BCMA and TACI were observed to be involved in extracellular signal-regulated kinase (ERK)1/2 activation in A549 cells. Overall, the present study provides evidence that APRIL and its receptors, BCMA and TACI, may play roles in the biological processes of NSCLC tumors through the ERK1/2 signaling pathway.

Association Study of a Proliferation-inducing Ligand, Spermatogenesis Associated 8, Platelet-derived Growth Factor Receptor-alpha, and POLB Polymorphisms with Systemic Lupus Erythematosus in Chinese Han Population.

Background:Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease with complex genetic inheritance. This study was conducted to examine whether the association of a proliferation-inducing ligand (APRIL), spermatogenesis associated 8 (SPATA8), platelet-derived growth factor receptor-alpha (PDGFRA), and DNA polymerase beta (POLB) with SLE can be replicated in a Chinese Han population.Methods:Chinese SLE patients (n = 1247) and ethnically and geographically matched healthy controls (n = 1440) were genotyped for the APRIL, SPATA8, PDGFRA, and POLB single-nucleotide polymorphisms (SNPs), rs3803800, rs8023715, rs1364989, and rs12678588 using the Sequenom MassARRAY System.Results:The Chinese Han SLE patients and controls had statistically similar frequencies of alleles and genotypes of four gene polymorphisms. Moreover, no association signal was detected on different genetic models (additive, dominant, and recessive, all, P > 0.05) or in SLE subgroups stratified by various clinical manifestations (all, P > 0.05).Conclusions:Different genetic backgrounds from different ancestries and various populations may result in different genetic risk factors for SLE. We did not detect any significant association with SNPs of APRIL, SPATA8, PDGFRA, and POLB.

Impact of heart rate variability, a marker for cardiac health, on lupus disease activity.

BackgroundDecreased heart rate variability (HRV) is associated with adverse outcomes in cardiovascular diseases and has been observed in patients with systemic lupus erythematosus (SLE). We examined the relationship of HRV with SLE disease activity and selected cytokine pathways.MethodsFifty-three patients from the Oklahoma Lupus Cohort were evaluated at two visits each. Clinical assessments included the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), British Isles Lupus Assessment Group (BILAG) index, physician global assessment (PGA), and Safety of Estrogens in Lupus Erythematosus National Assessment-SLEDAI Flare Index. HRV was assessed with a 5-minute electrocardiogram, and the following HRV parameters were calculated: square root of the mean of the squares of differences between adjacent NN intervals (RMSSD), percentage of pairs of adjacent NN intervals differing by more than 50 milliseconds (pNN50), high-frequency power (HF power), and low frequency to high frequency (LF/HF) ratio, which reflects sympathetic/vagal balance. Plasma cytokine levels were measured with a multiplex, bead-based immunoassay. Serum B lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL) were measured with an enzyme-linked immunosorbent assay. Linear regression analysis was applied.ResultsBaseline HRV (pNN50, HF power, LF/HF ratio) was inversely related to disease activity (BILAG, PGA) and flare. Changes in RMSSD between visits were inversely related to changes in SLEDAI (p = 0.007). Age, caffeine, tobacco and medication use had no impact on HRV. Plasma soluble tumor necrosis factor receptor II (sTNFRII) and monokine induced by interferon gamma (MIG) were inversely related with all baseline measures of HRV (p = 0.039 to <0.001). Plasma stem cell factor (SCF), interleukin (IL)-1 receptor antagonist (IL-1RA), and IL-15 showed similar inverse relationships with baseline HRV, and weaker trends were observed for interferon (IFN)-α, interferon gamma-induced protein (IP)-10, and serum BLyS. Changes in the LF/HF ratio between visits were also associated with changes in sTNFRII (p = 0.021), MIG (p = 0.003), IFN-α (p = 0.012), SCF (p = 0.001), IL-1RA (p = 0.023), and IL-15 (p = 0.010). On the basis of multivariate linear regression, MIG was an independent predictor of baseline HRV after adjusting for plasma IL-1RA, SCF, IFN-α, IP-10, and serum BLyS. In a similar model, the sTNFRII impact remained significant after adjusting for the same variables.ConclusionsImpaired HRV, particularly the LF/HF ratio, is associated with lupus disease activity and several cytokines related to IFN type II and TNF pathways. The strongest association was with MIG and sTNFRII, expanding previous immune connections of vagal signaling.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1087-x) contains supplementary material, which is available to authorized users.

Increased expression of TACI on NOD B cells results in germinal centre reaction anomalies, enhanced plasma cell differentiation and immunoglobulin production.

B cells have an important pathogenic role in the development of type 1 diabetes in the non-obese diabetic (NOD) mouse. We have previously reported that NOD mice display an increased percentage of TACIhigh -expressing B cells compared with C57BL/6 mice and this trait is linked to chromosomes 1 and 8. In this paper the genetic association of the transmembrane activator, calcium modulator and cyclophilin ligand interactor (TACI) trait was confirmed using double congenic NOD.B6C1/Idd22 mice. TACI ligation by a proliferation-inducing ligand (APRIL) has been shown to influence plasma cell differentiation, immunoglobulin production and isotype switch. Hence, the functional consequence of the up-regulation of TACI on NOD B cells was analysed both in vitro and in vivo. NOD B cells stimulated with APRIL showed an enhanced plasma cell differentiation and class switch to IgG and IgA compared with B cells from C57BL/6 mice. Moreover, flow cytometry analyses revealed that germinal centre B cells in NOD failed to down-regulate TACI. Availability of the TACI ligand B-cell activating factor (BAFF) has been shown to be a limiting factor in the germinal centre reaction. In line with this, upon immunization with 4-hydroxy-3-nitrophenylacetyl hapten-conjugated hen egg lysozyme, NOD mice produced higher titres of low-affinity antibodies compared with C57BL/6 mice. This observation was supported by the detection of increased levels of BAFF in NOD germinal centres after immunization compared with C57BL/6 by immunofluorescence. Our results support the hypothesis that increased TACI expression on NOD B cells contributes to the pathogenesis of type 1 diabetes in the NOD mouse.

Serum BAFF and APRIL Levels, T-Lymphocyte Subsets, and Immunoglobulins after B-Cell Depletion Using the Monoclonal Anti-CD20 Antibody Rituximab in Myalgic Encephalopathy/Chronic Fatigue Syndrome.

Myalgic Encephalopathy/Chronic Fatigue Syndrome (ME/CFS) is a disease of unknown etiology. We have previously suggested clinical benefit from B-cell depletion using the monoclonal anti-CD20 antibody rituximab in a randomized and placebo-controlled study. Prolonged responses were then demonstrated in an open-label phase-II study with maintenance rituximab treatment. Using blood samples from patients in the previous two clinical trials, we investigated quantitative changes in T-lymphocyte subsets, in immunoglobulins, and in serum levels of two B-cell regulating cytokines during follow-up. B-lymphocyte activating factor of the tumor necrosis family (BAFF) in baseline serum samples was elevated in 70 ME/CFS patients as compared to 56 healthy controls (p = 0.011). There were no significant differences in baseline serum BAFF levels between patients with mild, moderate, or severe ME/CFS, or between responders and non-responders to rituximab. A proliferation-inducing ligand (APRIL) serum levels were not significantly different in ME/CFS patients compared to healthy controls at baseline, and no changes in serum levels were seen during follow-up. Immunophenotyping of peripheral blood T-lymphocyte subsets and T-cell activation markers at multiple time points during follow-up showed no significant differences over time, between rituximab and placebo groups, or between responders and non-responders to rituximab. Baseline serum IgG levels were significantly lower in patients with subsequent response after rituximab therapy compared to non-responders (p = 0.03). In the maintenance study, slight but significant reductions in mean serum immunoglobulin levels were observed at 24 months compared to baseline; IgG 10.6–9.5 g/L, IgA 1.8–1.5 g/L, and IgM 0.97–0.70 g/L. Although no functional assays were performed, the lack of significant associations of T- and NK-cell subset numbers with B-cell depletion, as well as the lack of associations to clinical responses, suggest that B-cell regulatory effects on T-cell or NK-cell subsets are not the main mechanisms for the observed improvements in ME/CFS symptoms observed in the two previous trials. The modest increase in serum BAFF levels at baseline may indicate an activated B-lymphocyte system in a subgroup of ME/CFS patients.

Revisiting IL-6 antagonism in multiple myeloma.

IL-6, a cytokine with broad functions in inflammation and immunity, has been extensively studied for its role on normal antibody-producing plasma cells. In addition, IL-6 is recognized as a proliferative factor for multiple myeloma (MM), a malignant plasma cell tumor developing in the bone marrow. Blocking IL-6 signaling was thus developed into a therapeutic approach for MM already early after its discovery, in 1991. Unfortunately, the first clinical trials did not demonstrate a clear benefit, but despite this apparent failure hopes on IL-6 antagonism are still high and trials ongoing. The cellular source of IL-6 has long been a matter of debate. IL-6 was first recognized as an autocrine factor produced by the malignant plasma cells themselves, but later reports clearly showed that IL-6 was a paracrine factor, produced by the microenvironment, mostly by cells from the myeloid lineage. Recently, we have confirmed that IL-6 originates from myeloid lineage cells, mainly from myeloid precursors. We have also demonstrated that IL-6 amplifies the pool of myeloid cells producing a second key factor for MM, a proliferation inducing ligand (APRIL). These findings form a new rationale for IL-6 inhibition in MM and for new ways to use IL-6 blocking in the clinics.

Abstract 3283: APRIL/BCMA activation promotes human multiple myeloma progression and further induces immunosuppressive bone marrow microenvironment

Abstract Elevated B cell maturation antigen (BCMA) and its ligand a proliferation-inducing ligand (APRIL) may directly advance human multiple myeloma (MM) malignancy in vivo. Here, we first show that BCMA downregulation potently diminishes viability and colony formation of MM cells while BCMA overexpression augments MM cell growth and survival via induction of AKT, MAPK, and NFκB signaling cascades and molecules essential for proliferation and anti-apoptosis. Importantly, BCMA itself forces accelerated tumor growth of xenografted MM cells harboring p53 mutation in mice. BCMA-overexpressing tumors exhibit significantly enhanced CD31/microvessel density and VEGF than paired control tumors. Concurrently, these tumors express increased factors crucial for osteoclast activation, adhesion, and angiogenesis/metastasis, as well as immune inhibition including PD-L1, TGFβ and IL-10 which further triggers 38 IL-10 signaling molecules. In parallel, these identified target genes are induced by paracrine APRIL binding to BCMA in MM cells and they are potently blocked by an antagonistic anti-APRIL monoclonal antibody hAPRIL01A (01A). 01A is cytotoxic against MM cells protected by abnormal bone marrow (BM) myeloid cells, i.e., osteoclasts, macrophages, and plasmacytoid dendritic cells. It further decreases APRIL-induced adhesion and migration of MM cells via blockade of canonical and non-canonical NFκB pathways. It prevents in vivo MM cell growth within implanted human bone chips in SCID mice. 01A-inhibited MM cell viability induced by osteoclasts is further enhanced by lenalidomide and bortezomib. Taken together, these results further characterize new molecular mechanisms of APRIL/BCMA-induced in vivo MM progression and immunosuppressive BM microenvironment, strongly supporting targeting this prominent pathway in MM. Citation Format: Yu-Tzu Tai, Chirag Acharya, Gang An, Michele Moschetta, Mike Y. Zhong, Xiaoyan Feng, Michele Cea, Antonia Cagnetta, Kenneth Wen, Hans van Eenennaam, Andrea van Elsas, Nikhil Munshi, Kenneth Anderson. APRIL/BCMA activation promotes human multiple myeloma progression and further induces immunosuppressive bone marrow microenvironment. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3283.

B-cell-activating factor, a proliferation inducing ligand and co-stimulatory molecules in the pathogenesis of immune thrombocytopenia in childhood

The aim of this study was to measure the levels of B-cell-activating factor (BAFF), a proliferation-inducing ligand (APRIL), and co-stimulatory molecules in immune thrombocytopenia (ITP) of childhood to investigate the interaction between T and B lymphocytes and the impact of proliferation of B lymphocytes in the pathogenesis. Twenty newly diagnosed ITPs, 20 chronic ITPs, and 20 healthy controls between 2 and 18 years were enrolled in this study. Hemogram, BAFF, APRIL, interleukin-4, and interferon (IFN)-γ levels in sera and expressions of CD19, CD 3, CD21, CD40, and CD 154 on leukocytes were measured by ELISA and flow cytometry. Mean BAFF level in newly diagnosed ITP group was higher than the mean BAFF level in other groups. BAFF levels were significantly decreased after the treatment in newly diagnosed ITP group. APRIL, interleukin-4, and IFN-γ in newly diagnosed ITP group and BAFF, APRIL, interleukin-4, and IFN-γ in chronic ITP group were similar before and after treatment. There was no statistical difference for expressions of CD 19 and CD3 on lymphocytes, CD40 on leukocytes, CD154 on T cells, and for percentages of CD21/CD40, CD21/CD40, CD21/CD40 B cells, and CD19/CD3 lymphocytes for pretreatment and posttreatment levels in both ITP groups. In conclusion, our study strongly demonstrated that BAFF has an important role in the pathogenesis of newly diagnosed childhood ITP. It may be important in the follow-up and in novel therapy modalities of these patients.