APRIL modulates B and T cell immunity

Uncovering lupus nephritis-specific genes and the potential of TNFRSF17-targeted immunotherapy: a high-throughput sequencing study

Introduction

Lupus nephritis (LN) is a severe manifestation of systemic lupus erythematosus (SLE). This study aimed to identify LN specific-genes and potential therapeutic targets.

Methods

We performed high-throughput transcriptome sequencing on peripheral blood mononuclear cells (PBMCs) from LN patients. Healthy individuals and SLE patients without LN were used as controls. To validate the sequencing results, qRT-PCR was performed for 5 upregulated and 5 downregulated genes. Furthermore, the effect of the TNFRSF17-targeting drug IBI379 on patient plasma cells and B cells was evaluated by flow cytometry.

Results

Our analysis identified 1493 and 205 differential genes in the LN group compared to the control and SLE without LN groups respectively, with 70 genes common to both sets, marking them as LN-specific. These LN-specific genes were significantly enriched in the 'regulation of biological quality' GO term and the cell cycle pathway. Notably, several genes including TNFRSF17 were significantly overexpressed in the kidneys of both LN patients and NZB/W mice. TNFRSF17 levels correlated positively with urinary protein levels, and negatively with complement C3 and C4 levels in LN patients. The TNFRSF17-targeting drug IBI379 effectively induced apoptosis in patient plasma cells without significantly affecting B cells.

Discussion

Our findings suggest that TNFRSF17 could serve as a potential therapeutic target for LN. Moreover, IBI379 is presented as a promising treatment option for LN.

Allogeneic haematopoietic stem cell transplantation resets T- and B-cell compartments in sickle cell disease patients

Objectives

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is the only currently available curative treatment for sickle cell disease (SCD). Here, we comprehensively evaluated the reconstitution of T- and B-cell compartments in 29 SCD patients treated with allo-HSCT and how it correlated with the development of acute graft-versus-host disease (aGvHD).

Methods

T-cell neogenesis was assessed by quantification of signal-joint and β-chain TCR excision circles. B-cell neogenesis was evaluated by quantification of signal-joint and coding-joint K-chain recombination excision circles. T- and B-cell peripheral subset numbers were assessed by flow cytometry.

Results

Before allo-HSCT (baseline), T-cell neogenesis was normal in SCD patients compared with age-, gender- and ethnicity-matched healthy controls. Following allo-HSCT, T-cell neogenesis declined but was fully restored to healthy control levels at one year post-transplantation. Peripheral T-cell subset counts were fully restored only at 24 months post-transplantation. Occurrence of acute graft-versus-host disease (aGvHD) transiently affected T- and B-cell neogenesis and overall reconstitution of T- and B-cell peripheral subsets. B-cell neogenesis was significantly higher in SCD patients at baseline than in healthy controls, remaining high throughout the follow-up after allo-HSCT. Notably, after transplantation SCD patients showed increased frequencies of IL-10-producing B-regulatory cells and IgM⁺ memory B-cell subsets compared with baseline levels and with healthy controls.

Conclusion

Our findings revealed that the T- and B-cell compartments were normally reconstituted in SCD patients after allo-HSCT. In addition, the increase of IL-10-producing B-regulatory cells may contribute to improve immune regulation and homeostasis after transplantation.

Plasma levels of BAFF and APRIL are elevated in patients with asthma in Saudi Arabia

B-cell activation factor (BAFF) and a proliferation-inducing ligand (APRIL) are members of the tumor necrosis factor superfamily of cytokines and can induce B cell activation, differentiation, and antibody production via interaction with their receptors, including transmembrane activator, calcium modulator, and cyclophilin ligand interactor (TACI), B-cell maturation antigen (BCMA), and B-cell activating factor receptor (BAFF-R). Herein, we assessed the plasma protein levels of BAFF and APRIL in patients with asthma to determine whether their expression is correlated with total IgE production and examined the surface expression of BAFF/APRIL receptors on B cells. Blood samples were collected from 47 patients with controlled asthma symptoms and 20 healthy normal controls, and plasma levels of APRIL, BAFF, and total IgE protein were quantified by corresponding ELISA assays. Furthermore, lymphocytes were isolated and B cells were analyzed for the presence of BAFF-R, BCMA, and TACI receptors using flow cytometry. Our results showed that IgE, BAFF, and APRIL plasma levels were markedly increased in patients with asthma compared with healthy controls. Moreover, expression of BAFF-R and BCMA, but not that of TACI, was significantly increased in patients with asthma compared with healthy controls. Overall, the findings suggest BAFF and APRIL as key mediators of asthma, and determination of their plasma levels may be useful in monitoring asthma symptoms and treatment response.

Lymphoid and myeloid immune cell reconstitution after nicotinamide-expanded cord blood transplantation

Omidubicel (nicotinamide-expanded cord blood) is a potential alternative source for allogeneic hematopoietic cell transplantation (HCT) when an HLA-identical donor is lacking. A phase I/II trial with standalone omidubicel HCT showed rapid and robust neutrophil and platelet engraftment. In this study, we evaluated the immune reconstitution (IR) of patients receiving omidubicel grafts during the first 6 months post-transplant, as IR is critical for favorable outcomes of the procedure. Data was collected from the omidubicel phase I-II international, multicenter trial. The primary endpoint was the probability of achieving adequate CD4+ T-cell IR (CD4IR: > 50 × 106/L within 100 days). Secondary endpoints were the recovery of T-cells, natural killer (NK)-cells, B-cells, dendritic cells (DC), and monocytes as determined with multicolor flow cytometry. LOESS-regression curves and cumulative incidence plots were used for data description. Thirty-six omidubicel recipients (median 44; 13-63 years) were included, and IR data was available from 28 recipients. Of these patients, 90% achieved adequate CD4IR. Overall, IR was complete and consisted of T-cell, monocyte, DC, and notably fast NK- and B-cell reconstitution, compared to conventional grafts. Our data show that transplantation of adolescent and adult patients with omidubicel results in full and broad IR, which is comparable with IR after HCT with conventional graft sources.

Transmission of trained immunity and heterologous resistance to infections across generations

Intergenerational inheritance of immune traits linked to epigenetic modifications has been demonstrated in plants and invertebrates. Here we provide evidence for transmission of trained immunity across generations to murine progeny that survived a sublethal systemic infection with Candida albicans or a zymosan challenge. The progeny of trained mice exhibited cellular, developmental, transcriptional and epigenetic changes associated with the bone marrow-resident myeloid effector and progenitor cell compartment. Moreover, the progeny of trained mice showed enhanced responsiveness to endotoxin challenge, alongside improved protection against systemic heterologous Escherichia coli and Listeria monocytogenes infections. Sperm DNA of parental male mice intravenously infected with the fungus C. albicans showed DNA methylation differences linked to immune gene loci. These results provide evidence for inheritance of trained immunity in mammals, enhancing protection against infections.

TNFSF13 Is a Novel Onco-Inflammatory Marker and Correlates With Immune Infiltration in Gliomas

Existing therapeutic strategies for gliomas are restricted; hence, exploration for novel diagnostic indicator and treatment is essential. Here, we performed bioinformatic analyses for TNFSF13 (also known as APRIL), a proliferation-inducing ligand of the tumor necrosis factor (TNF) superfamily, aiming to assess its potential for predicting glioma patient’s prognosis and targeted therapy. TNFSF13 expression was upregulated in the increase of tumor grades based on Xiangya cohort. In high TNFSF13 gliomas, somatic mutation was proved to correlate with amplification of EGFR and deletion of CDKN2A; while mutation of IDH1 was more frequently observed in low TNFSF13 group. We also confirmed the positive correlation between TNFSF13 and infiltrating immune and stromal cells in glioma microenvironment. Further, TNFSF13 was found to be involved in immunosuppression via diverse immunoregulation pathways and was associated with other immune checkpoints and inflammation. Single-cell sequencing revealed an abundant expression of TNFSF13 in neoplastic cells and M2 macrophages, which TNFSF13 might potentially regulate the cell communication via IL-8, C3, and CD44. Lastly, TNFSF13 mediated the activities of transcription factors including FOXO3, MEIS2, and IRF8. Our analyses demonstrated the relevance between TNFSF13 and glioma progress and indicated the potential of TNFSF13 as a novel diagnostic onco-inflammatory biomarker and immunotherapy target of gliomas.

High levels of gut-homing immunoglobulin A+ B lymphocytes support the pathogenic role of intestinal mucosal hyperresponsiveness in immunoglobulin A nephropathy patients

Background

Immunoglobulin A nephropathy (IgAN) is the most frequent primary glomerulonephritis. The role of the microbiota and mucosal immunity in the pathogenesis of IgAN remains a key element. To date, the hypothetical relationship between commensal bacteria, elevated tumour necrosis factor (TNF) superfamily member 13 [also known as B-cell activating factor (BAFF)] levels, perturbed homoeostasis of intestinal-activated B cells and intestinal IgA class switch has not been clearly shown in IgAN patients.

Methods

We studied the intestinal–renal axis connections, analysing levels of BAFF, TNF ligand superfamily member 13 (APRIL) and intestinal-activated B cells in IgAN patients, healthy subjects (HSs) and patients with non-IgA glomerulonephritides.

Results

IgAN patients had increased serum levels of BAFF cytokine, correlating with higher amounts of five specific microbiota metabolites, and high APRIL cytokine serum levels. We also found that subjects with IgAN have a higher level of circulating gut-homing (CCR9⁺ β7 integrin⁺) regultory B cells, memory B cells and IgA⁺ memory B cells compared with HSs. Finally, we found that IgAN patients had high levels of both total plasmablasts (PBs) and intestinal-homing PBs. Interestingly, PBs significantly increased in IgAN but not in patients with other glomerulonephritides.

Conclusions

Our results demonstrate a significant difference in the amount of intestinal-activated B lymphocytes between IgAN patients and HSs, confirming the hypothesis of the pathogenic role of intestinal mucosal hyperresponsiveness in IgAN. The intestinal–renal axis plays a crucial role in IgAN and several factors may contribute to its complex pathogenesis and provide an important area of research for novel targeted therapies to modulate progression of the disease.

CNS Autoimmune Responses in BCMA-Deficient Mice Provide Insight for the Failure of Atacicept in MS

OBJECTIVE

B cells have emerged as a therapeutic target for MS. Anti-CD20 antibodies, which deplete B cells, are effective therapies for MS. However, atacicept (TACI-Fc), which blocks BAFF and APRIL and reduces B cells, unexpectedly exacerbates MS. We tested the hypothesis that B cell maturation antigen (BCMA), a receptor for BAFF and APRIL, plays a role in the paradoxical effects of anti-CD20 antibody and TACI-Fc using experimental autoimmune encephalomyelitis (EAE).

METHODS

EAE was induced in wild-type (BCMA^+/+) and BCMA-deficient (BCMA^-/-) mice with an immunization of rodent myelin oligodendrocyte glycoprotein (MOG)_35-55 peptide. Treatment with anti-CD20 antibody, TACI-Fc, and isotype controls was administered by intraperitoneal injections. CNS infiltration was evaluated by histology; immune cell phenotypes were evaluated by flow cytometry; MOG-specific antibodies were determined by ELISA. Mixed bone marrow chimeras and cell culture assays were used to identify the specific subsets of immune cells affected by BCMA deficiency.

RESULTS

First, we found that BCMA^-/- mice had more severe EAE compared with BCMA^+/+ mice and the increased disease was associated with elevated anti-MOG B-cell responses. Second, we found that anti-CD20 therapy attenuated EAE in BCMA^-/- mice but not in BCMA^+/+ mice. Third, TACI-Fc attenuated EAE in BCMA^+/+ mice but not in BCMA^-/- mice. Mixed bone marrow chimeric and cell culture experiments demonstrated that BCMA deficiency elevates inflammatory B-cell responses but inhibits inflammatory responses in macrophages.

CONCLUSIONS

BCMA has multifaceted roles during inflammation that affects therapeutic efficacies of anti-CD20 and TACI-Fc in EAE. Our results from BCMA-deficient mice provide insights into the failure of atacicept in MS.

Aberrant Expression of a Proliferation-Inducing Ligand Underlies Autoimmune Mechanisms in Immune Thrombocytopenia

Purpose

To study the relationship between surface membrane-bound APRIL and ITP.

Methods

The peripheral blood of all subjects, 50 patients diagnosed with ITP and 25 healthy controls, was collected. Flow cytometry was used to detect the expression of membrane-bound APRIL on immune cells and platelets. ELISA was used to detect the content of soluble APRIL in plasma.

Results

Membrane-bound APRIL was only expressed on the surface of platelets in both ITP patients and controls. APRIL expression on the platelet surface was significantly lower in newly diagnosed (P < 0.001) and chronic (P < 0.001) ITP patients than in controls. Platelet surface APRIL level was significantly enhanced in patients with complete remission after treatment (P = 0.02) but not in those with no response after treatment. Platelet surface APRIL level in ITP patients was negatively correlated with serum APRIL level (r = −0.09765, P = 0.0424).

Conclusions

Platelet surface APRIL may play a key immunoregulative role. Platelet surface APRIL is likely to be one source of the excessive serum APRIL in ITP patients. The effectiveness of treatment may be measured by determining the platelet surface APRIL levels in ITP patients.

Genetic and molecular biology of systemic lupus erythematosus among Iranian patients: an overview

BACKGROUND

Systemic lupus erythematosus (SLE) is a clinicopathologically heterogeneous chronic autoimmune disorder affecting different organs and tissues. It has been reported that there is an increasing rate of SLE incidence among Iranian population. Moreover, the Iranian SLE patients have more severe clinical manifestations compared with other countries. Therefore, it is required to introduce novel methods for the early detection of SLE in this population. Various environmental and genetic factors are involved in SLE progression.

MAIN BODY

In present review we have summarized all of the reported genes which have been associated with clinicopathological features of SLE among Iranian patients.

CONCLUSIONS

Apart from the reported cytokines and chemokines, it was interestingly observed that the apoptosis related genes and non-coding RNAs were the most reported genetic abnormalities associated with SLE progression among Iranians. This review clarifies the genetics and molecular biology of SLE progression among Iranian cases. Moreover, this review paves the way of introducing an efficient panel of genetic markers for the early detection and better management of SLE in this population.

High APRIL Levels Are Associated With Slow Disease Progression and Low Immune Activation in Chronic HIV-1-Infected Patients

Objective: B-cell-activating factor (BAFF) has been determined to be involved in HIV-1 infection and is correlated with disease progression, while its homologous molecule, a proliferation-inducing ligand (APRIL), is less frequently reported, and its role remains unclear. We aimed to characterize the APRIL levels in subjects with different HIV-1 infection statuses and determine the relationships with disease progression and immune activation.

Methods: The plasma levels of APRIL were compared among 17 long-term non-progressors (LTNPs), 17 typical progressors (TPs), 10 ART-treated patients, and 10 healthy donors (HDs). Seventeen LTNPs and a subset of TPs (n = 6) who initiated ART were assessed longitudinally. The correlations between the APRIL levels and markers of disease progression, B-cell count and specific antibody response, and markers of immune activation and functional cells were analyzed.

Results: The circulating APRIL levels were significantly elevated in the LTNPs relative to the TPs, ART-treated patients, and HDs. The longitudinal investigation revealed that the APRIL levels were decreased during follow-up in the LTNPs. ART did not significantly influence the APRIL levels. The levels of plasma APRIL were negatively correlated with the plasma HIV-1 viral load and cellular HIV-1 DNA levels and positively correlated with the CD4⁺ T-cell count and CD4/CD8 ratio. An inverse correlation was observed between the APRIL and BAFF levels. Furthermore, the APRIL levels were negatively correlated with the frequency of activated CD8⁺ T cells and levels of interferon gamma-induced protein 10 (IP-10) and monocyte chemoattractant protein-1 (MCP-1). Finally, positive correlations were observed among the APRIL levels, the frequency of CD8⁺CD28⁺ T cells, and natural killer (NK) cell count.

Conclusion: The APRIL levels were elevated in the LTNPs and negatively correlated with disease progression and immune activation, suggesting likely protective activity in HIV-1 infection.

Short-term Immunopathological Changes Associated with Pulse Steroids/IVIG/Rituximab Therapy in Late Kidney Allograft Antibody Mediated Rejection

Background

B-cell depletion is a common treatment of antibody-mediated rejection (ABMR). We sought to determine the specific immunopathologic effects of this therapeutic approach in kidney transplantation.

Methods

This was a prospective observational study of kidney transplant recipients diagnosed with late ABMR (>3 months after transplant). Patients received treatment with pulse steroids, IVIG, and rituximab. Donor specific HLA antibodies (DSA), kidney allograft pathology, renal function, immune cell phenotypes, and 47 circulating cytokines were assessed at baseline and at three months.

Results

We enrolled 23 patients in this study between April 2015 and March 2019. The majority of patients were male (74%) and Caucasian (78%) with an average age of 45.6±13.8 years. ABMR was diagnosed at 6.8±5.9 years (4 months-25 years) post-transplant. Treatment was associated with a significant decline in circulating HLA class I DSA (P=0.003) and class II DSA (P=0.002) and peritubular capillaritis (ptc, P=0.04) compared to baseline. Serum creatinine, BUN, eGFR, and proteinuria (UPC) remained stable. Circulating B-cells were depleted to barely detectable levels (P≤0.001), whereas BAFF (P=0.001), APRIL (P<0.001), and IL-10 (P=0.02), levels increased significantly post-treatment. Notably, there was a significant rise in circulating CD4+ (P=0.02) and CD8+ T-cells (P=0.003). We also noted a significant correlation between circulating cytotoxic CD8+ T-cells and BAFF (P=0.05), regulatory T-cells and IL10 (P=0.002), and HLA class I DSA (P=0.005).

Conclusions

Short-term pulse steroids/IVIG/rituximab therapy was associated with inhibition of ABMR (DSA and ptc), stabilization of kidney function, and increased regulatory B-cell and T-cell survival cytokines. Additional studies are needed to understand the implications of B cell-depletion on the crosstalk between T-cells, B-cells, and humoral components that regulate ABMR.

B cell ADAM17 controls T cell independent humoral immune responses through regulation of TACI and CD138

ADAM17 is known to contribute to the immune system through its shedding of tumor necrosis factor alpha (TNFα). However, the role of ADAM17 in B cell biology is not well characterized. To determine whether B cell ADAM17 contributes to T cell-independent humoral immune responses, we crossed CD19 Cre transgenic mice with mice bearing a floxed allele of ADAM17 (ADAM17^CD19). In this study, we show a B cell intrinsic role for ADAM17 in regulating marginal zone B cell (MZB) numbers in mice. Interestingly, we demonstrate that the loss of B cell ADAM17 results in reduced MZB numbers in the naïve state and after immunization with T-independent antigen, yet enhanced humoral immunity to T cell independent antigens. We additionally find elevated TACI and CD138 levels on plasma cells following immunization in ADAM17^CD19 mice. Overall, these findings suggest that B cell ADAM17 may orchestrate T independent immune responses through both MZB numbers and plasma cell antibody production.

Serum Levels of BAFF and APRIL Predict Clinical Response in Anti-PLA2R-Positive Primary Membranous Nephropathy

Primary membranous nephropathy (PMN) is a renal-specific autoimmune disease caused by circulating autoantibodies that target glomerular podocyte antigens (PLA2R/THSD7A). However, very little is known on the molecular mechanisms controlling B cell response in this nephropathy. The present study was aimed at correlating the serum levels of B cell activators BAFF/BLyS and APRIL with the presence of anti-PLA2R antibodies in PMN patients and with long-term clinical outcome. To this aim, 51 patients with anti-PLA2R-positive biopsy-proven PMN and nephrotic range proteinuria (>3.5 g/24 hours) were enrolled between January 2009 and December 2015 and treated with conventional 6-month immunosuppressive therapy. After 6 months, 29 patients (56.9%) cleared circulating anti-PLA2R, while in remaining 22 (43.1%), they persisted. Intriguingly, in the first group, baseline serum levels of BAFF/BLyS and APRIL were significantly lower than those in the second one. Moreover, after 6 months of immunosuppressive therapy, an overall reduction in both cytokine serum levels was observed. However, in PMN patients with anti-PLA2R clearance, this reduction was more prominent, as compared with those with anti-PLA2R persistence. When related to clinical outcome, lower baseline BAFF/BLyS (<6.05 ng/mL) and APRIL (<4.20 ng/mL) serum levels were associated with significantly higher probability to achieve complete or partial remission after 24-month follow-up. After dividing the entire study cohort into three groups depending on both cytokine baseline serum levels, patients with both BAFF/BLyS and APRIL below the cut-off showed a significantly higher rate of complete or partial remission as compared with patients with only one cytokine above the cut-off, while the composite endpoint was achieved in a very low rate of patients with both cytokines above the cut-off. Taken together, these results provide new insights into the role of BAFF/BLyS and APRIL in both the pathogenesis of anti-PLA2R-positive PMN and the response to immunosuppressive therapy.

APRIL Induces a Novel Subset of IgA+ Regulatory B Cells That Suppress Inflammation via Expression of IL-10 and PD-L1

Regulatory B cells (Bregs) are immunosuppressive cells that modulate immune responses through multiple mechanisms. The signals required for the differentiation and activation of these cells remain still poorly understood. We have already shown that overexpression of A PRoliferation-Inducing Ligand (APRIL) reduces the incidence and severity of collagen-induced arthritis (CIA) in mice. Furthermore, we have described that APRIL, but not BAFF, promoted IL-10 production and regulatory functions in human B cells. Therefore, we hypothesized that APRIL, but not BAFF, may be involved in the induction and/or activation of IL-10 producing Bregs that suppress inflammatory responses in vitro and in vivo. Here, we describe that APRIL promotes the differentiation of naïve human B cells to IL-10-producing IgA⁺ B cells. These APRIL-induced IgA⁺ B cells display a Breg phenotype and inhibit T cell and macrophage responses through IL-10 and PD-L1. Moreover, APRIL-induced IL-10 producing Bregs suppress inflammation in vivo in experimental autoimmune encephalitis (EAE) and contact hypersensitivity (CHS) models. Finally, we showed a strong correlation between APRIL and IL-10 in the inflamed synovial tissue of inflammatory arthritis patients. Collectively, these observations indicate the potential relevance of this novel APRIL-induced IgA⁺ Breg population for immune homeostasis and immunopathology.

The association of tumor necrosis factor superfamily 13 with recurrence of immunoglobulin A nephropathy in living related kidney transplantation

BACKGROUND

An increasing amount of evidence has demonstrated an association between an increase in the level of tumor necrosis factor superfamily 13 (TNFSF13) and immunoglobulin A nephropathy (IgAN) progression. We aimed to evaluate if the level of pre-transplant serum TNFSF13 is predictive of IgAN recurrence after kidney transplantation.

METHODS

This analysis was based on the clinical and laboratory data of 69 patients with IgAN who underwent first kidney transplantation with no evidence of mesangial IgA deposits in zero-time transplantation biopsy. We measured pre-transplant serum TNFSF13, total IgA, and galactose-deficient IgA1 levels.

RESULTS

The recurrence rate of IgAN over a median follow-up duration of 5.1 years was 15.9% (11/69 patients), with a mean time to the first recurrence of 1.7 years. The high pre-transplant TNFSF13 level was associated with IgAN recurrence after kidney transplantation among patients who received a graft from a living related donor.

CONCLUSIONS

This study highlights association of TNFSF13 levels in recurrent IgAN patients who undergo living related donor transplantation. Further research is needed to clarify mechanisms by which TNFSF13 affects the recurrence of IgA nephropathy.

Regulation of IgM+ B Cell Activities by Rainbow Trout APRIL Reveals Specific Effects of This Cytokine in Lower Vertebrates

Tumor necrosis factor ligand superfamily members such as B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) have been identified in mammals as key regulators of B cell homeostasis and activation. However, the immune functions of APRIL are not as well defined as those of BAFF. Furthermore, while BAFF is present in all vertebrates, APRIL is missing in some animal groups, suggesting that BAFF has compensated the functions of APRIL in these species. In this context, we thought of great interest to explore the effects of APRIL on teleost B cells, given that APRIL appears for the first time in evolution in bony fish. Thus, in this study, we have performed an extensive analysis of the effect of APRIL on B cells using rainbow trout (Oncorhynchus mykiss) as a model species. Our results demonstrate that APRIL induces a specific proliferation of IgM⁺ B cells by itself and increases IgM secretion without promoting a terminal differentiation to plasma cells. APRIL also increased the levels of surface MHC II and augmented the capacity of these cells to process antigen, effects that were exclusively exerted on IgM⁺ B cells. Although our results point to a highly conserved role of APRIL on B cell homeostasis and activation throughout evolution, some specific differential effects have been observed in fish in comparison to the effects of APRIL previously described in mammals. Finally, the effects that APRIL induces on rainbow trout IgM⁺ B cells described in this paper have been compared with those previously reported in response to BAFF.

Delayed onset of autoreactive antibody production and M2-skewed macrophages contribute to improved survival of TACI deficient MRL-Fas/Lpr mouse

Anti-B cell activating factor belonging to TNF-family (BAFF) antibody therapy is indicated for the treatment of patients with active systemic lupus erythematosus (SLE). We hypothesized that the BAFF receptor, transmembrane activator and calcium-modulator and cyclophilin interactor (TACI) may be responsible for the generation of antibody secreting plasma cells in SLE. To test this hypothesis, we generated TACI deficient MRL-Fas/Lpr (LPR-TACI−/−) mouse. TACI deficiency resulted in improved survival of MRL-Fas/Lpr mice and delayed production of anti-dsDNA and anti-SAM/RNP antibodies. There was also a delay in the onset of proteinuria and the accumulation of IgG and inflammatory macrophages (Mϕs) in the glomeruli of young LPR-TACI−/− mice compared to wild-type mice. Underscoring the role of TACI in influencing Mϕ phenotype, the transfer of Mϕs from 12-week-old LPR-TACI−/− mice to age-matched sick wild-type animals led to a decrease in proteinuria and improvement in kidney pathology. The fact that, in LPR-TACI−/− mouse a more pronounced delay was in IgM and IgG3 autoreactive antibody isotypes and the kinetics of follicular helper T (Tfh) cell-development was comparable between the littermates suggest a role for TACI in T cell-independent autoantibody production in MRL-Fas/Lpr mouse prior to the onset of T cell-dependent antibody production.

BAFF and APRIL expression as an autoimmune signature of membranous nephropathy

Background

Based 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).

Results

The 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.

Conclusions

Expression profile of BAFF and APRIL in MN is similar to that of other autoimmune disease, which affects the kidney outcomes.

Methods

Plasma 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.

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.

mTOR intersects antibody-inducing signals from TACI in marginal zone B cells

Mechanistic target of rapamycin (mTOR) enhances immunity in addition to orchestrating metabolism. Here we show that mTOR coordinates immunometabolic reconfiguration of marginal zone (MZ) B cells, a pre-activated lymphocyte subset that mounts antibody responses to T-cell-independent antigens through a Toll-like receptor (TLR)-amplified pathway involving transmembrane activator and CAML interactor (TACI). This receptor interacts with mTOR via the TLR adapter MyD88. The resulting mTOR activation instigates MZ B-cell proliferation, immunoglobulin G (IgG) class switching, and plasmablast differentiation through a rapamycin-sensitive pathway that integrates metabolic and antibody-inducing transcription programs, including NF-κB. Disruption of TACI-mTOR interaction by rapamycin, truncation of the MyD88-binding domain of TACI, or B-cell-conditional mTOR deficiency interrupts TACI signaling via NF-κB and cooperation with TLRs, thereby hampering IgG production to T-cell-independent antigens but not B-cell survival. Thus, mTOR drives innate-like antibody responses by linking proximal TACI signaling events with distal immunometabolic transcription programs.

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.

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.

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.

APRIL gene polymorphism and serum sAPRIL levels in children with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multi-factor autoimmune disorder with diverse clinical manifestations and unclear pathogenesis. Genetic components play important roles in the incidence and development of SLE. Among these, APRIL as a cytokine has roles in the stimulation and antibody production in B cells. APRIL was hypothesized to be associated with SLE. The aim of this study was to assess the involvement of the APRIL gene in SLE susceptibility in Iranian patients. A single-nucleotide polymorphism (SNP) for rs11552708 of APRIL gene was analyzed by real-time PCR in 60 SLE Iranian children and 64 healthy controls. DNA samples of patients and healthy controls were extracted from peripheral blood leukocytes by phenol-chloroform. Serum samples obtained from 45 children with SLE and 45 healthy controls were assayed by enzyme-linked immunosorbent assay (ELISA). The G/G genotype (odds ratio (OR) 0.67, 95% confidence interval (CI) 0.22-2.07; P = 0.68) and G allele (OR 0.81, 95% CI 0.25-2.56; P = 0.89) frequencies of polymorphism at codon 67 (67G) do not differ significantly in the SLE patients compared with those in the healthy controls. The serum APRIL levels in the SLE patients (mean ± SD = 29.27 ng/ml ± 20.77, range from 0 to 55.33 ng/ml) were significantly higher than those in the healthy controls (P = 0.02). Our results demonstrated that rs11552708 of the APRIL gene is not associated with SLE susceptibility in Iranian children. Likewise, these findings suggest that APRIL antagonist could be a potential therapeutic target to control SLE in children.

Impact of the B Cell Growth Factor APRIL on the Qualitative and Immunological Characteristics of Atherosclerotic Plaques

Studies on the role of B lymphocytes in atherosclerosis development, have yielded contradictory results. Whereas B lymphocyte-deficiency aggravates atherosclerosis in mice; depletion of mature B lymphocytes reduces atherosclerosis. These observations led to the notion that distinct B lymphocyte subsets have different roles. B1a lymphocytes exert an atheroprotective effect, which has been attributed to secretion of IgM, which can be deposited in atherosclerotic lesions thereby reducing necrotic core formation. Tumor necrosis factor (TNF)-family member 'A Proliferation-Inducing Ligand' (APRIL, also known as TNFSF13) was previously shown to increase serum IgM levels in a murine model. In this study, we investigated the effect of APRIL overexpression on advanced lesion formation and composition, IgM production and B cell phenotype. We crossed APRIL transgenic (APRIL-Tg) mice with ApoE knockout (ApoE-/-) mice. After a 12-week Western Type Diet, ApoE-/-APRIL-Tg mice and ApoE-/- littermates showed similar increases in body weight and lipid levels. Histologic evaluation showed no differences in lesion size, stage or necrotic area. However, smooth muscle cell (α-actin stain) content was increased in ApoE-/-APRIL-Tg mice, implying more stable lesions. In addition, increases in both plaque IgM deposition and plasma IgM levels were found in ApoE-/-APRIL-Tg mice compared with ApoE-/- mice. Flow cytometry revealed a concomitant increase in peritoneal B1a lymphocytes in ApoE-/-APRIL-Tg mice. This study shows that ApoE-/-APRIL-Tg mice have increased oxLDL-specific serum IgM levels, potentially mediated via an increase in B1a lymphocytes. Although no differences in lesion size were found, transgenic ApoE-/-APRIL-Tg mice do show potential plaque stabilizing features in advanced atherosclerotic lesions.

Characterization of Lamprey BAFF-like Gene: Evolutionary Implications

BAFF (TNF superfamily [TNFSF] 13B/Blys) and APRIL (TNFSF13) are important regulatory factors for lymphocyte activation and survival in mammals. A BAFF/APRIL-like relative called BAFF- and APRIL-like molecule (BALM) has also been identified in cartilaginous and bony fishes, and we report in this study a BAFF-like gene in lampreys. Our phylogenetic analysis of these genes and a related TNFSF12 gene called TNF-like weak inducer of apoptosis (TWEAK) suggest that, whereas an ancestral homolog of BAFF and APRIL was already present in a common ancestor of jawed and jawless vertebrates, TWEAK evolved early on in the jawed vertebrate lineage. Like mammalian BAFF and APRIL, the lamprey BAFF-like gene is expressed in T-like, B-like, and innate immune cells. The predicted protein encoded by this BAFF-like gene in lampreys exhibits higher sequence similarity with mammalian BAFF than APRIL. Correspondingly, we find BAFF orthologs in all of the jawed vertebrate representatives that we examined, although APRIL and/or BALM orthologs are not identifiable in certain jawed vertebrates. For example, BALM is not identifiable in tetrapods, and APRIL is not identifiable in several bony fishes or in birds, the latter of which also lack a TWEAK-like gene. Our analysis further suggests that a hybrid molecule called TWE-PRIL, which is a product of an in-genomic fusion between APRIL and TWEAK genes evolved early in mammalian evolution.

Characterisation of inflammatory processes in Helicobacter pylori-induced gastric lymphomagenesis in a mouse model

Gastric MALT lymphoma (GML) can be induced by Helicobacter pylori infection in BALB/c mice thymectomised at day 3 post-birth (d3Tx). This represented a unique opportunity to investigate the inflammatory process involved in the recruitment, proliferation and structuration of lymphoid infiltrates in the gastric mucosa of mice developing GML. Complementary molecular and proteomic approaches demonstrated that Th1 and Th2 cytokines were upregulated, along with activators/regulators of the lymphoid response and numerous chemokines. Interleukin-4, interferon γ, lymphotoxin-α and -β were significantly upregulated and correlated with the inflammatory scores for all the d3Tx mice. GML lesions in d3Tx mice infected with H. pylori were associated with the presence of the inflammatory response. The dysregulation of numerous members of the tumour necrosis factor superfamily was also evident and suggests that they could play an important role in GML pathology, especially in light of their ability to promote and control lymphocyte proliferation.

Pharmacological advantages of melatonin in immunosenescence by improving activity of T lymphocytes

Melatonin plays a critical role in regulating photoperiodic signals and has recently been shown to decrease immunosenescence with age. In this study, we examined whether melatonin activates T lymphocytes as major adaptive immune cells in in vitro and in vivo models. Splenocytes, CD4⁺, and naïve CD4 T lymphocytes were isolated from the spleen of BALB/c mice and the cell population patterns and mRNA profiles associated with T cell activation (CD28 and p21) and the melatonin receptor (MT1A and MT1B) were assessed. The T cell activation-related proteins Ki67 and Bcl2 were also evaluated to confirm the relationship between gene and protein levels. Our data clearly revealed that CD28, p21, MT1A, and MT1B mRNA were highly expressed in the presence of melatonin. Co-culture of CD4⁺ T lymphocyte and peritoneal macrophage 7 days after melatonin administration to young and aged mice significantly increased APRIL mRNA, suggesting induction or maintenance of T lymphocyte responses. We also found that the intracellular amount of Ki67 and Bcl2 proteins were significantly upregulated in aged CD4⁺ T lymphocytes, suggesting enhancing T cell proliferation and ling-term maintenance of memory T cells. Taken together, we conclude that melatonin supplementation may enhance immunity in aged individuals by upregulating immunosenescence indices in association with T lymphocytes and may be an attractive pharmacological candidate for aged and immunocompromised individuals.

Tumor necrosis factor superfamily member APRIL contributes to fibrotic scar formation after spinal cord injury

Background

Fibrotic scar formation contributes to the axon growth-inhibitory environment that forms following spinal cord injury (SCI). We recently demonstrated that depletion of hematogenous macrophages led to a reduction in fibrotic scar formation and increased axon growth after SCI. These changes were associated with decreased TNFSF13 (a proliferation inducing ligand (APRIL)) expression, but the role of APRIL in fibrotic scar formation after SCI has not been directly investigated. Thus, the goal of this study was to determine the role of APRIL in fibrotic scar formation after SCI.

Methods

APRIL knockout and wild-type mice received contusive SCI and were assessed for inflammatory cytokine/chemokine expression, leukocyte infiltration, fibrotic scar formation, axon growth, and cell proliferation.

Results

Expression of APRIL and its receptor BCMA is increased following SCI, and genetic deletion of APRIL led to reduced fibrotic scar formation and increased axon growth. However, the fibrotic scar reduction in APRIL KO mice was not a result of changes in fibroblast or astrocyte proliferation. Rather, APRIL knockout mice displayed reduced TNFα and CCL2 expression and less macrophage and B cell infiltration at the injury site.

Conclusions

Our data indicate that APRIL contributes to fibrotic scar formation after SCI by mediating the inflammatory response.

The Origin and Activities of IgA1-Containing Immune Complexes in IgA Nephropathy

IgA nephropathy (IgAN) is the most common primary glomerulonephritis, frequently leading to end-stage renal disease, as there is no disease-specific therapy. IgAN is diagnosed from pathological assessment of a renal biopsy specimen based on predominant or codominant IgA-containing immunodeposits, usually with complement C3 co-deposits and with variable presence of IgG and/or IgM. The IgA in these renal deposits is galactose-deficient IgA1, with less than a full complement of galactose residues on the O-glycans in the hinge region of the heavy chains. Research from the past decade led to the definition of IgAN as an autoimmune disease with a multi-hit pathogenetic process with contributing genetic and environmental components. In this process, circulating galactose-deficient IgA1 (autoantigen) is bound by antiglycan IgG or IgA (autoantibodies) to form immune complexes. Some of these circulating complexes deposit in glomeruli, and thereby activate mesangial cells and induce renal injury through cellular proliferation and overproduction of extracellular matrix components and cytokines/chemokines. Glycosylation pathways associated with production of the autoantigen and the unique characteristics of the corresponding autoantibodies in patients with IgAN have been uncovered. Complement likely plays a significant role in the formation and the nephritogenic activities of these complexes. Complement activation is mediated through the alternative and lectin pathways and probably occurs systemically on IgA1-containing circulating immune complexes as well as locally in glomeruli. Incidence of IgAN varies greatly by geographical location; the disease is rare in central Africa but accounts for up to 40% of native-kidney biopsies in eastern Asia. Some of this variation may be explained by genetically determined influences on the pathogenesis of the disease. Genome-wide association studies to date have identified several loci associated with IgAN. Some of these loci are associated with the increased prevalence of IgAN, whereas others, such as deletion of complement factor H-related genes 1 and 3, are protective against the disease. Understanding the molecular mechanisms and genetic and biochemical factors involved in formation and activities of pathogenic IgA1-containing immune complexes will enable the development of future disease-specific therapies as well as identification of non-invasive disease-specific biomarkers.

New developments in the genetics, pathogenesis, and therapy of IgA nephropathy

Recent years have brought notable progress in the field of IgA nephropathy. Here, we highlight important new directions and latest developments, including successful discovery of several genetic susceptibility loci, formulation of the multihit pathogenesis model, introduction of the Oxford pathology scoring system, and formalization of the Kidney Disease Improving Global Outcomes (KDIGO) consensus treatment guidelines. We focus on the latest genetic findings that confirm a strong contribution of inherited factors and explain some of the geoethnic disparities in disease susceptibility. Most IgA nephropathy susceptibility loci discovered to date encode genes involved in the maintenance of the intestinal epithelial barrier and response to mucosal pathogens. The concerted pattern of interpopulation allelic differentiation across all genetic loci parallels the disease prevalence and correlates with variation in local pathogens, suggesting that multilocus adaptation might have shaped the present-day landscape of IgA nephropathy. Importantly, the 'Intestinal Immune Network for IgA Production' emerged as one of the new targets for potential therapeutic intervention. We place these findings in the context of the multihit pathogenesis model and existing knowledge of IgA immunobiology. Lastly, we provide our perspective on the existing treatment options, discuss areas of clinical uncertainty, and outline ongoing clinical trials and translational studies.

MyD88-dependent pro-inflammatory activity in Vi polysaccharide vaccine against typhoid promotes Ab switching to IgG

Vi capsular polysaccharide is currently in use as a vaccine against human typhoid caused by Salmonella Typhi. The vaccine efficacy correlates with IgG anti-Vi Abs. We have recently reported that Vi can generate inflammatory responses through activation of the TLR2/TLR1 complex. In the present study, we show that immunization with Vi produces IgM as well as IgG Abs in wild type mice. This ability is not compromised in mice deficient in T cells. However, immunization of mice lacking the TLR adaptor protein, MyD88, with Vi elicits only IgM Abs. These results suggest that MyD88-dependent pro-inflammatory ability of the Vi vaccine might be vital in generating IgG Abs with this T-independent Ag.

Identification of the sAPRIL binding peptide and its growth inhibition effects in the colorectal cancer cells

BACKGROUND

A proliferation-inducing ligand (APRIL) is a member of the tumor necrosis factor (TNF) super family. It binds to its specific receptors and is involved in multiple processes during tumorigenesis and tumor cells proliferation. High levels of APRIL expression are closely correlated to the growth, metastasis, and 5-FU drug resistance of colorectal cancer. The aim of this study was to identify a specific APRIL binding peptide (BP) able to block APRIL activity that could be used as a potential treatment for colorectal cancer.

METHODS

A phage display library was used to identify peptides that bound selectively to soluble recombinant human APRIL (sAPRIL). The peptides with the highest binding affinity for sAPRIL were identified using ELISA. The effects of sAPRIL-BP on cell proliferation and cell cycle/apoptosis in vitro were evaluated using the CCK-8 assay and flow cytometry, respectively. An in vivo mouse model of colorectal cancer was used to determine the anti-tumor efficacy of the sAPRIL-BP.

RESULTS

Three candidate peptides were characterized from eight phage clones with high binding affinity for sAPRIL. The peptide with the highest affinity was selected for further characterization. The identified sAPRIL-BP suppressed tumor cell proliferation and cell cycle progression in LOVO cells in a dose-dependent manner. In vivo in a mouse colorectal challenge model, the sAPRIL-BP reduced the growth of tumor xenografts in nude mice by inhibiting proliferation and inducing apoptosis intratumorally. Moreover, in an in vivo metastasis model, sAPRIL-BP reduced liver metastasis of colorectal cancer cells.

CONCLUSIONS

sAPRIL-BP significantly suppressed tumor growth in vitro and in vivo and might be a candidate for treating colorectal cancers that express high levels of APRIL.

Profile of atacicept and its potential in the treatment of systemic lupus erythematosus

The importance of B cell activating factors in the generation of autoantibodies in patients with systemic lupus erythematosus (SLE) is now recognized. The two key factors, known as BAFF and APRIL, produced by a variety of cells including monocytes, dendritic cells and T cells, also help to regulate B cell maturation, function and survival. Biologic agents that block these factors have now been developed and tried out in large scale clinical trials in SLE patients. Benlysta which blocks BAFF has met some of its end points in clinical trials and is approved for use in patients with skin and joint disease who have failed conventional drugs. In contrast, clinical trials using atacicept which blocks both BAFF and APRIL have been more challenging to interpret. An early study in lupus nephritis was, mistakenly, abandoned due to serious infections thought to be linked to the biologic when in fact the dramatic fall in the immunoglobulin levels took place when the patients were given mycophenolate, prior to the introduction of the atacicept. Likewise the higher dose arm (150 mgm) of a flare prevention study was terminated prematurely when 2 deaths occurred. However, the mortality rate in this study was identical to that seen in the Benlysta studies and a post hoc analysis found a highly significant benefit for the 150mgm arm compared to the lower dose (75 mgm) and placebo arms. Other trials with both Benlysta and atacicept are on-going.

Evaluation of B lymphocyte stimulator and a proliferation inducing ligand as candidate biomarkers in lupus nephritis based on clinical and histopathological outcome following induction therapy

Objectives

Lupus nephritis (LN) is a major cause of morbidity in patients with systemic lupus erythematosus (SLE). B cells have a central role in the pathogenesis of SLE. B lymphocyte stimulator (BLyS) and a proliferation inducing ligand (APRIL) are pivotal in B cell homeostasis. We aimed to investigate a potential role of serum BLyS and APRIL as biomarkers in LN, especially as predictors of treatment response.

Methods

Sixty-four patients with active LN (52 proliferative lupus nephritis (PLN); 12 membranous LN) were included. Renal biopsies were performed at baseline and after immunosuppressive treatment. Serum levels of BLyS, APRIL and autoantibodies were measured on both biopsy occasions and in 64 individually matched controls. Renal biopsies were evaluated using the International Society of Nephrology/Renal Pathology Society classification, and scored for Activity Index and Chronicity Index. Clinical responders (CR) were required to have ≥50% reduction in proteinuria, normal or improved renal function, and inactive urinary sediment. Histopathological responders (HR) were required to have ≥50% improvement in Activity Index.

Results

Baseline BLyS levels were significantly higher in LN patients compared with controls (p<0.001) and remained unchanged following induction treatment. APRIL levels were significantly higher in patients compared with controls at baseline (p=0.005) and decreased following treatment (p<0.001). Among PLN patients, APRIL levels decreased significantly only in responders (CR: p=0.009; HR: p=0.01). Baseline BLyS levels <1.5 ng/mL predicted treatment response, attaining a positive predictive value of 92% for CR with PLN at baseline.

Conclusions

BLyS and APRIL were affected differently by immunosuppression; BLyS levels remained unchanged following therapy while APRIL levels decreased. Despite unchanged BLyS levels following therapy, low baseline levels predicted both clinical and histopathological improvement. Our data support APRIL as a candidate biomarker of renal disease activity in lupus patients with proliferative glomerulonephritis and point to low baseline BLyS levels predicting treatment response in LN, especially in PLN.

Cellular signaling and production of galactose-deficient IgA1 in IgA nephropathy, an autoimmune disease

Immunoglobulin A (IgA) nephropathy (IgAN), the leading cause of primary glomerulonephritis, is characterized by IgA1-containing immunodeposits in the glomeruli. IgAN is a chronic disease, with up to 40% of patients progressing to end-stage renal disease, with no disease-specific treatment. Multiple studies of the origin of the glomerular immunodeposits have linked elevated circulating levels of aberrantly glycosylated IgA1 (galactose-deficient in some O-glycans; Gd-IgA1) with formation of nephritogenic Gd-IgA1-containing immune complexes. Gd-IgA1 is recognized as an autoantigen in susceptible individuals by anti-glycan autoantibodies, resulting in immune complexes that may ultimately deposit in the kidney and induce glomerular injury. Genetic studies have revealed that an elevated level of Gd-IgA1 in the circulation of IgAN patients is a hereditable trait. Moreover, recent genome-wide association studies have identified several immunity-related loci that associated with IgAN. Production of Gd-IgA1 by IgA1-secreting cells of IgAN patients has been attributed to abnormal expression and activity of several key glycosyltransferases. Substantial evidence is emerging that abnormal signaling in IgA1-producing cells is related to the production of Gd-IgA1. As Gd-IgA1 is the key autoantigen in IgAN, understanding the genetic, biochemical, and environmental aspects of the abnormal signaling in IgA1-producing cells will provide insight into possible targets for future disease-specific therapy.

The genetics and immunobiology of IgA nephropathy

IgA nephropathy (IgAN) represents the leading cause of kidney failure among East Asian populations and the most frequent form of primary glomerulonephritis among Europeans. Patients with IgAN develop characteristic IgA1-containing immune complexes that deposit in the glomerular mesangium, producing progressive kidney injury. Recent studies define IgAN as an autoimmune trait of complex architecture with a strong genetic determination. This Review summarizes new insights into the role of the O-glycosylation pathway, anti-glycan immune response, mucosal immunity, antigen processing and presentation, and the alternative complement pathway in the pathogenesis of IgAN.

Increased serum APRIL differentially correlates with distinct cytokine profiles and disease activity in systemic lupus erythematosus patients

Cytokines play an important role in the pathogenesis of systemic lupus erythematosus (SLE). Among the cytokines that regulate B cell homeostasis is a proliferation-inducing ligand (APRIL). This study aimed to determine whether serum levels of APRIL are raised in patients with SLE and correlate with disease activity or proinflammatory cytokines production, or both. Serum APRIL, interleukin-17 (IL-17), IL-4 and interferon gamma (IFN-γ) levels were measured in forty patients with SLE and 30 healthy controls. Disease activity was assessed by SLE disease activity index (SLEDAI), and results were correlated with serum APRIL levels. Serum APRIL levels were significantly higher in patients with SLE than in healthy controls. Positive correlation was found between serum APRIL levels and total SLEDAI score and anti-dsDNA antibody titers. Moreover, serum APRIL levels was significantly higher in patients with arthritis, mucocutaneous manifestations and proteinuria. APRIL is increased in patients with active SLE accompanying the increase of IL-17 and IFN-γ. Significant positive correlations between serum levels of APRIL and IL-17 and IFN-γ and a negative correlation between serum levels of APRIL and IL-4 were found. The results suggest that APRIL may be an important marker of disease activity in patients with SLE. We provide the analyses of APRIL levels in patients with SLE, suggesting new tools for the diagnosis, prognosis and possible therapeutic management of SLE.

APRIL mediates peritoneal B-1 cell homeostasis

BLyS (B lymphocyte stimulator) family cytokines and receptors play key roles in B-2 cell maturation and survival, but their importance for B-1 cells remains less clear. Here we use knockout mice to show that APRIL (A proliferation-inducing ligand), but not BLyS, plays a role in peritoneal B-1 cell maintenance. APRIL likely exerts its effects on peritoneal B-1 cells through binding to HSPG (heparan sulfate proteoglycans) rather than to the TACI (transmembrane activator and cyclophilin ligand interactor) receptor. Finally, we show that peritoneal macrophages express high levels of APRIL message, and are a likely local source of the cytokine in this anatomic locale.

Future prospects in biologic therapy for systemic lupus erythematosus

With the approval by the FDA in 2011 of a biologic agent (namely belimumab) for the treatment of systemic lupus erythematosus (SLE), optimism abounds that additional biologic (and nonbiologic) agents will be similarly endorsed. Given the numerous immune-based abnormalities associated with SLE, the potential therapeutic targets for biologic agents and the candidate biologic approaches are also numerous. These approaches include: biologic agents that promote B-cell depletion, B-cell inactivation, or the generation of regulatory B cells; biologic agents that induce T-cell tolerance, block T-cell activation and differentiation, or alter T-cell trafficking; biologic agents that target the B-cell activating factor (BAFF) axis, type I interferons, IL-6 and its receptor, or TNF; and the adoptive transfer of ex vivo-generated regulatory T cells. Owing to the great heterogeneity inherent to SLE, no single approach should be expected to be effective in all patients. As our understanding of the pathogenic mechanisms of SLE continues to expand, additional therapeutic targets and approaches will undoubtedly be identified and should be fully exploited.

Genetic studies of IgA nephropathy: what have we learned from genome-wide association studies

Primary IgA nephropathy (IgAN) is the most common glomerulonephritis in the world. It is most common in Asian populations, followed by Caucasians, yet relatively infrequent amongst African populations. The striking difference in the prevalence of IgAN between world populations, together with the known familial aggregation of disease, suggests an inherited mechanism. Recently three genome-wide association studies (GWAS) of IgAN have identified seven susceptibility loci, providing initial insight into the genetic architecture of this trait. While genetic studies of complex traits are challenging, applying new techniques and methods of analysis, especially Next-Generation Sequencing, will push the genetic studies of IgAN forward.

To target or not to target APRIL in systemic lupus erythematosus: that is the question!

Among the cytokines that regulate B-cell homeostasis are the TNF-like ligands B-lymphocyte stimulator (BLyS; also B-cell activation factor) and a proliferation-inducing ligand (APRIL). BLyS and APRIL share two receptors; that is, B-cell maturation antigen and transmembrane activator and CAML interactor. Therapeutic approaches using biologics are limited for treatment of lupus patients. One previously approved drug is belimumab, which antagonizes the B-cell stimulator BLyS. Atacicept, another biologic inhibiting BLyS and APRIL, was terminated for serious adverse events - raising the question of whether APRIL should be neutralized in autoimmune diseases.

Roles for BLyS family members in meeting the distinct homeostatic demands of innate and adaptive B cells

B-1 and B-2 B cell populations have different progenitors, receptor diversity, anatomic location, and functions – suggesting vastly differing requisites for homeostatic regulation. There is evidence that the B lymphocyte stimulator (BLyS) family of cytokines and receptors, key factors in the homeostatic regulation of B-2 B cell subsets, is also a major player in the B-1 compartment. Here we review the development and differentiation of these two primary B cell lineages and their immune functions. We discuss evidence that BLyS or a proliferation-inducing ligand (APRIL) availability in different anatomic sites, coupled with signature BLyS receptor expression patterns on different B cell subsets, may be important for homeostatic regulation of B-1 as well as B-2 populations. Finally, we extend our working model of B cell homeostasis to integrate B-1s.

Biologic differences between various inhibitors of the BLyS/BAFF pathway: should we expect differences between belimumab and other inhibitors in development?

For the first time in more than 50 years, the US Food and Drug Administration has approved a drug specifically for the treatment of systemic lupus erythematosus (SLE). This drug, belimumab, is a monoclonal antibody that neutralizes the B-cell survival factor, B-lymphocyte stimulator (BLyS). Although belimumab has demonstrated a very favorable safety profile, many SLE patients have failed to clinically improve from belimumab therapy. Three additional BLyS antagonists (atacicept, blisibimod, tabalumab) are currently undergoing clinical testing. These antagonists subtly differ from belimumab in their biologic targets, and each is administered through a route (subcutaneous) that differs from the route through which belimumab is currently delivered (intravenous). Whether these differences will have meaningful consequences for efficacy and safety remains to be determined.

Genome-wide scan identifies variant in TNFSF13 associated with serum IgM in a healthy Chinese male population

IgM provides a first line of defense during microbial infections. Serum IgM levels are detected routinely in clinical practice. And IgM is a genetically complex trait. We conducted a two-stage genome-wide association study (GWAS) to identify genetic variants affecting serum IgM levels in a Chinese population of 3495, including 1999 unrelated subjects in the first stage and 1496 independent individuals in the second stage. Our data show that a common single nucleotide polymorphism (SNP), rs11552708 located in the TNFSF13 gene was significantly associated with IgM levels (p = 5.00×10⁻⁷ in first stage, p = 1.34×10⁻³ in second stage, and p = 4.22×10⁻⁹ when combined). Besides, smoking was identified to be associated with IgM levels in both stages (P<0.05), but there was no significant interaction between smoking and the identified SNP (P>0.05). It is suggested that TNFSF13 may be a susceptibility gene affecting serum IgM levels in Chinese male population.

Pathogenesis of immunoglobulin A nephropathy: recent insight from genetic studies

Recent genome-wide association studies (GWAS) have identified multiple susceptibility loci for immunoglobulin A nephropathy (IgAN), the most common form of glomerulonephritis, implicating independent defects in adaptive immunity (three loci on chromosome 6p21 in the MHC region), innate immunity (8p23 DEFA locus, 17p23 TNFSF13 locus, 22q12 HORMAD2 locus), and the alternative complement pathway (1q32 CFH/CFHR locus). In geospatial analysis of 85 populations, a genetic risk score based on the replicated GWAS loci is highest in Asians, intermediate in Europeans, and lowest in Africans, capturing the known difference in prevalence among world populations. The genetic risk score also uncovered a previously unsuspected increased prevalence of IgAN-attributable kidney failure in Northern Europe. The IgAN risk alleles have opposing effects on many immune-mediated diseases, suggesting that selection has contributed to variation in risk allele frequencies among different populations. Incorporating genetic, immunologic, and biochemical data, we present a multistep pathogenesis model that provides testable hypotheses for dissecting the mechanisms of disease.

Dispensability of APRIL to the development of systemic lupus erythematosus in NZM 2328 mice

OBJECTIVE

To determine the role of APRIL in the development of systemic lupus erythematosus (SLE) in mice.

METHODS

Wild-type (WT) NZM 2328, NZM. April(-/-) , NZM.Baff(-/-) , and NZM.Baff(-/-) .April(-/-) mice were evaluated for lymphocyte phenotype by flow cytometry, for serum total IgG and IgG autoantibody levels by enzyme-linked immunosorbent assay, for glomerular deposition of IgG and C3 by immunofluorescence, for renal changes by histopathology, and for clinical disease by laboratory assessment (severe proteinuria).

RESULTS

In comparison to WT mice, NZM.April(-/-) mice harbored increased spleen B cells, T cells, and plasma cells (PCs), increased serum levels of IgG antichromatin antibodies, and decreased numbers of bone marrow (BM) PCs. Glomerular deposition of IgG and C3 was similar in NZM.April(-/-) mice and WT mice, renal changes on histopathology tended to be more severe in NZM.April(-/-) mice than in WT mice, and development of clinical disease was identical in NZM.April(-/-) mice and WT mice. BM (but not spleen) PCs and serum IgG antichromatin and anti-double-stranded DNA antibody levels were lower in NZM.Baff(-/-) .April(-/-) mice than in NZM.Baff(-/-) mice, whereas renal immunopathology in each cohort was equally mild.

CONCLUSION

APRIL is dispensable for the development of full-blown SLE in NZM mice. Moreover, the elimination of both APRIL and BAFF had no discernible effect on the development of renal immunopathology or clinical disease beyond that of elimination of BAFF alone. The reduction in BM PCs in hosts doubly deficient in APRIL and BAFF beyond that in hosts deficient only in BAFF raises concern that combined antagonism of APRIL and BAFF may lead to greater immunosuppression without a concomitant increase in therapeutic efficacy.

The TNF family member APRIL promotes colorectal tumorigenesis

The tumor necrosis factor (TNF) family member APRIL (A proliferation inducing ligand) is a disease promoter in B-cell malignancies. APRIL has also been associated with a wide range of solid malignancies, including colorectal cancer (CRC). As evidence for a supportive role of APRIL in solid tumor formation was still lacking, we studied the involvement of APRIL in CRC. We observed that ectopic APRIL expression exacerbates the number and size of adenomas in Apc(Min) mice and in a mouse model for colitis-associated colon carcinogenesis. Furthermore, knockdown of APRIL in primary spheroid cultures of colon cancer cells and both mouse and human CRC cell lines reduced tumor clonogenicity and in vivo outgrowth. Taken together, our data therefore indicate that both tumor-derived APRIL and APRIL produced by non-tumor cells is supportive in colorectal tumorigenesis.

Serum BAFF and APRIL levels in patients with IgG4-related disease and their clinical significance

INTRODUCTION

B cell-activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) play a crucial role in B cell development, survival, and antibody production. Here we analyzed the serum levels of BAFF and APRIL and their respective clinical associations in patients with an immunoglobulin (Ig) G4-related disease (IgG4-RD).

METHODS

We measured serum levels of BAFF and APRIL in patients with IgG4-RD, primary Sjögren's syndrome (pSS), and healthy individuals. Serum BAFF and APRIL levels in IgG4-RD were assessed for correlations with serological parameters, including Ig, particularly IgG4, and the number of affected organs. Serum BAFF and APRIL levels in IgG4-RD were monitored during glucocorticoid (GC) therapy.

RESULTS

Serum BAFF and APRIL levels in patients with IgG4-RD were significantly higher (P < 0.01) than in healthy individuals. The BAFF levels of patients with IgG4-RD were comparable to those of patients with pSS. Although clinical parameters, such as serum IgG4 and the number of affected organs, were not correlated with the levels of BAFF, serum APRIL levels were inversely correlated with serum IgG4 levels (r = -0.626, P < 0.05). While serum BAFF levels decreased following GC therapy, serum APRIL levels increased during follow-up.

CONCLUSION

These results indicate that BAFF and APRIL might be useful markers for predicting disease activity in IgG4-RD. Further studies are needed to elucidate the role of BAFF and APRIL in the pathogenesis of IgG4-RD.