Mycophenolic acid and 6-mercaptopurine both inhibit B-cell proliferation in granulomatosis with polyangiitis patients, whereas only mycophenolic acid inhibits B-cell IL-6 production

Defects in B-lymphopoiesis and B-cell maturation underlie prolonged B-cell depletion in ANCA-associated vasculitis

OBJECTIVES

B-cell depletion time after rituximab (RTX) treatment is prolonged in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) compared with other autoimmune diseases. We investigated central and peripheral B-cell development to identify the causes for the defect in B-cell reconstitution after RTX therapy.

METHODS

We recruited 91 patients with AAV and performed deep phenotyping of the peripheral and bone marrow B-cell compartment by spectral flow and mass cytometry. B-cell development was studied by in vitro modelling and the role of BAFF receptor by quantitative PCR, western blot analysis and in vitro assays.

RESULTS

Treatment-naïve patients with AAV showed low transitional B-cell numbers, suggesting impaired B-lymphopoiesis. We analysed bone marrow of treatment-naïve and RTX-treated patients with AAV and found reduced B-lymphoid precursors. In vitro modelling of B-lymphopoiesis from AAV haematopoietic stem cells showed intact, but slower and reduced immature B-cell development. In a subgroup of patients, after RTX treatment, the presence of transitional B cells did not translate in replenishment of naïve B cells, suggesting an impairment in peripheral B-cell maturation. We found low BAFF-receptor expression on B cells of RTX-treated patients with AAV, resulting in reduced survival in response to BAFF in vitro.

CONCLUSIONS

Prolonged depletion of B cells in patients with AAV after RTX therapy indicates a B-cell defect that is unmasked by RTX treatment. Our data indicate that impaired bone marrow B-lymphopoiesis results in a delayed recovery of peripheral B cells that may be further aggravated by a survival defect of B cells. Our findings contribute to the understanding of AAV pathogenesis and may have clinical implications regarding RTX retreatment schedules and immunomonitoring after RTX therapy.

Cellular Immunobiology and Molecular Mechanisms in Alloimmunity-Pathways of Immunosuppression

Current maintenance immunosuppression commonly comprises a synergistic combination of tacrolimus as calcineurin inhibitor (CNI), mycophenolic acid, and glucocorticoids. Therapy is often individualized by steroid withdrawal or addition of belatacept or inhibitors of the mechanistic target of rapamycin. This review provides a comprehensive overview of their mode of action, focusing on the cellular immune system. The main pharmacological action of CNIs is suppression of the interleukin-2 pathway that leads to inhibition of T cell activation. Mycophenolic acid inhibits the purine pathway and subsequently diminishes T and B cell proliferation but also exerts a variety of effects on almost all immune cells, including inhibition of plasma cell activity. Glucocorticoids exert complex regulation via genomic and nongenomic mechanisms, acting mainly by downregulating proinflammatory cytokine signatures and cell signaling. Belatacept is potent in inhibiting B/T cell interaction, preventing formation of antibodies; however, it lacks the potency of CNIs in preventing T cell-mediated rejections. Mechanistic target of rapamycin inhibitors have strong antiproliferative activity on all cell types interfering with multiple metabolic pathways, partly explaining poor tolerability, whereas their superior effector T cell function might explain their benefits in the case of viral infections. Over the past decades, clinical and experimental studies provided a good overview on the underlying mechanisms of immunosuppressants. However, more data are needed to delineate the interaction between innate and adaptive immunity to better achieve tolerance and control of rejection. A better and more comprehensive understanding of the mechanistic reasons for failure of immunosuppressants, including individual risk/benefit assessments, may permit improved patient stratification.

Bioequivalue of two mycophenolate sodium enteric-coated tablets and the drug monitoring based on limited sampling strategy: A single-center, randomized, open-label, three-period, reference-replicated, crossover study

OBJECTIVE

A mycophenolate sodium enteric-coated tablet has shown a satisfying anti-rejection effect in patients receiving solid organ transplantation. The current study evaluated the bioequivalence between the test (Ruiyirong®) vs. reference (Myfortic®) formulations by exploring equations for predicting their area under the concentration-time curve (AUC) using a limited sampling strategy in healthy subjects.

METHODS

Forty-eight healthy Chinese subjects were randomized into three administration sequences (test-reference-reference, reference-reference-test, and reference-test-reference) to receive the Ruiyirong or Myfortic treatment on days 1, 8, and 15.

RESULTS

The 90% confidential interval (CI) of the geometric mean ratios (test/reference) of maximum plasma concentration (Cmax), the AUC from time 0 to the last timepoint (AUC0-t), and the AUC from 0 to infinity (AUC0-∞) was 92.90%-110.57%, 96.91%- 101.80%, and 96.71%-101.84%, respectively. All these values fell into the bioequivalence criteria of 80.00%-125.00% (based on the criteria of the Food and Drug Administration). The adverse events were 10.4% in Ruiyirong test group and 14.6% in Myfortic reference group. Eight equations for estimating the AUC of the Ruiyirong test and Myfortic reference formulations were evaluated; most of them worked well with the R-value >0.8. Among the four chosen equations, the intragroup verification exhibited a high agreement with the R-value ranging from 0.857 to 0.971 and with the low predictive error (PE > 5% with absolute PE > 15%). Meanwhile, the intergroup verification indicated a high inter-agreement with the R-value ranging from 0.896 to 0.974 (all P < 0.001).

CONCLUSION

The Ruiyirong test vs. Myfortic reference formulations meet the bioequivalent criteria and are well tolerated. The further linear regression analysis explores eight equations predicting the AUC value and the chosen four equations for the Ruiyirong test and Mayfortic reference formulations are interchangeable.

Perspectives on Mycophenolate Mofetil in the Management of Autoimmunity

Before becoming a cornerstone in the treatment of numerous immune-mediated diseases, mycophenolate mofetil (MMF) was first introduced as an immunosuppressive agent in transplant immunology and later received the attention of rheumatologists and clinicians involved in the management of autoimmune diseases. MMF is now a widespread immunosuppressive drug for the treatment of several conditions, including lupus nephritis, interstitial lung disease associated with systemic sclerosis, and anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis while being efficacious also as rescue therapy in various orphan diseases, including dermatomyositis and IgA-associated nephropathy. Similarly, case reports or series support a possible use of MMF in other rare autoimmune diseases. Beyond modulating lymphocyte activation, MMF acts on other immune and non-immune cells and these effects may explain the therapeutic profile of this medication. The effects of MMF are broadly characterized by the impact on the immune system and the antiproliferative and antifibrotic changes induced. In this latter case, mechanistic data on fibroblasts may in the future allow to reevaluate the use of MMF in selected patients with inflammatory arthritis or systemic sclerosis. Attention must be paid towards the possible occurrence of adverse events, such as gastrointestinal complaints and teratogenicity, while the risk of infections and cancer related to MMF needs to be further investigated.

Infections after organ transplantation and immune response

Organ transplantation has provided another chance of survival for end-stage organ failure patients. Yet, transplant rejection is still a main challenging factor. Immunosuppressive drugs have been used to avoid rejection and suppress the immune response against allografts. Thus, immunosuppressants increase the risk of infection in immunocompromised organ transplant recipients. The infection risk reflects the relationship between the nature and severity of immunosuppression and infectious diseases. Furthermore, immunosuppressants show an immunological impact on the genetics of innate and adaptive immune responses. This effect usually reactivates the post-transplant infection in the donor and recipient tissues since T-cell activation has a substantial role in allograft rejection. Meanwhile, different infections have been found to activate the T-cells into CD₄⁺ helper T-cell subset and CD₈⁺ cytotoxic T-lymphocyte that affect the infection and the allograft. Therefore, the best management and preventive strategies of immunosuppression, antimicrobial prophylaxis, and intensive medical care are required for successful organ transplantation. This review addresses the activation of immune responses against different infections in immunocompromised individuals after organ transplantation.

Translational implications of humoral and cellular immune dysfunction in granulomatosis with polyangiitis

Granulomatosis with polyangiitis (GPA) is a rare systemic ANCA (Anti-neutrophil cytoplasmic antibodies) associated vasculitis (AAV). In the last couple of decades, GPA has emerged as a disease of concern due to rapid increase in the prevalence and incidence especially in developing countries. Unknown aetiology and rapid progression have made GPA a critical disease. Thus, establishing specific tools to facilitate early and faster disease diagnosis and efficient disease management has immense importance. GPA may develop in genetically predisposed individuals on receiving the external stimulus (i.e. microbial pathogen, pollutant etc.) that triggers the immune response. B-cell activating factor (BAFF) produced by the neutrophils, promotes the B-cell maturation and survival which leads to increased ANCA production. Abnormal B-cell and T-cell proliferation and their cytokine response plays a major role in disease pathogenesis and granuloma formation. ANCA interacts with neutrophils and induces the neutrophil extracellular traps (NETs) formation and reactive oxygen species (ROS) production which leads to the endothelial cell injury. This review article summarizes the critical pathological events and how cytokines and immune cells shape the GPA pathogenesis. Decoding this complex network would facilitate in developing tools for diagnosis, prognosis and disease management. Recently developed specific monoclonal antibodies (MAbs) targeting cytokines and immune cells are being used for safer treatment and achieving longer remission.

New Insights into Pathogenesis and Treatment of ANCA-Associated Vasculitis: Autoantibodies and Beyond

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a group of rare systemic diseases affecting small-caliber vessels. The damage caused by AAV mainly involves the lung and kidneys. AAV includes three different types: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). Although the different phenotypic forms of AAV share common features, recent studies have shown that there are significant differences in terms of pathogenetic mechanisms involving both the adaptive and innate immune systems. Advances in our understanding of pathogenesis have enabled the development of immuno-targeted therapies. This review illustrates the characteristics of the various forms of AAV and the new therapies available for this disease that can have lethal consequences if left untreated.

B cells in autoimmune hepatitis: bystanders or central players?

B cells are central for the adaptive immune system to mount successful immune responses not only as antibody producers but also as regulators of cellular immunity. These multifaceted features are also reflected in autoimmunity where autoreactive B cells can fuel disease by production of cytotoxic autoantibodies, presentation of autoantigens to autoreactive T cells, and secretion of cytokines and chemokines that either promote detrimental immune activation or impair regulatory T and B cells. The role of B cells and autoantibodies in autoimmune hepatitis (AIH) have been controversially discussed, with typical autoantibodies and hypergammaglobulinemia indicating a key role, while strong HLA class II association suggests T cells as key players. In this review, we summarize current knowledge on B cells in AIH and how different B cell subpopulations may drive AIH progression beyond autoantibodies. We also discuss recent findings of B cell-directed therapies in AIH.

Implantable Immunosuppressant Delivery to Prevent Rejection in Transplantation

An innovative immunosuppressant with a minimally invasive delivery system has emerged in the biomedical field. The application of biodegradable and biocompatible polymer forms, such as hydrogels, scaffolds, microspheres, and nanoparticles, in transplant recipients to control the release of immunosuppressants can minimize the risk of developing unfavorable conditions. In this review, we summarized several studies that have used implantable immunosuppressant delivery to release therapeutic agents to prolong allograft survival. We also compared their applications, efficacy, efficiency, and safety/side effects with conventional therapeutic-agent administration. Finally, challenges and the future prospective were discussed. Collectively, this review will help relevant readers understand the different approaches to prevent transplant rejection in a new era of therapeutic agent delivery.

SARS-CoV-2 Nsp14 protein associates with IMPDH2 and activates NF-κB signaling

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to NF-κB activation and induction of pro-inflammatory cytokines, though the underlying mechanism for this activation is not fully understood. Our results reveal that the SARS-CoV-2 Nsp14 protein contributes to the viral activation of NF-κB signaling. Nsp14 caused the nuclear translocation of NF-κB p65. Nsp14 induced the upregulation of IL-6 and IL-8, which also occurred in SARS-CoV-2 infected cells. IL-8 upregulation was further confirmed in lung tissue samples from COVID-19 patients. A previous proteomic screen identified the putative interaction of Nsp14 with host Inosine-5'-monophosphate dehydrogenase 2 (IMPDH2), which is known to regulate NF-κB signaling. We confirmed the Nsp14-IMPDH2 protein interaction and identified that IMPDH2 knockdown or chemical inhibition using ribavirin (RIB) and mycophenolic acid (MPA) abolishes Nsp14- mediated NF-κB activation and cytokine induction. Furthermore, IMPDH2 inhibitors (RIB, MPA) or NF-κB inhibitors (bortezomib, BAY 11-7082) restricted SARS-CoV-2 infection, indicating that IMPDH2-mediated activation of NF-κB signaling is beneficial to viral replication. Overall, our results identify a novel role of SARS-CoV-2 Nsp14 in inducing NF-κB activation through IMPDH2 to promote viral infection.

B Lineage Cells in ANCA-Associated Vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic autoimmune disease that affects small sized blood vessels and can lead to serious complications in the lungs and kidneys. The prominent presence of ANCA autoantibodies in this disease implicates B cells in its pathogenesis, as these are the precursors of the ANCA-producing plasma cells (PCs). Further evidence supporting the potential role of B lineage cells in vasculitis are the increased B cell cytokine levels and the dysregulated B cell populations in patients. Confirmation of the contribution of B cells to pathology arose from the beneficial effect of anti-CD20 therapy (i.e., rituximab) in AAV patients. These anti-CD20 antibodies deplete circulating B cells, which results in amelioration of disease. However, not all patients respond completely, and this treatment does not target PCs, which can maintain ANCA production. Hence, it is important to develop more specific therapies for AAV patients. Intracellular signalling pathways may be potential therapeutic targets as they can show (disease-specific) alterations in certain B lineage cells, including pathogenic B cells, and contribute to differentiation and survival of PCs. Preliminary data on the inhibition of certain signalling molecules downstream of receptors specific for B lineage cells show promising therapeutic effects. In this narrative review, B cell specific receptors and their downstream signalling molecules that may contribute to pathology in AAV are discussed, including the potential to therapeutically target these pathways.

Immunopathological events surrounding IL-6 and IFN-α: A bridge for anti-lupus erythematosus drugs used to treat COVID-19

With the outbreak and rapid spread of COVID-19, the world health situation is unprecedentedly severe. Systemic lupus erythematosus (SLE) is a common autoimmune disease, which can cause multiple organ damage. Numerous studies have shown that immune factors have important roles in the pathogenesis of both COVID-19 and SLE. In the early stages of COVID-19 and SLE pathogenesis, IFN-α expression is frequently increased, which aggravates the virus infection and promotes SLE development. In addition, increased IL-6 levels, caused by different mechanisms, are observed in the peripheral blood of patients with severe COVID-19 and SLE, stimulating a series of immune cascades that lead to a cytokine storm, as well as causing B cell hyperfunction and production of numerous of antibodies, aggravating both COVID-19 and SLE. In this review, we explore the background immunopathological mechanisms in COVID-19 and SLE and analyze the advantages and disadvantages of commonly used SLE drugs for patients with COVID-19, to optimize treatment plans for patients with SLE who develop COVID-19.