The future of immunoglobulin therapy: An overview of the 2nd international workshop on natural antibodies in health and disease

Mouse Models of Rheumatoid Arthritis for Studies on Immunopathogenesis and Preclinical Testing of Fc Receptor-Targeting Biologics

<b><i>Background:</i></b> Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes inflammation, swelling, and pain in the joints and involves systemic complications. Mouse models of RA have been extensively used to model the pathogenesis of RA and to develop effective therapies. Although many components of the immune system have been studied in these models, the role of crystallizable fragment (Fc) gamma receptors (FcγRs) in RA has been sorely neglected. The aim of this review was to introduce the different mouse models of RA and to describe the different drug development strategies that have been tested in these models to target FcγR function, with the focus being on drugs that have been made from the Fc of immunoglobulin G (IgG). <b><i>Summary:</i></b> Evidence suggests that FcγRs play a major role in immune complex-induced inflammation in autoimmune diseases, such as RA. However, there is limited knowledge on the importance of FcγRs in the human disease even though there has been extensive work in mouse models of RA. Numerous mouse models of RA are available, with each model depicting certain aspects of the disease. Induced models of RA have nonspecific immune activation with cartilage-directed autoimmunity, whereas spontaneous models of RA develop without immunization, which results in a more chronic form of arthritis. These models have been used to test FcγR-targeting monoclonal antibodies, intravenous immunoglobulin (IVIg), subcutaneously administered IVIg, and recombinant Fcs for their ability to interact with and modify FcγR function. Recombinant Fcs avidly bind FcγRs and exhibit enhanced therapeutic efficacy in mouse models of RA. <b><i>Key Message:</i></b> The therapeutic utility of targeting FcγRs with recombinant Fcs is great and should be explored in human clinical trials for autoimmune diseases, such as RA.

The effect of Intravenous Immunoglobulin (IVIG) on \textit{ex vivo} activation of human leukocytes

INTRODUCTION

Intravenous immunoglobulin (IVIG) has been widely used to treat various conditions, including inflammatory and autoimmune diseases. IVIG has been shown to have a direct influence on neutrophils, eosinophils and lymphocytes. However, many aspects IVIG's effect on neutrophils activation still remain unknown.

OBJECTIVE

To evaluate the effect of IVIG on PMA-induced activation of neutrophils, with and without priming with TNF-α, in a series of in vitro experiments performed on whole blood.

RESULTS

Our data coincided with well-known literature indicating that the effect of phorbol 12-myristate 13-acetate (PMA) on human leukocytes includes activation of neutrophils, monocytes and eosinophils, increase of chemiluminescence (CL) and induction of netosis, resulting in assembly of traps. In presence of IVIG (10 mg/mL), CL was reduced by 25% in response to PMA compared to PMA-induced leukocyte activation without IVIG. Decreasing IVIG concentration to 1 mg/mL and below did not inhibit PMA-induced activation of CL.PMA-induced activation after TNF-α priming resulted in approximately 50% increase of amplitude of CL response to PMA. Moreover, maximum CL was reached by minute 5, which was more rapid than in the absence of TNF-α-priming (in this case maximum CL was reached by minute 15).The IVIG concentrations did not affect morphological changes of leukocytes after sequential addition of TNF-α and PMA. IVIG had no effect on leukocyte content and on PMA-induced CL of primed leukocytes.Addition of IVIG under TNF-α priming significantly increased the number of traps in the smears in response to PMA activation. Of note, such an increase in the number of traps was depended on the IVIG concentration in plasma.

CONCLUSION

In conclusion, we suggest that IVIG is able to reduce the degradation of traps under priming with TNF-α. Moreover, IVIG might switch the activation of primed leukocytes to netosis.

IVIG in autoimmune disease - Potential next generation biologics

Polyclonal plasma-derived IgG is a mainstay therapeutic of immunodeficiency disorders as well as of various inflammatory autoimmune diseases. In immunodeficiency the primary function of IVIG/SCIG is to replace missing antibody specificities, consequently a diverse Fab-based repertoire is critical for efficacy. Attempts to capture the Ig repertoire and express it as a recombinant IVIG product are currently ongoing. Likewise correction of the defective genes by gene therapy has also been tried. However, both approaches are far from becoming mainstream treatments. In contrast, some of the most important effector mechanisms relevant in therapy of autoimmunity are based on the Fc-portion of IgG; they include scavenging of complement and blockade/modulation of IgG receptors (Fc gamma receptor [FcγR] or the neonatal Fc receptor [FcRn]). These effects might be achieved with appropriately formulated Fc-fragments instead of full-length IgG, as suggested by a pilot study with monomeric plasma-derived Fc in children with ITP and in Kawasaki disease in the 1990s. Since then it has been proposed that structured multimerization of Fc fragments might confer efficacy at much lower doses than with IVIG. Accordingly, various molecular strategies are currently being explored to achieve controlled Fc multimerization, e.g. by fusion of IgG1 Fc to the IgG2 hinge-region or to the IgM tail-piece. Safety considerations will be crucial in the evaluation of these new entities. In a different approach, mutant Fc fragments and monoclonal antibodies have been designed for blockade of the FcRn.

Intravenous IgG (IVIG) and subcutaneous IgG (SCIG) preparations have comparable inhibitory effect on T cell activation, which is not dependent on IgG sialylation, monocytes or B cells

IVIG modulates T cell activation in vitro and inflammatory-autoimmune conditions in vivo. Sialylation of IgG, Fc receptor interactions, modulation of monocyte/macrophage/B cell functions have been implicated in IVIG effects. Subcutaneous IgG (SCIG) therapy is increasingly used for IgG replacement but whether these preparations share the effects of IVIG on T cell modulation is not documented. We compared the potency of SCIG-Hizentra™ (20% IgG preparation) with IVIG-Privigen® (10% IgG) for T cell inhibition, and assessed the involvement of IgG sialylation, monocytes and B cells in this process. Human PBMCs or sorted cells were cultured 3-7 days, and T cells were stimulated with immobilized anti-CD3 mAb or Candida antigen. Thymidine incorporation into DNA was quantitated and cytokines assayed by ELISA/Luminex® assay. IVIG and SCIG both dose-dependently (1-20mg/ml) inhibited (up to >80%) T cell proliferation to anti-CD3 mAb. Response to Candida albicans was comparably inhibited by IVIG and SCIG by 50-80% at 10mg/ml with inhibition even at 3mg/ml (P<0.05). These effects were not affected by depletion of sialic acid containing IgG using neuraminidase treatment or lectin affinity chromatography. With anti-CD3 or Candida stimulation, IL-1β, IL-2, IL-5, IL-6, IL-13, GMCSF, TNF-α, interferon-γ (with anti-CD3) and IL-17 (with Candida) levels were suppressed by IVIG or SCIG, with no effect on IL-4, IL-10, IL-12, IL-15 or TGFβ. Monocytes or B cells were not required for IgG-induced suppression of proliferation, in fact depletion of monocytes potentiated the IgG-induced inhibition. Reconstitution with monocytes restored the original inhibitory effect. These data show that IVIG (Privigen®) and SCIG (Hizentra™) have comparable inhibitory effects on T cell activation, which do not require sialylation of IgG. Inhibition is independent of monocytes or B cells. There is a potent suppression of multiple effector cytokines. Like IVIG, SCIG therapy is expected to show immunomodulatory activity.

Regulatory T cell microRNA expression changes in children with acute Kawasaki disease

Kawasaki disease (KD) is a type of systemic vasculitis syndrome related to immune dysfunction. Previous studies have implicated that dysfunctional regulatory T cells (Treg ) may be associated with the immune dysfunction in KD. In the absence of microRNAs (miRNAs), forkhead box protein 3 (FoxP3)(+)  Treg develop but fail to maintain immune homeostasis. This study was designed to investigate the effects of miR-155, miR-21 and miR-31 on Treg in children with KD. The proportions of CD4(+) CD25(+) FoxP3(+) Treg and the mean fluorescence intensity (MFI) of phosphorylated-signal transducer and activator of transcription (pSTAT)-5 and pSTAT-3 protein in CD4(+) CD25(+) Treg were analysed by flow cytometry. The concentration of interleukin (IL)-6 in plasma was measured by cytometric bead array. Real-time polymerase chain reaction was performed to detect the levels of microRNAs and associated factors in CD4(+) CD25(+) Treg . The proportion of Treg and the mRNA levels of the associated factors [FoxP3, glucocorticoid-induced tumour necrosis factor-receptor (GITR), cytotoxic T lymphocyte antigen (CTLA)-4)] were significantly lower in KD patients (P < 0·05). MiR-155 and miR-21 levels were significantly down-regulated and miR-31 expression was higher in KD patients (P < 0·05). Plasma interleukin (IL)-6 concentrations, pSTAT-3 protein levels and suppressors of cytokine signalling (SOCS)-1 mRNA expression were remarkably elevated in acute KD (P < 0·05), while pSTAT-5 protein levels were remarkably decreased in acute KD (P < 0·05). These findings were reversed after intravenous immunoglobulin treatment (P < 0·05). Our results demonstrate that FoxP3 mRNA levels were primarily affected by the miR-155/SOCS1 and the miR-31 signalling pathways. These results suggest that the decrease in FoxP3(+) Treg might be associated with decreased expression of miR-155, leading to aberrant SOCS1/STAT-5 signalling and overexpression of miR-31 in patients with acute KD.

Impact of treatment on survival in polymyositis and dermatomyositis. A single-centre long-term follow-up study

OBJECTIVE

To assess the long-term outcome in polymyositis (PM) and dermatomyositis (DM), with a particular emphasis on mortality and influence of treatment.

METHODS

Diagnosis was based according to the Bohan and Peter's criteria. Patients have been followed up by a standardised protocol. Deaths were registered and causes of death were ascertained. Survival probability at 5 and 10years was estimated according to the Kaplan-Meier method, in the overall series and by a diagnostic group and an initial treatment. Mortality hazard ratios (95% CI) for major clinical and demographic features were estimated through univariate and multivariate Cox proportional hazard models.

RESULTS

91 patients (43 PM and 48 DM) were available for the study. Baseline characteristics were not different from those previously reported. Twenty-two patients (24%) died after a median follow-up of 8.7years. As for idiopathic myositis, the survival probabilities at 5 and 10years from the diagnosis were 96.2% and 88.8% for PM respectively; and 93.9% for DM, whereas a higher mortality was documented for cancer-associated myositis and overlap myositis. Male sex [HR=2.4, 95% CI 1.0 to 5.6], heart involvement (HR=1.8), interstitial lung disease (HR=2.3) and arthritis (HR=1.8) increased the risk of mortality, these risk excesses were confirmed in the multivariate analysis. Independent of these features, a higher mortality was documented for patients treated with glucocorticoids (HR=2.3) or immunosuppressants (HR=2.1) when compared to patients treated with immunoglobulins.

CONCLUSION

Our study, with longitudinal and statistical analyses, suggests that survival has considerably increased in patients with PM/DM. Prognostic factors for mortality are male sex, and heart and lung involvement. Immunoglobulin treatment, intravenously or subcutaneously, is associated with a better survival.

Salvage therapy with high dose Intravenous Immunoglobulins in acquired Von Willebrand Syndrome and unresponsive severe intestinal bleeding

A 91-year-old woman affected with acquired Von Willebrand (VW) syndrome and intestinal angiodysplasias presented with severe gastrointestinal bleeding (hemoglobin 5 g/dl). Despite replacement therapy with VW factor/factor VIII concentrate qid, bleeding did not stop (eleven packed red blood cell units were transfused over three days). High circulating levels of anti-VW factor immunoglobulin M were documented immunoenzimatically. Heart ultrasound showed abnormalities of the mitral and aortic valves with severe flow alterations. When intravenous immunoglobulins were added to therapy, prompt clinical and laboratory responses occurred: complete cessation of bleeding, raise in hemoglobin, VW factor antigen, VW ristocetin cofactor and factor VIII levels as well as progressive reduction of the anti-VWF autoantibody levels.

Therapeutic effect of IVIG on inflammatory arthritis in mice is dependent on the Fc portion and independent of sialylation or basophils

High-dose i.v. Ig (IVIG) is used to treat various autoimmune and inflammatory diseases; however, the mechanism of action remains unclear. Based on the K/BxN serum transfer arthritis model in mice, IVIG suppression of inflammation has been attributed to a mechanism involving basophils and the binding of highly sialylated IgG Fc to DC-SIGN-expressing myeloid cells. The requirement for sialylation was examined in the collagen Ab-induced arthritis (CAbIA) and K/BxN serum transfer arthritis models in mice. High-dose IVIG (1-2 g/kg body weight) suppressed inflammatory arthritis when given prophylactically. The same doses were also effective in the CAbIA model when given subsequent to disease induction. In this therapeutic CAbIA model, the anti-inflammatory effect of IVIG was dependent on IgG Fc but not F(ab')2 fragments. Removal of sialic acid residues by neuraminidase had no impact on the anti-inflammatory activity of IVIG or Fc fragments. Treatment of mice with basophil-depleting mAbs did not abrogate the suppression of either CAbIA or K/BxN arthritis by IVIG. Our data confirm the therapeutic benefit of IVIG and IgG Fc in Ab-induced arthritis but fail to support the significance of sialylation and basophil involvement in the mechanism of action of IVIG therapy.

Mechanisms and potential therapeutic targets in allergic inflammation: recent insights

Deeper insight into pathogenetic pathways and into the biological effects of immunomodulatory agents will help to optimize or adopt therapeutic strategies for atopic disorders. In this article, we highlight selected findings of potential therapeutic relevance that emerged from recent mechanistic studies with focus on molecular and cellular aspects of allergic inflammation. Furthermore, the often complex mechanisms of action of pleiotropic immunomodulatory agents, such as glucocorticoids, vitamin D, or intravenous immunoglobulin (IVIG), are discussed, as their dissection might reveal targets for novel therapeutics or lead to a more rational use of these compounds. Besides reporting novel evidence, this article points to areas of current debate or uncertainty and aims at stimulating scientific discussion and experimental work.