How Times Have Changed! A Cornucopia of Antigens for Membranous Nephropathy

The identification of the major target antigen phospholipase A2 receptor (PLA2R) in the majority of primary (idiopathic) cases of membranous nephropathy (MN) has been followed by the rapid identification of numerous minor antigens that appear to define phenotypically distinct forms of disease. This article serves to review all the known antigens that have been shown to localize to subepithelial deposits in MN, as well as the distinctive characteristics associated with each subtype of MN. We will also shed light on the novel proteomic approaches that have allowed identification of the most recent antigens. The paradigm of an antigen normally expressed on the podocyte cell surface leading to in-situ immune complex formation, complement activation, and subsequent podocyte injury will be discussed and challenged in light of the current repertoire of multiple MN antigens. Since disease phenotypes associated with each individual target antigens can often blur the distinction between primary and secondary disease, we encourage the use of antigen-based classification of membranous nephropathy.

Troponin interference with special regard to macrocomplex formation

Biomarkers, such as troponin-T and troponin-I, are regarded as the gold standard laboratory parameter for diagnosing many cardiological diseases. These parameters have been approved for clinical use. Many cardiological guidelines recommend the analysis of troponins in the majority of cardiological disease diagnoses and to also gain prognostic information. Nonetheless, many medical circumstances could cause false troponin elevations. In this article, we focus on troponin artifacts, particularly macro-immune complex formation, as important interference factors. Therefore, we performed a literature search from 2006 to 06/2021.

Poly-IgA Complexes and Disease Severity in IgA Nephropathy

Background and objectives: Poly-IgA immune complex formation and glomerular deposition play a key role in IgA nephropathy. Our study sought to develop a new methodology for one-step serological detection of poly-IgA levels. Design, setting, participants, and measurements: A novel ELISA method using recombinant CD89 as 'capturing' probe was established for detecting poly-IgA immune complex in the plasma. We applied semiquantitative measurements of these poly-IgA indices in patients recruited at Peking University First Hospital with IgA nephropathy or other kidney disease types, as compared to healthy controls. The longitudinal trend of the poly-IgA index, together with the association with pathological parameters and treatment responses were evaluated. Finally, we analyzed the molecular composition of poly-IgA complexes in patients by mass spectrometry. Results: Recombinant CD89-mounted ELISA plates specifically captured plasma poly-IgA. The levels of poly-IgA immune complex (26.7, IQR 17.1-42.6 units/ml) in IgA nephropathy were significantly higher than those in healthy (15.5, IQR 10.7- 20.0 units/ml; P<0.001), or non-IgA nephropathy disease controls (14.8, IQR 10.5-21.9 units/ml; P<0.001). Higher levels of poly-IgA immune complex were associated with lower eGFR and worse kidney outcome. Accuracy parameters and concordant statistics showed good discrimination between IgA nephropathy and healthy controls based on poly-IgA index levels (AUC, 0.78; 95% CI, 0.72-0.83; P<0.001), significantly outperforming galactose deficient-IgA1 levels (AUC, 0.70; P=0.05). Corticosteroid and immunosuppressant treatments lowered poly-IgA indices. Following a recombinant CD89-directed workflow in conjunction with mass spectrometry, we also analyzed the molecular compositions of IgA immune complex in IgA nephropathy patients. Conclusions: Higher level of recombinant CD89-bound poly-IgA immune complex was associated with the severity of the disease, as well as treatment response to steroids and immunosuppressants.

Antibodies against human endogenous retrovirus K102 envelope activate neutrophils in systemic lupus erythematosus

Neutrophil activation and the formation of neutrophil extracellular traps (NETs) are hallmarks of innate immune activation in systemic lupus erythematosus (SLE). Here we report that the expression of an endogenous retrovirus (ERV) locus ERV-K102, encoding an envelope protein, was significantly elevated in SLE patient blood and correlated with autoantibody levels and higher interferon status. Induction of ERV-K102 in SLE negatively correlated with the expression of epigenetic silencing factors. Anti-ERV-K102 IgG levels in SLE plasma correlated with higher interferon stimulated gene expression, and further promoted enhanced neutrophil phagocytosis of ERV-K102 envelope protein through immune complex formation. Finally, phagocytosis of ERV-K102 immune complexes resulted in the formation of NETs consisting of DNA, neutrophil elastase, and citrullinated histone H3. Together, we identified an immunostimulatory ERV-K envelope protein that in an immune complex with SLE IgG is capable of activating neutrophils.

A Highly Expressing, Soluble, and Stable Plant-Made IgG Fusion Vaccine Strategy Enhances Antigen Immunogenicity in Mice Without Adjuvant

Therapeutics based on fusing a protein of interest to the IgG Fc domain have been enormously successful, though fewer studies have investigated the vaccine potential of IgG fusions. In this study, we systematically compared the key properties of seven different plant-made human IgG1 fusion vaccine candidates using Zika virus (ZIKV) envelope domain III (ZE3) as a model antigen. Complement protein C1q binding of the IgG fusions was enhanced by: 1) antigen fusion to the IgG N-terminus; 2) removal of the IgG light chain or Fab regions; 3) addition of hexamer-inducing mutations in the IgG Fc; 4) adding a self-binding epitope tag to create recombinant immune complexes (RIC); or 5) producing IgG fusions in plants that lack plant-specific β1,2-linked xylose and α1,3-linked fucose N-linked glycans. We also characterized the expression, solubility, and stability of the IgG fusions. By optimizing immune complex formation, a potently immunogenic vaccine candidate with improved solubility and high stability was produced at 1.5 mg IgG fusion per g leaf fresh weight. In mice, the IgG fusions elicited high titers of Zika-specific antibodies which neutralized ZIKV using only two doses without adjuvant, reaching up to 150-fold higher antibody titers than ZE3 antigen alone. We anticipate these findings will be broadly applicable to the creation of other vaccines and antibody-based therapeutics.

Crucial Role of AIM/CD5L in the Development of Glomerular Inflammation in IgA Nephropathy

BackgroundIgA nephropathy (IgAN) begins with aberrant IgA deposition in glomeruli, progresses to IgM/IgG/complement codeposition, and results in chronic inflammation and glomerular damage. However, the mechanism that drives such phlogogenic cascade has been unclear. Recently, apoptosis inhibitor of macrophage (AIM) protein was shown to modulate macrophages’ function in various pathologic conditions, thereby profoundly affecting the progression of renal disorders, including AKI. A spontaneous IgAN model, grouped ddY (gddY) mouse, revealed the requirement of AIM for the overall inflammatory glomerular injury following IgA deposition.MethodsWe established an AIM-deficient IgAN model (AIM−/−gddY) using CRISPR/Cas9 and compared its phenotype with that of wild-type gddY with or without recombinant AIM administration. An IgA-deficient IgAN model (IgA−/−gddY) was also generated to further determine the role of AIM.ResultsIn both human and murine IgAN, AIM colocalized with IgA/IgM/IgG in glomeruli, whereas control kidneys did not exhibit AIM deposition. Although AIM−/−gddY showed IgA deposition at levels comparable with those of wild-type gddY, they did not exhibit glomerular accumulation of IgM/IgG complements, CD45+ leukocyte infiltration, and upregulation of inflammatory/fibrogenic genes, indicating protection from glomerular lesions and proteinuria/hematuria. Recombinant AIM administration reconstituted the IgAN phenotype, resulting in IgM/IgG/complement IgA codeposition. Neither spontaneous IgM/IgG codeposition nor disease was observed in IgA−/−gddY mice.ConclusionsAIM may contribute to stable immune complex formation in glomeruli, thereby facilitating IgAN progression. Therefore, AIM deposition blockage or disassociation from IgM/IgG may present a new therapeutic target on the basis of its role in IgAN inflammation initiation.

Targeting mitochondrial oxidative stress with MitoQ reduces NET formation and kidney disease in lupus-prone MRL-lpr mice

ObjectivesRecent investigations in humans and mouse models with lupus have revealed evidence of mitochondrial dysfunction and production of mitochondrial reactive oxygen species (mROS) in T cells and neutrophils. This can provoke numerous cellular changes including oxidation of nucleic acids, proteins, lipids and even induction of cell death. We have previously observed that in T cells from patients with lupus, the increased mROS is capable of provoking oligomerisation of mitochondrial antiviral stimulator (MAVS) and production of type I interferon (IFN-I). mROS in SLE neutrophils also promotes the formation of neutrophil extracellular traps (NETs), which are increased in lupus and implicated in renal damage. As a result, in addition to traditional immunosuppression, more comprehensive treatments for lupus may also include non-immune therapy, such as antioxidants.MethodsLupus-prone MRL-lpr mice were treated from weaning for 11 weeks with the mitochondria-targeted antioxidant, MitoQ (200 µM) in drinking water. Mice were then assessed for ROS production in neutrophils, NET formation, MAVS oligomerisation, serum IFN-I, autoantibody production and renal function.ResultsMitoQ-treated mice manifested reduced neutrophil ROS and NET formation, decreased MAVS oligomerisation and serum IFN-I, and reduced immune complex formation in kidneys, despite no change in serum autoantibody .ConclusionsThese findings reveal the potential utility of targeting mROS in addition to traditional immunosuppressive therapy for lupus.

Case of paradoxical adverse response to mepolizumab with mepolizumab-induced alopecia in severe eosinophilic asthma

Recent years have seen an increase in use of mepolizumab and other biological therapies for the treatment of severe eosinophilic asthma. A few cases of paradoxical responses to mepolizumab therapy have now been reported and are hypothesised as being a response to immune complex formation. We present a case of mepolizumab-induced alopecia in a patient with paradoxical adverse response to mepolizumab given for severe eosinophilic asthma. We postulate this could be secondary to autoimmune mechanisms and that it could help herald poor response to treatment, thereby facilitating early identification of patients having paradoxical responses.