The pathogenetic role of immunoglobulin G from patients with systemic lupus erythematosus in the development of lupus pleuritis

Natural Antibodies Produced in Vaccinated Patients and COVID-19 Convalescents Recognize and Hydrolyze Oligopeptides Corresponding to the S-Protein of SARS-CoV-2

The S-protein is the major antigen of the SARS-CoV-2 virus, against which protective antibodies are generated. The S-protein gene was used in adenoviral vectors and mRNA vaccines against COVID-19. While the primary function of antibodies is to bind to antigens, catalytic antibodies can hydrolyze various substrates, including nucleic acids, proteins, oligopeptides, polysaccharides, and some other molecules. In this study, antibody fractions with affinity for RBD and S-protein (RBD-IgG and S-IgG) were isolated from the blood of COVID-19 patients vaccinated with Sputnik V. The fractions were analyzed for their potential to hydrolyze 18-mer oligopeptides corresponding to linear fragments of the SARS-CoV-2 S-protein. Here, we show that the IgG antibodies hydrolyze six out of nine oligopeptides efficiently, with the antibodies of COVID-19-exposed donors demonstrating the most significant activity. The IgGs of control donors not exposed to SARS-CoV-2 were found to be inactive in oligopeptide hydrolysis. The antibodies of convalescents and vaccinated patients were found to hydrolyze oligopeptides in a wide pH range, with the optimal pH range between 6.5 and 7.5. The hydrolysis of most oligopeptides by RBD-IgG antibodies is inhibited by thiol protease inhibitors, whereas S-IgG active centers generally combine several types of proteolytic activities. Ca2+ ions increase the catalytic activity of IgG preparations containing metalloprotease-like active centers. Thus, the proteolytic activity of natural antibodies against the SARS-CoV-2 protein is believed to be due to the similarity of catalytic antibodies' active centers to canonical proteases. This work raises the question of the possible physiological role of proteolytic natural RBD-IgG and S-IgG resulting from vaccination and exposure to COVID-19.

Salivary Immunoglobulin Gamma-3 Chain C Is a Promising Noninvasive Biomarker for Systemic Lupus Erythematosus

We aimed to characterize the salivary protein components and identify biomarkers in patients with systemic lupus erythematosus (SLE). A proteomic analysis using two-dimensional gel electrophoresis and mass spectrometry was performed to determine the alterations of salivary proteins between patients with SLE and healthy controls, and the concentrations of the candidate proteins were measured through Western blot analysis and the enzyme-linked immunosorbent assay. The 10 differentially expressed protein spots were immunoglobulin gamma-3 chain C region (IGHG3), immunoglobulin alpha-1 chain C region, protein S100A8, lactoferrin, leukemia-associated protein 7, and 8-oxoguanine DNA glycosylase. The patients with SLE exhibited enhanced salivary IGHG3 (3.9 ± 2.15 pg/mL) and lactoferrin (4.7 ± 1.8 pg/mL) levels compared to patients with rheumatoid arthritis (1.8 ± 1.01 pg/mL and 3.2 ± 1.6 pg/mL, respectively; p < 0.001 for both) or healthy controls (2.2 ± 1.64 pg/mL and 2.2 ± 1.7 pg/mL, respectively; p < 0.001 for both). The salivary IGHG3 levels correlated with the erythrocyte sedimentation rate (r = 0.26, p = 0.01), anti-double-stranded DNA (dsDNA) antibody levels (r = 0.25, p = 0.01), and nephritis (r = 0.28, p = 0.01). The proteomic analysis revealed that the salivary IGHG3 levels were associated with SLE and lupus disease activity, suggesting that salivary IGHG3 may be a promising noninvasive biomarker for SLE.

Lupus Nephritis IgG Induction of Calcium/Calmodulin-Dependent Protein Kinase IV Expression in Podocytes and Alteration of Their Function

OBJECTIVE

Kidney podocytes and their slit diaphragms prevent urinary protein loss. T cells from patients with systemic lupus erythematosus display increased expression of calcium/calmodulin-dependent protein kinase IV (CaMKIV). The present study was undertaken to investigate the role of CaMKIV in podocyte function in lupus nephritis (LN).

METHODS

We treated kidney podocytes with IgG derived from healthy individuals or patients with LN and then analyzed gene expression using a DNA microarray. The localization of IgG in podocytes was analyzed by immunofluorescence staining, with or without silencing of neonatal Fc receptor (FcRn). In addition, we silenced CAMK4 in podocytes and analyzed the expression of selected genes. We also examined the expression of CD86 in kidney podocytes from MRL/lpr, MRL/lpr.camkiv(-/-), and MRL/MPJ mice by in situ hybridization.

RESULTS

We found that exposure of podocytes to IgG resulted in entry of IgG into the cytoplasm. IgG entered podocytes via the FcRn because less IgG was found in the cytoplasm of podocytes treated with FcRn small interfering RNA. DNA microarray studies of podocytes exposed to LN-derived IgG revealed up-regulation of genes related to the activation of immune cells or podocyte damage. Interestingly, CD86 expression decreased after silencing CAMK4 in podocytes. Also, in situ hybridization experiments showed that the expression of CD86 was reduced in podocytes from MRL/lpr.camkiv(-/-) mice.

CONCLUSION

LN-derived IgG enters podocytes and up-regulates CAMK4, which is followed by increased expression of genes known to be linked to podocyte damage and T cell activation. Targeted inhibition of CAMK4 in podocytes may prove to be clinically useful in patients with LN.

Chinese SLE Treatment and Research group (CSTAR) registry VII: prevalence and clinical significance of serositis in Chinese patients with systemic lupus erythematosus

Objectives

To investigate both the prevalence and clinical characteristics of serositis in Chinese patients with systemic lupus erythematosus (SLE) in a large cohort in the Chinese SLE Treatment and Research group (CSTAR) database.

Methods

A prospective cross-sectional study of patients with SLE was conducted based on the data from the CSTAR registry. Serositis was defined according to the 1999 revised American College of Rheumatology (ACR) criteria for SLE – that is, pleuritis/pleural effusion and/or pericarditis/pericardial effusion detected by echocardiography, chest X-ray or chest computerized tomography (CT) scan. Peritonitis/peritoneal effusion were confirmed by abdominal ultrasonography. We analysed the prevalence and clinical associations of serositis with demographic data, organ involvements, laboratory findings and SLE disease activity.

Results

Of 2104 patients with SLE, 345 were diagnosed with serositis. The prevalence of lupus nephritis (LN), interstitial lung disease and pulmonary arterial hypertension, as well as the presence of leukocytopenia, thrombocytopenia, hypocomplementemia and anti-dsDNA antibodies was significantly higher in patients with serositis ( P < 0.05). Significantly higher SLE disease activity scores were found in patients with serositis compared to those patients without serositis ( P < 0.05). Lupus-related peritonitis had similar clinical manifestations and laboratory profiles as serositis caused by SLE.

Conclusions

There is a significant association of nephropathy, interstitial lung disease, pulmonary arterial hypertension, hypocomplementemia, leukocytopenia, thrombocytopenia and elevated anti-dsDNA antibodies with serositis. The results suggest that higher SLE disease activity contributes to serositis development, and should be treated aggressively.

Asbestos-associated mesothelial cell autoantibodies promote collagen deposition in vitro

Fibrosis, characterized by excessive collagen protein deposition, is a progressive disease that can fatally inhibit organ function. Prolonged exposure to pathogens or environmental toxicants such as asbestos can lead to chronic inflammatory responses associated with fibrosis. Significant exposure to amphibole asbestos has been reported in and around Libby, Montana due to local mining of asbestos-contaminated vermiculite. These exposures have been implicated in a unique disease etiology characterized predominantly by pleural disorders, including fibrosis. We recently reported the discovery of mesothelial cell autoantibodies (MCAAs) in the sera of Libby residents and demonstrated a positive and significant correlation with pleural disease; however, a mechanistic link was not determined. Here we demonstrate that MCAAs induce pleural mesothelial cells to produce a collagen matrix but do not affect production of the pro-inflammatory cytokine tumor growth factor-β. While autoantibodies commonly induce a pro-fibrotic state by inducing epithelial-mesenchymal transition (EMT) of target cells, we found no evidence supporting EMT in cells exposed to MCAA positive human sera. Although implicated in other models of pulmonary fibrosis, activity of the protein SPARC (secreted protein, acidic and rich in cysteine) did not affect MCAA-induced collagen deposition. However, matrix formation was dependent on matrix metalloproteinase (MMP) activity, and we noted increased expression of MMP-8 and -9 in supernatants of mesothelial cells incubated with MCAA positive sera compared to control. These data suggest a mechanism by which MCAA binding leads to increased collagen deposition through altering MMP expression and provides an important mechanistic link between MCAAs and asbestos-related, autoimmune-induced pleural fibrosis.

Pathogenic autoantibodies from patients with lupus nephritis cause reduced tyrosine phosphorylation of podocyte proteins, including tubulin

INTRODUCTION

The tertiary structure of normal podocytes prevents protein from leaking into urine. Patients with lupus nephritis (LN) develop proteinuria, and kidney biopsies from these patients display a number of podocyte abnormalities including retraction of podocyte processes. Autoantibodies have been shown to deposit in the kidneys of patients and mice with LN and are believed to play a key role in causing renal inflammation and dysfunction. The objective of this research was to study the effects of IgG antibodies from patients with LN on cultured human podocytes.

METHODS

We exposed a human podocyte cell line to heat-inactivated (HI) plasma and purified polyclonal IgG from the following groups of subjects; patients with LN, patients with lupus without nephritis, patients with rheumatoid arthritis and healthy controls. We measured expression and intracellular distribution of podocyte-specific proteins and global phosphorylation of tyrosine. We then used mass spectrometry to identify the major protein targets of this phosphorylation.

RESULTS

HI LN plasma did not alter expression or cellular distribution of podocyte-specific proteins but caused a significant reduction in podocyte protein tyrosine phosphorylation compared with plasma from healthy controls (p=0.0008). This result was replicated using purified IgG but was not seen with plasma from rheumatoid arthritis or non-renal lupus patients. The dominant tyrosine phosphorylated protein in podocytes was 55 kDa in size and was identified as tubulin.

CONCLUSIONS

Since tubulin is an important component of podocyte major processes, these results suggest that autoantibodies from LN patients may exert an important pathogenic effect by dephosphorylation of this protein in podocytes.

Sterile empyematous pleural effusion in a patient with systemic lupus erythematosus: a diagnostic challenge

Herein we present a case of a patient with systemic lupus erythematosus (SLE) and a sterile empyematous pleural effusion, a complication not generally associated with SLE. A discussion of the diagnostic and treatment dilemmas follows the case presentation.

A common repertoire of autoantibodies is shared by cancer and autoimmune disease patients: Inflammation in their induction and impact on tumor growth

The repertoire of autoantibodies found in cancer patients partly overlaps with that typical of patients with autoimmune diseases. Beside the biochemical and immunological properties of the target antigens and their altered expression in tumor tissues, the intratumoral inflammatory context can play a key role in the induction of autoimmune disease-associated autoantibodies in cancer patients. Furthermore, the impact of such antibodies on cancer growth and progression can be deeply influenced by the interplay with inflammation. The characterization of the spontaneous humoral responses occurring in cancer patients, of the mechanisms that trigger and sustain the autoantibody response and of the biological effects of such autoantibodies may help the rational design of anti-cancer immunotherapeutic protocols.

Effect of human anti-DNA antibodies on proximal renal tubular epithelial cell cytokine expression: implications on tubulointerstitial inflammation in lupus nephritis

This study aimed to investigate the effects of human anti-DNA antibodies (Ab) from patients with lupus on renal proximal tubular epithelial cells (PTEC), focusing on alterations in cell morphology and proinflammatory cytokine synthesis. Immunohistochemistry showed increased tubulointerstitial IL-6 expression and IgG deposition in renal biopsies from patients with diffuse proliferative lupus nephritis, not observed in controls or membranous lupus nephritis, which correlated with the severity of inflammatory cell infiltration. Sera from patients with lupus nephritis contained IgG that bound to cultured PTEC. Such binding increased with disease activity and correlated with the level of anti-DNA Ab. Incubation of PTEC with anti-DNA Ab that were isolated during active (active Ab) or inactive (inactive Ab) disease induced IL-6 synthesis, both apically and from the basolateral aspect. This was accompanied by altered cell morphology, increased cell proliferation (P < 0.05), and lactate dehydrogenase release (P < 0.05). The binding of inactive Ab and active Ab to PTEC resulted in differential and sequential upregulation of TNF-alpha, IL-1beta, and IL-6 secretion (P < 0.05). Early induction of TNF-alpha was observed with active Ab; the two then acted synergistically to induce IL-6 secretion. Exposure of PTEC to inactive Ab was associated with modest induction of TNF-alpha, which was not involved in downstream induction of other proinflammatory peptides. These data suggest distinct immunopathogenetic mechanisms during disease flare or remission. Conditioned media from human mesangial cells acted synergistically with anti-DNA Ab to induce cytokine secretion in PTEC. Results from these studies underscore the pivotal role of PTEC in the pathogenesis of tubulointerstitial inflammation and fibrosis in lupus nephritis.