Renal deposition and clearance of recombinant poly‐IgA complexes in a model of IgA nephropathy

Abstract

IgA nephropathy (IgAN) is the most common type of glomerulonephritis worldwide, which follows a chronic but nonetheless highly variable course of progression. IgA immune complexes are the primary source of renal deposits in IgAN. Apart from the presence of granular IgA1 deposits in the glomerular mesangium and mesangial hypercellularity as common features, the detailed process of IgA1 deposition and clearance in the kidney remains unclear. We sought to examine the dynamics of IgA deposition and tissue plasticity in response to deposits including their intrarenal clearance. We followed a synthetic approach to produce a recombinant fusion between IgA Fc (rIgA) and a biotin tag, which was subsequently induced with streptavidin (SA) to form an oligomeric poly‐IgA mimic. Both uninduced rIgA (mono‐rIgA) and polymeric SA‐rIgA (poly‐rIgA) were injected intravenously into Wistar rats. Plasma IgA levels and renal and liver histology were examined in a time series. In contrast to mono‐rIgA, this synthetic poly‐rIgA analog formed renal deposits exclusively in the glomerulus and were mostly cleared in 3 h. However, repeated daily injections for 12 days caused long‐lasting and stronger glomerular IgA deposition together with IgG and complement C3, in association with mesangial cell proliferation, matrix expansion, and variable degrees of albuminuria and hematuria that phenocopied IgAN. Ex vivo, poly‐rIgA bound cultured mesangial cells and elicited cytokine production, in addition to activating plasma C3 that was consistent with the actions of IgA immune complexes in IgAN pathogenesis. Remarkably, the kidneys were able to reverse all pathologic manifestations and restore normal glomerular histology 2 weeks after injections were halted. The synthetic model showed the kinetics between the intricate balance of renal deposition and clearance, as well as glomerular plasticity towards healing. Together, the results revealed a priming effect of existing deposits in promoting stronger and longer‐lasting IgA deposition to cause renal damage. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Propensity of IgA to self-aggregate via tailpiece cysteine-471 and treatment of IgA nephropathy using cysteamine

“…We used a passive induction model with 5 daily i.v. injections of purified recombinant rat rIgA in rats ( 17 ) ( Figure 6A , left). Rats developed prominent IgA deposition in the glomerulus ( Figure 6B , top).…”

“…Human IgA1-Fc CH2-CH3-TP cDNA and its mutant for C471S were fused to sequences encoding IL-2 signal peptide and 6×His-tag at the 5′-end in pcDNA3 vector (Invitrogen). Methods for protein expression and purification were described previously ( 17 ). Briefly, rat IgA analogs were expressed in the BL21 DE3 strain of E .…”

“…Human IgA1-Fc CH2-CH3-TP cDNA and its mutant for C471S were fused to sequences encoding IL-2 signal peptide and 6×His-tag at the 5'-end in pcDNA3 vector (Invitrogen, Carlsbad, CA). Methods for protein expression and purification were described previously (17). Briefly, rat IgA analogs were expressed in BL21 DE3 strain of E. coli and recombinant protein were purified using Histrap HP columns (GE Healthcare), whereas human recombinant IgA mimetics were produced from human embryo kidney cells (HEK293) by transfection of the plasmids.…”

History of IgA Nephropathy Mouse Models

“…These studies showed that the receptors cleaning the mesangium can be saturated if the IgA deposition rate is high. This hypothesis has recently been mentioned [61].…”

Integration of three machine learning algorithms identifies characteristic RNA binding proteins linked with diagnosis, immunity and pyroptosis of IgA nephropathy

“…IgA nephropathy has been an important cause of end-stage renal disease among young adults. The predominant histological characteristics are immune deposits dominated by granular diffuse IgA (primarily comprising polymeric IgA1) in the mesangial region, usually linked to increased mesangial cells along with matrix expansion ( Xie et al, 2021 ). In China, IgA nephropathy occupies 45.26% of primary glomerular diseases, and remains the most common cause of uremia (26.69%) ( Li Y. et al, 2021 ).…”