Autoantibodies against podocytic UCHL1 are associated with idiopathic nephrotic syndrome relapses and induce proteinuria in mice

Abstract

Idiopathic steroid sensitive nephrotic syndrome (INS), the most frequent childhood nephropathy, is thought to be mediated by a circulating soluble factor that reversibly affects the renal protein sieving. The efficiency of rituximab therapy recently highlighted the involvement of B cells. Here we studied the involvement of a specific immunoglobulin G (IgG) in the disease. After plasma fractionation by size exclusion chromatography, a detachment of cultured podocyte was observed with one IgG-containing fraction from 47% patients in relapse, 9% of patients in remission and 0% of controls. Podocyte protein lysates were immunoprecipitated by IgG from those plasma fractions identifying a list of 41 podocyte proteins after proteomic analysis. Five podocyte targets were selected on statistical and biological criteria. Specific antibodies were tested and only anti-Ubiquitin Carboxyl-Terminal Hydrolase L1 (UCHL1) IgG led to podocyte detachment. UCHL1 was mainly found inside the podocyte but also weakly expressed on podocyte cell surface. Incubation of either anti-UCHL1 IgG or plasma fractions with recombinant UCHL1 prevented podocyte detachment. Plasma levels of anti-UCHL1 IgG were significantly increased in relapsing INS patients compared to patients in remission and controls. Proteinuria correlated with anti-UCHL1 IgG level at various stages of the disease. Purified patient anti-UCHL1 antibodies induced proteinuria and podocyte foot effacement in mice. Altogether, these results identified UCHL1 as a target podocyte protein of autoantibodies in a set of relapsing patients and support a causative role of anti-UCHL1 autoantibodies in the development of INS.

Remission of proteinuria in multidrug‐resistant idiopathic nephrotic syndrome following immunoglobulin immunoadsorption

“…Anti CD40 IgG antibodies have been identified to be closely linked with the recurrence of massive proteinuria after renal graft and were pathogenic for human cultured podocytes . More recently, IgG autoantibodies against podocytic UCHL1 were associated to the relapses in INS, the detachment of cultured podocytes and the transfer of proteinuria to mice . These reports are compatible with a circulating immunoglobulin interacting with a podocyte target that might lead to podocyte disruption and massive proteinuria.…”

Extended infusion of rituximab combined with steroids is effective in inducing remission and reducing relapse in adult minimal change disease

“…T helper 2 (TH2) cell mediated immunity and its related cytokines, such as IL-4 and IL-13 have been verified to cause proteinuria in murine model through inducing foot process effacement [ 43 , 44 ]. Additionally, IgG-antibody directed against Ubiquitin Carboxyl-Terminal Hydrolase L1 (UCHL1) was shown to cause podocyte detachment and associated with relapses of idiopathic NS in mice [ 45 ]. Apart from the direct influence on B cell, RTX has been proven to bind directly to podocyte Sphingomyelin Phosphodiesterase Acid Like 3b (SMPDL3b) in vitro, which demonstrated its antiproteinuric effect independent of B cell depletion [ 34 ].…”

A global antiB cell strategy combining obinutuzumab and daratumumab in severe pediatric nephrotic syndrome

“…All those RNAs, including EBER1 and EBER2 are powerful TLR3 agonists [ 35 ] susceptible to interact with TLR3 expressed on the podocyte and to affect podocyte integrity in a similar way as previously described by Shimada and Garin. Moreover, the transmission of proteinuria to mice by antiUCHL1 IgG antibodies purified from a relapsing patient [ 36 ], as well as the efficacy of immunoglobulin adsorption in the multiresistant forms of INS [ 37 ] are also relevant arguments to involve antibodies as the second podocyte hit that leads to massive proteinuria. It turns out that EBNA1 and UCHL1 share two short peptide sequences located in the immunogen domain of EBNA1 and in close vicinity at the surface of UCHL1 (blast in https://web.expasy.org/sim/ ; reference of protein sequences: YP_401677.1 and NP_004172.2 respectively).…”