Multi-Autoantibody Signature and Clinical Outcome in Membranous Nephropathy

Patients with membranous nephropathy can have circulating autoantibodies against membrane-bound (phospholipase A2 receptor 1 [PLA2R1] and thrombospondin type-1 domain containing 7A [THSD7A]) and intracellular (aldose reductase, SOD2, and α-enolase) podocyte autoantigens. We studied their combined association with clinical outcomes.

Serum levels of anti-PLA2R1, anti-THSD7A, anti-aldose reductase, anti-SOD2, and anti-α-enolase autoantibodies were determined in 285 patients at diagnosis and during follow-up using standardized and homemade assays. An eGFR>60 ml/min per 1.73 m² and remission of proteinuria (<0.3/<3.5 g per d) after 12 months were the outcomes of interest.

At diagnosis, 182 (64%), eight (3%), and 95 (33%) patients were anti-PLA2R1⁺, anti-THSD7A⁺, and double negative, respectively. The prevalence of a detectable antibody to at least one intracellular antigen was similarly distributed in patients who were anti-PLA2R1⁺ (n=118, 65%) and double negative (n=64, 67%). Positivity for anti-PLA2R1, anti-SOD2, and anti-α-enolase antibodies and higher titers at diagnosis were associated with poor clinical outcome independently to each other. Combined positivity for anti-PLA2R1, anti-SOD2, and anti-α-enolase was associated with highest risk of poor outcome (odds ratio, 5.5; 95% confidence interval, 1.2 to 24; P=0.01). In Kaplan-Meier analysis, patients who were anti-PLA2R1⁺/anti-SOD2⁺ or anti-PLA2R1⁺/anti-α-enolase⁺ had lower eGFR at 12 months compared with patients who were anti-PLA2R1⁺/anti-SOD2^- or anti-α-enolase^-. Predictive tests (net reclassification index and area under the curve-receiver-operating characteristic analysis) showed that combined assessment of antibodies improved classification of outcome in 22%-34% of cases for partial remission of proteinuria and maintenance of normal eGFR. For patients with nephrotic syndrome at diagnosis, anti-SOD2 positivity and high anti-PLA2R1 titer were associated with a lack of complete remission. Patients who were anti-PLA2R1^-/anti-intracellular antigens^- had the lowest proteinuria and the highest eGFR at diagnosis and the lowest risk of lower eGFR at 12 months. Epitope spreading was present in 81% of patients who were anti-PLA2R1⁺ and was associated with increased positivity for intracellular antigens and poor eGFR at diagnosis and 12 months.

Combined serological analysis of autoantibodies targeting membrane-bound and intracellular autoantigens identifies patients with poor clinical outcomes.