Serum IgG2 antibody multi-composition in systemic lupus erythematosus and in lupus nephritis (Part 2): prospective study

Abstract

Objectives: Circulating anti-ENO1 and anti-H2A IgG2 have been identified as specific signatures of LN in a cross-over approach. We sought to show whether the same antibodies identify selected population of patients with LN with potentially different clinical outcomes.

Methods: Here we report the prospective analysis over 36 months of circulating IgG2 levels in patients with newly diagnosed LN (n=91) and SLE (n=31) and in other patients with SLE recruited within 2 years from diagnosis (n=99). Anti-podocyte (ENO1), anti-nucleosome (DNA, histone 2 A, histone 3) and anti-circulating proteins (C1q, AnnexinA1-ANXA1) IgG2 antibodies were determined by home-made techniques.

Results: LN patients were the main focus of the study. Anti-ENO1, anti-H2A and anti-ANXA1 IgG2 decreased in parallel to proteinuria and normalized within 12 months in the majority of patients while anti-dsDNA IgG2 remained high over the 36 months. Anti-ENO1 and anti-H2A had the highest association with proteinuria (Heat Map) and identified the highest number of patients with high proteinuria (68% and 71% respectively) and/or with reduced estimated glomerula filtration rate (eGFR) (58% for both antibodies) compared with 23% and 17% of anti-dsDNA (agreement analysis). Anti-ENO1 positive LN patients had higher proteinuria than negative patients at T0 and presented the maximal decrement within 12 months.

Conclusions: Anti-ENO1, anti-H2A and anti-ANXA1 antibodies were associated with high proteinuria in LN patients and Anti-ENO1 also presented the maximal reduction within 12 months that paralleled the decrease of proteinuria. Anti-dsDNA were not associated with renal outcome parameters. New IgG2 antibody signatures should be utilized as tracers of personalized therapies in LN.

Trial registration: The Zeus study was registered at https://clinicaltrials.gov (study number: NCT02403115).

Keywords: anti-C1q antibodies; anti-ENO1 antibodies; anti-Histone 2A antibodies; biomarkers; lupus nephritis; systemic lupus erythematosus.

Fig. 1

Circulating levels of anti-dsDNA, anti-histone 2 A and anti-histone 3 IgG2 Circulating levels of anti-dsDNA, anti-histone 2A and anti-histone 3 IgG2 were determined in a cohort of 91 LN patients recruited at the time of the diagnosis and were then followed for 36 months. In all cases, antibodies were of the IgG2 isotype and levels were calculated as Relative Intensity value (RU/ml) given the absence of WHO international standards. * indicates a statistical difference with T₀. WHO: World Health Organisation.

Fig. 2

Circulating levels of anti-ENO1, anti-annexin A1 and anti-C1q IgG2 Circulating levels of anti-ENO1, anti-ANXA1 IgG2 and anti-C1q IgG2 were determined in the same group of LN patients of Fig. 1. In all cases, antibodies were of the IgG2 isotype and levels were calculated as Relative Intensity value (RU/ml) given the absence of WHO international standards .* indicates a statistical difference with T_0. WHO: World Health Organisation.

Fig. 3

Variations of circulating antibodies within 12 months of follow-up in LN patients Variations of circulating levels of each antibody from T₀ were determined after 12 months of follow-up in LN patients. The decrement of proteinuria is reported for comparison. It is shown that anti-ENO1 and anti-ANXA1 had the maximal decrement and that anti-dsDNA had no variation at all. Results are shown as median and interquartile range. *indicates a statistical difference between anti-dsDNA and anti-ANXA1 with anti-ENO1.

Fig. 4

Time course of proteinuria and of circulating levels of antibodies in LN patients Circulating levels of each antibody were determined every 12 months for 3 years in LN patients. Results are reported together with proteinuria determined at the same time points. Statistical significance of the decrement in circulating antibodies is reported in Figs 1–3. Statistical significance of proteinuria decrements is reported in Supplementary Fig. S1, available at Rheumatology online.

Fig. 5 Proteinuria at T₀ and modifications during the follow-up in anti-ENO1 positive and negative LN patients Proteinuria at T₀ and % changes during the first 12 months of follow-up are reported for patients positive and negative for anti-ENO1. In the former case (proteinuria levels) a statistical difference was observed between the two groups. Also, the decrement of proteinuria was more evident in anti-ENO1 positive patients. The same parameters are reported sub-dividing the whole LN group in respect to positivity for anti-dsDNA IgG2.