222 Circulating pentraxin3-specific B cells are decreased in lupus nephritis

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173 Immunosuppressant discontinuation in systemic lupus erythematosus: prevalence, risk of subsequent flare and effect on damage accrual

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Deletions in VANGL1 are a risk factor for antibody-mediated kidney disease

We identify an intronic deletion in VANGL1 that predisposes to renal injury in high risk populations through a kidney-intrinsic process. Half of all SLE patients develop nephritis, yet the predisposing mechanisms to kidney damage remain poorly understood. There is limited evidence of genetic contribution to specific organ involvement in SLE.(1,2) We identify a large deletion in intron 7 of Van Gogh Like 1 (VANGL1), which associates with nephritis in SLE patients. The same deletion occurs at increased frequency in an indigenous population (Tiwi Islanders) with 10-fold higher rates of kidney disease compared with non-indigenous populations. Vangl1 hemizygosity in mice results in spontaneous IgA and IgG deposition within the glomerular mesangium in the absence of autoimmune nephritis. Serum transfer into B cell-deficient Vangl1(+/-) mice results in mesangial IgG deposition indicating that Ig deposits occur in a kidney-intrinsic fashion in the absence of Vangl1. These results suggest that Vangl1 acts in the kidney to prevent Ig deposits and its deficiency may trigger nephritis in individuals with SLE

Novel Pathogenic Pathways and Therapeutic Implications in Lupus Nephritis: The Emerging Role of PTX3-Related Immunity

Background. Abnormalities affecting regulatory molecules and pentraxin (PTX) 3 have been suggested to contribute to development of lupus glomerulonephritis (LN). Characterization of novel pathogenic pathways could pave the way to targeted therapeutic approaches. Aims. To investigate the role and relevance of PTX3/anti-PTX3 related immunity in systemic lupus erythematosus (SLE) patients and in lupus murine models and to explore the in vivo effects of restoration of SERPINB3 levels. Methods. The overall project comprised four experimental phases. Three out of four experiments were carried out on murine models of SLE, either New Zealand Black/White (NZB/W F1) or Mrl/lpr mice, while one experiment was conducted in humans. In the first experiment, intraperitoneal administration of recombinant SERPINB3 (7.5 μg/0.1mL or 15 μg/0.1mL) or placebo (PBS 0.1 ml) was carried out in 40 NZB/W F1 mice divided into four groups of 10 mice each. Group 1 and 2 were treated before (preventive approach and group 3 and 4 after (therapeutic approach) development of proteinuria ≥100mg/dl. Two additional groups included 20 MRL/lpr mice which were prophylactically injected with SERPINB3 (10 mice, group 5) or PBS (10 mice, group 6). The second experiment involved 30 NZB/W F1 mice which underwent subcutaneous immunization with PTX3+alum (n=10), PBS+alum (n=10) or PBS alone (n=10) three times three weeks apart, starting before development of proteinuria. For both experiments, time of occurrence and levels of anti-dsDNA and anti-C1q antibodies, proteinuria and serum creatinine, overall- and proteinuria-free survival were assessed in mice followed up to natural death. Subanalysis regarding anti-PTX3 antibody levels and function were performed in the second experiment. The last experiment on mice involved 22 NZB/W F1 female littermates divided into two groups of 10 mice each and treated with the same approach described in the second experiment. Ten mice (5 from each group) were sacrificed at week 22 and the other 10 at 29 weeks. Histological and ultrastructural lesions were compared using optical microscopy, immunoelectron microscopy (IEM), immunofluorescence (IF) and confocal microscopy. Data on humans were retrieved enrolling 38 SLE patients (12 with biopsy-proven LN and 26 without LN) and 22 matched healthy donors (HD). Characterization and comparison of circulating levels of PTX3 specific (PTX3+) B cells between patients and controls was performed by flow-cytometry. The differences between groups for nonparametric continuous variables were analyzed using Mann-Whitney U test or Kruskal-Wallis’s ANOVA test when appropriate; proteinuria-free survival rate (proteinuria <300 mg/dl) and survival rates were evaluated by Kaplan-Meyer method using Mantel-Cox test for comparison. Chi-squared test was used for histological comparison. A p value<0.05 was considered statistically significant. Results. Experiments on mice showed positive results in terms of clinical effects deriving from restoration of SERPINB3 levels or immunization with PTX3. SERPINB3-administered mice displayed a milder LN, with lower and delayed occurrence of nephritogenic antibodies and milder proteinuria at several timepoints, as well as a prolonged survival versus PBS groups. Immunization with PTX3 evoked a vaccine-like response with occurrence of anti-PTX3 antibodies only in immunized mice and delayed and decreased levels of nephritogenic antibodies and proteinuria, resulting in a significantly longer disease-free and overall survival. Among mice sacrificed at given timepoints, notable differences were observed at IEM, IIF and confocal microscopy. PTX3-immunized mice displayed less or no electron-dense deposits (EDD) along the glomerular basement membrane and the mesangium, and remarkably decreased glomerular deposition of IgG, C1q and PTX3 compared to PBS-treated mice. Moreover, PTX3 was found inside the EDD at IEM and was shown to co-localized with nuclear material. LN patients displayed significantly lower levels of circulating PTX3+ B cells in comparison to SLE and HD, showing a persistent decrease among naïve and memory PTX3+ specific subsets. Conclusions. Clinical improvement of a lupus-like disease following restoration of SERPINB3 levels and immunization with PTX3 in lupus murine models suggests that very early abnormalities affecting molecules involved in tissue homeostasis, apoptosis and removal of apoptotic debris may induce further development of SLE and SLE-specific manifestations within an unpredictable lag time. PTX3 more strikingly emerged as a novel antigen in LN progression and PTX3/anti-PTX3 immunity appear to function as an early level of regulation which may fail in patients developing LN. Consistently, acquisition of a targeted anti-PTX3 immunity could hinder the progression from the preclinical to the clinical stages of disease. Altogether, these findings may add a piece of knowledge on the mechanisms supporting LN development and progression, and suggest that a targeted modulation of the native immunity could improve renal manifestations in selected patients. In the short term, dosage of serum anti-PTX3 antibodies may become a handful tool to help in stratifying lupus patients according to the risk of developing LN.