POS0244 ASSOCIATION OF PROTEINASE 3 GENE (PRTN3) Val119Ile POLYMORPHISM (SNP rs351111) WITH RISK OF RELAPSE AMONG HOMOZYGOUS PATIENTS WITH PR3 ANCA-ASSOCIATED VASCULITIS

Background

The frequency of the proteinase 3 gene (PRTN3) polymorphisms in patients with ANCA-associated vasculitis (AAV) is not well characterized. We hypothesize that PRTN3 gene polymorphisms induce allosteric changes in PR3 conformation which may alter its interaction with ligands and PR3-ANCA during inflammation with potential implications for disease presentation and clinical outcomes.

Objectives

To analyze the association of PRTN3 Val119Ile polymorphism (SNP rs351111) with risk of relapse risk among homozygous patients with PR3 ANCA-associated vasculitis.

Methods

DNA variant calling for SNP rs351111 (chr.19:844020, c.355G>A) in PRTN3 gene assessed the allelic frequency in patients with PR3-AAV included in the Rituximab versus Cyclophosphamide (RAVE) trial. This was followed by RNA-seq variant calling to characterize the mRNA expression. We compared clinical presentation and outcomes between patients homozygous for PR3-Ile119 or PR3-Val119.

Results

Serum samples for DNA calling were available in 188 of the 197 patients with AAV in the RAVE cohort. 75 PR3-AAV patients had the allelic variant: 13 patients were homozygous for PR3-Ile119 and 62 patients were heterozygous PR3-Val119Ile with an allele frequency threshold of 29.3 – 55.1% of reads (Figure 1A and 1B). RNA-seq was available for 89 patients and the mRNA corresponding to the allelic variant was found in 35 PR3-AAV patients: 13 patients were homozygous for PR3-Ile119 and 22 patients were heterozygous PR3-Val119Ile with an allele frequency threshold of 11.1 – 62.8% of reads (Figure 1A and 1C). The agreement between the DNA calling results and the mRNA expression of the 86 patients that overlapped was 100%. We found an additional homozygous patient for PR3-Val119 in which blood was not available for DNA calling. We compared the clinical presentation and outcomes of 74 patients with PR3-AAV: 13 homozygous for PR3-Ile119 and 51 homozygous for PR3-Val119 (Table 1). The frequency of severe flares at 18 months in homozygous PR3-Ile119 was ≥ 2x higher when compared with homozygous PR3-Val119 (46.2% vs. 19.6%, p=0.048). We found no differences in clinical presentation.

Figure 1.

RAVE trial population distribution according to the zygosity status for PRTN3 gene (PR3 and MPO-ANCA patients) and DNA or RNA variant calling (panel A). Allelic frequency for rs351111, chr.19:844020 (c.355G>A) in PRTN3 among patients with AAV (PR3 and MPO-ANCA) in the DNA (panel B) and RNA (panel C) variant calling.

Table 1.

Outcomes of patients with PR3-ANCA according with PRTN3 zygosity.

PR3-ANCA (n=64)Homozygous PR3-Val119(n=51)HomozygousPR3-Ile119(n=13)p-value Remission, n (%)45 (88.2)13 (100)0.194 Complete remission, n (%)36 (70.6)10 (76.9)0.650 Any flare 18 months, n (%)30 (58.8)7 (53.8)0.746 Severe Relapse* 18 months, n (%)10 (19.6)6 (46.2)0.048

* Relapse was considered “Severe” if Birmingham Vasculitis Activity Score for Wegener’s Granulomatosis (BVAS/WG) > 3 or one major item as per the RAVE trial definition.

Abbreviations: ANCA - anti-neutrophil cytoplasmic antibody; Ile – isoleucine; n- number; PR3 - proteinase 3; Val - valine.

Conclusion

In patients with PR3-AAV the presence of PRTN3 Val119Ile polymorphism was associated with higher frequency of severe relapse. Further studies are necessary to understand the association of this observation with the risk of severe relapse.

References

[1]Stone JH et al N Engl J Med 2010; 363:221-232

Disclosure of Interests

None declared

THU0040 PROTEINASE 3-REACTIVE B CELL RECONSTITUTION AFTER TREATMENT WITH RITUXIMAB FOR ANCA-ASSOCIATED VASCULITIS

Background:

Proteinase 3 (PR3)-reactive B cells are present in PR3-ANCA-associated vasculitis (AAV) at levels higher than healthy controls.

Objectives:

To evaluate the dynamics of the PR3-reactive B cell repopulation in patients with PR3-AAV after treatment with rituximab, and to analyze possible associations between these immunological changes and long-lasting remissions.

Methods:

We analyzed all available frozen peripheral blood mononuclear cells (n=148) from 23 randomly-selected PR3-AAV patients who participated in the RAVE trial and achieved complete remission (BVAS=0, prednisone=0) after treatment with rituximab.

We measured PR3-reactive B cells and the relative subsets by a multi-color flow cytometry panel including CD19, IgD, CD27, CD38, CD24, and a biotinylated PR3 revealed by fluorescent streptavidin. The clinical data of the trial were correlated with flow-cytometry data.

Results:

10/23 (43%) patients relapsed during the follow up, 8/10 relapses were severe. At baseline, clinical features, PR3-ANCA levels, % of total PR3-reactive B cells and PR3-reactive B cell subsets were similar between relapsers and non-relapsers. All patients were followed until the end of the trial, for a mean of 44 months (25-75%IQR 31-54), without difference in follow-up time between relapsers and non-relapsers (p=0.98).

The majority of patients had B cell repopulation at 12 (range 12-24) months after rituximab. At the time of B cell repopulation, transitional (CD19+CD24+CD38+) and naïve (CD19+CD27+IgD-) B cells were higher compared to baseline, while total plasmablasts (PB) were unchanged, and mature B cells significantly decreased in both relapsers and non relapsers. PR3-reactive B cells reappeared in all the patients, and the % of PR3-reactive of B cells were higher at the B cell repopulation visit compared to baseline (5.82% vs 4.25%, p<0.05), while total B cells were lower (66/μL vs 151/μL, p<0.01), regardless of future relapse.

Within PR3-reactive B cells, only the % of PB (CD19+CD27+CD38+PR3+) were higher in relapsers vs. non-relapsers (median [25-75%IQR]; 1.95% [1.315-3.845] vs 0.84% [0.05-1.66], p=0.022) and severe relapsers vs non-severe relapsers (2.165% [1.66-4.315] vs 0.84% [0.1-1.74], p=0.015). Time-to-relapse and time-to severe-relapse were significantly shorter in patients with circulating PR3-PB higher than the median value of the cohort (1.6%) during B cell reconstitution (Figure 1A-B).

Conclusion:

In PR3-AAV, during B cell reconstitution after rituximab, the total fraction of PR3-B cells increases, due to the expansion of the transitional and naïve B cell compartments. Circulating PR3-PB within PR3-B cells are enriched in the peripheral blood of relapsing and severely relapsing patients compared to non-relapsing patients. Higher levels of PR3-PB after rituximab during B cell reappearance significantly increased the risk of subsequent relapse and severe relapse.

References:

[1]Cornec D, Berti A, Hummel A, et al. J Autoimmun. 2017

Disclosure of Interests:

Alvise Berti: None declared, Sophie Hillion: None declared, Amber Hummel: None declared, Eva Carmona: None declared, Tobias Peikert: None declared, Carol Langford: None declared, Peter A. Merkel: None declared, Paul Monach: None declared, Philip Seo: None declared, Robert Spiera Grant/research support from: Roche-Genetech, GSK, Boehringer Ingelheim, Chemocentryx, Corbus, Forbius, Sanofi, Inflarx, Consultant of: Roche-Genetech, GSK, CSL Behring, Sanofi, Janssen, Chemocentryx, Forbius, Mistubishi Tanabe, E. William St. Clair: None declared, Fernando Fervenza: None declared, Kristina Harris: None declared, John H. Stone Grant/research support from: Roche, Consultant of: Roche, Jacques-Olivier Pers: None declared, Ulrich Specks: None declared, Divi Cornec: None declared

Paradoxical body and kidney growth in potassium deficiency

In the growing animal, K deficiency (KD) retards body growth, but paradoxically stimulates renal growth. If KD persists, interstitial infiltrates appear and eventually tubulointerstitial fibrosis develops. In patients with chronic KD, renal cysts may form and with time tubulointerstitial disease with renal failure develops. Since early in KD, kidney IGF-I levels increase and may be a cause of the renal hypertrophy, and as TGF-beta promotes hypertrophy and fibrosis, we examined the expression of these growth factors in chronic KD. Rats were given a KD diet or pair or ad-lib fed a normal K diet. After 21 days, KD rats weighed less than pair fed controls, while the kidneys were 49% larger Serum IGF-I and kidney IGF-I protein levels were depressed, as were IGF-I mRNA levels, and is largely attributable to decreased food intake. Kidney IGFBP-1 and TGF-beta mRNA levels were increased (p < 0.05). There was marked hypertrophy and adenomatous hyperplasia of outer medullary collecting ducts, hypertrophy of thick ascending limbs of Henle (TALH) and interstitial infiltrates. Both nephron segments stained strongly for IGF-I and IGFBP-1. Only the non-hyperplastic TALH was strongly TGF-beta positive. Interstitial infiltrates containing monocytes/macrophages were prominent. These findings are consistent with a sustained role for IGF-I in promoting the renal hypertrophy of KD and appear to be caused by local trapping of IGF-I by the over-expressed IGFBP-1. Localization of TGF-beta to the hypertrophied non-hypoplastic tubules containing IGF-I, suggests that TGF-beta may be acting to convert the proliferative action of IGF-I into a hypertrophic response. TGF-beta may also contribute to the genesis of the tubulointerstitial infiltrate. Finally, the reduced levels of serum IGF-1 levels may be a cause of the blunted body growth.

Cerebral venous thrombosis in nephrotic syndrome

This report describes cerebral venous sinus thrombosis, a rare and perhaps under-diagnosed complication of nephrotic syndrome. We review the pathophysiology of the coagulopathy associated with nephrotic syndrome including abrupt renal loss of antithrombin III. We propose a rationale approach to treating this condition with low-molecular-weight heparin and antithrombin III replacement.

Acute renal failure due to postinfectious glomerulonephritis during pregnancy

Acute renal failure is a rare but potentially devastating complication of pregnancy. Among its many potential causes is acute postinfectious glomerulonephritis. We describe a case of acute renal failure during pregnancy, provide the histologic features of the renal biopsy, and discuss the differential diagnosis. Postinfectious glomerulonephritis can present rapidly after clinical infection and cause acute renal failure in pregnancy.