AB0146 BAFF, APRIL y BAFFR: DIFFERENTIAL BIOMARKERS BETWEEN IgA VASCULITIS AND IgA NEPHROPATHY?

Abstract

BackgroundIgA vasculitis (IgAV) and IgA nephropathy (IgAN) are inflammatory conditions [1, 2], that share pathogenic mechanisms [1], in which B-lymphocytes are described as key cells implicated in these processes. BAFF, APRIL and BAFF-R are cytokines implicated in the development of B-lymphocytes [3, 4] and in autoimmune processes [5, 6]. In this regard, an influence of BAFF, APRIL and BAFFR polymorphisms was observed on several immune-mediated conditions, being BAFF GCTGT>A a shared insertion-deletion variant for inflammatory conditions [7, 8].ObjectivesTo determine whether BAFF, APRIL and BAFFR could be used as differential biomarkers between IgAV and IgAN.MethodsBAFF rs374039502 (which colocalizes with BAFF GCTGT>A), two tag variants within APRIL (rs11552708 and rs6608) and two tag variants within BAFFR (rs7290134 and rs77874543) were genotyped in 394 Caucasian IgAV patients, 95 patients with IgAN and 832 matched healthy controls.ResultsSimilar genotype and allele frequencies were observed in the whole cohort of patients with IgAV when compared to those with IgAN when BAFF, APRIL and BAFFR variants were analyzed independently (Table 1). In accordance with that, no BAFF, APRIL and BAFFR genotype or allele differences were detected between IgAV patients who developed nephritis and patients with IgAN (Table 1). Additionally, no statistically significant differences were observed between the whole cohort of patients with IgAV and healthy controls as well as between patients with IgAN and healthy controls when each when BAFF, APRIL and BAFFR genetic variant was also analyzed independently (Table 1). Similar results were disclosed when haplotype frequencies of APRIL and BAFFR were compared between the different comparative groups above mentioned (data not shown).Table 1.Genotype and allele frequencies of BAFF, APRIL and BAFFR in the whole cohort of patients with IgAV, patients with IgAV who developed nephritis, patients with IgAN and healthy controls.PolymorphismChangeData setGenotypes, % (n)Alleles, % (n)1/21/11/22/212BAFF rs374039502T/AIgAV92.1 (363)7.9 (31)0.096.1 (757)3.9 (31)IgAV with nephritis90.1 (128)9.9 (14)0.095.1 (270)4.9 (14)IgAN91.6 (87)8.4 (8)0.095.8 (182)4.2 (8)Controls91.8 (764)7.8 (65)0.4 (3)95.7 (1593)4.3 (71)APRIL rs11552708G/AIgAV78.7 (310)20.1 (79)1.3 (5)88.7 (699)11.3 (89)IgAV with nephritis81.1 (116)18.9 (27)0.090.6 (259)9.4 (27)IgAN75.8 (72)23.2 (22)1.1 (1)87.4 (166)12.6 (24)Controls78.7 (655)19.7 (164)1.6 (13)88.6 (1474)11.4 (190)APRIL rs6608C/TIgAV72.6 (286)25.4 (100)2.0 (8)85.3 (672)14.7 (116)IgAV with nephritis75.5 (108)23.1 (33)1.4 (2)87.1 (249)12.9 (37)IgAN65.3 (62)30.5 (29)4.2 (4)80.5 (153)19.5 (37)Controls71.0 (591)26.6 (221)2.4 (20)84.3 (1403)15.7 (261)BAFFR rs7290134A/GIgAV58.9 (232)35.5 (140)5.6 (22)76.6 (604)23.4 (184)IgAV with nephritis60.1 (86)32.2 (46)7.7 (11)76.2 (218)23.8 (68)IgAN57.9 (55)38.9 (37)3.2 (3)77.4 (147)22.6 (43)Controls58.7 (488)35.1 (292)6.3 (52)76.2 (1268)23.8 (396)BAFFR rs77874543G/CIgAV83.2 (328)15.5 (61)1.3 (5)91.0 (717)9.0 (71)IgAV with nephritis83.1 (118)16.9 (24)0.091.5 (260)8.5 (24)IgAN86.3 (82)13.7 (13)0.093.2 (167)6.8 (13)Controls83.7 (696)16.0 (133)0.4 (3)91.6 (1525)8.4 (139)IgAV: IgA vasculitis; IgAN: IgA nephropathy.ConclusionOur results reveal a similar BAFF, APRIL and BAFFR genetic distribution in IgAV and IgAN, suggesting that these genes could not be used as differential biomarkers between these pathologies.