An interleukin 6-based genetic risk score strengthened with interleukin 10 polymorphisms associated with long-term kidney allograft outcomes

Abstract

Of all kidney transplants, half are still lost in the first decade after transplantation. Here, using genetics, we probed whether interleukin 6 (IL-6) could be a target in kidney transplantation to improve graft survival. Additionally, we investigated if a genetic risk score (GRS) based on IL6 and IL10 variants could improve prognostication of graft loss. In a prospective cohort study, DNA of 1271 donor-recipient kidney transplant pairs was analyzed for the presence of IL6, IL6R, IL10, IL10RA, and IL10RB variants. These polymorphisms and their GRS were then associated with 15-year death-censored allograft survival. The C|C-genotype of the IL6 polymorphism in donor kidneys and the combined C|C-genotype in donor-recipient pairs were both associated with a reduced risk of graft loss (p = .043 and p = .042, respectively). Additionally, the GRS based on IL6, IL6R, IL10, IL10RA, and IL10RB variants was independently associated with the risk of graft loss (HR 1.53, 95%-CI [1.32-1.84]; p < .001). Notably, the GRS improved risk stratification and prediction of graft loss beyond the level of contemporary clinical markers. Our findings reveal the merits of a polygenic IL-6-based risk score strengthened with IL-10- polymorphisms for the prognostication and risk stratification of late graft failure in kidney transplantation.

Keywords: interleukins; kidney transplantation; long-term graft survival; polymorphisms.

FIGURE 1

(A) IL‐6‐related single‐nucleotide polymorphisms (SNPs) examined in the present study: rs1800795 causing a G→C nucleotide substitution resulting in an intronic variant of the IL‐6 gene (IL6) promoter region and rs2228145 (formerly rs8192284) leading to an A→C nucleotide substitution and an Asp→Ala missense mutation of IL‐6 receptor (IL6R) gene (IL6R). (B) IL‐10‐related single‐nucleotide polymorphisms (SNPs) examined in the present study: rs3135932 causing an A→C nucleotide variant and a Ser→Gly missense mutation in IL‐10Rα; rs2229113 leading to an A→C variant and an Arg→Gly missense mutation in IL‐10 receptor alpha‐unit (IL10Rα) gene (IL10RA); rs2834167 precipitating an A→C variant and a Lys→Glu missense mutation in IL‐10 receptor beta‐unit (IL10Rβ) gene (IL10RB); rs1800896 and rs1800871 causing C→T and A→G nucleotide substitutions, respectively, underlying independent upstream IL‐10 gene (IL10) variants; and, rs3024498 underpinning a T→C substitution resulting in a non‐coding transcript variant. Ala, alanine; Arg, arginine; Asp, aspartic acid; g., gene; Glu, glutamic acid; Gly, glycine; IL10(Rα/β), interleukin 10 (receptor alpha/beta) gene; IL6(R), interleukin 6 (receptor) gene; Lys, lysine; p., protein; Ser, serine.

FIGURE 2

Kaplan‐Meier survival curves of 15‐year death‐censored kidney allografts survival stratified by IL6 rs1800795 genotypes in the donors and donor‐recipient transplant pairs. (A) Cumulative death‐censored survival of kidney allografts based on the IL6 rs1800795 single nucleotide polymorphism (SNP) genotypes in allograft donors. The homozygous C|C‐genotype (homozygous model; green line) was compared to the heterozygous C|G‐genotype combined with the refence homozygous G|G‐genotype (black line). (B and C) Cumulative death‐censored survival of kidney allografts among transplant recipients with (B) female and (C) male allograft donors based on the IL6 rs1800795 single nucleotide polymorphism (SNP) genotypes. The homozygous C|C‐genotype (homozygous model; blue line) was compared to the heterozygous C|G‐genotype combined with the refence homozygous G|G‐genotype (black line). (D) Cumulative death‐censored survival of kidney allografts based on the donor‐recipient paired genotypes of the IL6 rs1800795 SNP, comparing (i) pairs with neither donor nor recipient C|C‐genotype presence (black line), (ii) presence of the C|C‐genotype in either donor or recipient (dark blue line), with (iii) C|C‐genotype presence in both the donor and recipient (light blue line). Data represent death‐censored survival curves. p‐values were calculated using log‐rank tests. IL6, interleukin 6 gene.

FIGURE 3

Kaplan‐Meier survival curves of 15‐year death‐censored kidney allograft survival stratified by IL‐6/‐10 genetic risk score tertiles in donor‐recipient kidney transplant pairs. (A) Cumulative death‐censored graft survival of kidney transplants based on tertiles of the interleukin 6 (IL‐6)/interleukin 10 (IL‐10) genetic risk score (GRS). The log‐rank test was used to compare the incidence of graft loss between the groups. (B) Forest plot of the hazard ratio of the IL‐6/‐10 with 15‐year death‐censored graft loss in our kidney transplant population and relevant subgroups. Data represent the hazard ratios with 95% confidence intervals of the GRS for 15‐year death‐censored graft survival in each population. The P‐interaction represents the P‐value for the interaction term between the GRS and the subgroup characteristic to identify potential modifiers in the Cox regression models. DBD, donation after brain death; DCD, donation after circulatory death; GRS, genetic risk score; HLA, human leukocyte antigen; hr, hour(s); min, minute(s); yr, year(s).