Is typing for HLA class II alleles beneficial in Indian children with idiopathic nephrotic syndrome?

Strong Association of the HLA-DR/DQ Locus with Childhood Steroid-Sensitive Nephrotic Syndrome in the Japanese Population

Background Nephrotic syndrome is the most common cause of chronic glomerular disease in children. Most of these patients develop steroid-sensitive nephrotic syndrome (SSNS), but the loci conferring susceptibility to childhood SSNS are mainly unknown.Methods We conducted a genome-wide association study (GWAS) in the Japanese population; 224 patients with childhood SSNS and 419 adult healthy controls were genotyped using the Affymetrix Japonica Array in the discovery stage. Imputation for six HLA genes (HLA-A, -C, -B, -DRB1, -DQB1, and -DPB1) was conducted on the basis of Japanese-specific references. We performed genotyping for HLA-DRB1/-DQB1 using a sequence-specific oligonucleotide-probing method on a Luminex platform. Whole-genome imputation was conducted using a phased reference panel of 2049 healthy Japanese individuals. Replication was performed in an independent Japanese sample set including 216 patients and 719 healthy controls. We genotyped candidate single-nucleotide polymorphisms using the DigiTag2 assay.Results The most significant association was detected in the HLA-DR/DQ region and replicated (rs4642516 [minor allele G], combined P_allelic=7.84×10^-23; odds ratio [OR], 0.33; 95% confidence interval [95% CI], 0.26 to 0.41; rs3134996 [minor allele A], combined P_allelic=1.72×10^-25; OR, 0.29; 95% CI, 0.23 to 0.37). HLA-DRB1*08:02 (Pc=1.82×10^-9; OR, 2.62; 95% CI, 1.94 to 3.54) and HLA-DQB1*06:04 (Pc=2.09×10^-12; OR, 0.10; 95% CI, 0.05 to 0.21) were considered primary HLA alleles associated with childhood SSNS. HLA-DRB1*08:02-DQB1*03:02 (Pc=7.01×10^-11; OR, 3.60; 95% CI, 2.46 to 5.29) was identified as the most significant genetic susceptibility factor.Conclusions The most significant association with childhood SSNS was detected in the HLA-DR/DQ region. Further HLA allele/haplotype analyses should enhance our understanding of molecular mechanisms underlying SSNS.

Association of HLA-DR/DQ alleles and haplotypes with nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is a debilitating renal problem in children resulting from an interaction between environmental and genetic factors including human leukocyte antigen genes (HLA). The aim of this work was to study the probable link between HLA alleles/haplotypes and NS in south India.

METHODS

HLA DRB1*/DQB1* alleles were genotyped in 183 NS (76 steroid sensitive-SSNS; 107 steroid resistant-SRNS) and paediatric healthy controls (PHCs; n = 91) using polymerase chain reaction-sequence specific primers (PCR-SSP). HLA-A/-B genotyping was performed for patients (n = 70) positive for DRB1*07-DQB1*02 haplotype to identify four locus extended haplotype.

RESULTS

The following alleles and haplotypes were strongly associated with NS (P < 0.05 as significant): DRB1*07 (SSNS, P < 7.98 × 10(-6) ; SRNS, P < 0.008), DQB1*02 (SSNS, P < 3.99 × 10(-6) ; SRNS, P < 0.002), DRB1*07-DQB1*02 (SSNS, P < 1.32 × 10(-4) ; SRNS, P < 0.010), DRB1*07-DQB1*0301,0304 (DQ7) (SSNS, P < 0.001) and DRB1*03-DQB1*02 (SRNS, P < 0.048). Protective associations were observed for alleles DRB1*10 (SRNS, P < 0.013), DQB1*05 (SSNS, P < 4.34 × 10(-6) ; SRNS, P < 0.01), DQB1*06 (SSNS, P < 0.003), and haplotypes DRB1*10-DQB1*06 (SSNS, P < 0.046; SRNS, P < 0.032) and DRB1*15-DQB1*05 (SSNS, P < 0.018). HLA-A/-B typing of 70 NS cases with two locus haplotype DRB1*07-DQB1*02 (70/183; 38.25%) revealed the presence of an extended haplotype 'A*03-B*07-DRB1*07-DQB1*02' (n = 35; 50%).

CONCLUSION

Our study revealed strong susceptible association of DRB1*07 with SRNS and DQB1*02 with SSNS. A gender predominant protective association was observed for DRB1*10 with SRNS females; DQB1*05 with SSNS and SRNS males. Further, the study documented the presence of an extended haplotype and pleiotropic action of DRB1*/DQB1* alleles in immune-mediated aetiology of NS in south India.

Genetic and in vivo determinants of glucocorticoid sensitivity in relation to clinical outcome of childhood nephrotic syndrome

Following initial glucocorticoid treatment, the clinical course in children with nephrotic syndrome is highly variable. Intrinsic sensitivity to glucocorticoids might be a determinant of this variability. Functional polymorphisms of the glucocorticoid receptor gene NR3C1 have been associated with either relatively impaired (GR-9β) or increased (BclI) glucocorticoid sensitivity. Here, in a prospective, well-defined cohort of children with nephrotic syndrome, we evaluated both carriage of GR-9β+TthIII-1 and BclI haplotypes in 113 children and a dexamethasone suppression test in 90 children in relation to their clinical outcome over a median follow-up of 4.4 years. Carriers of GR-9β+TthIII-1 had a significantly higher incidence of steroid dependence 13/25 (52%) compared with noncarriers 19/75 (25%) with a hazard ratio adjusted for gender, age, and descent of 3.04 with 95% confidence interval 1.37-6.74. Both first and frequent relapses happened significantly more often in GR-9β+TthIII-1 carriers than in noncarriers. There were no significant differences in therapeutic outcomes between carriers and noncarriers of the BclI haplotype. Results of the dexamethasone test showed no associations with clinical outcome. Thus, the GR-9β+TthIII-1 haplotype of the glucocorticoid receptor gene offers new insights into the clinical course of children with nephrotic syndrome.

Evaluation and management of steroid-sensitive nephrotic syndrome

PURPOSE OF REVIEW

This review examines new literature published in 2006 and 2007 on steroid-sensitive nephrotic syndrome.

RECENT FINDINGS

Steroid-sensitive nephrotic syndrome has long been thought to be due to lymphocyte-derived circulating factors leading to podocyte injury with subsequent proteinuria. New studies support this mechanism and implicate the T helper 2 cytokine IL-13. In addition a genetic mutation in familial nephrotic syndrome has been reported in a child, who responded to corticosteroid therapy. There are new clinical trial data supporting the efficacy of levamisole in steroid-sensitive nephrotic syndrome and preliminary trial data on mycophenolate mofetil supporting its efficacy as a steroid-sparing agent. Case reports support the use of the B cell-depleting antibody rituximab in steroid-sensitive nephrotic syndrome. Finally there is a meta-analysis of six studies suggesting an increase in the incidence of focal and segmental glomerulosclerosis in steroid-sensitive nephrotic syndrome over the last 20 years.

SUMMARY

Progress has been made towards elucidating the cause of steroid-sensitive nephrotic syndrome. Data from adequately powered randomized controlled trials are still required to evaluate therapies for frequently relapsing and steroid-dependent steroid-sensitive nephrotic syndrome.