Urinary CD80: a biomarker for a favorable response to corticosteroids in minimal change disease

Clinical significance of T lymphocyte subsets, immunoglobulin and complement expression in peripheral blood of children with steroid-dependent nephrotic syndrome/frequently relapsing nephrotic syndrome

OBJECTIVE

To investigate the clinical significance of T lymphocyte subsets, immunoglobulin and complement expression in the peripheral blood of children with steroid-dependent nephrotic syndrome/frequently relapsing nephrotic syndrome (SDNS/FRNS).

METHODS

A prospective study was conducted on 285 children with nephrotic syndrome (NS). Among the 285 patients, 187 children had steroid-sensitive nephrotic syndrome (SSNS) and 98 children had SDNS/FRNS according to their sensitivity to hormones. Meanwhile, 50 healthy children in the same period were selected as the control group. Serum albumin (ALB), blood urea nitrogen (BUN), serum creatinine (SCr), estimated glomerular filtration rate (eGFR), high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), CD3+, CD4+, CD8+, immunoglobulin IgA, IgG, IgM and complement C3 and C4 were measured upon admission, and the content of urinary CD80 was also determined.

RESULTS

Compared with the control group, BUN, SCr, hs-CRP and IL-6 levels, urinary CD80, IgA, IgM and C3 in the SDNS/FRNS and SSNS groups were significantly higher, while ALB, eGFR, CD3+, CD4+, CD4+/CD8+, IgG and IgG/IgM were significantly lower (all P<0.05). Compared with the SSNS group, BUN, SCr, hs-CRP and IL-6 levels in the SDNS/FRNS group were significantly higher, while ALB and eGFR levels were significantly lower (all P<0.05). Compared with the SDNS/FRNS group, IgM in the SSNS group was significantly lower, while CD4+/CD8+, urinary CD80 and IgG/IgM were significantly higher (all P<0.001).

CONCLUSION

Renal function decline and inflammatory response existed in children with NS. CD3+, CD4+, CD4+/CD8+ and IgG/IgM in peripheral blood were decreased, while IgA, IgM, C3 and urinary CD80 were increased. Moreover, renal function decline, increase of inflammatory factors, decrease of IgG/IgM and CD4+/CD8+ were more obvious in the SDNS/FRNS group.

CD80 Insights as Therapeutic Target in the Current and Future Treatment Options of Frequent-Relapse Minimal Change Disease

Minimal change disease (MCD) is the most common cause of idiopathic nephrotic syndrome in children, and it is well known for its multifactorial causes which are the manifestation of the disease. Proteinuria is an early consequence of podocyte injury and a typical sign of kidney disease. Steroid-sensitive patients react well with glucocorticoids, but there is a high chance of multiple relapses. CD80, also known as B7-1, is generally expressed on antigen-presenting cells (APCs) in steroid-sensitive MCD patients. Various glomerular disease models associated with proteinuria demonstrated that the detection of CD80 with the increase of urinary CD80 was strongly associated closely with frequent-relapse MCD patients. The role of CD80 in MCD became controversial because one contradicts finding. This review covers the treatment alternatives for MCD with the insight of CD80 as a potential therapeutic target. The promising effectiveness of CD20 (rituximab) antibody and CD80 inhibitor (abatacept) encourages further investigation of CD80 as a therapeutic target in frequent-relapse MCD patients. Therapeutic-based antibody towards CD80 (galiximab) had never been investigated in MCD or any kidney-related disease; hence, the role of CD80 is still undetermined. A new therapeutic approach towards MCD is essential to provide broader effective treatment options besides the general immunosuppressive agents with gruesome adverse effects.

Predicting the functional consequences of genetic variants in co-stimulatory ligand B7-1 using in-silico approaches

The purpose of this research is to identify and characterize deleterious genetic variants in the co-stimulatory ligand B7-1, also known as the human cluster of differentiation CD80 marker. The B7-1 ligand and the major histocompatibility complex class II (MHC II) molecules are the main determinants that provide B-cells the required competency to act as antigen presenting cells. For this, participation of both MHC class II molecules and CD80 is required. The interaction of the CD80 ligand with CD28 on the surface 7 of T_H cells plays a key role in the activation of TH cells and progression of B cells through the S phase, hence, leading to their proliferation in mitosis. A set of 2313 genetic variants in the B7-1 ligand have been mapped and retrieved from dbSNP database. Subsequently, 150 non-synonymous single nucleotide polymorphisms (nsSNPs) were mapped and subjected to the sequence and structural homology based predictions, which were further analyzed for protein stability and the disease phenotypes. Finally, we identified 7 potentially damaging nsSNPs in the B7-1 ligand that may affect its interaction with the cognitive receptor CD28, hence, may also interfere with TH cell activation and B cell proliferation. We propose that subsequent experimental analyses (stability, expression and interactions) on these proteins can provide a deep understanding about the effect of these variants on the structure and function of CD80.

CD80 expression and infiltrating regulatory T cells in idiopathic nephrotic syndrome of childhood

BACKGROUND

CD80 (also known as B7-1) is a co-stimulatory molecule that is expressed in biopsies and also excreted in urine in patients with minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). CD80 is inhibited by the cytotoxic T-lymphocyte-associated-antigen 4 (CTLA4), which is mainly expressed on regulatory T cells (Tregs). Ineffective circulating Treg response is involved in the pathogenesis of nephrotic syndrome. In this study, we evaluated CD80 expression and infiltrating Tregs in children with MCD and FSGS.

METHODS

Evaluation of CD80 expression and semi-quantitative evaluation of Tregs (FOXP3-positive CD4 T cells) were carried out in 31 kidney biopsies (12 MCD, 19 FSGS) with immunofluorescence and immunohistochemistry staining.

RESULTS

All MCD sections were stained negative; whereas six out of 19 FSGS sections (all from steroid-resistant (SR) patients), including one from a Wilms' tumor 1 (WT1) mutation-positive FSGS patient, stained positive for anti-CD80 goat antibody, and negative for anti-CD80 rabbit antibody. FSGS biopsy specimens had significantly higher FOXP3-positive cells/mm² compared with MCD and control samples (P < 0.001). Biopsy samples from SR-FSGS patients (n = 12) with positive CD80 staining (n = 6) had significantly less Tregs (FOXP3-positive CD4 T cells) compared with CD80 (-) biopsies (n = 6; P = 0.004).

CONCLUSION

CD80 expression was not detected in the majority of the archival biopsy sections and the results were not consistent across the different antibodies. In the SR-FSGS sections, however, CD80-positive biopsies had decreased FOXP3-positive CD4 T cells, suggesting that a decreased anti-inflammatory milieu may be the cause of increased CD80 expression.