Post-transplant recurrence of steroid resistant nephrotic syndrome in children: the Italian experience

Background: Steroid resistant nephrotic syndrome (SRNS) is a frequent cause of end stage renal disease in children and post-transplant disease recurrence is a major cause of graft loss. Methods: We identified all children with SRNS who underwent renal transplantation in Italy, between 2005 and 2017. Data were retrospectively collected for the presence of a causative gene mutation, sex, histology, duration of pre-transplant dialysis, age at onset and transplant, HLA matching, recurrence, therapy for recurrence, and graft survival. Results: 101 patients underwent a first and 22 a second renal transplant. After a median follow-up of 58.5 months, the disease recurred on the first renal transplant in 53.3% of patients with a non-genetic and none with a genetic SRNS. Age at transplant > 9 years and the presence of at least one HLA-AB match were independent risk factors for recurrence. Duration of dialysis was longer in children with relapse, but did not reach statistical significance. Overall, 24% of patients lost the first graft, with recurrence representing the commonest cause. Among 22 patients who underwent a second transplant, 5 suffered of SRNS recurrence. SRNS relapsed in 5/9 (55%) patients with disease recurrence in their first transplant and 2 of them lost the second graft. Conclusions: Absence of a causative mutation represents the major risk factor for post-transplant recurrence in children with SRNS, while transplant can be curative in genetic SRNS. A prolonged time spent on dialysis before transplantation has no protective effect on the risk of relapse and should not be encouraged. Retransplantation represents a second chance after graft loss for recurrence

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo (2): Planted Antigens.

Glomerular planted antigens (histones,DNA,andC1q) arepotential targets of autoimmunity in lupus nephritis (LN). However, the characterization of these antigens in human glomeruli in vivo remains inconsistent. We eluted glomerular autoantibodies recognizing planted antigens from laser-microdissected renal biopsy samples of 20 patientswith LN. Prevalent antibody isotypes were defined, levelswere determined, and glomerular colocalization was investigated. Renal and circulating antibodieswerematched, and serum levelswere compared in 104 patients with LN, 84 patients with SLE without LN, and 50 patients with rheumatoid arthritis (RA). Autoantibodies against podocyte antigens (antia-enolase/antiannexin AI) were also investigated. IgG2 autoantibodies against DNA, histones (H2A, H3, and H4), and C1q were detected in 50%, 55%, and 70% of biopsy samples, respectively. Anti-DNA IgG3 was the unique non-IgG2 anti-DNA deposit, and anti-C1q IgG4 was mainly detected in subepithelial membranous deposits. Anti-H3, anti-DNA, and anti-C1q IgG2 autoantibodies were also prevalent in LN serum, which also contained IgG3 against the antigen panel and anti-C1q IgG4. Serum and glomerular levels of autoantibodies were not strictly associated. High serum levels of all autoantibodies detected, including anti a-enolase and antiannexin AI, identified LN versus SLE and RA. Anti-H3 and antia-enolase IgG2 levels had the most remarkable increase in LN serum and represented a discriminating feature of LN in principal component analysis. The highest levels of these two autoantibodies were also associated with proteinuria.3.5 g/24 hours and creatinine>1.2 mg/dl. Our findings suggest that timely autoantibody characterization might allow outcome prediction and targeted therapies for patients with nephritis

Autoantibody-mediated impairment of DNASE1L3 activity in sporadic systemic lupus erythematosus

Antibodies to double-stranded DNA (dsDNA) are prevalent in systemic lupus erythematosus (SLE), particularly in patients with lupus nephritis, yet the nature and regulation of antigenic cell-free DNA (cfDNA) are poorly understood. Null mutations in the secreted DNase DNASE1L3 cause human monogenic SLE with anti-dsDNA autoreactivity. We report that >50% of sporadic SLE patients with nephritis manifested reduced DNASE1L3 activity in circulation, which was associated with neutralizing autoantibodies to DNASE1L3. These patients had normal total plasma cfDNA levels but showed accumulation of cfDNA in circulating microparticles. Microparticle-associated cfDNA contained a higher fraction of longer polynucleosomal cfDNA fragments, which bound autoantibodies with higher affinity than mononucleosomal fragments. Autoantibodies to DNASE1L3- sensitive antigens on microparticles were prevalent in SLE nephritis patients and correlated with the accumulation of cfDNA in microparticles and with disease severity. DNASE1L3-sensitive antigens included DNA-associated proteins such as HMGB1. Our results reveal autoantibody-mediated impairment of DNASE1L3 activity as a common nongenetic mechanism facilitating antidsDNA autoreactivity in patients with severe sporadic SLE

Glomerular autoimmune multicomponents of human lupus nephritis in vivo: α-enolase and annexin AI

Renal targets of autoimmunity in human lupus nephritis (LN) are unknown. We sought to identify autoantibodies and glomerular target antigens in renal biopsy samples from patients with LN and determine whether the same autoantibodies can be detected in circulation. Glomeruli were microdissected from biopsy samples of 20 patients with LN and characterized by proteomic techniques. Serum samples from large cohorts of patients with systemic lupus erythematosus (SLE) with and without LN and other glomerulonephritides were tested. Glomerular IgGs recognized 11 podocyte antigens, with reactivity varying by LN pathology. Notably, IgG2 autoantibodies against \u3b1-enolase and annexin AI were detected in 11 and 10 of the biopsy samples, respectively, and predominated over other autoantibodies. Immunohistochemistry revealed colocalization of \u3b1-enolase or annexin AI with IgG2 in glomeruli. High levels of serum anti-\u3b1-enolase (>15 mg/L) IgG2 and/or anti-annexin AI (>2.7 mg/L) IgG2 were detected in most patients with LN but not patients with other glomerulonephritides, and they identified two cohorts: patients with high anti-\u3b1-enolase/low anti-annexin AI IgG2 and patients with low anti-\u3b1-enolase/high anti-annexin AI IgG2. Serum levels of both autoantibodies decreased significantly after 12months of therapy for LN. Anti-\u3b1-enolase IgG2 recognized specific epitopes of \u3b1-enolase and did not cross-react with dsDNA. Furthermore, nephritogenic monoclonal IgG2 (clone H147) derived from lupus-prone MRL-lpr/lpr mice recognized human \u3b1-enolase, suggesting homology between animal models and human LN. These data show a multiantibody composition in LN, where IgG2 autoantibodies against \u3b1-enolase and annexin AI predominate in the glomerulus and can be detected in serum

Genetic drivers of kidney defects in the digeorge syndrome

BACKGROUND The DiGeorge syndrome, the most common of the microdeletion syndromes, affects multiple organs, including the heart, the nervous system, and the kidney. It is caused by deletions on chromosome 22q11.2; the genetic driver of the kidney defects is unknown. METHODS We conducted a genomewide search for structural variants in two cohorts: 2080 patients with congenital kidney and urinary tract anomalies and 22,094 controls. We performed exome and targeted resequencing in samples obtained from 586 additional patients with congenital kidney anomalies. We also carried out functional studies using zebrafish and mice. RESULTS We identified heterozygous deletions of 22q11.2 in 1.1% of the patients with congenital kidney anomalies and in 0.01% of population controls (odds ratio, 81.5; P = 4.5×1014). We localized the main drivers of renal disease in the DiGeorge syndrome to a 370-kb region containing nine genes. In zebrafish embryos, an induced loss of function in snap29, aifm3, and crkl resulted in renal defects; the loss of crkl alone was sufficient to induce defects. Five of 586 patients with congenital urinary anomalies had newly identified, heterozygous protein-Altering variants, including a premature termination codon, in CRKL. The inactivation of Crkl in the mouse model induced developmental defects similar to those observed in patients with congenital urinary anomalies. CONCLUSIONS We identified a recurrent 370-kb deletion at the 22q11.2 locus as a driver of kidney defects in the DiGeorge syndrome and in sporadic congenital kidney and urinary tract anomalies. Of the nine genes at this locus, SNAP29, AIFM3, and CRKL appear to be critical to the phenotype, with haploinsufficiency of CRKL emerging as the main genetic driver

BRAIN METABOLISM OF AMINO ACIDS AND AMMONIA IN PATIENTS WITH CHRONIC RENAL INSUFFICIENCY

Brain metabolism of amino acids and ammonia in patients with chronic renal insufficiency. The cerebral metabolism of amino acids (AA) and ammonia in the postabsorptive state was evaluated in 8 subjects with normal renal function and in 6 patients with chronic renal insufficiency (CRI) by measuring the differences between the arterial and the internal jugular venous concentrations of free AA and ammonia. In normal conditions, the brain extracts serine, glutamine, proline, glycine, valine, ½cystine, isoleucine, leucine, and lysine. In CRI, cerebral glycine and ½cystine uptake increases, valine and isoleucine extraction decreases, glutamine uptake disappears, and ammonia extraction becomes evident. The cerebral extraction of glycine is correlated with the arterial concentration of glycine, serine, and branched-chain AA. The extraction of ½cystine is correlated with the arterial concentration of ½cystine and tyrosine. Finally, the extractions of valine and ammonia are correlated with the arterial concentration of valine and ammonia, respectively. It follows that alterations of blood AA and ammonia concentrations observed in CRI markedly affect the cerebral uptake of some AA and ammonia. The lack of cerebral glutamine extraction might be due to an enhanced production and/or, more likely, to an impaired utilization of this AA by the brain. Data reported here suggest that in CRI cerebral nitrogen metabolism is altered; such alterations may play a pathogenic role in uremic encephalopathy.Métabolisme cérébral des acides aminés et de l'ammoniaque chez les malades atteints d'insuffisance rénale chronique. Le métabolisme cérébral des acides aminés (AA) et de l'ammoniaque dans la phase post absorption a été étudié chez 8 sujets ayant une fonction rénale normale et 6 malades atteints d'insuffisance rénale chronique par la mesure de la différence de concentration artério-vieneuse jugulaire interne des AA et de l'ammoniaque. Dans les conditions normales le cerveau extrait la serine, la glutamine, la proline, la glycine, la valine, la ½ cystine, l'isoleucine, la leucine et la lysine. Dans l'insuffisance rénale chronique la captation cérébrale de glycine et de ½ cystine augmente, l'extraction de valine et d'isoleucine diminue, la captation de glutamine disparait et l'extraction d'ammoniaque devient évidente. L'extraction cérébrale de glycine est corrélée à la concentration artérielle de glycine, de serine et des AA à chaine latérale. L'extraction de la ½ cystine est corrélée à la concentration artérielle de ½ cystine et de tyrosine. Enfin les extractions de valine et d'ammoniaque sont corrélées respectivement avec les concentrations de valine et d'ammoniaque. Il en résulte que les modifications des concentrations sanguines des AA et de l'ammoniaque observées dans l'insuffisance rénale chronique affectent de façon importante la captation cérébrale de certains A A et de l'ammoniaque. L'absence d'extraction cérébrale de glutamine pourrait être due à une augmentation de la production et/ou, plus probablement, à une utilisation défectueuse de cet acide aminé par le cerveau. Les résultats rapportés suggèrent qu'au cours de l'insuffisance rénale chronique le métabolisme cérébral de l'azote est modifié. Ces modifications pourraient jouer un rôle pathogénique dans l'encéphalopathie urémique