What Is Hidden in Patients with Unknown Nephropathy? Genetic Screening Could Be the Missing Link in Kidney Transplantation Diagnosis and Management.

Between 15-20% of patients with end stage renal disease (ESRD) do not know the cause of the primary kidney disease and can develop complications after kidney transplantation. We performed a genetic screening in 300 patients with kidney transplantation, or undiagnosed primary renal disease, in order to identify the primary disease cause and discriminate between overlapping phenotypes. We used a custom-made panel for next-generation sequencing (Agilent technology, Santa Clara, CA, USA), including genes associated with Fabry disease, podocytopaties, complement-mediated nephropathies and Alport syndrome-related diseases. We detected candidate diagnostic variants in genes associated with nephrotic syndrome and Focal Segmental Glomerulosclerosis (FSGS) in 29 out of 300 patients, solving about 10% of the probands. We also identified the same genetic cause of the disease (PAX2: c.1266dupC) in three family members with different clinical diagnoses. Interestingly we also found one female patient carrying a novel missense variant, c.1259C>A (p.Thr420Lys), in the GLA gene not previously associated with Fabry disease, which is in silico defined as a likely pathogenic and destabilizing, and associated with a mild alteration in GLA enzymatic activity. The identification of the specific genetic background may provide an opportunity to evaluate the risk of recurrence of the primary disease, especially among patient candidates living with a donor kidney transplant.

FHR5 Binds to Laminins, Uses Separate C3b and Surface-Binding Sites, and Activates Complement on Malondialdehyde-Acetaldehyde Surfaces.

Factor H related-protein 5 (CFHR5) is a surface-acting complement activator and variations in the CFHR5 gene are linked to CFHR glomerulonephritis. In this study, we show that FHR5 binds to laminin-521, the major constituent of the glomerular basement membrane, and to mesangial laminin-211. Furthermore, we identify malondialdehyde-acetaldehyde (MAA) epitopes, which are exposed on the surface of human necrotic cells (Homo sapiens), as new FHR5 ligands. Using a set of novel deletion fragments, we show that FHR5 binds to laminin-521, MAA epitopes, heparin, and human necrotic cells (HUVECs) via the middle region [short consensus repeats (SCRs) 5-7]. In contrast, surface-bound FHR5 contacts C3b via the C-terminal region (SCRs8-9). Thus, FHR5 uses separate domains for C3b binding and cell surface interaction. MAA epitopes serve as a complement-activating surface by recruiting FHR5. The complement activator FHR5 and the complement inhibitor factor H both bind to oxidation-specific MAA epitopes and FHR5 competes with factor H for binding. The C3 glomerulopathy-associated FHR21-2-FHR5 hybrid protein is more potent in MAA epitope binding and activation compared with wild-type FHR5. The implications of these results for pathology of CFHR glomerulonephritis are discussed. In conclusion, we identify laminins and oxidation-specific MAA epitopes as novel FHR5 ligands and show that the surface-binding site of FHR5 (SCRs5-7) is separated from the C3b binding site (SCRs8-9). Furthermore, FHR5 competes with factor H for binding to MAA epitopes and activates complement on these modified structures.

The complement system in the pathogenesis and progression of kidney diseases: What doesn't kill you makes you older.

The Complement System is an evolutionarily conserved component of immunity that plays a key role in host defense against infections and tissue homeostasis. However, the dysfunction of the Complement System can result in tissue damage and inflammation, thereby contributing to the development and progression of various renal diseases, ranging from atypical Hemolytic Uremic Syndrome to glomerulonephritis. Therapeutic interventions targeting the complement system have demonstrated promising results in both preclinical and clinical studies. Currently, several complement inhibitors are being developed for the treatment of complement-mediated renal diseases. This review aims to summarize the most recent insights into complement activation and therapeutic inhibition in renal diseases. Furthermore, it offers potential directions for the future rational use of complement inhibitor drugs in the context of renal diseases.

Case report: Novel FHR2 variants in atypical Hemolytic Uremic Syndrome: A case study of a translational medicine approach in renal transplantation.

Atypical hemolytic-uremic syndrome (aHUS) is a severe thrombotic microangiopathy in which kidney involvement is common. aHUS can be due to either genetic or acquired abnormalities, with most abnormalities affecting the alternative complement pathway. Several genetic factors/alterations can drive the clinical presentation, therapeutic response, and risk of recurrence, especially recurrence following kidney transplantation. We report here the case of a 22-year-old man who developed a severe form of aHUS. Renal biopsy revealed thrombotic microangiopathy and features of chronic renal damage. Despite two eculizumab infusions, the patient remained dialysis dependent. Two novel rare variants, c.109G>A (p.E37K) and c.159 C>A (p.Y53*), were identified in the factor H-related 2 (FHR2) gene, and western blot analysis revealed a significant reduction in the level of FHR2 protein in the patient's serum. Although FHR2 involvement in complement 3 glomerulopathy has been reported previously, a role for FRH2 as a complement modulator has not yet been definitively shown. In addition, no cases of aHUS in individuals with FHR2 variants have been reported. Given the role of FHRs in the complement system and the fact that this patient was a candidate for a kidney transplant, we studied the relevance of low FHR2 plasma levels through a set of functional in vitro assays. The aim of our work was to determine if low FHR2 plasma levels could influence complement control at the endothelial surface with a view to identifying a therapeutic approach tailored to this specific patient. Interestingly, we observed that low FHR2 levels in the patient's serum could induce complement activation, as well as C5b-9 deposition on human endothelial cells, and affected cell morphology. As C5b-9 deposition is a prerequisite for endothelial cell damage, these results suggest that extremely low FHR2 plasma levels increase the risk of aHUS. Given their ability to reduce C5b-9 deposition, recombinant FHR2 and eculizumab were tested in vitro and found to inhibit hemolysis and endothelial cell surface damage. Both molecules showed effective and comparable profiles. Based on these results, the patient underwent a kidney transplant, and received eculizumab as induction and maintenance therapy. Five years after transplantation, the patient remains in good general health, with stable graft function and no evidence of disease recurrence. To our knowledge, this is first reported case of an aHUS patient carrying FHR2 mutations and provides an example of a translational therapeutic approach in kidney transplantation.

Severe COVID-19 by SARS-CoV-2 Lineage B.1.1.7 in Vaccinated Solid-Organ Transplant Recipients: New Preventive Strategies Needed to Protect Immunocompromised Patients.

BACKGROUND: Solid-organ transplant (SOT) recipients are at a high risk of severe COVID-19, and are priority for vaccination. Here, we describe three cases of severe COVID-19 caused by SARS-CoV-2 B.1.1.7 lineage in vaccinated SOT recipients. METHODS: Three SOT patients were hospitalized in the Policlinico Hospital of Bari (southern Italy) and underwent nasopharyngeal swabs for molecular detection of SARS-CoV-2 genes and spike protein mutations by real-time PCR. One sample was subjected to whole-genome sequencing. RESULTS: One patient was a heart transplant recipient and two were kidney transplant recipients. All were hospitalized with severe COVID-19 between March and May 2021. Two patients were fully vaccinated and one had received only one dose of the BNT162b2 mRNA vaccine. All the patients showed a high viral load at diagnosis, and molecular typing revealed the presence of B.1.1.7 lineage SARS-CoV-2. In all three cases, prolonged viral shedding was reported. CONCLUSIONS: The three cases pose concern about the role of the B.1.1.7 lineage in severe COVID-19 and about the efficacy of COVID-19 vaccination in immunocompromised patients. Protecting immunocompromised patients from COVID-19 is a challenge. SOT recipients show a suboptimal response to standard vaccination, and thus, an additive booster or a combined vaccination strategy with mRNA, protein/subunit, and vector-based vaccines may be necessary. This population should continue to practice strict COVID-19 precautions post-vaccination, until new strategies for protection are available.

Sphingomonas paucimobilis outbreak in a dialysis room: Case report and literature review of an emerging healthcare associated infection.

Sphingomonas paucimobilis is an emerging aerobic, nonfermenting gram-negative, opportunistic bacterium involved in many healthcare-associated infections. We herein report the first outbreak of S paucimobilis catheter related bacteriemia occurred on the same day in 3 patients sharing a dialysis room. This report suggests that S paucimobilis could represent a further emerging cause of rapidly spreading healthcare-associated infections, and highlights the importance of a high level of surveillance and control measures.

Mid-Aortic Syndrome: A Rare Cause of Renovascular Hypertension in Childhood Treated Percutaneously with an Unusual Vascular Access.

INTRODUCTION: Mid-Aortic Syndrome (MAS) is a rare vascular malformation characterized by segmental narrowing of the abdominal aorta and stenosis of its principal branches. Patients affected by MAS typically present malignant renovascular hypertension, with variable clinical symptoms like claudication, abdominal angina, and headache. Moreover, they can develop other complications, such as hypertensive encephalopathy, congestive heart failure and vascular brain accidents. Hypertension with MAS is often resistant to multidrug therapy, requiring a surgical approach to treat the clinical symptoms, prevent or block organ damage and normalize the blood pressure. CASE REPORT: Here, the case of a 4-year-old boy showing elevated blood pressure with left ventricular hypertrophy leading to idiopathic MAS, who was successfully treated with percutaneous transcatheter renal angioplasty (PTRA) using an unusual, anterograde access, is reported. DISCUSSION AND CONCLUSION: In children and adolescents, vascular malformations like MAS must be considered as a possible cause of hypertension. PTRA is a successful therapeutic strategy in children with severe renovascular hypertension. Anterograde access, using an axillary artery, can be a valid approach for PTRA when femoral access is difficult to achieve.

Mutational Spectrum of CYP24A1 Gene in a Cohort of Italian Patients with Idiopathic Infantile Hypercalcemia.

BACKGROUND/AIMS: Loss-of-function mutations in the CYP24A1 gene, which encodes the vitamin D-24 hydroxylase, have been recognized as a cause of elevated 1,25-dihydroxyvitamin D concentrations, hypercalcemia, hypercalciuria, nephrocalcinosis and nephrolithiasis in infants and adults. As only a case report describing 2 adult patients has been reported in Italian population, we report here the mutation analysis of CYP24A1 gene in an Italian cohort of 12 pediatric and adult patients with idiopathic infantile hypercalcemia (IIH). METHODS: We performed mutational screening of CYP24A1 gene in a cohort of 12 Italian patients: 8 children with nephrocalcinosis, hypercalcemia and PTH levels <10 pg/ml and 4 adult patients with nephrolithiasis, mild hypercalcemia and PTH levels <10 pg/ml from 11 unrelated Italian families. Clinical and biochemical data were collected. Genomic DNA was extracted from peripheral blood leucocytes using standard methods, and whole coding sequence of CYP24A1 gene was analysed in all patients and family members by polymerase chain reaction and direct sequencing. The potential pathogenicity of the newly identified missense mutations was evaluated by 3 different in silico approaches (Sorting Intolerant from Tolerant, Polyphen and Mutation Taster) and by comparative analysis in 14 different species using ClustalW software. RESULTS: CYP24A1 bi-allelic mutations were found in 8 individuals from 7 Italian families (7/11; 64%). Overall, 6 different CYP24A1 mutations, including one small deletion (p.Glu143del), 4 missense mutations (p.Leu148Pro; p.Arg396Trp; p.Pro503Leu; p.Glu383Gln) and one nonsense mutation (p.Tyr220*) were identified. Two out of 6 mutations (p.Tyr220* and p.Pro503Leu) were not previously described. Moreover, a new CYP24A1 variant was identified by genetic screening of asymptomatic controls. CONCLUSION: To the best of our knowledge, this is the first report of a CYP24A1 molecular analysis performed in an Italian cohort of adult and pediatric Italian patients. This study (1) confirms that CYP24A1 plays a causal role in some but not all cases of IIH (64%); (2) expands the spectrum of known CYP24A1 pathogenic mutations; (3) describes 2 hotspots detected in 50% of all Italian cases; and (4) emphasizes the importance of recognition and genetic diagnosis of CYP24A1 defects in infantile as well as adult hypercalcemia.