A novel hybrid CFHR1/CFH gene causes atypical hemolytic uremic syndrome

Background

Mutations in complement factor H (CFH) are associated with complement dysregulation and the development of an aggressive form of atypical hemolytic uremic syndrome (aHUS) that progresses to end-stage renal disease (ESRD) and in most patients has a high rate of recurrence following transplantation. Sequence analysis of CFH and its downstream complement factor H-related genes (CFHR1-5) reveals several macrohomologous blocks caused by large genomic duplications. This high degree of sequence identity renders this area susceptible to nonallelic homologous recombination (NAHR) events, resulting in large-scale deletions, duplications, and the generation of hybrid CFH genes.

Case-Diagnosis

Here, we report the finding of a novel CFHR1/CFH hybrid gene created by a de novo NAHR event in a 14-year-old girl with aHUS. The resulting fusion protein contains the first three short consensus repeats (SCRs) of CFHR1 and the terminal two SCRs of CFH.

Conclusions

This finding demonstrates a novel pathogenic mechanism for the development of aHUS. Additionally, since standard Sanger sequencing is unable to detect such rearrangements, all aHUS patients should receive comprehensive genetic screening that includes analysis of copy number variation in order to identify patients with poor clinical prognoses.     

Renal Transplantation Under Prophylactic Eculizumab in Atypical Hemolytic Uremic Syndrome With CFH/CFHR1 Hybrid Protein

We report the first observation of successful kidney transplantation under pre‐emptive eculizumab treatment in a 7‐year‐old boy with atypical hemolytic uremic syndrome (aHUS) and a known hybrid CFH/CFHR1 gene, who was dependent on plasma therapy during the 3‐year dialysis period. The hybrid CFH/CFHR1 protein has an altered C3b/C3d binding, is incapable to protect cells from complement attack and is directly implicated in aHUS pathogenesis. There was no evidence of recurrence during the first 16‐month follow‐up period. We conclude that eculizumab alone, without plasma therapy (plasma infusion and/or plasma exchange), is sufficient to prevent recurrence of aHUS and to maintain long‐term graft function.     

Risk factors for hyperlipidemia in long-term pediatric renal transplant recipients

Hyperlipidemia (HL) is a common problem in adult renal transplant (TP) recipients, contributing to an increased risk of cardiovascular disease and chronic TP nephropathy. There are multiple causes of HL post renal TP in adult patients, including pre TP HL, immunosuppressive agents, renal dysfunction, hypoalbuminemia secondary to nephrotic syndrome, obesity, and conditions that lead to end-stage renal disease (ESRD). We evaluated the incidence and risk factors of HL in 62 pediatric renal TP recipients (15.4±4.2 years, range-3.0–22.3 years) with long-term (6.7±3.1 years) functioning [glomerular filtration rate (GFR) 66.7±23.2 ml/min per 1.73 m²] allografts. The mean serum cholesterol (C) level was 205.5±43.6 mg/dl. Thirty-two patients (51.6%) exhibited elevated serum C levels. The mean serum triglyceride (TG) level was 157.3±88.4 mg/dl. Serum TG levels were elevated in 32 patients (51.6%). In patients with elevated serum levels of either C or TG, the mean low-density lipoprotein level (LDL) was 138.6±44.1 mg/dl (normal <130 mg/dl) and the high-density lipoprotein (HDL) level 54.6±15.9 mg/dl (normal>34 mg/dl). Of those patients studied, 45.5% had high LDL levels, whereas 9.1% exhibited low HDL levels. The two risk factors for elevated serum C levels in our patient population were pre-TP HL and increased years since TP. The only risk factor for elevated serum TG levels was reduced GFR. A family history of HL had a significant deleterious impact upon serum levels of C (P=0.01), but did not affect serum TG levels (P=0.7). Years on dialysis prior to TP, history of prior TP, gender, body mass index, and disease leading to ESRD had no influence upon the development of post-TP HL. We conclude that post-renal TP HL is a significant problem in pediatric renal TP recipients. Received: 13 January 1999 / Revised: 19 May 1999 / Accepted: 21 May 1999     

A hybrid CFHR3-1 gene causes familial C3 glomerulopathy

Controlled activation of the complement system, a key component of innate immunity, enables destruction of pathogens with minimal damage to host tissue. Complement factor H (CFH), which inhibits complement activation, and five CFH-related proteins (CFHR1-5) compose a family of structurally related molecules. Combined deletion of CFHR3 and CFHR1 is common and confers a protective effect in IgA nephropathy. Here, we report an autosomal dominant complement-mediated GN associated with abnormal increases in copy number across the CFHR3 and CFHR1 loci. In addition to normal copies of these genes, affected individuals carry a unique hybrid CFHR3-1 gene. In addition to identifying an association between these genetic observations and complement-mediated kidney disease, these results provide insight into the protective role of the combined deletion of CFHR3 and CFHR1 in IgA nephropathy.     

H1N1 vaccination in pediatric renal transplant patients

Background

Solid organ transplant recipients undergoing immunosuppressive therapy are considered to be at high risk of serious infectious complications. In 2009, a new influenza pandemic caused serious infections and deaths, especially among children and immunocompromised patients. Herein we have reported the safety and efficacy of a single-shot monovalent whole-virus vaccine against H1N1 infection in the pediatric renal transplant population.

Methods

In November and December 2009, we vaccinated 37 renal transplant children and adolescents and measured their antibody responses. Seroprotection, seroconversion, and seroconversion factors were analyzed at 21 days after vaccination.

Results

None of the vaccinated patients experienced vaccine-related side effects. None of the patients had an H1N1 influenza infection after vaccination. All of the patients showed elevations in antibody titer at 21 days after vaccination. In contrast, only 29.72% of the patients achieved a safe seroprotection level and only 18.75% a safe seroconversion rate. More intense immunosuppressive treatment displayed negative effect on seroprotection and seroconversion, and antibody production significantly increased with age. No other factor was observed to influence seroprotection.

Conclusions

We recommend vaccination of children and adolescent renal transplant recipients against H1N1 virus. However, a single shot of vaccine may not be sufficient; to achieve seroprotection, a booster vaccination and measurement of the antibody response are needed to assure protection of our patients.     

Sirolimus-based therapy with or without cyclosporine: long-term follow-up in renal transplant patients

This open-label, phase 3b, extension trial in renal transplant recipients (Sirolimus Study 311) assessed the long-term safety of sirolimus (SRL) administered with cyclosporine (CsA) (SRL + CsA group, n = 98) or without CsA (SRL group, n = 69). Renal transplant recipients who had either completed one of seven previous SRL studies sponsored by Wyeth Research or had participated for > or =3 months and reached a protocol-designated endpoint were eligible for enrollment. Data were available for 167 patients, all of whom initially received steroids. Mean total SRL exposure was 1526 days, including previous study participation. After enrollment in the extension study, there were significantly more acute rejections in the SRL + CsA group (6.1% vs 0%, P < .05). Differences in rates of graft loss (3.1% vs 1.4%) and death (6.1% vs 1.4%) were not significantly different between SRL + CsA and SRL groups, respectively. At 48 months after transplantation, calculated GFR (53.4 vs 70.9 mL/min) and hemoglobin (124.9 vs 136.6 g/L) were significantly better in the SRL group. Lipid values were not significantly different between groups at 48 months. The incidence of treatment-emergent increased creatinine, anemia, hypertension, headache, epistaxis, abnormal kidney function, and upper respiratory infection were significantly higher in the SRL + CsA group, whereas no adverse events were significantly higher in the SRL group. Malignancies were reported more frequently (11.2% vs 0%) with SRL + CsA. Results from this extension study indicate that SRL-based therapy without CsA is a safe alternative to combination therapy with CsA, offering long-term improvement in renal function with no increased risk of late acute rejection.     

Effect of cyclosporine A on long-term allograft function in pediatric renal transplant recipients

There have been concerns regarding long-term adverse effects of cyclosporine A (CSA) on renal allograft function. In a retrospective study, we compared long-term allograft function up to 70 months after renal transplantation in pediatric recipients treated with and without CSA, using iothalamate clearance to assess glomerular filtration rate. Patients received CSA, prednisone, and azathioprine (CSA group,n=16) or prednisone and azathioprine alone (Pred/AZA,n=11). At 48 months post transplant, the iothalamate clearances (mean±SD) were 57.9±26.8 ml/min per 1.73 m² in the CSA group and 68.5±20.2 in the Pred/AZA group (P>0.05). The mean of the slopes of individual iothalamate clearances versus time during the first 70 months following transplantation were –0.156 in the CSA group and –0.095 in the Pred/AZA group. Neither slope was statistically different from zero. These data suggest that allograft function is not significantly depressed by CSA at 48 months post transplantation and that there is no greater rate of decline in allograft function up to 70 months post transplantation in patients receiving CSA when compared with the AZA/Pred group.     

Anemia in pediatric renal transplant recipients

The aim of this study was to establish the prevalence of anemia in stable pediatric renal transplant recipients and to examine the association of anemia with renal function, immunosuppressants, angiotensin converting enzyme inhibitors, and growth, as well as iron, vitamin B₁₂, and folate stores. This is a cross-sectional study of the 50 renal transplant recipients currently followed at our center. Patient data were collected regarding hematological parameters, growth, medications, renal function, underlying renal disease, delayed graft function, episodes of rejection, and iron or erythropoietin therapy post transplantation. The mean hemoglobin level (Hb) was 110 g/l and the overall prevalence of anemia was 60%, including 30% who were severely anemic (Hb<100 g/l). There was a high rate of iron deficiency (34%) and serum iron was the parameter of iron metabolism most closely associated with anemia. Hb in patients with low serum iron was 90.7 g/l versus 114.4 g/l in those with normal serum iron (P<0.01). Both univariate and multiple linear regression determined tacrolimus dose and creatinine clearance to be significant factors associated with anemia. Tacrolimus dose correlated with a 10 g/l reduction in Hb for every increase of tacrolimus dose of 0.054 mg/kg per day (P=0.001). The dose of mycophenolate was positively correlated with Hb, but this was likely to be confounded by our practice of dose reduction in the setting of anemia. Angiotensin converting enzyme inhibitor use was not associated with anemia. Severely anemic patients tended to be shorter, with a mean Z-score for height of –1.8 compared with –0.9 for those with normal Hb (P=0.02). Anemia is a significant and common problem in pediatric renal transplant patients. Deteriorating renal function is an important cause, but other factors like iron deficiency and immunosuppression are involved. Definition of iron deficiency is difficult and serum iron may be a valuable indicator. Medication doses, nutritional status, need for erythropoietin and iron, as well as poor graft function and growth require systematic scrutiny in the care of the anemic renal transplant recipient.     

Gout in pediatric renal transplant recipients

Clinical gout has rarely been described after pediatric renal transplantation (RTx), although asymptomatic hyperuricemia is common in these patients. We describe three male pediatric patients who presented with gouty arthritis 7–8.5 years following RTx. Since receiving allopurinol, all patients had been free of gouty symptoms. To prevent severe bone marrow depletion, the dosage of azathioprine, an immunosupressant drug, was reduced by 50% to prevent interaction with allopurinol. Because atypical presentation of gout can occur, a high index of suspicion is needed to allow appropriate diagnosis of this disease in patients with skeletal pain after RTx.     

Growth in pediatric renal transplant recipients

One of the fundamental challenges in managing pediatric renal transplant recipient is to ensure normal growth and development. The goal of renal transplant is not just to prolong life but to optimize quality of life. Short stature during childhood may be associated with academic underachievement and development of comorbidities such as attention deficit hyperactivity disorder, learning disability, and mood disorders. The most important factors affecting growth are use of corticosteroids, allograft function, and age and height deficit at the time of transplant. Aggressive conservative management of chronic renal failure and early use of growth hormone therapy will help in optimizing height at time of transplant. Early transplant, steroid minimization or withdrawal, and growth hormone therapy will help in achieving normal adult height in a majority of renal post transplant population. Steroid avoidance to achieve good growth still needs to be validated.     

Eculizumab induces long-term remission in recurrent post-transplant HUS associated with C3 gene mutation

A 15-year-old male patient developed atypical hemolytic uremic syndrome (aHUS) at 16 months of age leading to end-stage renal disease. The family history was suggestive of autosomal dominant aHUS, and he was more recently found to have a C3 heterozygous gene mutation (1835C>T mutation in exon 14, which determines the amino-acidic substitution R570W) with no other complement abnormalities. He had two renal transplants, the first at 2.5 years, and the second at 8 years of age, but allograft dysfunction developed in both transplants leading to graft failure due to recurrent HUS at 5 years and 18 months post-transplantation respectively. At 15 years of age he received a third transplant from a deceased donor with pre-emptive plasmapheresis. He had immediate graft function and nadir serum creatinine was 1.3–1.4 mg/dl. Severe allograft dysfunction and hypertension developed 2 months after transplantation following influenza infection. Renal allograft biopsy showed thrombotic microangiopathy. He received plasmapheresis followed by eculizumab therapy. Allograft function returned to baseline 3 weeks after starting therapy, and post-treatment allograft biopsies showed improvement in thrombotic microangiopathy. He continues to receive eculizumab every 2 weeks with stable graft function 13 months after transplantation.     

Successful Renal Transplantation in Factor H Autoantibody Associated HUS with CFHR1 and 3 Deficiency and CFH Variant G2850T

Factor H (CFH) autoantibodies are associated with atypical hemolytic uremic syndrome (aHUS). Peritransplantation plasma exchange therapy and intensification of immunosuppression, with adjuvant use of anti-CD20 monoclonal antibodies has recently been advocated for cases of CFH-autoantibody associated aHUS. In this report, we describe successful deceased donor renal transplantation in a case of CFH-autoantibody associated aHUS with combined CFHR1 and 3 deficiency in addition to the CFH sequence variant, (cG2850T, pGln950His). CFH-autoantibodies were detected 2 weeks prior to transplantation. Disease recurrence was not observed using basiliximab, an IL2-receptor antagonist and high-dose corticosteroids with mycophenolate mofetil. Adjuvant therapies such as Rituximab nor intensification of plasma therapy were employed. Consequently, careful consideration needs to be given to the use of additional immunosuppression in certain cases of CFH-autoantibody associated aHUS. Serial measurement of CFH-autoantibodies is required in the immediate pre- and posttransplantation period to further clarify their role as a factor in the recurrence of aHUS posttransplantation. Furthermore, delineation of the functional significance of CFH-autoantibodies is warranted in individual cases.     

Pyeloileocystostomy for ureteral necrosis in pediatric renal transplant recipient

A pediatric renal transplant patient who had ureteral necrosis treated initially by nephrostomy followed by a subsequent pyeloileocystostomy is reported. This unusual approach to a renal transplant complication is recommended, but only when other methods cannot be utilized.     

Desensitization protocols for prospective pediatric renal transplant recipients

Desensitization protocols should be considered for children with positive crossmatches awaiting renal transplantation. Children are sensitized usually due to previous renal (and/or other solid-organ) transplants but can be from administration of blood and/or platelet transfusions, infections, and immunizations (as sensitization from pregnancy is a rare occurrence in pediatric patients). However, the definition of HLA-incompatible (HLAi) renal transplantation in the literature varies and is best considered only when there is a positive cross-match (positive baseline flow cytometric cross-match or positive complement-dependent cytotoxic cross-match). Renal transplantation where the recipient has donor-specific antibodies (DSA) but a negative cross-match should not fall into this category, although they are higher risk.     

Symptomatic cholelithiasis in pediatric renal transplant recipients

We report two cases of symptomatic cholelithiasis in pediatric renal transplant recipients immunosuppressed with cyclosporine (CsA), prednisone and azathioprine. CsA was present in the bile and in the cholesterol gallstones of one patient. The diagnosis of cholelithiasis was established in both cases by abdominal ultrasound examination.     

Renin-angiotensin-aldosterone system in long-term renal transplant patients

Seventeen anephric patients who constituted the subjects of this study received renal allografts between the years 1969 to 1973. The renin-angiotensin-aldosterone mechanism was evaluated in relation to either a normotensive or hypertensive clinical state in these subjects. Group I (Controls) were normotensive and on a normal diet; Group II were normotensive, on sodium restriction for five days, followed by saline infusion on the seventh day; and Group III were hypertensive, on similar sodium restriction for five days, followed by saline infusion on the seventh day. Glomerular filtration rates and levels of plasma renin and aldosterone, and the secretion rate of the latter were obtained on appropriate days. These studies confirm that an intact renin-angiotensin-aldosterone relationship exists in human renal transplant patients. The presence of high aldosterone secretion rate without hypertension is a new but unexplained finding. The lack of correlation of high aldosterone secretion rates in our normotensive and hypertensive patients suggests that aldosterone does not play a detectable or significant role in the pathogenesis of chronic or sustained transplant hypertension.     

西罗莫司在肾移植术后远期各类并发症患者中的转换应用

目的 探讨以钙调磷酸酶抑制剂(CNI)为主要免疫抑制方案的肾移植受者术后远期发生各类并发症时,应用两罗莫司(SRL)转换治疗方案的有效性及安全性.方法 肾移植术后远期38例采用CNI的患者因发生各类并发症而转换为SRL治疗,其中慢性移植肾肾病(CAN)17例、肿瘤10例、糖尿病3例、移植肾动脉狭窄(TRAS)球囊扩张术后2例、CNI毒性肝损害2例、丙型肝炎病毒(HCV)感染2例、面容改变1例及马兜铃酸肾病1例.SRL首剂负荷剂量为4～6 mg,维持剂量为1～2 mg/d,血SRL浓度维持在4～8 μg/L.使用SRL当天,CNI的用量减少一半,并在达到血SRL目标浓度的2～4周内逐渐撤除.转换后对患者随访了3～46个月,动态观察血常规、血肌酐、血糖、血脂及尿蛋白等指标,观察不良反应及监测急性排斥反应、移植肾功能丧失和肺部感染等并发症的发生.结果 转换治疗后.17例CAN患者中12例肾功能明显好转,血肌酐水平由转换前的(195.8±40.0)μmol/L降至(159.1±37.5)μmol/L(P<0.05);10例肿瘤患者中7例存活良好,2例发生肿瘤远处转移,1例死亡,血肌酐水平由转换前的(102.8±28.0)μmol/L降至转换后3个月的(77.8±25.6)μmol/L(P<0.05);2例TRAS球囊扩张术后患者肾功能恢复正常,TRAS未再发生;3例糖尿病患者血糖水平有所改善;2例CNI肝毒性者转换后肝功能恢复正常;2例HCV感染者肝功能稳定,病毒RNA拷贝水平下降;1例面容改变者症状明显好转;1例马兜铃酸肾病者未发生肿瘤.转换治疗后,所有患者均未发生急性排斥反应,不良反应主要为高脂血症3例、蛋白尿3例及白细胞减少1例.结论 肾移植术后采用CNI者发生CAN等远期并发症时,将CNI转换为西罗莫司治疗是安全,有效的.