Infection and chronic allograft dysfunction

The applications of DNA methylation as a biomarker in kidney transplantation: a systematic review

BACKGROUND

Although kidney transplantation improves patient survival and quality of life, long-term results are hampered by both immune- and non-immune-mediated complications. Current biomarkers of post-transplant complications, such as allograft rejection, chronic renal allograft dysfunction, and cutaneous squamous cell carcinoma, have a suboptimal predictive value. DNA methylation is an epigenetic modification that directly affects gene expression and plays an important role in processes such as ischemia/reperfusion injury, fibrosis, and alloreactive immune response. Novel techniques can quickly assess the DNA methylation status of multiple loci in different cell types, allowing a deep and interesting study of cells' activity and function. Therefore, DNA methylation has the potential to become an important biomarker for prediction and monitoring in kidney transplantation.

PURPOSE OF THE STUDY

The aim of this study was to evaluate the role of DNA methylation as a potential biomarker of graft survival and complications development in kidney transplantation. MATERIAL AND METHODS: A systematic review of several databases has been conducted. The Newcastle-Ottawa scale and the Jadad scale have been used to assess the risk of bias for observational and randomized studies, respectively.

RESULTS

Twenty articles reporting on DNA methylation as a biomarker for kidney transplantation were included, all using DNA methylation for prediction and monitoring. DNA methylation pattern alterations in cells isolated from different tissues, such as kidney biopsies, urine, and blood, have been associated with ischemia-reperfusion injury and chronic renal allograft dysfunction. These alterations occurred in different and specific loci. DNA methylation status has also proved to be important for immune response modulation, having a crucial role in regulatory T cell definition and activity. Research also focused on a better understanding of the role of this epigenetic modification assessment for regulatory T cells isolation and expansion for future tolerance induction-oriented therapies.

CONCLUSIONS

Studies included in this review are heterogeneous in study design, biological samples, and outcome. More coordinated investigations are needed to affirm DNA methylation as a clinically relevant biomarker important for prevention, monitoring, and intervention.

Asymptomatic Bacteriuria in Post Renal Transplant Patients: To Treat or Not?

Urinary tract infections (UTIs) can commonly occur within the first few weeks following kidney transplantation procedures. Although the management of asymptomatic bacteriuria and acute graft pyelonephritis is important to reduce the risk of graft rejections following kidney transplantation, the efficacy of antibiotics administration remains controversial among studies in the literature. The aim of this review is to elaborate more on asymptomatic bacteriuria following kidney transplantation and try to formulate proper evidence about the efficacy of antibiotics administration on eliminating the frequency of infections and enhancing the quality of care for patients. Most studies in the literature are observational, which are usually biased in the interventions. However, the current evidence regarding the management and screening of asymptomatic bacteriuria seems to discourage such an approach. Almost all of the included studies reported that antibiotic administration did not significantly lower the rates of secondary symptomatic UTIs or enhance the functions of the graft. In addition, there is no significant impact on mortality and other clinical outcomes. Lastly, the frequent administration of antibiotics can significantly increase the risk of recurrence due to the emergence of novel strains of bacteria that are resistant to the currently administered antibiotics making it unfavorable.

Design and evaluation of Taqman low density array for monitoring post-transplant viral infections

BACKGROUND

The majority of transplant recipients undergo immunosuppressive treatment to prevent organ or tissue rejection. Consequently, they are more susceptible to infection agents including a number of viruses causing a significant morbidity and mortality. Only a limited number of viruses are currently tested for in transplant donors and recipients due to the cost and complexity. Taqman low density array (TLDA) may provide a suitable format to address more systematic testing approach.

METHODS

One hundred and one liver transplant recipient samples were retrospectively tested for 48 viral targets including two controls (bovine viral diarrhea virus and MS2) and two common viruses (TTV and HPgV), using a custom designed TLDA. Eight samples were analysed simultaneously on 384-well TLDA. Samples giving a signal considered positive/indeterminant were re-tested by different individual confirmatory assays.

RESULTS

Infections with six previously untested for viruses-EBV, HPIV3, HuPuV9, KIV, HMPV and HPV-were detected in fourteen patients. Previously detected HCV infections were also confirmed. These infections did not seem have an effect on 5 year post-transplant outcome. 55 of 79 and 17 of 87 samples available for confirmatory assays were positive for TTV and HPgV, included for the evaluation of the TLDA performance.

CONCLUSIONS

The custom viral TLDA can be successfully used for simultaneous detection of a range of post-transplant viral infections. To fully exploit its potential for monitoring and intervention, a whole blood testing should be applied in a prospective setting.

Assessment of serum Tim-3 and Gal-9 levels in predicting the risk of infection after kidney transplantation

Infection remains a major cause of morbidity and mortality after kidney transplantation (KT). Reliable biomarkers to predict post-transplant infection are lacking. We investigated the predictive performance of pre- and post-transplant levels of T-cell immunoglobulin and mucin domain-3 (Tim-3) and Galectin-9 (Gal-9), two pleiotropic immunomodulatory molecules, in early identification of infection. Serum Tim-3 and Gal-9 were paired measured before and 30 days after transplantation (PTD 30) in 95 KT recipients (KTRs). The decline rates of Tim-3 and Gal-9 were calculated relative to pre-transplant levels. KTRs with infection history had significantly higher levels of PTD 30 Tim-3 and Gal-9, and slower decrease rates of Gal-9 compared to non-infected recipients, while no difference was observed between two groups regarding pre-transplant levels. The AUCs for predicting 1-year post-transplant infection were 0.653 and 0.711 for post-transplant Tim-3 and Gal-9, 0.664 and 0.670 for relative Tim-3 and Gal-9, respectively. After adjusting for potential confounders, PTD 30 Tim-3, Gal-9 and relative Gal-9 remained as independent risk factors for post-transplant infection. Our results suggested that PTD 30 Tim-3 and Gal-9 and relative decrease of Gal-9 were promising predictors for identifying KTRs with high risk of infection, while pre-transplant Tim-3 and Gal-9 showed no predictive power to infection.

Antibiotic Treatment Versus No Treatment for Asymptomatic Bacteriuria in Kidney Transplant Recipients: A Multicenter Randomized Trial

Background

Whether antibiotic treatment of asymptomatic bacteriuria (AB) can prevent acute graft pyelonephritis (AGP) in kidney transplant (KT) recipients has not been elucidated.

Methods

In this multicenter, open-label, nonblinded, prospective, noninferiority, randomized controlled trial, we compared antibiotic treatment with no treatment for AB in KT recipients in the first year after transplantation when urinary catheters had been removed. The primary endpoint was the occurrence of AGP. Secondary endpoints included bacteremic AGP, cystitis, susceptibility of urine isolates, graft rejection, graft function, graft loss, opportunistic infections, need for hospitalization, and mortality.

Results

We enrolled 205 KT recipients between 2013 and 2015. AB occurred in 41 (42.3%) and 46 (50.5%) patients in the treatment and no treatment groups, respectively. There were no differences in the primary endpoint in the intention-to-treat population (12.2% [5 of 41] in the treatment group vs 8.7% [4 of 46] in the no treatment group; risk ratio, 1.40; 95% confidence interval, 0.40–4.87) or the per-protocol population (13.8% [4 of 29] in the treatment group vs 6.7% [3 of 45] in the no treatment group; risk ratio, 2.07, 95% confidence interval, 0.50–8.58). No differences were found in secondary endpoints, except for antibiotic susceptibility. Fosfomycin (P = .030), amoxicillin-clavulanic (P < .001) resistance, and extended-spectrum β-lactamase production (P = .044) were more common in KT recipients receiving antibiotic treatment for AB.

Conclusions

Antibiotic treatment of AB was not useful to prevent AGP in KT recipients and may increase antibiotic resistance. However, our findings should be regarded with caution, due to the small sample size analyzed.

Long-term Outcome of 1-step Kidney Transplantation and Bladder Augmentation Procedure in Pediatric Patients

BACKGROUND

Guidelines for bladder augmentation (BA) in kidney transplantation (KT) recipients are not well-defined. In our center, simultaneous BA with KT (BA-KT) is performed. We assessed transplantation outcomes of this unique extensive procedure.

METHODS

A case-control single center retrospective study. Transplantation outcomes were compared with those of KT recipients who did not need BA.

RESULTS

Compared with 22 patients who underwent KT only, for 9 who underwent BA-KT, surgical complications and the need for revision in the early posttransplantation period were similar; early graft function was better: estimated glomerular filtration rate, 96.5 ± 17.1 versus 79.4 ± 16.6 mL/min at 0 to 6 months (P = 0.02); posttransplantation clean intermittent catheterization was more often needed: by 78% (7/9) versus 13% (3/22); and asymptomatic bacteriuria was more common: 100% versus 9% during the first 6 months (P < 0.001), 55% versus 9% (P = 0.02) and 66.6% versus 9% during the first and second years, respectively (P = 0.004). Urinary tract infection (UTI) incidence was also higher: 100% versus 23% during the first 6 months and 44% versus 9% during the second year posttransplantation. Graft function deteriorated significantly in the BA-KT group by the fifth posttransplantation year: estimated glomerular filtration rate was 47.7 ± 39.7 mL/min versus 69 ± 21.3 mL/min, with only 6 (66%) of 9 functioning grafts versus 100% in the KT only group. Causes of graft loss were noncompliance with drug therapy in 2 patients and recurrent UTIs in 2 patients.

CONCLUSIONS

Excellent short-term outcome for simultaneous BA-KT is threatened by graft loss due to a high prevalence of UTIs and patient noncompliance with the demanding complex posttransplantation therapy.

Circulating miR-150, miR-192, miR-200b, and miR-423-3p as Non-invasive Biomarkers of Chronic Allograft Dysfunction

BACKGROUND AND AIMS

Chronic allograft dysfunction (CAD) is the major cause of renal allograft loss and can only be diagnosed by invasive histological examinations. The current study aimed to determine whether or not the circulating miR-125a, miR-150, miR-192, miR-200b, miR-423-3p and miR-433 could serve as predictors of graft outcome in the renal transplant recipients with CAD.

METHODS

To evaluate the expression levels of miRNAs, we used quantitative real-time PCR (qPCR) and analyzed the plasma samples of 53 renal transplant recipients, including: 27 recipients with stable graft function (SGF), 26 recipients with biopsy-proven interstitial fibrosis and tubular atrophy (IFTA) and 15 healthy controls. Possible correlation between the clinicopathological parameters and the studied circulating miRNAs was also evaluated.

RESULTS

miR-150 (p <0.001), miR-192 (p = 0.003), miR-200b (p = 0.048) and miR-423-3p (p <0.001) were differentially expressed between IFTA and SGF plasma samples. Creatinine correlated with miR-192 (r = 0.414, p = 0.036) and miR-423-3p (r = -0.431, p = 0.028). Moreover, the estimated glomerular filtration rate (eGFR) significantly correlated with the circulating miR-192 (r = -0.390, p = 0.049) and miR-423 (r = 0.432, p = 0.028). Receiver operating characteristic (ROC) analysis indicated that four miRNAs possessed the best diagnostic value for discriminating IFTA from SGF recipients with the areas under the curve (AUC) of 0.87 and high sensitivity and specificity values of 78% and 91%, respectively.

CONCLUSIONS

The results suggest that aberrant plasma levels of these miRNAs are associated with the renal allograft dysfunction. Therefore, they are proposed to be considered as potential diagnostic biomarkers for monitoring of renal graft function.

Epigenetics in Kidney Transplantation: Current Evidence, Predictions, and Future Research Directions

Epigenetic modifications are changes to the genome that occur without any alteration in DNA sequence. These changes include cytosine methylation of DNA at cytosine-phosphate diester-guanine dinucleotides, histone modifications, microRNA interactions, and chromatin remodeling complexes. Epigenetic modifications may exert their effect independently or complementary to genetic variants and have the potential to modify gene expression. These modifications are dynamic, potentially heritable, and can be induced by environmental stimuli or drugs. There is emerging evidence that epigenetics play an important role in health and disease. However, the impact of epigenetic modifications on the outcomes of kidney transplantation is currently poorly understood and deserves further exploration. Kidney transplantation is the best treatment option for end-stage renal disease, but allograft loss remains a significant challenge that leads to increased morbidity and return to dialysis. Epigenetic modifications may influence the activation, proliferation, and differentiation of the immune cells, and therefore may have a critical role in the host immune response to the allograft and its outcome. The epigenome of the donor may also impact kidney graft survival, especially those epigenetic modifications associated with early transplant stressors (e.g., cold ischemia time) and donor aging. In the present review, we discuss evidence supporting the role of epigenetic modifications in ischemia-reperfusion injury, host immune response to the graft, and graft response to injury as potential new tools for the diagnosis and prediction of graft function, and new therapeutic targets for improving outcomes of kidney transplantation.

Infection-related hospitalizations over 30 years of follow-up in patients starting renal replacement therapy at pediatric age

BACKGROUND

Pediatric renal replacement therapy (RRT) patients surviving long-term are at a much higher risk of mortality compared with the age-matched general population. Recently, we demonstrated a transition from cardiovascular disease to infection as the main cause of death in a long-term follow-up study of pediatric RRT. Here, we explore the burden of infections requiring hospitalization over 30 years of follow-up on RRT.

METHODS

The cohort comprised all 234 Dutch patients on RRT under 15 years of age between 1972 and 1992. We analyzed infection-related hospitalizations during the period 1980–2010. We evaluated the Hospital Admission Rate (HAR) per patient-years (py) and infectious over noninfectious HAR ratio (HARR).

RESULTS

The HAR decreased significantly over time for all patients. The rate of hemodialysis-related infections decreased between 1980 and 1999, but stabilized during 2000–2010, whereas peritoneal dialysis-related infections decreased progressively. Transplantation-related infections did not change, except for urinary tract infections (UTIs), which increased significantly from 3.3/100 py [95%CI 3.2–3.4] in 1980–1989 to 4.4/100 py [4.2–4.5] in 2000–2010 (p <0.001). The contribution of infection to HAR increased significantly in transplanted patients (HARR: 1980–1989: 0.25 [0.2–0.3]; 2000–2010: 1.0 [0.79–1.27], p <0.001).

CONCLUSIONS

Our findings indicate a relative increase in infections requiring hospitalization over time in patients starting RRT during the pediatric age, especially severe UTIs in transplantation. More attention paid to urological abnormalities in cases of recurrent UTI and tailored adjustment of immunosuppression may reduce risk in these patients.

The Impact of Infection on Chronic Allograft Dysfunction and Allograft Survival After Solid Organ Transplantation

Infectious diseases after solid organ transplantation (SOT) are a significant cause of morbidity and reduced allograft and patient survival; however, the influence of infection on the development of chronic allograft dysfunction has not been completely delineated. Some viral infections appear to affect allograft function by both inducing direct tissue damage and immunologically related injury, including acute rejection. In particular, this has been observed for cytomegalovirus (CMV) infection in all SOT recipients and for BK virus infection in kidney transplant recipients, for community-acquired respiratory viruses in lung transplant recipients, and for hepatitis C virus in liver transplant recipients. The impact of bacterial and fungal infections is less clear, but bacterial urinary tract infections and respiratory tract colonization by Pseudomonas aeruginosa and Aspergillus spp appear to be correlated with higher rates of chronic allograft dysfunction in kidney and lung transplant recipients, respectively. Evidence supports the beneficial effects of the use of antiviral prophylaxis for CMV in improving allograft function and survival in SOT recipients. Nevertheless, there is still a need for prospective interventional trials assessing the potential effects of preventive and therapeutic strategies against bacterial and fungal infection for reducing or delaying the development of chronic allograft dysfunction.

Pneumococcal disease in adult solid organ transplantation recipients

In solid organ transplant (SOT) recipients, Streptococcus pneumoniae can cause substantial morbidity and mortality ranging from non-invasive to invasive diseases, including pneumonia, bacteremia, and meningitis, with a risk of invasive pneumococcal disease 12 times higher than that observed in non-immunocompromised patients. Moreover, pneumococcal infection has been related to graft dysfunction. Several factors have been involved in the risk of pneumococcal disease in SOT recipients, such as type of transplant, time since transplantation, influenza activity, and nasopharyngeal colonization. Pneumococcal vaccination is recommended for all SOT recipients with 23-valent pneumococcal polysaccharides vaccine. Although immunological rate response is appropriate, it is lower than in the rest of the population, decreases with time, and its clinical efficacy is variable. Booster strategy with 7-valent pneumococcal conjugate vaccine has not shown benefit in this population. Despite its relevance, there are few studies focused on invasive pneumococcal disease in SOT recipients. Further studies addressing clinical, microbiological, and epidemiological data of pneumococcal disease in the transplant setting as well as new strategies for improving the protection of SOT recipients are warranted.

Endothelium and Regulatory Inflammatory Mechanisms During Organ Rejection

Endothelial integrity is mandatory for physiologic organ function; however, endothelium dysfunction can be caused by systemic inflammation, occurring during sepsis or organ rejection after transplantation. This article will address our current understanding of endothelial involvement in organ transplantation and rejection. Overall, more detailed studies focusing on the endothelial modulation after organ transplantation would be necessary to investigate the role of endothelium activation during organ rejection.

Value of routine voiding cystourethrography after renal transplantation

The impact of vesicoureteral reflux (VUR) on renal allograft outcomes is debatable, with small cohort studies reporting controversial results. The objective of this retrospective study was to evaluate long-term clinical effects of early VUR in a large cohort of kidney transplant patients. Posttransplantation voiding cystourethrography was used to evaluate 646 consecutive kidney transplant recipients before discharge. The study endpoints included VUR grade, death-censored graft or patient survival, renal function, proteinuria and occurrence of urinary tract infections (UTIs). Of the 646 recipients, 263 (40.7%) were diagnosed with VUR. VUR grade II was most common (19.8%), followed by grades III (10.2%), I (7.9%) and IV (2.8%). VUR was less common in transplantations performed by experienced compared to inexperienced surgeons (36% vs. 48%; p = 0.004). VUR did not affect death-censored graft or patient survival and was not associated with proteinuria or occurrence of UTIs. Patients with VUR had a lower eGFR at 1 year after transplantation than did patients without VUR (60 vs. 52 mL/min/1.73 m(2) ; p = 0.02), although this difference was not observed at 3 and 5 years after transplantation. We conclude that early VUR, a common finding among renal transplant patients, may not have a meaningful impact on long-term transplant outcomes.