Infectious Disease Risk in Dialysis Patients: A Transdisciplinary Approach

PURPOSE OF REVIEW

Infections are a major contributor to morbidity and mortality in end-stage renal disease (ESRD) patients. A better understanding of the interplay between infectious processes and ESRD may eventually lead to the development of targeted treatment strategies aimed at lowering overall disease morbidity and mortality. Monogenic causes are a major contributor to the development of adult chronic kidney disease (CKD). Recent studies identified a genetic cause in 10% to 20% of adults with CKD. With the introduction of whole-exome sequencing (WES) into clinical mainstay, this proportion is expected to increase in the future. Once patients develop CKD/ESRD due to a genetic cause, secondary changes, such as a compromised immune status, affect overall disease progression and clinical outcomes. Stratification according to genotype may enable us to study its effects on secondary disease outcomes, such as infectious risk. Moreover, this knowledge will enable us to better understand the molecular interplay between primary disease and secondary disease outcomes.

SOURCES OF INFORMATION

We conducted a literature review using search engines such as PubMed, PubMed central, and Medline, as well as cumulative knowledge from our respective areas of expertise.

METHODS

This is a transdisciplinary perspective on infectious complications in ESRD due to monogenic causes, such as autosomal dominant polycystic kidney disease (ADPKD), combining expertise in genomics and immunology.

KEY FINDINGS

In ADPKD, infection is a frequent complication manifesting primarily as lower urinary tract infection and less frequently as renal infection. Infectious episodes may be a direct consequence of a specific underlying structural abnormality, for example the characteristic cysts, among others. However, evidence suggests that infectious disease risk is also increased in ESRD due to secondary not-well-understood disease mechanisms. These disease mechanisms may vary depending on the underlying nature of the primary disease. While the infectious disease risk is well documented in ADPKD, there are currently insufficient data on the risk in other monogenic causes of ESRD. WES in combination with novel technologies, such as RNA sequencing and single-cell RNA sequencing, can provide insight into the molecular mechanisms of disease progression in different monogenic causes of CKD/ESRD and may lead to the development of novel risk-stratification profiles in the future.

LIMITATIONS

This is not a systematic review of the literature and the proposed perspective is tainted by the authors' point of view on the topic.

IMPLICATIONS

WES in combination with novel technologies such as RNA sequencing may enable us to fully unravel underlying disease mechanisms and secondary disease outcomes in monogenic causes of CKD and better characterize individual risk profiles. This understanding will hopefully facilitate the development of novel targeted therapies.

Lymphocyte populations and apoptosis of peripheral blood B and T lymphocytes in children with end stage renal disease

BACKGROUND

End stage renal disease (ESRD) is a worldwide devastating health problem due to its increased prevalence in the population and high association with several pathologic conditions including immunodeficiency, which makes a significant contribution to morbidity and mortality.

AIM

The present study aimed at analysis of T and B lymphocyte subpopulation and the detection of flowcytometric apoptosis markers on peripheral B and T lymphocytes in a cohort of children with ESRD.

SUBJECTS AND METHODS

A case-control study was conducted on 28 children with ESRD. In addition, 30 age and sex matched healthy children were included as a control group. We used Annexin V-FITC binding assay as a sensitive probe for identifying cells undergoing apoptosis.

RESULTS

Circulating neutrophils, T and B lymphocytes were lower in patient group. In addition, apoptotic B and T lymphocytes occurred more frequently in children with ESRD than in the control group.

CONCLUSION

Our finding of low numbers of circulating neutrophils, T and B lymphocytes, and increased portion of apoptotic B and T lymphocytes in children with ESRD, may emphasize the fact that these derangements are the main mechanisms responsible for the impairment of the immune system in ESRD children, also it adds to the fact that both cellular and humoral immunity affected in ESRD children. Finally, uremia and increased peripheral lymphocyte apoptosis were the major causes of lymphocyte populations' depletion in our ESRD patients.

Elevated serum levels of B-cell activating factor in pediatric renal transplant patients

BACKGROUND

B-cells are increasingly recognized as important players in alloimmunity. B cell-activating factor (BAFF) and its receptor BAFF-R are essential for B-cell differentiation and survival. Data on BAFF levels in pediatric renal transplant (RT) patients are scarce.

OBJECTIVE

It is known from adult data that elevated BAFF levels correlate with an unfavorable outcome in bone marrow and kidney recipients. To analyze this hypothesis in pediatric renal transplant patients we performed a cross-sectional analysis of serum BAFF levels, lymphocyte surface BAFF-R expression, and clinical variables in a cohort of 43 pediatric renal transplant patients.

METHODS

We studied serum BAFF, CD19+ B-, and FoxP3+ regulatory T-cells (Tregs) and BAFF-R expression in 43 children 2.9 (0.1-12.4) years after RT on maintenance immunosuppression. Twenty-two healthy children and 19 children with chronic kidney disease stage 5 (CKD5) served as controls.

RESULTS

BAFF levels were significantly higher in RT patients than in healthy children (1,435±574 vs 894±189 pg/mL; p<0.0001) whereas numbers of B-cells and Tregs were significantly lower. BAFF-R expression on B-cells was decreased after RT (531±334 vs 707±257 MFI; p<0.005), BAFF inversely correlated with BAFF-R (r=-0.5022, p<0.006), but not with B-cell count. BAFF was elevated in CKD5 patients (1,276±294 pg/mL). In RT patients BAFF was significantly higher in those with eGFR <60 ml/min/1.73m(2) (1,553±447 vs 1,234±323 pg/mL; p=0.02). BAFF levels and BAFF-R expression did not correlate with HLA antibody status, time after transplantation, age or gender of the patients.

CONCLUSION

Serum BAFF concentrations were significantly elevated in pediatric RT patients. They correlated with decreased BAFF-R expression on CD19+ B-cells and impaired allograft function. Our findings of a dysregulated BAFF/BAFF-R axis may be of clinical relevance after renal transplantation and therefore underline the importance of further research into BAFF-dependent mechanisms.

Patterns and prognostic value of total and differential leukocyte count in chronic kidney disease

BACKGROUND AND OBJECTIVES

The purpose of this study was to evaluate the levels and patterns of total and differential leukocyte counts and their prognostic importance in a cohort of people with and without chronic kidney disease (CKD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 153 veterans without CKD and 267 with, blood leukocyte count was measured at baseline and then repeatedly over a decade. The patterns of change in leukocyte count between the two groups were compared. In the CKD cohort, the spikes in leukocyte counts were compared to the combined endpoint of ESRD and death.

RESULTS

Patients with CKD had more granulocytes and eosinophils and fewer lymphocytes. Over time, granulocytes increased and lymphocytes decreased in those with and without CKD. In addition, in those with CKD, over time eosinophils fell and monocytes increased. Compared with their non-CKD counterparts, patients with CKD had between 1.5- and 3.0-fold more spikes in leukocyte counts. Independent risk factors for the combined endpoint were associated with spikes in the leukocyte counts of absolute and percent eosinophil count, percent granulocyte, and percent monocyte counts. In a multivariate adjusted joint model, both granulocyte and monocyte spikes were independently associated with ESRD and death (hazard ratio 1.67 and 1.52 respectively, P < 0.05).

CONCLUSIONS

Compared with those without CKD, patients with CKD have more eosinophils and granulocytes and fewer lymphocytes. Greater variation in leukocytes is seen. Spikes in granulocyte and monocyte percentages among patients with CKD are of independent prognostic importance.

Tacrolimus/Mycophenolate Mofetil Improved Natural Killer Lymphocyte Reconstitution One Year After Kidney Transplant by Reference to Cyclosporine/Azathioprine

BACKGROUND

Recently introduced immunosuppressive drugs are more potent to control graft rejection, but current concerns are raised regarding their potential to increase long-term neoplastic and infectious complications. Considering the role of B, T, or natural killer (NK) lymphocyte in controlling alloreactive, anti-infectious, and antitumoral immune responses, we compared the impact of two immunosuppressive regimens on lymphocyte subsets one year following kidney transplant.

METHODS

Multivariate regression analysis of variables affecting lymphocyte subset counts was retrospectively performed on 91 kidney-transplanted patients, analyzed before graft, at day 15 and 1-year postgraft. These patients were included in a randomized prospective open trial comparing tacrolimus/mycophenolate mofetil (FK/MMF) versus cyclosporine/azathioprine (CSA/Aza), both used in association with rabbit antithymocyte globulines (rATG) induction and prednisone.

RESULTS

Fifteen days postgraft, severe T and NK lymphocyte depletion were observed in all patients, while B cell counts were selectively higher in the FK/MMF group as compared to before graft. One-year posttransplant, NK cell counts and NK cell cytotoxicity was significantly higher in patients receiving FK/MMF therapy, as compared to CSA/Aza. Cytomegalovirus (CMV) infection during the first year posttransplant was also associated to higher NK, CD8, and CD4CD8 T cell counts at month 12.

CONCLUSIONS

In addition to its higher potential in preventing graft rejection, we show that after one year of transplant, FK/MMF better preserves NK innate immune effector cells and their cytotoxic potential. These data prompt to further evaluate the role of NK cells in relation to antiviral and tumoral surveillance of transplanted patients, which are common complications of long-term immunosuppression.

Intracellular cytokines in peripheral blood leucocytes in children with chronic renal failure

We have previously shown that children with mild renal impairment show significant changes in leucocyte subsets and circulating cytokines, indicating that these patients show an increased inflammatory state. We hypothesised that measurement of intracellular cytokine production by lymphocytes and monocytes would more precisely define the immunological mechanism associated with the inflammatory state in children with pre-dialytic chronic renal failure. Blood was collected from children with chronic renal failure (CRF) who were not yet on dialysis and an age-matched control group. Leucocyte subsets and intracellular cytokine production were determined using flow cytometry. Children with CRF showed increased production of interleukin (IL)-12 by monocytes accompanied by decreased production of interferon (IFN)-gamma and increased production of IL-4 by T cells. There were no significant changes in the production of IL-8, IL-10, IL-6, IL-1alpha or tumour necrosis factor (TNF)-alpha by monocytes or in IL-2 or TNF-alpha production by T cells. There were no significant differences in total white cell count or lymphocyte count. There was a significant decrease in both B and NK cells. This study examines intracellular cytokine production in children with CRF in detail. It is the first to show that children with relatively mild renal failure display significant immunological changes of lymphocyte subsets and leucocyte cytokine production. These data provide a more accurate understanding of the immunological changes that may contribute to the clinical manifestations and progression of the disease.

Changes in leukocyte subsets: clinical implications for children with chronic renal failure

Increased systemic inflammation and an impaired immune response are features of adult chronic renal failure (CRF). These patients have increased rates of infection, cardiovascular disease, anemia, and malnutrition. We measured inflammatory and immunological markers in a group of children with pre-dialytic CRF. No prior studies have explored these markers even though children with non-dialysed CRF exhibit similar complications to those seen in adults with CRF. Blood was collected from children with mild, moderate, or severe CRF and an age-matched control group. Functional leukocyte subsets were determined using flow cytometry. Circulating levels of interleukin (IL)-1beta, IL-6, IL-8, IL-12, IL-10, and tumor necrosis factor-alpha were measured using a flow cytometric bead assay. Children with severe CRF showed significantly reduced total white cell count and absolute neutrophil and lymphocyte counts. Absolute numbers of CD3+/CD45RO+ memory T cells and CD3+/CD45RO+/CD62L+ memory Th2 cells were significantly reduced in all CRF groups versus controls. Children with severe CRF showed increased CD11b expression on neutrophils and monocytes. Some patients showed increases in pro-inflammatory cytokines that were not related to their level of residual renal function. As CD11b expression mediates leukocyte adhesion to vascular endothelium, upregulation may contribute to the increased endothelial dysfunction observed in children with CRF. L-selectin mediates extravasation of leukocytes into tissue and homing of peripheral blood lymphocytes to lymph nodes. The reduction in L-selectin may inhibit these actions and predispose patients to increased infection later in life. This is the first study to comprehensively investigate leukocyte functional molecules and inflammatory cytokine profiles in children with pre-dialytic CRF and provides new immunological evidence for the clinical manifestations associated with the disease.

Peritoneal T cell responses can be polarized toward Th1 or Th2 in children on chronic peritoneal dialysis

Peritoneal T cell responses can be polarized toward Th1 or Th2 in children on chronic peritoneal dialysis. Previous studies on the peritoneal immune system described the presence of activated T lymphocytes in peritoneal effluents from subjects on chronic peritoneal dialysis (CPD). Since Th1/Th2 polarized response can influence the outcome of specific infectious diseases, we investigated if activated Th1/Th2 cells can be detected in peritoneal effluents during peritoneal dialysis, in order to better understand the role of T cells in the mechanisms of peritoneal defense. We have studied 8 children (4 males, 4 females, mean age 5.8 +/- 5.7 years, range 0.3-13.4) on CPD. Peritoneal cells have been isolated from peritoneal effluents by centrifugation. Immunofluorescent staining of intracellular cytokines for flow cytometric analysis was used to detect the percentage of T cells producing either IFN-gamma (Th1) or IL-4 (Th2). In the initial study 3 months after CPD initiation, high percentages of IFN-gamma positive peritoneal T cells (38% and 63%) were detected in two subjects; this finding is consistent with a Th1 polarization of peritoneal T cells. In another subject, high percentages of IL-4 positive T cells (31%) were detected, suggesting a Th2 polarization of peritoneal T cell response. Small amounts of either Th1 or Th2 T cells (2-4%) were also detected in the other subjects. At the 1 year follow-up, Th1 polarization persisted in one subject (18% IFN-gamma positive peritoneal T cells), in another a shift from Th1 to Th2 was observed, and in the other subject a down regulation of both T cell subsets occurred. The finding that a predominance of T cells producing either IFN-gamma or IL-4 was found in 3 out of 8 children strongly suggests that peritoneal T cell responses can be polarized toward Th1 or Th2. The decrease of Th1 and/or Th2 polarized T cells in the peritoneum of 4 out of 6 subjects (after 1 year) suggests that CPD can play an immunosuppressive role on T cell peritoneal responses. Further studies are needed in order to define whether different T helper activation patterns are associated with a higher risk of peritoneal infection or of peritoneal damage.