Safe use of citric acid-based dialysate and heparin removal in postdilution online hemodiafiltration.

BACKGROUND: Anticoagulation of the blood circuit with heparin is essential for hemodialysis, but exposes patients to several risks (bleeding, thrombocytopenia, etc.). The use of citric acid-based dialysate (CitA-D) allows the reduction of heparin in conventional hemodialysis. We evaluated the feasibility of using CitA-D in postdilution online hemodiafiltration (OL-HDF) and of removing heparin. METHODS: We prospectively compared chlorhydric acid-based dialysate with CitA-D in 10 patients treated by OL-HDF. First, we reduced heparin by half the dose and then we totally removed anticoagulation. RESULTS: For all 120 sessions using heparin-free CitA-D, only one clotting episode related to an arteriovenous fistula stenosis was observed. No adverse clinical effect was observed. (Kt/V)sp, predialytic serum bicarbonate, calcium, phosphate, parathroid hormone, and ß2-microglobulin remained the same in all cases. CONCLUSION: Our data suggest that the use of CitA-D in OL-HDF is safe and allows heparin removal in most patients.

COVID-19 in Patients Undergoing Hemodialysis: Prevalence and Asymptomatic Screening During a Period of High Community Prevalence in a Large Paris Center.

RATIONALE & OBJECTIVE: Due to extensive comorbid conditions, coronavirus disease 2019 (COVID-19) has a poor prognosis in people receiving maintenance hemodialysis. In this article, we describe our experience with 200 maintenance hemodialysis patients in a hemodialysis center that used universal reverse transcriptase-polymerase chain reaction testing, including 38 COVID-19-positive patients. STUDY DESIGN: Descriptive observational cohort, including the time line of patient diagnoses along with contextual events including precautions, testing, screening algorithms, clinical diagnostics and therapy, and the clinical course of COVID-19-infected patients and their final outcomes. SETTING & PARTICIPANTS: 200 patients within a single hemodialysis center with 2 dialysis clinics in Paris. RESULTS: Among 200 maintenance hemodialysis patients, 38 (19%) had COVID-19 diagnosed; of these, 15 (39.5%) were admitted to the hospital, including 4 who required intensive care unit (ICU) care. There were 8 (21%) deaths. The most common symptom was fever, followed by dry cough, fatigue, and dyspnea. All COVID-19-infected patients had lymphopenia and an increase in C-reactive protein levels. Median time from the onset of respiratory symptoms to ICU admission was 1 to 2 days. Durations of non-ICU hospitalizations and ICU stays were 7 and 13 days, respectively. LIMITATIONS: Retrospective study, single hemodialysis center. CONCLUSIONS: Dialysis patients are a highly susceptible population and hemodialysis centers are a high-risk area in a COVID-19 epidemic. "Unexplained" lymphopenia and/or an increase in C-reactive protein level should lead physicians to the diagnosis of COVID-19 and should, when possible, be followed by diagnostic testing with universal reverse transcriptase-polymerase chain reaction, as well as the reinforcement of contamination barrier measures.

Randomised trial on clinical performances and biocompatibility of four high-flux hemodialyzers in two mode treatments: hemodialysis vs post dilution hemodiafiltration.

This prospective multicenter randomized comparative cross-over trial aimed at evaluating the influence of hemodialysis vs post-dilution hemodiafiltration with high-flux dialyzers in solute clearance and biocompatibility profile. 32 patients were sequentially dialyzed with Leoceed-21HX, Polypure-22S+, Rexsys-27H and VIE-21A. Primary outcome was ß2-microglobulin removal. Secondary outcomes were (i) extraction of other uremic solutes (ii) parameters of inflammation and nutrition and (iii) comparative quantification of perdialytic albumin losses (using total 'TDC' vs partial 'PDC' collection of dialysate). Significant increases in removal rates of ß2-microglobulin (84.7 ± 0.8 vs 71.6 ± 0.8 mg/L), myoglobin (65.9 ± 1.3 vs 38.6 ± 1.3 µg/L), free immunoglobulin light chains Kappa (74.9 ± 0.8 vs 55.6 ± 0.8 mg/L), ß-trace protein (54.8 ± 1.3 vs 26.8 ± 1.4 mg/L) and orosomucoid (11.0 ± 1.1 vs 6.0 ± 1.1 g/L) but not myostatin (14.8 ± 1.5 vs 13.0 ± 1.5 ng/mL) were observed in HDF compared to HD when pooling all dialyzers. Rexsys and VIE-A use in both HD and HDF subgroups was associated to a better removal of middle/large-size molecules compared to Leoceed and Polypure, except ß2-microglobulin for Rexsys. Inflammatory parameters were unchanged between dialyzers without any interaction with dialysis modality. Mean dialysate albumin loss was comparable between TDC and PDC (1.855 vs 1.826 g/session for TDC and PDC respectively). In addition, a significant difference in albumin loss was observed between dialyzers with the highest value (4.5 g/session) observed using Rexsys. Use of all dialyzers was associated with good removals of the large spectrum of uremic toxins tested and good biocompatibility profiles, with an additional gain in removal performances with HDF. Larger surface area, thinner wall and resultant very high ultrafiltration coefficient of Rexsys should be taken into account in its clear performance advantages.

Understanding organ dysfunction in hemophagocytic lymphohistiocytosis.

OBJECTIVE: This review aims to help critical care clinicians maintain a high level of suspicion regarding the diagnosis of Hemophagocytic Histiolymphocytosis (HLH). It describes the clinical and laboratory features of HLH, outlines its pathophysiology and reviews the most frequent etiologies related to HLH. Prognostic factors and therapeutic options are also reported. DATA SOURCES: Review of the literature. RESULTS: The diagnosis of HLH relies on the association of clinical abnormalities and hemophagocytosis in bone marrow, spleen, or lymph node specimens. Liver, pulmonary, renal, cardiac and skin involvement may occur at various degrees possibly leading to multiple organ failure. Three main etiologies can be found, namely infections, lymphoproliferative diseases, or connective tissue diseases. Immune deficiency is often retrieved. Mortality can be as high as 50%. Although clinically mimicking severe sepsis, HLH has a distinct pathophysiology on which specific therapy is based. Early diagnosis and treatment is mandatory to increase the chances of survival. CONCLUSION: The comprehensive management of severe HLH requires the involvement of a multidisciplinary team in order to determine the best therapeutic strategy and to identify the underlying cause.

New therapeutic targets for antibodies and recombinant proteins in organ transplantation.

The development of immunosuppressive drugs for tolerance induction or maintenance of an allograft is the key to successful organ transplantation. Humanized mAbs are promising biological agents because of their reduced immunogenicity and favorable bioactivity. Although their clinical application has so far been limited to the anti-CD3 and anti-recombinant IL-2 mAbs, new antibodies have been developed against several targets, including cell-surface molecules involved in T-cell activation, proliferation and trafficking. In addition, developments within the field of bioengineering have allowed for the production of fusion molecules with enhanced bioactivity. One such molecule, belatacept, which inhibits the T-cell costimulatory pathway, has been shown to improve long-tern transplant outcome as part of a calcineurin inhibitor-free maintenance imnmunosuppressive regimen. The specialized immunosuppressive agents currently in clinical use, in preclinical development, and in early clinical trials for transplantation are discussed in this review.

Detection of HLA-G in serum and graft biopsy associated with fewer acute rejections following combined liver-kidney transplantation: possible implications for monitoring patients.

Human leukocyte antigen G (HLA-G) is a regulatory molecule that is expressed in the cytotrophoblast during implantation and is thought to allow the tolerance and the development of the semiallogeneic embryo. In vitro, HLA-G inhibits natural killer (NK) cell and CD8 T-cell cytotoxicity. HLA-G also decreases CD4 T-cell expansion. This suggests that it participates in the acceptance of allogeneic organ transplants in humans. We here describe the detection of high concentration of HLA-G in serum from liver-kidney transplant patients, but not in kidney transplant patients. This finding is supported by the ectopic expression of HLA-G in graft biopsies. Finally, its association with a low number of acute transplant rejections, especially in liver-kidney transplant patients led us to propose that HLA-G may serve to monitor transplant patients who are likely to accept their allograft and, thus, may benefit of a reduced immunosuppressive treatment.

Acute vascular humoral rejection in a sensitized cardiac graft recipient: diagnostic value of C4d immunofluorescence.

A 37-year-old female patient had a cardiac transplantation for dilated cardiomyopathy. She was sensitized by two pregnancies showing anti-human leukocyte antigen I and II antibodies. The pretransplantation crossmatch was negative, but she developed acute humoral rejection characterized by vascular C4d deposits, arteriolitis, and intravascular leukocyte accumulation and adhesion in venules. Although C4d deposits disappeared in 4 weeks, she had persistent endothelial cell activation (endothelial expression of ELAM-1, VCAM-1, or human leukocyte antigen class II) throughout the 6 months of follow-up. Although she received intensive immunosuppression, she presented three episodes of acute cellular rejection during that period of time. This case shows that C4d deposits represent a sensitive marker of acute humoral rejection in cardiac transplantation. Therefore, C4d immunofluorescence should be more frequently assessed in endomyocardial biopsies.

Ionic dialysance and determination of Kt/V in on-line hemodiafiltration with simultaneouspre- and post-dilution.

PURPOSE: A direct determination of Kt/V using ionic dialysance for estimating K and bio-impedancemetry for estimating V is compared with the usual indirect estimation based on the second generation Daugirdas equation during a new technique of hemodiafiltration with simultaneous pre- and post-dilution (mixed-HDF).
 METHODS: In 31 informed consented patients, the urea distribution volume (V) is estimated by total body water (VBCM ) measured by the Body Composition Monitor (BCM; Fresenius Medical Care, Bad Homburg, Germany) based on bio-impedance spectroscopy. The value (KOCM t)/VBCM is calculated during 114 mixed-HDF sessions (duration 4 hours) from the measurement of ionic dialysance KOCM by the OCM module, standard on the 5008 dialysis monitor (Fresenius Medical Care, Germany). The single pool (Kt/V)sp is determined from blood urea concentration measurements using the Daugirdas equation. RESULTS: Mixed-HDF is a very high-efficiency hemodialysis with a delivered dialysis dose Kt/V near from 2 per 4-hour session. (KOCM t)/VBCM (1.97 ± 0.28) is consistent with (Kt/V)sp (2.01 ± 0.34) with a correlation coefficient at 0.72. CONCLUSIONS: Direct calculation of Kt/V from estimating K by OCM and V by BCM is consistent with the usual indirect estimation by the second generation Daugirdas equation. Therefore, the regular determination of V by BCM allows the estimation of single-pool Kt/V at each session without the need of blood sampling.

[Online hemodiafiltration: is it really more expensive?]. / Hémodiafiltration en ligne : y a-t-il réellement un surcoût ?

Online hemodiafiltration has been shown to have many benefits in terms of morbi-mortality and to increase middle weight molecules removal. However, this technique is supposed to have an additional cost which may be an obstacle to increase its development in hemodialysis centers. The aim of the study is to achieve an accurate pharmaco-economic evaluation for determining the real overcost of online hemodiafiltration (OL-HDF) in comparison with high flux hemodialysis (HF-HD) using standard priming. We have identified the additional costs related to the consumables and monitors and the additional costs imposed by the technique itself (water consumption and microbiological analysis). In the center, more than 28,000 sessions per year are performed with 70% in OL-HDF (90% post-dilution). The consumable overcost ranges from -2.55 to +3.35 euros per session depending on the monitor and on the HDF modality. The overcost of microbiological analysis is +1.1 euros per session. The theoretical additional water consumption is calculated from different dialysat flow rates and OL-HDF modality. Its ranges from +50.8L to +74.8L per session increasing the water overcost from +0.15 to +0.23 euros per session. This accurate evaluation shows that the cost difference of OL-HDF depends on monitor used and on the OL-HDF modality. In our center, it ranges from -1.29 to +4.58 euros per session.

Effect of coadministered HIV-protease inhibitors on tacrolimus and sirolimus blood concentrations in a kidney transplant recipient.

A patient with human immunodeficiency virus infection and end-stage renal disease received a renal transplant. At the time of surgery, the patient was on quadruple antiretroviral therapy (lamivudine, zidovudine, and amprenavir/ritonavir). Immunosuppression was initiated with basiliximab, corticosteroid, mycophenolate mofetil, and a single 0.5 mg dose of tacrolimus. In the following days, an increase in tacrolimus concentration was observed with a peak of 37 ng/mL. Tacrolimus half-life was 6.5 days and tacrolimus maintenance dose was 0.5 mg every 4 days. Eleven months later, the patient had developed Kaposi sarcoma. Tacrolimus was replaced by sirolimus (first dose 1 mg), and the patient was stabilized with 1.5 mg of sirolimus once a week. Increased tacrolimus half-life and increased dose interval of sirolimus and tacrolimus were due to CYP3A4/5 and/or P-glycoprotein inhibition by protease inhibitors. Close monitoring is required in the management of tacrolimus and sirolimus dosing regimens when combined with ritonavir boosted HIV-1 protease inhibitors.

The blockade of T-cell co-stimulation as a therapeutic stratagem for immunosuppression: Focus on belatacept.

The development of immunosuppressive drugs has in recent years been focused on prevention of acute rejection. This has led to an increase in one-year allograft survival. However, these drugs have non-immune effects which contribute to the high incidence of late graft loss, as a consequence of chronic allograft nephropathy, and the death of patients. As an immune-specific alternative to conventional immunosuppressants, new biotechnology tools have been developed; they target the costimulation signal of T-cell activation, particularly by the "classical" B7/CD28 and CD40/CD40L pathways. Here, we review the limitations of current immunosuppressive protocols, the benefits of classical B7/CD28 costimulation blockade, and the first large-scale clinical application of this strategy to human transplantation with belatacept. We will also consider novel costimulatory molecules of the B7/CD28 and TNF/TNF-R families, which appear to be important for the functions of memory and effector T-cells.

Long-term effects of calcineurin inhibitor conversion to mycophenolate mofetil on renal function after liver transplantation.

Calcineurin inhibitors (CNIs) are the cornerstone of immunosuppression after liver transplantation. However, CNI treatment is frequently associated with chronic renal failure (CRF). The reduction or interruption of CNI may reduce renal failure. We prospectively studied 49 liver recipients treated with CNI (tacrolimus, n = 14; cyclosporine, n = 35) who secondarily developed CNI-associated CRF and for whom mycophenolate mofetil (MMF) was introduced to reduce or withdraw CNI. The creatinine clearance (CCl; 42.9 +/- 14 ml/minute) increased significantly after CNI reduction (48.8 +/- 17 ml/minute after 1 year, 49.9 +/- 18 ml/minute after 2 years, and 58.4 +/- 20 ml/minute after 3 years, P < 0.0001). CCl decreased during the 2 years before CNI reduction at a rate of -5.6 +/- 5 ml/minute/year; for the 2 years after CNI reduction, CCl increased significantly by +3.2 +/- 4.3 ml/minute/year (P < 0.0001). Ten patients did not have improved renal function after 1 year, but the rate of decrease in CCl slowed after CNI reduction. Three parameters were identified as risk factors for unresponsiveness to CNI reduction: (1) low CCl at MMF introduction, (2) a high rate of CCl decrease during the 2 years before conversion, and (3) alcoholic cirrhosis. The type of CNI molecule used did not impair the renal response. None of the patients developed acute or chronic graft rejection after the reduction or interruption of CNI. In liver recipients with CRF, a reduction or withdrawal of CNI concomitantly with the introduction of MMF was safe and was associated with an improvement in renal function.

CD3+CD4low and CD3+CD8low are induced by HLA-G: novel human peripheral blood suppressor T-cell subsets involved in transplant acceptance.

HLA-G is a tolerogenic molecule whose detection in sera and within allografted tissues is associated with better graft acceptance. HLA-G mediates T-cell differentiation into suppressor cells, which are thought to promote tolerance. Here, we investigated such T cells phenotypically and functionally and assessed their clinical relevance in the peripheral blood of patients who have undergone transplantation. Our results demonstrate that HLA-G expressed by antigen-presenting cells or present as soluble protein down-regulates the expression of CD4 and CD8 on allostimulated T cells at both transcriptional and posttranslational levels. These CD3(+)CD4(low) and CD3(+)CD8(low) T-cell subsets are characterized by an increased proportion of cells expressing CD45RA and HLA-DR, and a decreased number of cells expressing CD62L. In addition, these HLA-G-induced CD3(+)CD4(low) and CD3(+)CD8(low) subpopulations are Foxp3-negative suppressor T cells whose function involves IL-10. Biologic relevance came from analysis of patients who underwent transplantation, with high HLA-G plasma concentrations associated with better graft survival. Peripheral blood from these patients contains increased levels of IL-10 concomitantly to an enhanced representation of CD3(+)CD4(low) and CD3(+)CD8(low) T cells compared with HLA-G-negative patients who underwent transplantation and healthy individuals. These data define novel immunosuppressive subpopulations of peripheral blood T cells induced by HLA-G with potent implications in peripheral tolerance.

Costimulation blockade and its possible future use in clinical transplantation.

The nonimmune effects of currently used immunosuppressive drugs result in a high incidence of late graft loss due to nephrotoxicity and death of patients. As an immune-specific alternative to conventional immunosuppressants, new biotechnology tools can be used to block the costimulation signals of T-cell activation. Many experimental studies--particularly preclinical studies in nonhuman primates--have focused on blocking the 'classical' B7/CD28 and CD40/CD40L pathways, which are critical in primary T-cell activation. Here, we review the limitations, the recent advances and the first large-scale clinical application of the CTLA4-Ig fusion protein to block the B7/CD28 costimulation pathway. We also focus on new B7/CD28 and tumor necrosis factor (TNF)/TNF-R family costimulatory molecules that can deliver positive or negative costimulation signals regulating the alloimmune response. Strategies that use single agents to block costimulation have often proved to be insufficient. Given the diversity of the different costimulation molecules, future strategies for human transplantation may involve the simultaneous blockade of several selected pathways or the simultaneous use of conventional immunosuppressants.

Human leukocyte antigen-G (HLA-G) expression in biliary epithelial cells is associated with allograft acceptance in liver-kidney transplantation.

BACKGROUND/AIMS: Liver allograft is known to protect simultaneously transplanted organs from acute rejection. We have reported that only 6% of combined liver-kidney recipients, versus 32.5% of kidney recipients, develop kidney graft acute rejection. Release of soluble human leukocyte antigen (HLA) molecules by the liver has been proposed as a possible tolerogenic mechanism involved in the better acceptance of double transplants. The HLA-G molecule is acknowledged to possess tolerogenic properties. METHODS: We investigated the involvement of HLA-G in allogeneic transplant acceptance by analyzing its expression in kidney and liver biopsies of 40 combined transplanted patients. RESULTS: We demonstrate the presence of HLA-G in 14 out of 40 liver and five out of nine kidney transplants biopsies. HLA-G is expressed de novo by cells that are otherwise frequently susceptible target cells of acute rejection, i.e. liver biliary and renal tubular epithelial cells. We show a significant association between HLA-G expression in liver biliary epithelial cells and the absence of liver graft rejection. No acute or chronic rejection of the kidney graft was observed in patients in whom HLA-G was expressed in the liver graft. CONCLUSIONS: HLA-G expression in the liver allograft is associated with a lower frequency of hepatic and renal acute rejection and may be involved in the acceptance of simultaneously transplanted organs.

Incidence of renal and liver rejection and patient survival rate following combined liver and kidney transplantation.

Multiple organ transplantations are used to treat chronic multiple organ failure. However, long-term mortality and graft tolerance remain to be evaluated. We carried out a retrospective and comparative analysis of 45 patients who underwent a combined liver and kidney (LK) transplantation (LKT) from the same donor. They were compared to 86 matched patients who underwent kidney (K) transplantation (KT). All patients had an organic renal failure associated with cirrhosis (n = 35) or with inherited disease (n = 10). Nineteen (42.9%) had been transplanted previously. The patients' survival rate was 85% at 1 year and 82% at 3 years. Seven patients died within the first 3 months, due to severe polymicrobial infection. Two patients in the LK population (4.2%) developed acute rejection of the kidney graft compared to 24 of the 86 matched renal transplanted patients (32.6%). In parallel, acute liver rejection was observed in 14 cases (31.1%) in the LK population. The occurrence of acute rejection was not associated with panel-reactive lymphocytotoxic antibodies (n = 16), nor with positive cross-matches (n = 3). Four of the 45 patients (8.8%) subsequently developed chronic renal allograft rejection, and 16 cases of chronic hepatic dysfunction were noted (42.2%). In conclusion, the overall survival rate following combined liver kidney transplantation is acceptable, and LKT can be proposed to patients with kidney failure associated with liver dysfunction, primary oxaluria or amyloid neuropathy. The main cause of mortality in this population was severe infectious complications. The frequency of acute kidney rejection was lower than in single transplantation.

Alloreactive CD4+ and CD8+ T cells express the immunotolerant HLA-G molecule in mixed lymphocyte reactions: in vivo implications in transplanted patients.

HLA-G displays immunotolerogenic properties towards the main effector cells involved in graft rejection through inhibition of NK- and CTL-mediated cytolysis and CD4+ T cell alloproliferation. HLA-G expression is restricted in healthy tissues to trophoblast and thymus but is extended to various tissues under pathological conditions. HLA-G was detected in allograft biopsies and sera from transplanted patients who displayed a better graft acceptance. However, the cells involved in such de novo expression of HLA-G remain to be characterized. By flow cytometry and confocal microscopy, we demonstrated that, following allogeneic stimulation in vitro, both CD4+ and CD8+ T cell subsets can express membrane-bound HLA-G1 and/or soluble HLA-G5 molecules. Such HLA-G1/-G5 expression is regulated at the transcriptional level. Soluble HLA-G5 could be detected by using a novel monoclonal antibody, 5A6G7, specific for the intron 4-retaining sequence of HLA-G5. Finally, the biological relevance of these data was provided by analysis of transplanted patients in whom we identified both CD4+ and CD8+ T cells expressing HLA-G. The HLA-G-positive T cells we describe here may constitute a cellular source of HLA-G after allotransplantation and may be involved in the improved graft acceptance which is observed in HLA-G-positive transplanted patients.