Christophe Baron

Induction versus noninduction in renal transplant recipients with tacrolimus-based immunosuppression

Background. The aim of this study was to compare the efficacy and safety of induction treatment with antithymocyte globulins (ATG) followed by tacrolimus therapy with immediate tacrolimus therapy in renal transplant recipients. Methods. This 12-month, open, prospective study was conducted in 15 centers in France and 1 center in Belgium; 309 patients were randomized to receive either induction therapy with ATG (n=151) followed by initiation of tacrolimus on day 9 or immediate tacrolimus-based triple therapy (n=158). In both study arms, the initial daily tacrolimus dose was 0.2 mg/kg. Steroid boluses were given in the first 2 days and tapered thereafter from 20 mg/day to 5 mg/day. Azathioprine was administered at 1–2 mg/kg per day. Results. At month 12, biopsy-confirmed acute rejections were reported for 15.2% (induction) and 30.4% (noninduction) of patients (P =0.001). The incidence of steroid-sensitive acute rejections was 7.9% (induction) and 22.2% (noninduction)(P =0.001). Steroid-resistant acute rejections were reported for 8.6% (induction) and 8.9% (noninduction) of patients. A total of nine patients died. Patient survival and graft survival at month 12 was similar in both treatment groups (97.4% vs. 96.8% and 92.1% vs. 91.1%, respectively). Statistically significant differences in the incidence of adverse events were found for cytomegalovirus (CMV) infection (induction, 32.5% vs. noninduction, 19.0%, P =0.009), leukopenia (37.3% vs. 9.5%, P <0.001), fever (25.2% vs. 10.1%, P =0.001), herpes simplex (17.9% vs. 5.7%, P =0.001), and thrombocytopenia (11.3% vs. 3.2%, P =0.007). In the induction group, serum sickness was observed in 10.6% of patients. The incidence of new onset diabetes mellitus was 3.4% (induction) and 4.5% (noninduction). Conclusion. Low incidences of acute rejection were found in both treatment arms. Induction treatment with ATG has the advantage of a lower incidence of acute rejection, but it significantly increases adverse events, particularly CMV infection.

Supernatant from bifidobacterium differentially modulates transduction signaling pathways for biological functions of human dendritic cells.

Background Probiotic bacteria have been shown to modulate immune responses and could have therapeutic effects in allergic and inflammatory disorders. However, the signaling pathways engaged by probiotics are poorly understood. We have previously reported that a fermentation product from Bifidobacterium breve C50 (BbC50sn) could induce maturation, high IL-10 production and prolonged survival of DCs via a TLR2 pathway. We therefore studied the roles of mitogen-activated protein kinases (MAPK), glycogen synthase kinase-3 (GSK3) and phosphatidylinositol 3-kinase (PI3K) pathways on biological functions of human monocyte-derived DCs treated with BbC50sn. Methodology/Principal Findings DCs were differentiated from human monocytes with IL-4 and GM-CSF for 5 days and cultured with BbC50sn, lipopolysaccharide (LPS) or Zymosan, with or without specific inhibitors of p38MAPK (SB203580), ERK (PD98059), PI3K (LY294002) and GSK3 (SB216763). We found that 1) the PI3K pathway was positively involved in the prolonged DC survival induced by BbC50sn, LPS and Zymosan in contrast to p38MAPK and GSK3 which negatively regulated DC survival; 2) p38MAPK and PI3K were positively involved in DC maturation, in contrast to ERK and GSK3 which negatively regulated DC maturation; 3) ERK and PI3K were positively involved in DC-IL-10 production, in contrast to GSK3 that was positively involved in DC-IL-12 production whereas p38MAPK was positively involved in both; 4) BbC50sn induced a PI3K/Akt phosphorylation similar to Zymosan and a p38MAPK phosphorylation similar to LPS. Conclusion/Significance We report for the first time that a fermentation product of a bifidobacteria can differentially activate MAPK, GSK3 and PI3K in order to modulate DC biological functions. These results give new insights on the fine-tuned balance between the maintenance of normal mucosal homeostasis to commensal and probiotic bacteria and the specific inflammatory immune responses to pathogen bacteria.

TCF7L2 Polymorphism Associates with New-Onset Diabetes after Transplantation

New-onset diabetes after transplantation (NODAT) is a serious and frequent complication in transplant recipients. Whether NODAT shares the same susceptibility genes as type 2 diabetes is unknown. In this multicenter study, we genotyped 1076 white patients without diabetes at transplantation for 11 polymorphisms that associate with type 2 diabetes. We defined NODAT as a fasting plasma glucose > or =126 mg/dl on at least two occasions or de novo hypoglycemic therapy. We compared clinical and genetic factors between patients who developed NODAT within 6 mo of transplantation (n = 118; incidence 11%) and patients without diabetes (n = 958). In multivariate analysis, NODAT significantly associated with the following characteristics: TCF7L2 polymorphism (odds ratio [OR] 1.60 per each T allele; P = 0.002), age (OR 1.03 per year; P < 0.001), body mass index at transplantation (OR 1.09 per unit; P < 0.001), tacrolimus use (OR 2.26; P < 0.001), and the occurrence of a corticoid-treated acute rejection episode (OR 2.78; P < 0.001). In summary, our data show that the TCF7L2 rs7903146 polymorphism, a known risk factor for type 2 diabetes in the general population, also associates with NODAT.

hemolytic Uremic Syndrome: Recurrence after Renal Transplantation

: Hemolytic uremic syndrome (HUS) is an uncommon cause of end-stage renal failure in adults, and few data are available concerning the outcome of renal transplantation in these patients. We conducted this retrospective multicentric study to appreciate the outcome of adult renal transplant recipients whose primary disease was HUS. Sixteen patients, transplanted between 1975 and 1995, were included in the study. In each case, initial diagnosis of HUS was documented by a kidney biopsy. These 16 patients received a total of 25 allografts: 1 graft for 9 patients, 2 grafts for 5 patients, and 3 grafts for 2 patients. Nine patients (56%) developed definite clinical and pathologic evidence of recurrence on at least 1 graft. Four additional patients (25%) demonstrated only some clinical or pathologic evidence of recurrence which could not be distinguished from acute vascular rejection. Three patients had no sign of recurrence of the initial disease. The 1-year graft survival rate was 63% and the 5-year graft survival rate was 18.5%. In the group of patients with proven or possible recurrence (n = 13), the 1-year and 5-year graft survival rates were 49% and less than 10%, respectively. The recurrence was an early event, occurring before the end of the first month after transplantation in half the cases. The recurrence rate was 92% in non-nephrectomized patients and 50% in patients with bilateral nephrectomy. In the literature, 71 adult patients with primary HUS had received a total of 90 kidney grafts. Among them, 54% had a recurrence on their graft, which was diagnosed in 52% of the kidney transplants. It is note-worthy that when data from the literature are pooled with our results, the rate of recurrence appears to be significantly lower in binephrectomized patients than in patients with their native kidneys at the time of transplantation (5 of 14 versus 27 of 35 patients, respectively, p = 0.0155). By univariate analysis, no other risk factor for recurrence could be identified. Treatment with cyclosporine A did not influence the recurrence rate. We conclude that recurrence of HUS after renal transplantation is a frequent, early, and severe complication, leading rapidly to graft loss. Prospective studies are needed to confirm that bilateral nephrectomy prior to transplantation decreases the rate of recurrence.

Molecular Diagnosis of Renal-allograft Rejection: Correlation with Histopathologic Evaluation and Antirejection-therapy Resistance

Background. Because histopathologic criteria cannot always predict the pathogenesis and response to curative antirejection therapy, new hope derives from the molecular analysis of intragraft immunologic markers. We studied whether the cutoff of intragraft expression level of T-cell activation markers may define subgroups of acute rejection differing either in type of rejection or clinical outcome. Methods. Forty-three human renal-allograft biopsies were quantified for mRNA expression of granzyme B, Fas ligand, interferon (IFN)&ggr;, interleukin (IL)-4, and IL-6 with a reverse-transcriptase real-time quantitative polymerase chain reaction (RT-PCR) method. Expression levels were correlated with the histopathologic rejection type according to the Banff 1997 classification criteria, and with the sensitivity to the antirejection immunosuppressive therapy, by means of receiver operating-characteristic (ROC) curves. Results. Granzyme B and Fas ligand mRNA expression up-regulation correlated with all allograft rejection types (P<0.01 for all). Moreover, granzyme B showed the highest sensitivity (90%) and specificity (78%) for the potential detection of histologic borderline changes that will require immunosuppressive therapy (area under the curve [AUC]=0.856, P<0.01). Curative antirejection-therapy resistance of overt, acute-rejection episode was significantly associated with higher Fas ligand gene expression (AUC=0.764, P<0.01, sensitivity [71%], specificity [99.5%]). Conclusions. Real-time RT-PCR quantification of the over-expression of the granzyme B gene in kidney-graft biopsies has proved to be as reliable in detecting acute rejection as histologic assessment. Furthermore, we demonstrate that the simultaneous measurement of the mRNA up-regulation of Fas ligand might represent an efficient new tool for the prediction of pejorative outcome of acute rejection.

Association between a polymorphism in the IL-12p40 gene and cytomegalovirus reactivation after kidney transplantation.

Background. Cytomegalovirus (CMV) infection is associated with a significant rate of morbidity after organ transplantation. The genetic factors influencing its occurrence have been little investigated. IL-12 plays a crucial role in anti-infectious immune responses, especially by stimulating IFNγ production. An A-to-C single nucleotide polymorphism (SNP) within the 3′-untranslated region of the IL-12p40 gene has been characterized and was reported to be both functionally and clinically relevant. However, the impact of this single nucleotide polymorphism on events after organ transplantation has never been reported. Methods. In this study, we investigated the impact of the 3′-untranslated region polymorphism on the occurrence of CMV infection in 469 kidney recipients transplanted at the University Hospital of Tours between 1995 and 2005. The polymorphism was genotyped using the restriction fragment length polymorphism method and CMV infection was determined by pp65 antigenemia. Results. Multifactorial Cox regression analysis demonstrated that the presence of the C allele was an independent risk factor for CMV infection (OR=1.52, P=0.043), the risk being even higher when study was restricted to patients with positive CMV serological status before the graft and who did not receive any CMV prophylaxis (OR=1.88, P=0.028). Conclusions. This study identified a new genetic risk factor for CMV reactivation after kidney transplantation. The results of our study suggest that C carriers might especially benefit from CMV prophylaxis.

Revisiting the effects of CMV on long-term transplant outcome.

Purpose of the reviewIndirect effects of cytomegalovirus (CMV) in transplantation are of three types: increase in systemic immunosuppression, increased risk of malignancy (especially Epstein–Barr virus-related B-cell lymphoproliferative disease), and the possible contribution to allograft injury. Despite modern and potent antiviral drugs, the real impact of CMV in transplantation, especially kidney transplantation, remains a challenge because many confounding factors arise when analyzing this question.This review will fuel the discussion and review some of the recent data. Recent findingsA recent study on cardiac allograft in mice has shown that CMV in latently infected recipients could break graft acceptance. Although the exact nature of response was not addressed, this study suggested that CMV reactivation inside the graft played an important part in graft losses. Other recent results suggest that the quality of immune response against CMV influences graft outcome in both cardiac and kidney transplant patients. Other evidence suggests the link between CMV infection, immune senescence and vascular disease in the whole population. Studies have opened the perspective for new strategies to prevent indirect effects of CMV. SummaryAlthough a causal relationship between CMV reactivation and graft injury is supported by a large body of experimental and clinical data, definitive proof in clinical transplantation is still lacking to exclude an associative relationship. Large randomized clinical trials analyzing long-term graft survival and comparing prophylaxis with preemptive, especially D+/R+, is probably an efficient way to establish a causal relationship. Research on new antiviral strategies applicable over the long term is important.

Anti-CD25 antibodies affect cytokine synthesis pattern of human dendritic cells and decrease their ability to prime allogeneic CD4+ T cells

Anti‐CD25 monoclonal antibodies are widely used in clinical transplantation to prevent acute allograft rejection. Although their effects on T lymphocytes have been extensively studied, their impact on human dendritic cells (DC) has never been reported. Furthermore, the role of the IL‐2 in DC functions has not yet been fully elucidated. In this study, we confirm that the stimulation of human monocyte‐derived DC with LPS strongly induced the expression of CD25 and that LPS‐matured DC also expressed the β and γ chain of the IL‐2R. We also showed that adding anti‐CD25 monoclonal antibodies to LPS induced a decrease in IL‐12, IL‐1, TNF‐α, IL‐6, and IFN‐γ production and an increase in IL‐10 synthesis by DC compared with stimulation with LPS alone. Furthermore, we showed that these modifications diminished the T helper priming ability of DC and polarized the alloimmune response toward TH2. In contrast, humanized anti‐CD25 monoclonal antibodies did not affect the up‐regulation of CD86, CD80, CD83, HLADR, or CD40 induced upon LPS stimulation. Taken together, this study discloses some previously unrecognized effects of anti‐CD25 monoclonal antibodies on DC that may contribute to their clinical efficacy. In addition, this study also shed some light on the role of the IL‐2 in human DC activation.

Association between a polymorphism in the human programmed death-1 (PD-1) gene and cytomegalovirus infection after kidney transplantation

Background Cytomegalovirus (CMV) infection is the most frequent infectious disease following organ transplantation. Strategies to prevent this infection remain a matter for debate, and discovering genetic risk factors might assist in adapting preventive strategies. By inhibiting IFNγ production, programmed death 1 (PD-1) has a crucial role in anti-CMV immune response. A single nucleotide polymorphism (SNP) within intron 4 of the gene (rs11568821), called PD-1.3, has recently been reported to be clinically relevant in several immune disorders. However, its association with CMV infection has never been reported. Methods In this study, the risk of CMV infection according to PD-1.3 genotype was investigated in 469 kidney graft recipients transplanted between 1995 and 2005. Results It was found that the A allele was associated with the risk of CMV infection in seropositive patients who did not receive CMV prophylaxis (OR=2.60, p=0.006). Multivariate analysis including other risk factors for CMV infection showed that this allele was independently associated with CMV infection (OR=2.54; p=0.010). Interestingly, combined analysis of PD-1.3 with the IL12B 3′UTR SNPs (previously shown to be associated with CMV infection) revealed that patients with the PD-1.3 A allele had a much higher risk of CMV infection compared to those having neither risk allele (OR=3.76; p=0.0003). Conclusion This study identified a new genetic risk factor for CMV infection after kidney transplantation and suggests that an adjustment of CMV prophylaxis based on genetic markers would merit further investigation.

Induction of human CD4+ regulatory T cells by mycophenolic acid-treated dendritic cells

Depending on their degree of maturation, costimulatory molecule expression, and cytokine secretion, dendritic cells (DC) can induce immunity or tolerance. DC treated with mycophenolic acid during their maturation (MPA‐DC) have a regulatory phenotype and may therefore provide a new approach to induce allograft tolerance. Purified CD4+ T cells stimulated in a human in vitro model of mixed culture by allogeneic MPA‐DC displayed much weaker proliferation than T cells activated by mature DC and were anergic. This hyporesponsiveness was alloantigen‐specific. Interestingly, T cells stimulated by MPA‐DC during long‐term coculture in four 7‐day cycles displayed potent, suppressive activity, as revealed by marked inhibition of the proliferation of naive and preactivated control T cells. These regulatory T cells (Tregs) appeared to have antigen specificity and were contact‐dependent. Tregs induced by MPA‐DC were CD25+glucocorticoid‐induced TNFR+CTLA‐4+CD95+, secreted IL‐5 and large amounts of IL‐10 and TGF‐β, and displayed enhanced forkhead box p3 expression. These results obtained in vitro demonstrate that human MPA‐DC can induce allospecific Tregs that may be exploited in cell therapy to induce allograft tolerance.