Our study shows that BKV-associated nephropathy is a relevant complication in the pediatric kidney transplantation setting also. Identification of patients at risk of developing virus-associated nephropathy, through prospective quantification of viral load, could improve clinical outcome by allowing the use of timely preemptive therapy guided by BKV DNA levels.

The emerging role of humoral immunity in the pathogenesis of chronic allograft damage has prompted research aimed at assessing the role of anti-HLA antibody (Ab) monitoring as a tool to predict allograft outcome. Data on the natural history of allografts in children developing de novo Ab after transplantation are limited. Utilizing sera collected pretransplant, and serially posttransplant, we retrospectively evaluated 82 consecutive primary pediatric kidney recipients, without pretransplant donor-specific antibodies (DSA), for de novo Ab occurrence, and compared results with clinical-pathologic data. At 4.3-year follow up, 19 patients (23%) developed de novo DSA whereas 24 had de novo non-DSA (NDSA, 29%). DSA appeared at a median time of 24 months after transplantation and were mostly directed to HLA-DQ antigens. Among the 82 patients, eight developed late/chronic active C4d+ antibody-mediated rejection (AMR), and four C4d-negative AMR. Late AMR correlated with DSA (p < 0.01), whose development preceded AMR by 1-year median time. Patients with DSA had a median serum creatinine of 1.44 mg/dL at follow up, significantly higher than NDSA and Ab-negative patients (p < 0.005). In our pediatric cohort, DSA identify patients at risk of renal dysfunction, AMR and graft loss; treatment started at Ab emergence might prevent AMR occurrence and/or progression to graft failure.

These authors contributed equally to this work.Alloantibody-mediated graft injury is a major cause of kidney dysfunction and loss. The complementbinding ability of de novo donor-specific antibodies (dnDSAs) has been suggested as a prognostic tool to stratify patients for clinical risk. In this study, we analyzed posttransplant kinetics of complementfixing dnDSAs and their role in antibody-mediated rejection development and graft loss. A total of 114 pediatric nonsensitized recipients of first kidney allograft were periodically monitored for dnDSAs using flow bead assays, followed by C3d and C1q assay in case of positivity. Overall, 39 patients developed dnDSAs, which were C1q + and C3d + in 25 and nine patients, respectively. At follow-up, progressive acquisition over time of dnDSA C1q and C3d binding ability, within the same antigenic specificity, was observed, paralleled by an increase in mean fluorescence intensity that correlated with clinical outcome. C3d-fixing dnDSAs were better fit to stratify graft loss risk when the different dnDSA categories were evaluated in combined models because the 10-year graft survival probability was lower in patients with C3d-binding dnDSA than in those without dnDSAs or with C1q + /C3d À or non-complement-binding dnDSAs (40% vs. 94%, 100%, and 100%, respectively). Based on the kinetics profile, we favor dnDSA removal or modulation at first confirmed positivity, with treatment intensification guided by dnDSA biological characteristics.

The treatment of EBV-associated post-transplant lymphoproliferative disease (PTLD) poses a considerable challenge. Efforts have been made to define regimens based on combination of the available therapeutic agents, chosen and tailored on a patient-by-patient basis, with the aim of augmenting event-free patient and graft survival. Recently, autologous EBV-specific cytotoxic T-lymphocytes (CTL) have proved effective in enhancing EBV-specific immune responses and reducing viral load in organ transplant recipients with active infection. We investigated the use of a tailored combined approach including autologous EBV-specific CTL for the treatment of EBV-related PTLD developing after pediatric kidney transplantation.Five patients with disseminated monoclonal (n = 3) or localized polyclonal (n = 2) PTLD unresponsive to reduction of immunosuppression were enrolled. The patients with disseminated PTLD received 4-5 courses of reduced-dosage polychemotherapy, accompanied by rituximab on the first day of each course, while localized disease was removed surgically. At treatment completion, autologous EBV-specific CTL were infused. All patients showed a complete response to treatment, without therapy-related toxicity or rejection, and persist in remission with good renal function at a median follow-up of 31 months. These preliminary results suggest that a combined chemoimmunotherapy regimen including virus-specific T-cells is well tolerated and potentially effective as first-line treatment of EBV-related PTLD.

Preliminary data obtained in this patient indicate that EBV-specific CTLs are safe, may exert specific killing of NPC tumor cells in vitro, and induce antitumor effect in vivo.

Abstract. Polyoma BK virus (BKV)-associated interstitial nephritis has emerged as a relevant complication of immunocompromise after kidney transplantation, leading to reduced survival of the renal allograft. The limitations of current antiviral treatment and the high probability of rejection in kidney graft recipients when control of viral replication is attempted by reduction of immunosuppression warrant further efforts to develop alternative therapeutic tools. Cellular immunotherapy has proved to be a successful approach for prevention and/or treatment of other viral complications in the immunocompromised host. For assessing the feasibility of translating this strategy to the prevention of BKV-associated disease, a procedure for ex vivo reactivation of BKV-specific cytotoxic T cells (CTL) was developed from BKV-seropositive healthy donors and allograft recipients through stimulation with dendritic cells pulsed with inactivated BKV. The CTL lines thus obtained showed BKV specificity, as an efficient lysis of BKV-infected targets was accompanied by little or no reactivity against mock-infected autologous or allogeneic targets. In vitro killing of allogeneic BKV-infected targets, likely as a result of populations of TCR␥␦ϩ/CD3ϩ displaying MHC class I unrestricted cytotoxicity, was also displayed. Application of this culture system may allow a preemptive therapy approach to BKV-related complications in transplant recipients, based on CTL treatment guided by BKV DNA levels.

SummaryData on the different HLA-antibody (Ab) categories in pediatric kidney recipients developing de novo donor-specific Abs (DSA) after transplantation are scarce. We retrospectively evaluated 82 consecutive nonsensitized pediatric recipients of a first kidney graft for de novo HLA Ab occurrence and antigen specificity. At a median follow-up of 6 years, 29% of patients developed de novo DSA, while 45% had de novo non-DSA. DSA appeared at 25-month median time post-transplant and were mostly directed toward HLA-DQ antigens. Considering each HLA antigen, the estimated rate of DQ DSA (7.55 per 100 person-years) was much higher than the rates observed for non-DQ DSA. The HLA-DQ Ab recognized determinants of the DQb chain in 70% of cases, a chain in 25% of cases, and both chains in one patient. Non-DSA peaked earlier than DSA, and were largely directed against HLA class I specificities that belonged to HLA-A-and HLA-B-related cross-reacting epitope groups (CREG) in 56% of cases. Our results indicate a need for evaluating HLA-DQ compatibilities in kidney allocation, in order to minimize post-transplant development of de novo DSA, known to be responsible for antibody-mediated rejection and graft loss.

No abstract