Donor-specific anti-HLA antibody monitoring and removal in solid organ transplant recipients.

Based on our knowledge that donor specific anti-HLA antibodies (DSA) are a major cause of allograft loss, determining how to monitor patients for DSA and how to treat them is important. Current published studies indicate that patients with preformed DSA differ from those without. Approximately 15-18 percent of transplant patients will have preformed DSA, which increases risk for early antibody mediated rejection (AMR) and allograft loss. The fact that nearly all AMR episodes occur in the first 1-2 months, coupled with the finding that a reduction in preformed DSA intensity within the first few weeks post-transplant decreases the risk of AMR, makes early testing important. It has also been shown that clearance of DSA at 6 months and 1 year can result in a decreased risk of transplant glomerulopathy and therefore, these times may be prime testing points. This monitoring schedule differs slightly from that of the patients who do not have performed DSA (i.e. low risk patients). Low risk patients who develop de novo DSA are most likely to do so in the first 6 months. However, more frequent sampling in the early months does not improve predictability of acute rejections in low risk patients and therefore, it is not as essential. Rather, testing at 6 months and then annually or biannually, would be beneficial, as it would serve to identify the 5 percent of new patients who develop DSA annually. Once these patients are identified, studies have shown that preemptive treatment to a goal of antibody clearance can be used to improve graft function and survival. In addition to screening for new DSA, monitoring for clearance of DSA along with histologic reversal of rejection in patients with AMR is important. In sum, there is substantial evidence suggesting that all patients need to have some monitoring for DSA to identify new onset of DSA or clearance of DSA. Additionally, in all DSA scenarios, treatment of persistent DSA is important, as it can lead to improved allograft survival (read more).

A report of the epidemiology of de novo donor-specific anti-HLA antibodies (DSA) in "low-risk" renal transplant recipients.

The donor specific anti-HLA antibody (DSA) has been increasingly recognized as the major cause of allograft loss. Despite this, no published reports exist describing the true epidemiology of de novo DSA.Here we describe the epidemiology of DSA based on the results of one of the longest running antibody study in consecutive renal transplant recipients. The study includes 224 non-sensitized, non-HLA-identical patients who received a primary kidney transplant between 3/1999-3/2006. Protocol testing for DSA was done pre-transplant, at 1, 3, 6, 9, and 12 months, and then annually. DSA was tested using single antigen beads. Data from the East Carolina University transplant cohort indicate that the prevalence of DSA in the first year post-transplant is 12.1 cases per 100. The average annual incidence of DSA is 4.7 per 100 cases, per year. The highest incidence of DSA was in the first year post transplant. Although deceased donors and African-Americans have a higher incidence rate of DSA than the comparator living donors and non-African American groups, respectively, these factors were not associated with DSA onset. The one factor found to be predictive of DSA was DQ mismatch (p = 0.036). Based on these epidemiologic findings in combination with previous reports showing DSA is a cause of allograft failure, it seems reasonable that at least annual testing should be done even in "low-risk" transplant patients, because every year a new 5% of patients will develop DSA (read more)

De Novo DQ Donor-Specific Antibodies Are Associated With a Significant Risk of Antibody-Mediated Rejection and Transplant Glomerulopathy

Background: The importance of human leukocyte antigen (HLA) matching in renal transplantation is well recognized, with HLA-DR compatibility having the greatest influence. De novo DQ donor-specific antibodies (DSAbs) are the predominant HLA class II DSAb after transplantation. The aim of this study was to establish the incidence and outcomes after the development of DQ DSAbs along with the impact of class II HLA mismatch on their development.
Methods: We retrospectively analyzed 505 patients who received a renal-alone transplant between 2005 and 2010. We excluded patients who received an ABO- and HLA-incompatible allograft, which we defined as those with a positive crossmatch or preformed DSAbs detected by single-antigen beads only.
Results: Of 505 patients, 92 (18.2%) developed DSAbs, with 50 (54.3%) of these 92 patients having DQ DSAbs. Patients who developed DQ DSAbs were at significant risk for antibody-mediated rejection, transplant glomerulopathy, and allograft loss (P<0.0001). Of 505 patients, 108 (21.4%) were matched at both the DR and DQ loci, 284 (56.2%) were mismatched at both loci, 38 (7.5%) were matched at DR alone, and 75 (14.9%) were matched at DQ alone. Patients mismatched at both DR and DQ were at risk for developing class II DSAbs when compared with those mismatched at either DR or DQ alone, P=0.001, and were at risk for antibody-mediated rejection, P=0.001.
Conclusions: DQ DSAbs are associated with inferior allograft outcomes. This study shows the importance of establishing the DQ match before transplantation to define immunologic risk (read more).

Significance of low-level DSA detected by solid-phase assay in association with acute and chronic antibody-mediated rejection

We sought to clarify the controversial issue of whether detecting low-level anti-donor-specific HLA antibody (HLA-DSA) by single-antigen flow-bead assay (SAFB) may have a potential role in reducing acute and chronic antibody-mediated rejection (AMR). We retrospectively studied the preoperative serum of ABO-compatible living kidney transplantation recipients transplanted between 2001 and 2004 by SAFB using a Luminex platform. HLA-DSA was detected only by SAFB in 24 patients, although all of them showed negative T-cell and B-cell complement-dependent cytotoxicity (CDC) crossmatches. The HLA-DSA patients went on to have surprisingly high levels of acute and chronic AMR despite being only weakly sensitized (acute AMR, 33.3%; chronic AMR, 41.7%). After 2005, we implemented SAFB routinely and any patient having a positive HLA-DSA was considered to be a desensitization candidate. The 52 patients found to have HLA-DSA underwent kidney transplantation after prior treatment with a single dose of rituximab (RIT) and three or four sessions of double-filtration plasmapheresis (DFPP) in addition to regimens commonly used between 2001 and 2004. After 2005, there was a significant reduction in the occurrence of acute and chronic AMR (acute AMR, 4.7%, P < 0.001; chronic AMR, 4.7%, P < 0.001). The 5-year graft survival rate also improved after implementing SAFB (83.3–98.1%, P = 0.032). The RIT/DFPP-induction protocol may improve graft survival even in patients with low-level DSA (read more).

Preformed Donor HLA-DP-Specific Antibodies Mediate Acute and Chronic Antibody-Mediated Rejection Following Renal Transplantation

Donor-specific HLA alloantibodies may cause acute and chronic antibody-mediated rejection (AMR) and significantly compromise allograft survival. The clinical relevance of antibodies directed against some HLA class II antigens, particularly HLA-DP, is less clear with conflicting reports on their pathogenicity. We report two patients with high levels of pretransplant donor-specific HLA-DP antibodies who subsequently developed recurrent acute AMR and graft failure. In both cases, there were no other donor-specific HLA alloantibodies, suggesting that the HLA-DP-specific antibodies may be directly pathogenic (read more)

Patterns of De Novo Allo B Cells and Antibody Formation in Chronic Cardiac Allograft Rejection After Alemtuzumab Treatment

Even though the etiology of chronic rejection (CR) is multifactorial, donor specific antibody (DSA) is considered to have a causal effect on CR development. Currently the antibody-mediated mechanisms during CR are poorly understood due to lack of proper animal models and tools. In a clinical setting, we previously demonstrated that induction therapy by lymphocyte depletion, using alemtuzumab (anti-human CD52), is associated with an increased incidence of serum alloantibody, C4d deposition and antibody-mediated rejection in human patients. In this study, the effects of T cell depletion in the development of antibody-mediated rejection were examined using human CD52 transgenic (CD52Tg) mice treated with alemtuzumab. Fully mismatched cardiac allografts were transplanted into alemtuzumab treated CD52Tg mice and showed no acute rejection while untreated recipients acutely rejected their grafts. However, approximately half of long-term recipients showed increased degree of vasculopathy, fibrosis and perivascular C3d depositions at posttransplant day 100. The development of CR correlated with DSA and C3d deposition in the graft. Using novel tracking tools to monitor donor-specific B cells, alloreactive B cells were shown to increase in accordance with DSA detection. The current animal model could provide a means of testing strategies to understand mechanisms and developing therapeutic approaches to prevent chronic rejection (read more).