Onset and progression of de novo donor-specific anti-human leukocyte antigen antibodies after BK polyomavirus and preemptive immunosuppression reduction

BACKGROUND

BK polyomavirus (BKPyV) viremia/nephropathy and reduction in immunosuppression following viremia may increase the risk of alloimmune activation and allograft rejection. This study investigates the impact of BKPyV viremia on de novo donor anti-human leukocyte antigen (HLA)-specific antibodies (dnDSA).

PATIENTS AND METHODS

All primary renal transplants at East Carolina University from March 1999 to December 2010, with at least 1 post-transplant BKPyV viral load testing, were analyzed. Patients were negative for anti-HLA antibodies to donor antigens (tested via single antigen beads) at transplantation and at first BKPyV testing.

RESULTS

Nineteen of 174 patients (11%) tested positive for BKPyV viremia. Within 24 months of BKPyV viremia detection, 79% of BKPyV-viremic patients developed dnDSA. Only 20% of BKPyV viremia-persistent cases, compared to 86% of BKPyV viremia-resolved cases, developed dnDSA (P = 0.03). Poor allograft survival was evident in BKPyV viremia-persistent patients (60% failure by 2 years post BKPyV diagnosis) and in BKPyV viremia-resolved patients with dnDSA (5-year post BKPyV diagnosis allograft survival of 48%).

CONCLUSIONS

Post-transplant BKPyV viremia and preemptive immunosuppression reduction is associated with high rates of dnDSA. When preemptively treating BKPyV viremia, dnDSA should be monitored to prevent allograft consequences.

Higher risk of kidney graft failure in the presence of anti-angiotensin II type-1 receptor antibodies

Reports have associated non-HLA antibodies, specifically those against angiotensin II type-1 receptor (AT1R), with antibody-mediated kidney graft rejection. However, association of anti-AT1R with graft failure had not been demonstrated. We tested anti-AT1R and donor-specific HLA antibodies (DSA) in pre- and posttransplant sera from 351 consecutive kidney recipients: 134 with biopsy-proven rejection and/or lesions (abnormal biopsy group [ABG]) and 217 control group (CG) patients. The ABG's rate of anti-AT1R was significantly higher than the CG's (18% vs. 6%, p < 0.001). Moreover, 79% of ABG patients with anti-AT1R lost their grafts (vs. 0%, CG), anti-AT1R levels in 58% of those failed grafts increasing posttransplant. With anti-AT1R detectable before DSA, time to graft failure was 31 months-but 63 months with DSA detectable before anti-AT1R. Patients with both anti-AT1R and DSA had lower graft survival than those with DSA alone (log-rank p = 0.007). Multivariate analysis showed that de novo anti-AT1R was an independent predictor of graft failure in the ABG, alone (HR: 6.6), and in the entire population (HR: 5.4). In conclusion, this study found significant association of anti-AT1R with graft failure. Further study is needed to establish causality between anti-AT1R and graft failure and, thus, the importance of routine anti-AT1R monitoring and therapeutic targeting.

Haploidentical transplantation. Importance of histocompatibility testing and chimerism studies in allogeneic bone marrow/stem cell transplantation

The transplantation of hematopoietic stem cells is sometimes the only treatment option for certain types of malignancies and hematological disorders. The best way to ensure a positive outcome from this type of procedure is to secure an identical human lymphocyte antigen-matched donor or use an autologous graft. This article reviews the indications for transplantation, the recipient and donor selection process, and posttransplant follow-up. The advantages of using haploidentical donors and the typing process also will be discussed.

The facilitating effect of one-DR antigen sharing in renal allograft tolerance induced by donor bone marrow in rhesus monkeys

Infusion of donor bone marrow cells (DBMC), a long-standing, successful strategy for inducing tolerance in experimental rodent transplantation models, can promote long-term acceptance of life-sustaining renal allografts in rhesus monkeys with no maintenance immunosuppression. To investigate the immunological basis for heterogeneity in duration of long-term graft acceptance following infusion of the DR-/dim fraction of DBMC into RATG-treated rhesus monkeys, we examined the relationship of recipient-donor major histo-compatibility class I and II DR matching to the development of antidonor antibody-dependent cellular cytotoxicity (ADCC) and renal allograft survival. The findings indicate a requirement for sharing one DR allele to achieve long-term graft acceptance. The observed immunological consequence of DR sharing that correlated with functional graft tolerance in this model was the suppression of early antidonor ADCC+ IgG antibody responses. Significant associations were observed between graft survival and suppression of ADCC antibody (P < 0.0005), graft survival and DR sharing (P < 0.005), and DR sharing and suppression of ADCC (P < 0.02). Early antidonor ADCC antibody responses associated with failure to maintain graft tolerance and were most consistently directed to donor class I. The required one DR antigen sharing in DBMC-induced suppression of antidonor class I antibody suggests a restriction for recipient DR, implying critical regulation of a response to donor antigen presented on recipient cells. We hypothesize a DBMC tolerogenic mechanism in which presentation of donor class I peptide by a shared DR allele configuration allows a veto effect by DBMC. Thus DR sharing would allow DBMC veto cells to reduce clonal expansion elicited by both the direct and indirect antigen presentation pathways.

A comprehensive definition of the major antibody specificities in polyclonal rabbit antithymocyte globulin

The potent immunosuppressive action of rabbit antithymocyte globulin (RATG) in allotransplant recipients has been recognized for many years. Some of the antibody specificities and immunoregulatory effects of RATG have been described, but a comprehensive definition of RATG components has not been reported previously. In this study, we have identified 23 specificities that are consistent among different clinical RATG batches and represent the major antibody specificities in RATG. These specificities were defined by immunoprecipitation/gel electrophoresis and also antibody blocking/flow cytometry methods. Titration studies performed for semiquantitative analysis of RATG antibodies showed that the antibodies present in highest titer were directed to CD6, CD16, CD18, CD28, CD38, CD40, and CD58 (titer > 1:4000), most of which are not T cell-specific antibodies. In contrast, the RATG antibodies that persisted the longest in vivo in the plasma of rhesus monkeys transplant recipients are antibodies to CD3, CD4, CD8, CD11a, CD40, CD45, CD54, and class I. These antibodies, which are directed at signal transduction and adhesion molecules, were present during the early period of lymphocyte recovery. We suggest that the persistence of these antibodies in vivo is directly related to the prolonged anergy of circulating T cells after RATG treatment and to the unusual potency and complex tapestry of immunological effects in transplantation.

Further studies of veto activity in rhesus monkey bone marrow in relation to allograft tolerance and chimerism

Infusing the DR-/dim fraction of bone marrow cells (BMC) from an allogeneic kidney donor into rabbit antithymocyte globulin-treated transplant recipients delivers a tolerogenic signal, leading to functional allograft tolerance in rhesus monkeys without additional drug therapy. Our updated results in an expanded series show a median 131-day graft survival of recipients given DR-/dim donor BMC with a 23% 1-year survival (P < 0.00001 vs. rabbit antithymocyte globulin controls). Removing DRbright cells from donor BMC appeared to have a significant effect (P < 0.05). We have further investigated the tolerogenic mechanism within the experimental framework of the veto hypothesis in this preclinical model. In limiting dilution assays, we demonstrated the donor specificity of clonal inactivation of CTL precursors (CTLp) after in vitro or in vivo exposure to DR-/dim donor BMC, confirming specific tolerance. Additionally, in vitro studies confirmed the allogeneic specificity of CTLp inactivation in 3-cell MLR assays; minimal bystander effects were seen on normal CTLp responses to third party stimulator cells, while CTLp responses to the BMC donor's cells were abrogated in the same cultures. BMC mediating the veto effect were found to be resistant to L-leucyl-L-leucine methyl ester (Leu-leu-OMe), which excluded BMC-mediated cytotoxicity by NK or lymphokine-activated killer cells, CTL, or activated macrophages. In contrast, veto activity was abolished if the BMC were pretreated with either high dose UV-B light irradiation, mitomycin, or gamma-irradiation, indicating that BMC contained a UV-B-sensitive precursor of the veto effector, and that a proliferative step separated the two. Irradiation of DR-/dim donor BMC or administration of cyclophosphamide after infusion of nonirradiated BMC prevented the tolerogenic effect. Only recipients given nonirradiated DR-/dim donor BMC demonstrated PBL chimerism, which associated with functional deletion of antidonor CTLp and duration of graft survival. The Leu-leu-OMe resistance and the other properties of the allogeneic monkey CD3- CD2+ CD8+ BMC subpopulation that exhibits tolerance-promoting activity in vitro and in vivo lead us to postulate that a donor BMC-derived precursor population, possibly a dendritic cell population, may induce allogeneic unresponsiveness in this model.

Production of stable rabbit-mouse heterohybridomas: characterization of a rabbit monoclonal antibody recognizing a 180 kDa human lymphocyte membrane antigen

Polyclonal rabbit antihuman thymocyte globulin (RATG) remains a key component of immunosuppressive strategies in transplantation. The human thymus immunization regimen that produces highly immunosuppressive RATG induces unique antibody specificities in the rabbit. Rabbit monoclonal antibodies (RAb MAbs) to human T cell antigens would be of value in the effort to investigate and reproduce the multiple specificities of RATG. We have fused mouse Sp2/0 cells with splenocytes from rabbits immunized with human thymus and have identified 52 rabbit-mouse heterohybridomas which secrete RAb MAbs directed against human lymphocyte surface antigens. The technical aspects of hybridoma isolation, stabilization and characterization are presented. Analysis by flow cytometry, preabsorption and immunoprecipitation suggests that RAb MAb 1A8 IgG may recognize LFA-1, one of the principal lymphocyte surface antigens recognized by RATG. The 1A8 antigen is 180 kDa and is expressed by 80-90% human PBL and thymocytes. LFA-1 and the 1A8 antigen exhibit 100% co-expression in two-color FACS analysis using four different murine anti-LFA-1 MAbs. 1A8 markedly inhibits the mitogenic response of lymphocytes to PHA, as do murine anti-LFA-1 MAbs. A combination of rabbit antilymphocyte MAbs may potentially reproduce the multiple specificities found in polyclonal RATG and lead to the production of a superior immunosuppressive clinical agent.

Antigens expressed on NIH 3T3 cells following transformation with DNA from human pancreatic tumor

This report documents that the pancreatic adenocarcinoma cell line, HPAF, contains oncogene activity detected by transformation of NIH 3T3 cells through transfection with HPAF DNA. The HPAF transfected NIH 3T3 cells do not contain oncogenes homologous with c-H-ras, c-K-ras, c-N-ras, v-fms, c-myb, c-sis, v-fgr, c-mos, c-myc, c-fos, v-fes, v-src, v-erb A, v-erb B, c-N-myc, v-raf, or v-abl, other than the endogenous mouse genes. The transfectants do express proteins detected by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis which were not found in nontransfected NIH 3T3 cells. Monoclonal antibodies raised against the transfectants recognize proteins not found in untransfected NIH 3T3 cells that are antigenically identical to proteins found in the HPAF cells. These antigens are also detected on six other human pancreatic adenocarcinoma cell lines but show a much more restricted distribution on lymphoblastoid, melanoma, prostatic carcinoma, and normal skin fibroblast cell lines.