Evaluation of Epstein-Barr Virus (EBV) Antibody Screening of Organ Donors for Allocation of Organs to EBV Serostatus Matched Recipients

OBJECTIVE

Posttransplant lymphoproliferative disorder (PTLD) is a life-threatening complication following organ transplantation. The greatest risk is seen in Epstein-Barr virus (EBV)-seronegative patients receiving allografts from EBV-seropositive donors. The severity and frequency of PTLD are particular concerns for pediatric patients, who frequently are EBV negative and hence more likely to be EBV infected from an EBV-positive organ donor. The aim of this study was to analyze the EBV serostatus of deceased organ donors and to assess the likelihood of recipient/donor matching for EBV serostatus.

MATERIALS AND METHODS

Sera obtained from local deceased organ donors for the period 2004-2005 were retrospectively tested for EBV viral capsid antigen (VCA) IgG and IgM antibodies by an enzyme-linked immunosorbent assay (ELISA). The analysis included only data from those donors who were tested using a pretransfusion specimen (n = 459). The influence of various factors on the EBV serostatus of the donor was assessed, including age, gender, ethnicity, and cytomegalovirus (CMV) serostatus of the donor.

RESULTS

Overall, only 27 (6%) of the 459 donors were EBV seronegative, with 94% being positive for IgG antibodies to EBV. A higher percentage of the EBV-seronegative donors were younger donors (age < or =35 years), compared with EBV-seropositive donors, 74% (n = 27) vs 31% (n = 432), P < .0001. A higher percentage (85%) of the younger (age < or =35 years) EBV-seronegative donors (n = 20) were also CMV seronegative. There was also a greater likelihood for the younger (age < or =35 years) CMV-seronegative donors to be EBV seronegative, compared with the older (age >35 years) CMV-seronegative donors, 20% (n = 83) vs 1% (n = 93), P < .0001. There was no influence of other factors examined on EBV serostatus.

CONCLUSIONS

EBV-seronegative organ donors are infrequent and therefore provide only a limited supply of organs for patients in need of them. The higher frequency of EBV-seronegative donors being the younger donors will benefit the pediatric patients who have the greatest need for an EBV serostatus matched organ from a younger donor. Recent policy changes at the United Network for Organ Sharing (UNOS) giving priority to pediatric patients for kidneys from younger donors (age < or =35 years) and prospective EBV testing of donors will be helpful in the appropriate allocation of these organs.

An Evaluation of HLA Cross-Reactive Group Matching on Graft Survival in Deceased Donor Kidney Recipients

Since September 20, 1999, our organ procurement organization (OPO) serving an ethnically diverse local distribution area has allocated kidneys using a cross-reactive group (CREG)-based variance. This variance awards 7 points for 0-CREG,0-DR mismatches and 6 points for 0-A,B mismatches in addition to points given for waiting time (3) and panel-reactive antibodies (PRA) > or = 80% (3). Previously, we have shown that awarding points for 0-CREG,0-DR mismatches in kidney allocation improves the access to HLA-matched transplants for racial groups, especially for the black race. In this study, we evaluated if there are outcome benefits as well. One- and 3-year uncensored graft survival data and analyses for the influence of HLA mismatching on graft outcome in black and nonblack recipients were provided by Scientific Registry of Transplant Recipients (SRTR). Overall, 1-year graft survival was 87.4% and not significantly different for blacks (86.1%, n = 467) vs nonblacks (88.8%, n = 730); 3-year graft survival was 74.6% and significantly lower P = .0001 for blacks (68.5%, n = 480) vs nonblacks (78.4%, n = 765). No significant advantage was observed for either the black or nonblack recipients in any of the HLA-mismatched categories, including the 0-CREG,0-DR mismatch group. An HLA matching effect also was not seen when data were stratified for patients nonsensitized (PRA < or = 10%) and sensitized (PRA > 10%) at the time of transplantation, except for the improved graft survival in sensitized nonblack recipients of 0- A,B,DR-mismatched grafts. Of the patients who lost their grafts and returned to the waiting list for retransplantation, the 0-A,B,DR mismatched were the least sensitized group (6%, n = 16), and there was a trend for less sensitization in the 0-CREG,0-DR-mismatched group (33%, n = 9), compared to those with other HLA mismatches (68%, n = 137). Thus, based on 1-year and 3-year follow-up data, there are no apparent graft outcome benefits for either CREG matching or conventional HLA matching in our service area, except for sensitized nonblack recipients receiving 0-A,B,DR-mismatched grafts. Such benefits may become more apparent with longer follow-up.

Bone allografts are immunogenic and may preclude subsequent organ transplants

The authors report a case of a 41-year-old woman with diabetes and chronic renal failure in whom antihuman leukocyte antigen antibodies developed after she received a frozen bone allograft that limited her access to organ donors. The patient had a chondrosarcoma of the right distal femur. A wide resection with segmental total knee arthroplasty was followed by a revision using a composite bone allograft prosthesis. After revision, broadly reactive lymphocytotoxic antibodies developed in the patient. The patient's panel reactive antibody level rose from 28% to a peak of 70%. Panel reactive antibody expresses the percentage of a panel of human leukocyte antigen type T lymphocytes from 40 individuals (representative of all human leukocyte antigen Class I histocompatibility antigens) to which antihuman leukocyte antigen Class I lymphocytotoxic antibodies have developed in the recipient as measured by the antiglobulin crossmatch method. The specificity of the patient's primary antibody is found in 45% of donors available in Illinois since 1988 (N = 1606). Because a positive crossmatch precludes kidney and pancreas transplantation, at least 45% of cadaver organ donors were excluded from use for this patient. This is an unusual case that focuses on the potential impact of bone allografts in patients who may need subsequent organ transplantation.

Identification of patients at risk for inferior renal allograft outcome by a strongly positive B cell flow cytometry crossmatch

To evaluate the influence of a positive B cell flow cytometry crossmatch (FCXM) on transplant outcome, we retrospectively performed B cell FCXMs for 431 consecutive cadaver renal transplant recipients using the two most current pretransplant sera. All transplant recipients had a negative lymphocytotoxic antiglobulin T cell XM and a negative (< or = 10 channel shift) T cell FCXM. B cell FCXMs were performed using a two-color technique to identify binding of IgG antibody to donor lymph node B lymphocytes stained for CD20. The incidence and causes of graft failure posttransplant were determined by requesting this information from recipient transplant centers. Transplants that failed due to nonimmunological causes (n = 54, 13%) were excluded from the analysis. Minimum follow-up was 12 months. We found no difference in graft survival at one year for transplants where the B cell FCXM was positive in the range of 11 to 50 channel shift (n = 201) compared with those with a negative (< or = 10 channel shift) B cell FCXM (n = 141)--i.e., 90% vs. 91%, P = NS. However, when the positivity in the B cell FCXM was > 50 channel shift (n = 35), significantly fewer grafts survived at one year, compared with those where the channel shift was < or = 50 (n = 342), 63% vs. 91%, P < 0.001. This was true for first transplants as well as regrafts and for transplants performed with a positive as well as a negative standard B cell XM. The detrimental effect of a positive B cell FCXM was seen for sensitized (PRA > 10% at the time of transplant) as well as nonsensitized patients. However, this effect was observed only when the donor had at least a one-DR mismatch. We conclude that a strongly positive B cell flow cytometry crossmatch identifies patients who are at risk for graft loss. Since the risk appears to be only when there is a DR mismatch, the data suggest that the B cell-specific IgG antibody detected by flow cytometry may be specific for the mismatched MHC class II antigens of the donor.

The impact of HLA frequency differences in races on the access to optimally HLA-matched cadaver renal transplants. The Medical Advisory Committee

We examined the donor/recipient HLA match of 448 consecutive cadaver renal transplants to determine if donor race had an impact on the quality of HLA match that was achieved. Eighty (17.9%) kidneys from black donors and 368 (82.1%) from nonblack donors (87.8% caucasians) were distributed to the blood type compatible and crossmatch negative recipients on the basis of a local variance of the United Network for Organ Sharing (UNOS) point system. There were 278 (62%) nonblack and 170 (38%) black recipients, numbers close to those of nonblacks and blacks on the waiting list (59% and 41%, respectively). Kidneys from nonblack donors represented 86% (240/278) of transplants for nonblack and 75% (128/170) of transplants for black recipients. The best matches, i.e., zero-A,B,DR, zero-A,B, zero-B,DR, and 1-A,B,DR mismatches, for nonblack recipients were solely derived from the nonblack donors, and the few well-matched kidneys from black donors were distributed to black recipients. Black recipients with zero mismatches were few (3, 2%) compared with nonblacks (21, 8%). Kidneys received by black recipients were more likely to be poorly matched (5-6 mismatches) if coming from nonblack donors (57/128, 44%) than black donors (11/42, 26%), P = 0.035. It was also observed from HLA frequency comparisons that well-matched kidneys from nonblack donors were rarely distributed to black patients with HLA phenotypes unique to or more common in blacks who represented a sizeable portion of blacks on the waiting list. We conclude that better donor/recipient HLA matches are achieved when both donors and recipients are of the same race. Thus a larger number of black donors are needed to improve the quality of HLA matching for potential black kidney transplant recipients.

Evidence that HLA class II disparity is required for the induction of renal allograft enhancement by donor-specific blood transfusions in man

We studied 46 living-related primary renal allograft recipients between June 1980 and Jan 1988 to determine if enhancement of allograft survival by donor specific transfusions requires a major histocompatibility complex mismatch between the blood/kidney donor and the recipient. Recipients were matched for a single HLA haplotype, but differed at various HLA loci on the unshared haplotype. DST (200 ml) was administered either 3 times at two-week intervals pretransplant (n = 17), or once 3-4 weeks pretransplant, together with oral azathioprine (1 mg/kg/day/28 days) (n = 29). Patients were followed for at least 1 year and all clinical rejection episodes were confirmed histologically. Enhanced graft survival by DST was defined as a rejection-free posttransplant course. Incompatibility for class II determinants on the unshared haplotype of donor had a beneficial effect. A significantly greater proportion of recipients had stable, rejection-free, allograft function if incompatible for the DR locus (80% vs. 44%, P = 0.012), for class II public determinants (100% vs. 58%, P = 0.013), or for at least one of the class II gene products (DR, DQ, class II public) (81% vs. 40%, P = 0.006). Graft loss occurred in 7 of 46 (15%); 6 of the 7 recipients were HLA class II-compatible with their blood/kidney donor. Mismatches for HLA class I private or public determinants and other factors known to affect graft outcome did not influence the results. We conclude that enhanced kidney allograft survival by DST may be predicated by factors within the MHC--specifically class II disparity. These observations also suggest that better HLA matching at the class II locus may account for the apparent "disappearance" of the transfusion effect in cadaver renal transplants in the cyclosporine era.

The relationship between flow cytometer crossmatch results and subsequent rejection episodes in cadaver renal allograft recipients

Flow cytometry (FC) T and B cell crossmatches were done retrospectively for 38 cadaver renal transplant recipients (29 first and 9 retransplants--minimum follow-up 12 months) using both current pretransplant serum and peak-reactive sera. An increase in median fluorescence intensity (channel shift) and/or an increase in the number of donor T and/or B cells binding antibody in test sera occurred in 23 cases. These 23 patients experienced a greater number of reversible rejection episodes as compared with patients with negative FC crossmatches (65% vs. 33%), P = 0.031. Graft outcome, however, was not different in the two groups. Thus, a positive FC crossmatch allows for the detection of subliminal levels of donor presensitization and is associated with a greater number of rejection episodes. A positive FC crossmatch is not predictive of ultimate graft loss.

The splenic microenvironment and self recognition as factors in allograft rejection in rats. A study using indium-111-labeled cells

Splenectomy facilitates organ allograft survival in some rat strains, and in weak donor-recipient histoincompatible pairs. We have found using a heart spleen "twin" graft model, using ACI rats as recipients and Lewis rats as donors, that the transplanted heart will survive in most recipients after delayed host splenectomy. The presence of a viable mass of splenic tissue will allow rejection to proceed only when the transplanted spleen is of host origin, and not when it comes from the donor (i.e., when it is allogeneic). The use of 111In-labeled cells has allowed us to show that lymphocyte traffic and trapping is markedly altered in the transplanted allogeneic spleens, when compared with control transplanted syngeneic spleens. Thus, despite the presence of the splenic "microenvironment," cardiac allograft rejection does not occur in the absence of syngeneic splenic tissue. We conclude that the role of the spleen in the immune response is to facilitate the recognition of self and the acquisition of alloreactivity in weak responder rat strains and donor-recipient pairs.

Heart and spleen "twin grafts" in rats: IV. Influence of donor spleen cell mass on allograft survival

Heart and spleen twin grafts from LEW to ACI rats may survive permanently, whereas those grafted from ACI to LEW rats do not. This strain difference in graft acceptance was analyzed quantitatively by transplanting one to three ACI spleens into LEW rats in order to compensate for the relatively small size of ACI spleens (Fig. 1). Under these conditions permanent graft survival was not observed in LEW recipients. However, during host splenectomy 3 days after transplantation, a nonimmunological factor was observed. The transplanted ACI spleens showed congestion and infarctions, while in the LEW to ACI transplant model the LEW spleens did not. This observation could be explained by the size of the vascular pedicle in ACI spleens. Although no problem was encountered immediately after completing the anastomoses, allogeneic spleens react by increasing in size, to such an extent that their size exceeds the capacity of the smaller vascular pedicle in ACI rats and results in congestion. Hence, the concept is formulated that early compromise of hemodynamics on a nonimmunological base may determine the fate of ACI spleen graft before immunological factors have a chance to become effective.

In vitro stimulation of natural killer (NK) cells by soluble factor(s) generated in antigen-stimulated rhesus monkey peripheral blood lymphocyte cultures

Peripheral blood lymphocytes from rhesus monkeys (Macaca mulatta) sensitized to keyhole limpet hemocyanin (KLH), when stimulated in vitro with KLH, developed natural killer (NK) cell activity that was assayed with Rous Sarcoma virus-transformed marmoset fibroblasts as targets in a 4-hr 51Cr-release assay. The supernatant fluids from 24- to 25-hr KLH-activated cultures were capable of stimulating NK development in nonsensitive lymphocyte cultures. The effector cells were neither macrophages nor B cells (plastic and nylon-wool nonadherent) and did not form E-rosettes with neuraminidase-treated sheep red blood cells. Cultures depleted of EA-rosetting cells, i.e., Fc-receptor-bearing lymphocytes, were incapable of generating NK activity when stimulated in vitro. Kinetic studies showed that peak DNA synthesis, as measured by 3H-T incorporation, preceded maximum cytotoxicity. Elimination of dividing cells by 5-bromo-2'deoxyuridine (BrdU) and light treatment during the interval from day 1 to day 4 inhibited the development of cytotoxicity on day 7. Cell replication was required for the induction of NK cells with KLH as well as with antigen-activated culture supernatant fluids. When cultures were left unstimulated for 4 days, NK activity could not be developed subsequently either by adding antigen, mitogen (PHA), or supernatant fluids from activated cultures.