Apheresis of Deceased Donors as a New Source of Mobilized Peripheral Blood Hematopoietic Stem Cells for Transplant Tolerance

BACKGROUND

Solid organ transplantation is the therapy of choice for many patients with end-stage organ failure; however, recipients must remain on lifelong immunosuppression, leaving them susceptible to infections and cancer. The study of transplant tolerance to prolong graft survival in the absence of immunosuppression has been restricted to recipients of living donor allografts; however, deceased donors significantly outnumber living donors. Mobilization of hematopoietic stem cells (HSCs) from the bone marrow to peripheral blood (PB) could allow PB-HSCs to be used to induce tolerance in deceased donor kidney recipients; however, a major concern is the well-known concomitant mobilization of immune cells into the liver.

METHODS

We mobilized HSCs to the PD using a protocol of 2 doses of granulocyte colony-stimulating factor and 1 dose of plerixafor, followed by the collection of mobilized cells via apheresis in 3 deceased donors. The physiological, laboratory, and radiographic parameters were monitored throughout the procedure. Longitudinal biopsies were performed to assess the potential for ectopic liver mobilization.

RESULTS

The use of both agents led to the successful mobilization of peripheral blood CD34+ cells, demonstrating the potential for use in transplant tolerance protocols. Increased immune cell trafficking into the liver was not observed, and apheresis of mobilized cells resulted in a uniform decrease in all liver leukocyte subsets.

CONCLUSIONS

HSCs can be mobilized and collected from the PB of brain-dead donors. This new approach may facilitate the dissemination of immune tolerance trials beyond living-donor kidney transplantation to deceased-donor transplantation, without sacrificing the transplantability of the liver.

Solid organ transplantation from hepatitis B virus-positive donors: consensus guidelines for recipient management

Use of organs from donors testing positive for hepatitis B virus (HBV) may safely expand the donor pool. The American Society of Transplantation convened a multidisciplinary expert panel that reviewed the existing literature and developed consensus recommendations for recipient management following the use of organs from HBV positive donors. Transmission risk is highest with liver donors and significantly lower with non-liver (kidney and thoracic) donors. Antiviral prophylaxis significantly reduces the rate of transmission to liver recipients from isolated HBV core antibody positive (anti-HBc+) donors. Organs from anti-HBc+ donors should be considered for all adult transplant candidates after an individualized assessment of the risks and benefits and appropriate patient consent. Indefinite antiviral prophylaxis is recommended in liver recipients with no immunity or vaccine immunity but not in liver recipients with natural immunity. Antiviral prophylaxis may be considered for up to 1 year in susceptible non-liver recipients but is not recommended in immune non-liver recipients. Although no longer the treatment of choice in patients with chronic HBV, lamivudine remains the most cost-effective choice for prophylaxis in this setting. Hepatitis B immunoglobulin is not recommended.

Investigating geographic variation in mortality in the context of organ donation

Organ procurement organizations (OPOs) report a nearly fourfold difference in donor availability as measured by eligible deaths per million population (PMP) based on hospital referrals. We analyzed whether mortality data help explain geographic variation in organ supply as measured by the number of eligible deaths for organ donation. Using the 2007 National Center for Health Statistics' mortality data, we analyzed deaths occurring in acute care hospitals, aged ≤ 70 years from cerebrovascular accidents and trauma. These deaths were mapped at the county level and compared to eligible deaths reported by OPOs. In 2007, there were 2 428 343 deaths reported in the United States with 42 339 in-hospital deaths ≤ 70 years from cerebrovascular accidents (CVA) or trauma that were correlated with eligible deaths PMP (r(2) = 0.79.) Analysis revealed a broad range in the death rate across OPOs: trauma deaths: 44-118 PMP; deaths from CVA: 34-118 PMP; and combined CVA and trauma: 91-229 PMP. Mortality data demonstrate that deaths by neurologic criteria of people who are likely to be suitable deceased donors are not evenly distributed across the nation. These deaths are correlated with eligible deaths for organ donation. Regional availability of organs is affected by deaths which should be accounted for in the organ allocation system.

Can machine perfusion decrease the likelihood of discard among biopsied kidneys?

Many factors, such as donor risk factors and renal function, have been shown to be associated with an increased likelihood of discard after recovering kidneys from deceased donors. When these factors are insufficient for assessment, renal biopsy is often performed at the time of harvest to assess suitability. Our aims were to identify factors that predict the discard of a biopsied kidney and to assess the impact of machine perfusion (MP) on kidney discard. We biopsied 678 kidneys from deceased donors aged >or=40 years from 2001 to 2006. We used a logistic regression model to estimate the adjusted odds ratios for kidney discard. Thirty-nine percent (n = 261) of biopsied kidneys were discarded. Kidneys with glomerulosclerosis (GS) > 20% had the highest likelihood of discard. Other significant predictors of discard included extreme donor age, final resistance (>40), atherosclerosis, interstitial fibrosis, arteriolosclerosis, and terminal serum creatinine value (SCr) > 1.5 mg/dL. MP kidneys (n = 69) were less likely to be discarded than cold storage (CS) kidneys after adjusting for other factors (adjusted odds ratio = .13, P < .001). In conclusion, abnormal biopsy findings were associated with the highest likelihood of discard. MP was used in only 10% of the cases; however, the use of MP was associated with a decreased likelihood of discard among biopsied kidneys.

Organ donation and utilization in the United States, 1997-2006

Deceased organ donation has increased rapidly since 2002, coinciding with implementation of the Organ Donation Breakthrough Collaborative. The increase in donors has resulted in a corresponding increase in the numbers of kidney, liver, lung and intestinal transplants. While transplants for most organs have increased, discard and nonrecovery rates have not improved or have increased, resulting in a decrease in organs recovered per donor (ORPD) and organs transplanted per donor (OTPD). Thus, the expansion of the consent and recovery of incremental donors has frequently outpaced utilization. Meaningful increases in multicultural donation have been achieved, but donations continue to be lower than actual rates of transplantation and waiting list registrations for these groups. To counteract the decline in living donation, mechanisms such as paired donation and enhanced incentives to organ donation are being developed. Current efforts of the collaborative have focused on differentiating ORPD and OTPD targets by donor type (standard and expanded criteria donors and donors after cardiac death), utilization of the OPTN regional structure and enlisting centers to increase transplants to match increasing organ availability.

High seroprevalence of anti-HTLV-I/II antibodies among solid organ donors necessitates confirmatory testing

BACKGROUND

Human T-cell lymphotrophic virus (HTLV) type I has been linked to adult T-cell leukemia/lymphoma (ATL) and HTLV-I associated myelopathy (HAM). Transmission of HTLV by blood and organ transplantation has been documented, with some infections leading to clinical disease. Organ donors are tested for anti-HTLV antibodies and donor suitability is determined primarily by results from enzyme immunoassays (EIA). Confirmatory testing is not routinely performed, and the number of false positive organ donors is unknown.

METHODS

In order to investigate the contemporary seroprevalence of anti-HTLV I/II antibodies among solid organ donors and determine the number of false positive samples, we tested 1,408 specimens from prospective organ donors in 2002 and 2003. All specimens were tested for anti-HTLV antibodies by a commercial EIA. Repeatedly reactive specimens underwent confirmatory testing using a commercial Western blot.

RESULTS

There were 22 repeatedly EIA reactive donor specimens (1.56%). Five specimens did not undergo further testing because of case shutdown or insufficient sample quantity. HTLV I/II western blot confirmed six positives, whereas five were negative and six were indeterminate. The majority of confirmed specimens were positive for antibodies to HTLV-II.

CONCLUSIONS

Our data shows that 29% of initially reactive specimens were false positives. With the increasing demand for organs, the unnecessary rejection of organs that are falsely positive for HTLV antibodies becomes of tremendous importance and stresses the need for timely confirmatory testing for HTLV.

Prevalence of Antibodies to Trypanosoma cruzi among Solid Organ Donors in Southern California: A Population at Risk

Trypanosoma cruzi, a parasite that causes Chagas' disease, is endemic in parts of Mexico, South America, and Central America. Transmission of T. cruzi infection by solid organ transplantation has been reported in Latin America and recently in the United States. To determine the prevalence of T. cruzi antibodies in Southern California organ donors, 404 samples from deceased organ donors between May 2002 to April 2004 were screened using a qualitative enzyme-linked immunosorbent assay (EIA) and confirmed with an immunofluorescence assay (IFA) available through the Centers for Disease Control (CDC). Six donors were initially reactive by EIA. Three donors were repeatedly reactive after repeat testing and were sent to the CDC for confirmation. One donor (0.25%) had an IFA-confirmed reactivity to anti-T. cruzi antibodies. In areas where there is a high number of immigrants from T. cruzi endemic countries, screening for anti-T. cruzi donor antibodies may be beneficial.

Role of nucleic acid testing in cadaver organ donor screening: detection of hepatitis C virus RNA in seropositive and seronegative donors

Hepatitis C virus (HCV) transmission by both seropositive and seronegative cadaver organ donors has been documented, yet nucleic acid testing is not routinely used to identify active infection in these donors prior to transplantation. Between November 2001 and February 2004, we screened 1445 cadaver organ donors for anti-HCV antibodies with either HCV EIA-2.0 (Abbott Diagnostics, Chicago, IL, USA) and/or Ortho HCV Version 3.0 ELISA (Ortho-Clinical Diagnostics, Raritan, NJ, USA) and confirmed seropositive samples with Chiron RIBA3.0 SIA (Chiron Corporation, Emeryville, CA, USA). Samples with sufficient volume (n = 726) were tested by the VERSANT HCV [transcription-mediated amplification (TMA)] Qualitative assay (Bayer Healthcare LLC, Tarrytown, NY, USA) which can be performed in approximately 5 h. Those with detectable HCV RNA and sufficient volume were quantified by the VERSANT HCV 3.0 (bDNA) Assay (Bayer Healthcare LLC) and/or the HCV RNA TMA Quantitative Assay (n = 23) and genotyped (n = 57). Seventy-seven of 1445 (5.3%) donors were seropositive, reactive by either one or both anti-HCV assays. Fifty-two of 63 (82.5%) of the seropositive samples had detectable HCV RNA and were genotyped. Seventeen of these samples had quantifications ranging from 128,123 to >7,692,307 IU/mL. Six of 663 (0.9%) seronegative samples had detectable HCV RNA. Their quantifications ranged from <9.3 to 1,464,799 IU/mL, and five of these six were successfully genotyped. As HCV RNA was demonstrated in samples from both our seropositive and seronegative cadaver organ donors, we are now incorporating nucleic acid testing into our donor screening/diagnostic algorithm.