Neither Donor nor Recipient Mitochondrial Haplotypes Are Associated with Unrelated Donor Transplant Outcomes: A Validation Study from the CIBMTR.

Graft-versus-host-disease (GVHD) is a multistep process that involves T-cell recognition and priming toward alloantigen, expansion, acquisition of effector function, and repeated tissue injury, resulting in clinical manifestations of the disease. All of these processes have considerable metabolic demands and understanding the key role of mitochondria in cellular metabolism as it relates to GVHD has increased significantly. Mitochondrial DNA (mtDNA) haplotypes have been linked to functional differences in vitro, suggesting they have functional differences at an organismal level. We previously used mtDNA typing to assess the impact of mtDNA haplotypes on outcomes of ~400 allo-HCT patients. This pilot study identified uncommon mtDNA haplotypes potentially associated with inferior outcomes. We sought to validate pilot findings of associations between donor and recipient mitochondrial haplotypes and transplant outcome. We examined a cohort of 4143 donor-recipient pairs obtained from the Center for International Blood and Marrow Transplant Research. MtDNA was extracted from whole blood or peripheral blood mononuclear cells from donors and recipients and sequenced to discern haplotype. We used multiple regression analysis to examine the independent association of mtDNA haplotype with overall survival and grade III-IV acute GVHD (aGVHD) adjusting for known risk factors for poor transplant outcome. Neither recipient nor donor mtDNA haplotype reached groupwise significance for overall survival (P =.26 and .39, respectively) or grade III-IV aGVHD (P = .68 and.57, respectively). Adjustment for genomically determined ancestry in the subset of donor-recipient pairs for which this was available did not materially change results. We conclude that our original finding was due to chance in a small sample size and that there is essentially no evidence that mtDNA haplotype or haplotype mismatch contributes to risk of serious outcomes after allogeneic transplantation.

Early Adaptive Natural Killer Cell Expansion Is Associated with Decreased Relapse After Autologous Transplantation for Multiple Myeloma.

Adaptive natural killer (NK) cells are long-lived and exhibit properties of immunologic memory against cytomegalovirus (CMV). We previously reported that expansion of adaptive NK cells after CMV reactivation in recipients of allogeneic hematopoietic cell transplantation (HCT) was associated with a lower rate of relapse of acute myelogenous leukemia. In the present study, we examined the impact of adaptive NK cell expansion in a cohort of 110 individuals who underwent autologous HCT (AHCT) for a lymphoid malignancy (lymphoma or multiple myeloma [MM]). In this cohort, higher absolute numbers of adaptive NK cells (>1.58/µL) at day 28 post-AHCT were associated with significantly decreased risk of relapse in patients with MM. No significant association was seen in patients with lymphoma. Further stratification of MM patients by CMV serostatus found a strong protective effect of adaptive NK cells only in CMV-seropositive individuals. These findings suggest that strategies to increase adaptive NK cells after AHCT may be a therapeutic option in patients with MM.

Cytomegalovirus infection after allogeneic transplantation: comparison of cord blood with peripheral blood and marrow graft sources.

Cytomegalovirus (CMV) infection is an important complication following allogeneic hematopoietic stem cell transplant (HSCT), but the natural history in the cord blood setting has not been well studied. We assessed CMV infection episodes in 753 consecutive allogeneic HSCT recipients at the University of Minnesota between January 1, 1998 and December 31, 2003. The 6-month cumulative incidence of viremia/antigenemia was 22% by day +182: 21% (95% confidence interval 16%-26%) in cord blood recipients (UCB), 24% (20%-28%) in marrow (BM), and 22% (16%-28%) using peripheral blood grafts (PBSC). CMV disease incidence was 6% (2%-10%) in UCB, 8% (5%-11%) in BM, and 9% (6%-12%) in PBSC. In multivariate analysis, CMV infection (viremia/antigenemia and disease) was significantly more likely in patients who were seropositive to CMV, in those with acute graft versus host disease, and in those receiving T cell-depleted grafts. Graft source did not independently contribute to the risk of CMV infection and did not impact survival after CMV infection. These data confirm that recipient CMV serostatus remains the dominant risk factor for CMV infection. Recipients of UCB have similar risks of CMV infection, responses to antiviral therapy, and survival following CMV infection as recipients of either marrow or PBSC.