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BK virus (BKV), a human polyomavirus that remains latent in renal epithelial cells, can be reactivated after hematopoietic stem cell transplantation (HSCT) leading to hemorrhagic cystitis. The incidence of BK viremia is higher after Umbilical cord blood transplantation (UCBT) than HSCT from adult donors. Data regarding the role of immune recovery after UCBT in BKV reactivation is lacking. We examined the correlation between the development of BK viremia and immune reconstitution in 27 adult recipients of UCBT. The incidence of BK viremia was 52% and developed most frequently within the first 8 weeks after the transplantation, but persisted in seven patients at 6 months, and three patients at 1-year post UCBT. Detection of BK viremia 1 year after transplant was negatively associated with the number of CD8+ cells (p = 0.03) and CD8+CD45RO+ cells (p = 0.05) at 6 months, and the number of CD4+ (p = 0.03) and CD4+CD45RO+ cells (p = 0.03) at 12 months after UCBT. Conversely, BK viremia at 6 and 12 months was positively correlated with the number of T regulatory (Treg) cells at 1 month (p = 0.005 and p = 0.016, respectively). Because UCB Treg have highly potent immunosuppressive function, our findings indicate that sustained BK viremia in UCBT recipients might be associated with the increase of Treg cells early after transplantation, which mediate impaired and delayed reconstitution of CD4+ and CD8+ T effector cells.

Utilization of the adaptive immune system against malignancies, both by immune-based therapies to activate T cells in vivo to attack cancer and by T-cell therapies to transfer effector cytolytic T lymphocytes (CTL) to the cancer patient, represent major novel therapeutic advancements in oncologic therapy. Allogeneic hematopoietic stem cell (HSC) transplantation (HSCT) is a form of cell-based therapy, which replaces the HSC in the patient's bone marrow but also serves as a T-cell therapy due to the Graft-vs.-leukemia (GVL) effect mediated by donor T cells transferred with the graft. Allogeneic HSCT provides one potentially curative option to patients with relapsed or refractory leukemia but Graft-vs.-Host-Disease (GVHD) is the main cause of non-relapse mortality and limits the therapeutic benefit of allogeneic HSCT. Metabolism is a common cellular feature and has a key role in the differentiation and function of T cells during the immune response. Naïve T cells and memory T cells that mediate GVHD and GVL, respectively, utilize distinct metabolic programs to obtain their immunological and functional specification. Thus, metabolic targets that mediate immunosuppression might differentially affect the functional program of GVHD-mediating or GVL-mediating T cells. Components of the innate immune system that are indispensable for the activation of alloreactive T cells are also subjected to metabolism-dependent regulation. Metabolic alterations have also been implicated in the resistance to chemotherapy and survival of malignant cells such as leukemia and lymphoma, which are targeted by GVL-mediating T cells. Development of novel approaches to inhibit the activation of GVHD-specific naïve T cell but maintain the function of GVL-specific memory T cells will have a major impact on the therapeutic benefit of HSCT. Here, we will highlight the importance of metabolism on the function of GVHD-inducing and GVL-inducing alloreactive T cells as well as on antigen presenting cells (APC), which are required for presentation of host antigens. We will also analyze the metabolic alterations involved in the leukemogenesis which could differentiate leukemia initiating cells from normal HSC, providing potential therapeutic opportunities. Finally, we will discuss the immuno-metabolic effects of key drugs that might be repurposed for metabolic management of GVHD without compromising GVL.

Umbilical cord blood transplantation (UCBT) is an alternative for patients who need hematopoietic stem cell transplant (HSCT), but lack HLA-matched adult donors. Rabbit anti-thymoglobulin (ATG) has been used in UCBT conditioning to achieve T cell depletion, but ATG-induced immunosuppression is associated with delayed immune reconstitution, increased infectious complications and higher non-relapse mortality. In a clinical trial of reduced intensity double-unit UCBT (dUCBT), we substituted low dose total body irradiation (TBI) for ATG to determine whether dUCBT without ATG would alter kinetics and quality of immune reconstitution. Thirty-one patients with hematopoietic malignancies and a median age of 58 yr were treated with Flu/Mel/TBI, followed by dUCBT and GVHD prophylaxis with tacrolimus and sirolimus. We examined reconstitution of immune cell populations, thymic regeneration by quantifying T cell receptor excision circles (TREC) and serum cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IFN-γ, TNF-α, IL-12p70, GM-CSF) using the LUNARISTM Human 11-Plex Cytokine Biochip384 from AYOXXA Biosystems. Assessments were done prior to and at 1, 2, 3, 6, 12 and 24 months after dUCBT. Results are based on 28 evaluable patients. The 2-yr overall survival and progression-free survival were 53% and 48%. Median time to neutrophil and platelet engraftment was 25 and 52 days, respectively. Before UCBT, the median values for most leukocyte subsets were below normal limits, except for monocytes. CD3+ cells remained depressed until 2 months post-transplant when gradually began to re-emerge. However, CD4+ and CD8+ subsets had distinct reconstitution kinetics (Figure 1). CD4+ T cells declined at 1 month but gradually increased and exceeded pre-transplant levels by 9 months after UCBT. In contrast, at 9 months, CD8+ lymphocytes remained depressed to 50% of pre-transplant levels, but increased thereafter and reached normal values by 2-yr. NK cells and monocytes reached normal values at 3 months post-UCBT. B cells were mostly undetectable for the first 6 months, followed by a 10-fold increase at 9 months and exceeded the upper normal limit by 2-yr. TREC, which were within normal range before transplant, decreased after UCBT but remained detectable between 1-6 months and recovered to normal levels by 9 months. Among cytokines, only IL-8, IL-6 and TNF-α displayed significant changes. IL-8 and IL-6 peaked at day 100 and 9 months, and subsequently declined. In contrast, TNF-α increased by day 100 and remained elevated thereafter. To evaluate functional immunity, we assessed correlations between viral reactivation and reconstitution of immune cell populations and thymic function. Nineteen patients experienced 24 clinically significant viral reactivations or infections, with 1-year cumulative incidence of 62%, which was comparable to 53% observed in dUCBT cohorts receiving ATG-containing conditioning. Although there was no difference in CMV, EBV, adenovirus and VZV reactivation, there was a significant increase in the incidence of HHV-6 reactivation. HHV-6 viremia was observed in 24 of 28 (86%) patients during the first month after dUCBT. Six of these 24 (25%) patients developed HHV-6-related encephalitis. There was a correlation between development of encephalitis and HHV-6 viral load ≥50.000 copies/ml (p=0.007). Pre-transplant TREC levels ≥1.200 copies/ml negatively correlated with subsequent HHV-6 reactivation (p=0.04), indicating that baseline reserve of thymic function has a significant role in post-transplant immune reconstitution. On days 30, 60 and 100 post-transplant, higher TREC levels correlated with lack of HHV-6 viremia (p Figure 1 Disclosures Defilipp: Incyte: Research Funding. Politikos:Angiocrine Bioscience Inc: Research Funding. Armand:Otsuka: Research Funding; Roche: Research Funding; Affimed: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Infinity: Consultancy; Sigma Tau: Research Funding; ADC Therapeutics: Consultancy; Tensha: Research Funding; Genentech: Research Funding; Pfizer: Consultancy. Ho:Jazz Pharmaceuticals: Consultancy. Koreth:Amgen: Consultancy; Equillium: Consultancy; Cugene: Consultancy. Avigan:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Research Funding; Juno: Membership on an entity's Board of Directors or advisory committees; Partners Tx: Membership on an entity's Board of Directors or advisory committees; Partner Tx: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy; Parexel: Consultancy; Takeda: Consultancy. Rosenblatt:Celgene: Research Funding; Amgen: Other: Advisory Board; Merck: Other: Advisory Board; BMS: Other: Advisory Board ; Parexel: Consultancy; Imaging Endpoint: Consultancy; Partner Tx: Other: Advisory Board; Dava Oncology: Other: Education; BMS: Research Funding. Chen:Abbvie: Consultancy; Incyte: Consultancy; Magenta: Consultancy; Takeda: Consultancy; Kiadis: Consultancy. Soiffer:Gilead, Mana therapeutic, Cugene, Jazz: Consultancy; Juno, kiadis: Membership on an entity's Board of Directors or advisory committees, Other: DSMB; Mana therapeutic: Consultancy; Kiadis: Other: supervisory board; Jazz: Consultancy; Cugene: Consultancy. Cutler:Kadmon: Consultancy; Incyte: Consultancy; Pharmacyclics: Consultancy; Fate Therapeutics: Consultancy. Ritz:Equillium: Research Funding; Merck: Research Funding; Kite Pharma: Research Funding; Aleta Biotherapeutics: Consultancy; Celgene: Consultancy; Avrobio: Consultancy; LifeVault Bio: Consultancy; Draper Labs: Consultancy; Talaris Therapeutics: Consultancy; TScan Therapeutics: Consultancy.