No abstract

CTLA-4 (cytotoxic T-lymphocyte antigen-4) plays a pivotal role in inhibiting T cell activation through competitive interaction with B7 molecules and interruption of costimulatory signals mediated by CD28. Polymorphisms on the CTLA-4 gene have been previously associated with autoimmune diseases, predisposition to leukemic relapse, and with graft-versus-host disease (GVHD) or relapse after allogeneic transplant. As CTLA-4 is expressed on T-lymphocytes, the aim of this study was to determine whether the donor CTLA-4 CT60 genotype also influences clinical outcome even after T cell depletion with CD34-positive selection. We studied 136 patient-donor pairs. Overall survival (OS) was worse for those patients who received grafts from a donor with the CT60 AA genotype rather than from a donor with the AG or GG genotype (35.6% vs 49.4%; P = .043). This association was confirmed through multivariate analysis, which identified the donor CT60 genotype as an independent risk factor for OS (P = .008; hazard ratio [HR]: 2.24, 95% confidence interval [CI]: 1.23-4.08). The donor CT60 AA genotype was also associated with lower disease-free survival, this being related to an increased risk of relapse (P = .001; HR: 3.41, 95% CI: 1.67-6.96) and a trend toward higher transplant-related mortality. These associations were stronger when considering only patients in the early stage of disease. Our results suggest that graft-versus-leukemia (GVL) activity after T cell depletion is conditioned by the donor CTLA-4 genotype.

The FOXP3 gene encodes for a protein (Foxp3) involved in the development and functional activity of regulatory T cells (CD4+/CD25+/Foxp3+), which exert regulatory and suppressive roles over the immune system. After allogeneic stem cell transplantation, regulatory T cells are known to mitigate graft versus host disease while probably maintaining a graft versus leukemia effect. Short alleles (≤(GT)15) for the (GT)n polymorphism in the promoter/enhancer of FOXP3 are associated with a higher expression of FOXP3, and hypothetically with an increase of regulatory T cell activity. This polymorphism has been related to the development of auto- or alloimmune conditions including type 1 diabetes or graft rejection in renal transplant recipients. However, its impact in the allo-transplant setting has not been analyzed. In the present study, which includes 252 myeloablative HLA-identical allo-transplants, multivariate analysis revealed a lower incidence of grade III-IV acute graft versus host disease (GVHD) in patients transplanted from donors harboring short alleles (OR = 0.26, CI 0.08–0.82, p = 0.021); without affecting chronic GVHD or graft versus leukemia effect, since cumulative incidence of relapse, event free survival and overall survival rates are similar in both groups of patients.

Minor histocompatibility antigen (miHA) mismatches have been related to graft-versus-host disease (GVHD) after allogeneic stem cell transplantation, but this association remains controversial due to the lack of consistency in the results obtained by different groups. The CTLA-4 genotype of the donor has been reported to be relevant in the appearance of acute GVHD. We explored the effect of the donor's CTLA-4 genotype in the incidence of acute GVHD associated with HA-1, HA-8, or H-Y miHA mismatches in a large cohort of 1295 patients receiving an allogeneic transplant from an HLA-identical sibling donor. The incidence of acute GVHD was higher if the donor and recipient were mismatched for HA-1, HA-8, or H-Y, but only when the donor had the CTLA-4 rs231775 AA genotype (hazard ratio [HR], 2.18; 95% confidence interval [CI], 1.27 to 3.75; P = .005; HR, 2.11, 95% CI, 1.06 to 4.18; P = .033; and HR, 1.50; 95% CI, 1.05 to 2.15; P = .025, respectively). In contrast, this increased risk of developing acute GVHD was not found when the donor presented the CTLA-4 rs231775 AG or GG genotypes. We conclude that the immune response to specific miHA mismatches is modulated by the CTLA-4 genotype of the donor.