Single Nucleotide Polymorphisms (SNPs) of the Caspase Recruitment Domain (CARD) 15 gene, also known as the Nucleotide-binding Oligomerisation Domain (NOD) 2 gene, have recently been implicated in the onset and pathogenicity of malignant diseases as well as in several inflammatory disorders, particularly Crohn’s Disease and Blau syndrome. More specifically, NOD2/CARD15 polymorphisms have been implicated with a significant increase in Transplant Related Mortality (TRM) and on the incidence of clinically significant acute Graft versus Host Disease (aGvHD) post-Haematopoietic Stem Cell Transplant (HSCT). In order to establish the impact of these SNPs on Unrelated Donor (UD) HSCT, NOD2/CARD15 genotyping was performed on 196 patients diagnosed with Acute Leukaemia and their volunteer UD. Transplants occurred between 1996 and 2003 at one of 25 transplant centres in the UK. Diagnoses were Acute Lymphoblastic Leukaemia (98/196, 50%) and Acute Myeloid Leukaemia (98/196, 50%). Recipients and donors were a 10/10 HLA allele match, that is HLA-A, -B, -C, -DRB1, and -DQB1, in 64% of pairs. Of these, 16% were a 12/12 HLA match (i.e. they were also matched at an allele level for HLA-DPB1). Myeloablative conditioning regimens were used in 78% of transplants. T-cell depletion was included in 83% of conditioning protocols, the majority of which was achieved using in-vivo alemtuzumab. Peripheral blood stem cells were used as a graft in 19% of transplants, with the remaining 81% using bone marrow. Two forms of post-transplant immunosuppression predominated, Cyclosporine A in combination with Methotrexate in 47% of transplants and Cyclosporine A alone in 31% of transplants. Polymorphisms of the NOD2/CARD15 gene within an UD-HSCT pair resulted in a significant increase in disease relapse and mortality. The estimated two-year incidence of disease relapse was 70% in pairs with NOD2/CARD15 SNPs as compared to 43% in pairs with wild type genotype (Log rank, P=0.0003). This resulted in a significant increase in mortality. The estimated three-year overall survival for the cohort was 22% and 44% for pairs with and without NOD2/CARD15 polymorphism respectively (Log rank, P=0.0087). These findings persisted in multivariate analysis. NOD2/CARD15 genotype was found to be the most significant factor for an adverse outcome other than being transplanted in a disease stage of relapse. We conclude that in contrast to previous findings, the presence of a NOD2/CARD15 SNP in the genotype of an Acute Leukaemia UD-HSCT pair results in a significant increase in disease relapse and subsequently a decrease in overall survival. These novel data show an important role for NOD2/CARD15 genotyping in transplantation and suggest a possible effect of the NOD2 protein in alloreactivity and tumour surveillance. Genotyping recipients and donors prior to transplant may allow for prediction of transplant outcome, and thus present critical information for donor selection.

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