Donor CTLA-4 Gene Polymorphism Associations with Acute GvHD After Allogeneic Hematopoietic Stem Cell Transplantation

Abstract 2010

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been widely carried out as a therapy for several hematological malignances and non malignant disorders.

Graft–versus -host disease is one of the major complications after allo-HSCT with main cause of morbidity and mortality. Donor T lymphocytes play the crucial role in alloimmune recognition and their ability to detect non –self antigens can lead to aGvHD.

The effective recognition and activation of naïve T-cells requires two independent signals. The first, an antigen-specific signal, is sent via the T-cell receptor (TCR) on T-cells. The second signal, termed co-stimulation, is critical for allowing full activation, sustaining cell proliferation, preventing anergy and/or apoptosis, inducing differentiation to effector cells. CD28 is the primary T-cell co-stimulatory molecule. Cytotoxic T-cell antigen (CTLA-4) is a homologous molecule of CD28 which plays an inhibitory role in the early and late stages of T-cell activation. CTLA-4 ligation provides a negative signal for regulation of the cell cycle and inhibits the activity of the transcriptional factors: nuclear factor-kB (NF-kB), nuclear factor of activated T-cells (NF-AT), and activator protein 1 (AP-1). Moreover, CTLA-4 binds to CD28 ligands (CD80 and CD86) with higher affinity and avidity and in that way also inhibits T-cell activation. Since co-stimulatory and down regulatory molecules synthesis depend on the rate of gene transcription and/or translation, polymorphisms in the corresponding genes might result in abnormal expression, function as well as dysregulated trafficking of these molecules within cellular compartments. The human CTLA-4 gene is located on 2q33 which is susceptibility region for autoimmune diseases.

The aim of this study is to investigate the associations between polymorphisms in CTLA-4 gene: CTLA-4c.49A>G (rs231775), CTLA-4g.319C>T (rs5742909), CTLA-4g6230G>A (CT60, rs3087243), CTLA-4g.10223G>T (Jo31, rs11571302) in donors of HSTC and occurrence of aGvH disease in recipients after allogeneic hematopoietic stem cell transplantation. Altogether 136 donors of HSCT (58- related donors, 88 haploidentical unrelated donors) were genotyped for all polymorphisms using allelic discrimination methods with the TaqMan^Ò SNP Genotyping Assay.

In patients without aGvHD and in patients with aGvHD grade I-IV the similar distribution of alleles and genotypes for all investigated polymorphisms in donors was observed. However, we have noticed trend toward increased frequency of CT60 [G] donor allele among recipients with aGvHD I-IV (0.48 vs. 0.39, p=0.1, OR 1.49, 95% CI: 0.90–2.49) compared to recipients without aGvHD in whole group of patients. In patients transplanted from related donor also increased risk of aGvHD grade I-IV was observed for CT60 [G] donor allele (0.75 vs. 0.55, p=0.09, OR 2.11, 95%CI: 0.88–5.26). In contrary the frequencies of CT60 [G] donor allele in patients transplanted from unrelated donors are similar in recipients with and without aGvH symptoms. Haplotype estimation analysis indicated that donor haplotype CTLA-4c.49A>G[A], CTLA-4g.319C>T[C], CT60 [A], Jo31 [T] tended to be protective against aGvHD grade I-IV in whole studied group of patients (0.28 vs. 0.40, p=0.06, OR 0.60, 95% CI: 0.36–1.02) This association reach statistical significance in recipients of related transplantation (0.18 vs. 0.43, p=0.01, OR 0.29, 95% CI: 0.14–0.97)

Our study indicated that donor CT60 polymorphism might be associated with occurrence of aGvHD, especially in recipients transplanted from HLA-identical sibling donors.