Bone marrow or stem cell transplantation
Little is known about the role of intra-graft γδ T-cell receptor (TCR) repertoire on clinical outcome following hematopoietic stem cell transplantation (HSCT). Using next-generation sequencing (NGS), we sought to analyze the TCR δ-chain (TRG) repertoire within donor stem cell grafts and address its potential impact on clinical response. We analyzed twenty peripheral blood stem cell grafts from matched unrelated donors, classified as CMV-positive/negative. γδ T-cells were isolated and the gDNA extracted for NGS (ImmunoSEQ, Adaptive Biotechnologies). The respective acute myeloid leukemia recipients were followed for disease relapse and acute graft-versus-host disease (aGvHD) development. Grafts received by non-relapse patients had increased proportion of long CDR3 sequences (54-57 nucleotides) and higher usage of V2-JP1 pairing than relapse patients. Grafts from CMV-positive donors presented lower TCR usage of the pairs V2-J2, V2-JP2, V4-JP2, V9-JP, V9-JP2; significantly reduced diversity; and skewed non-Gaussian distribution of CDR3 sequences, with hyperexpanded clones taking up 2.5 times more space than CMV-negative grafts. We identified twelve unique public clones in addition to four private over-represented sequences exclusively present in grafts given to non-relapse patients, taking from 2.00% to 6.23% of the TRG repertoire and longer than 45 nucleotides. We also identified five private over-represented and one public CDR3 sequence associated to CMV infection. CMV-positive grafts presented the highest percentage or repertoire taken by private over-represented clones, ranging from 13.72% to 41.61%. Our findings show that the TRG composition is not associated to aGvHD incidence, CMV infection reshapes the TRG repertoire and several public sequences are associated to clinical remission.