The human cathepsin H gene encodes two novel minor histocompatibility antigen epitopes restricted by HLA‐A*3101 and ‐A*3303

Abstract

Summary Minor histocompatibility antigens (mHags) play crucial roles in the induction of graft versus host disease (GVHD) and/or graft versus leukaemia (GVL) effects following human leucocyte antigen (HLA)‐identical haematopoietic stem cell transplantation (HSCT). Using HLA‐A*3101‐ and ‐A*3303‐restricted cytotoxic T lymphocyte (CTL) clones generated from different post‐HSCT recipients, we identified two novel mHag epitopes encoded by the leader sequence of cathepsin H (CTSH) isoform a. The nonameric sequence ATLPLLCAR was defined as an HLA‐A*3101‐restricted epitope (CTSHR/A31), while a decameric peptide featuring a one N‐terminal amino acid extension, WATLPLLCAR, was presented by HLA‐A*3303 (CTSHR/A33). The immunogenicity of both epitopes was totally dependent on the polymorphic C‐terminal arginine residue and substitution with glycine completely abolished binding to the corresponding HLA molecules. Thus, the immunogenicity of this mHag is exerted by differential HLA binding capacity. CTSH is relatively ubiquitously expressed at protein levels, thus it may be involved in GVHD and anti‐leukaemic/tumour responses. Interestingly, however, CTL clones predominantly lysed targets of haematopoietic cell origin, which could not be explained in terms of the immunoproteasome system. Although the mechanisms involved in the differential susceptibility remain to be determined, these data suggest that CTSH‐encoded mHags could be targets for GVL effects.

Alternative splicing due to an intronic SNP in HMSD generates a novel minor histocompatibility antigen

“…11 The patient developed grade 1 acute GVHD in the first 2 years after transplantation and then suffered from glomerular IgG deposition and mild bronchiolitis obliterans organizing pneumonia. He is alive and in good condition and has been disease free for more than 3 years.…”

“…Real-time PCR analysis was performed using the TaqMan assay as described previously. 11 Because of uncertainty of which allele(s) were included in each cDNA pool from the MTC panels, quantitative PCR primers and a probe were designed to detect the exon 3-4 boundary, which is shared by both alleles. The following sequences spanning the exon 3-4 boundary were used as primers with TaqMan probe to detect both HMSD and HMSD-v transcripts simultaneously: sense, 5Ј-AGAACTGCCAACGGGCTCTT-3Ј; antisense, 5Ј-TTGGTAGAATTTGCCACAGGAAT-3Ј; probe, 5Ј-(FAM)-CTTAT-GATTTCCTCACAGGTT-(MGB)-3Ј.…”

“…11 The cDNA library was constructed from mRNA of a B-LCL derived from an AML patient (UPN-027) using the SuperScript Plasmid System (Invitrogen). The library contained 1.5 ϫ 10 6 cDNA clones with an average insert size of approximately 2500 bp.…”

“…Immunogenicity of most autosomal mHAs identified to date results from single-nucleotide polymorphisms (SNPs) that cause amino-acid substitutions within epitopes, leading to the differential display/recognition of peptides between HCT donor and recipient via several mechanisms: peptide binding to MHC observed in HA-1/A2-, 4 HA-2-, 5 and CTSH-encoded mHAs 11 ; proteasomal cleavage in HA-3 12 ; peptide transport in HA-8 13 ; and altered recognition of MHC-peptide complex by cognate T cells in HB-1, 8,9 HA-1/B60, 14 ECGF1/B7, 15 and SP110/A3. 7 Other examples of mechanisms of mHA generation include differential protein expression due to a nonsense mutation in PANE1 10 and a frame-shift mutation in P2X5.…”

“…CTL clones were isolated by standard limiting dilution and expanded in CTL medium as previously described. 11,20 Chromium release assay Target cells were labeled with 3.7 MBq of 51 Cr for 2 hours, and 10 3 target cells/well were mixed with CTLs at the effector-target (E/T) ratio indicated in a standard 4-hour cytotoxicity. All assays were performed at least in duplicate.…”