The canine MHC class Ia allele DLA-88*508:01 presents diverse self- and canine distemper virus-origin peptides of varying length that have a conserved binding motif.

Ideally， CD8+ T-cell responses against virally infected or malignant cells are defined at the level of the specific peptide and restricting MHC class I element， a determination not yet made in the dog. To advance the discovery of canine CTL epitopes， we sought to determine whether a putative classical MHC class Ia gene， Dog Leukocyte Antigen (DLA)-88， presents peptides from a viral pathogen， canine distemper virus (CDV). To investigate this possibility， DLA-88*508:01， an allele prevalent in Golden Retrievers， was expressed as a FLAG-tagged construct in canine histiocytic cells to allow affinity purification of peptide-DLA-88 complexes and subsequent elution of bound peptides. Pattern analysis of self peptide sequences， which were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS)， permitted binding preferences to be inferred. DLA-88*508:01 binds peptides that are 9-to-12 amino acids in length， with a modest preference for 9- and 11-mers. Hydrophobic residues are favored at positions 2 and 3， as are K， R or F residues at the C-terminus. Testing motif-matched and -unmatched synthetic peptides via peptide-MHC surface stabilization assay using a DLA-88*508:01-transfected， TAP-deficient RMA-S line supported these conclusions. With CDV infection， 22 viral peptides ranging from 9-to-12 residues in length were identified in DLA-88*508:01 eluates by LC-MS/MS. Combined motif analysis and surface stabilization assay data suggested that 11 of these 22 peptides， derived from CDV hemagglutinin， large polymerase， matrix， nucleocapsid， and V proteins， were processed and presented， and thus， potential targets of anti-viral CTL in DLA-88*508:01-bearing dogs. The presentation of diverse self and viral peptides indicates that DLA-88 is a classical MHC class Ia gene.