title: The common equine class I molecule Eqca-1*00101 (ELA-A3.1) is characterized by narrow peptide binding and T cell epitope repertoires.
abstract: Here we describe a detailed quantitative peptide-binding motif for the common equine leukocyte antigen (ELA) class I allele Eqca-1*00101, present in roughly 25 % of Thoroughbred horses. We determined a preliminary binding motif by sequencing endogenously bound ligands. Subsequently, a positional scanning combinatorial library (PSCL) was used to further characterize binding specificity and derive a quantitative motif involving aspartic acid in position 2 and hydrophobic residues at the C-terminus. Using this motif, we selected and tested 9- and 10-mer peptides derived from the equine herpesvirus type 1 (EHV-1) proteome for their capacity to bind Eqca-1*00101. PSCL predictions were very efficient, with an receiver operating characteristic (ROC) curve performance of 0.877, and 87 peptides derived from 40 different EHV-1 proteins were identified with affinities of 500 nM or higher. Quantitative analysis revealed that Eqca-1*00101 has a narrow peptide-binding repertoire, in comparison to those of most human, non-human primate, and mouse class I alleles. Peripheral blood mononuclear cells from six EHV-1-infected, or vaccinated but uninfected, Eqca-1*00101-positive horses were used in IFN-γ enzyme-linked immunospot (ELISPOT) assays. When we screened the 87 Eqca-1*00101-binding peptides for T cell reactivity, only one Eqca-1*00101 epitope, derived from the intermediate-early protein ICP4, was identified. Thus, despite its common occurrence in several horse breeds, Eqca-1*00101 is associated with a narrow binding repertoire and a similarly narrow T cell response to an important equine viral pathogen. Intriguingly, these features are shared with other human and macaque major histocompatibility complex (MHC) molecules with a similar specificity for D in position 2 or 3 in their main anchor motif.
authors.affiliation: Institut für Virologie, Freie Universtiät Berlin, 14163, Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bergmann
authors.affiliation: Department of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA, 92037, USA.
authors.forename: Carrie
authors.initials: C
authors.lastname: Moore
authors.affiliation: Department of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA, 92037, USA.
authors.forename: John
authors.initials: J
authors.lastname: Sidney
authors.affiliation: Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Donald
authors.initials: D
authors.lastname: Miller
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Tallmadge
authors.affiliation: Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Harman
authors.affiliation: Department of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA, 92037, USA.
authors.forename: Carla
authors.initials: C
authors.lastname: Oseroff
authors.affiliation: Department of Chemistry, University of Virginia, Charlottesville, VA, 22904, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Wriston
authors.affiliation: Department of Chemistry, University of Virginia, Charlottesville, VA, 22904, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Shabanowitz
authors.affiliation: Department of Chemistry, University of Virginia, Charlottesville, VA, 22904, USA.|Department of Pathology, University of Virginia, Charlottesville, VA, 22904, USA.
authors.forename: Donald F
authors.initials: DF
authors.lastname: Hunt
authors.affiliation: Institut für Virologie, Freie Universtiät Berlin, 14163, Berlin, Germany.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Osterrieder
authors.affiliation: Department of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA, 92037, USA.
authors.forename: Bjoern
authors.initials: B
authors.lastname: Peters
authors.affiliation: Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Antczak
authors.affiliation: Department of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA, 92037, USA. alex@lji.org.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Sette
mesh_terms: D000483:Alleles; D000818:Animals; D018984:Epitopes, T-Lymphocyte / Q000276:immunology* / Q000378:metabolism*; D006566:Herpesviridae Infections / Q000235:genetics / Q000276:immunology / Q000662:veterinary / Q000821:virology; D004861:Herpesvirus 1, Equid / Q000235:genetics / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology* / Q000378:metabolism; D006734:Horse Diseases / Q000235:genetics / Q000276:immunology / Q000821:virology; D006736:Horses; D006801:Humans; D007963:Leukocytes, Mononuclear; D051379:Mice; D010446:Peptide Fragments / Q000276:immunology* / Q000378:metabolism*; D011485:Protein Binding; D020543:Proteome / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D018984:Epitopes, T-Lymphocyte; D015395:Histocompatibility Antigens Class I; D010446:Peptide Fragments; D020543:Proteome
keywords: Equus caballus (Eqca); MHC binding motif; MHC class I; Peptide binding; T cell epitope