Evolutionary History of MHC Class I Genes in the Mammalian Order Perissodactyla

Abstract

We carried out an analysis of partial sequences from expressed major histocompatibility complex (MHC) class I genes isolated from a range of equid species and more distantly related members of the mammalian order Perissodactyla. Phylogenetic analysis revealed a minimum of six groups, five of which contained genes and alleles that are found in equid species and one group specific to the rhinoceros. Four of the groups contained only one, or very few sequences, indicating the presence of relatively nonpolymorphic loci, while another group contained the majority of the equid sequences identified. These data suggest that a diversification of MHC genes took place after the split between the Equidae and the Rhinocerotidae yet before the speciation events within the genus Equus.

Presentation and Binding Affinity of Equine Infectious Anemia Virus CTL Envelope and Matrix Protein Epitopes by an Expressed Equine Classical MHC Class I Molecule

“…referred to henceforth as ncA1) and C1 (22). These two putative nonclassical genes contained a 9-to 15-base insertion and/or a 6-base deletion in the sequence encoding the transmembrane domain (22). The finding of ncA1 and C1 genes in horse A2152 further supports, but does not prove, that these are nonclassical MHC class I genes.…”

“…Cells were reacted with a control mAb, mAb H6A to equine MHC class I (class I), and mAb to human ␤ 2 -microglobulin (␤2M). referred to henceforth as ncA1) and C1 (22). These two putative nonclassical genes contained a 9-to 15-base insertion and/or a 6-base deletion in the sequence encoding the transmembrane domain (22).…”

“…The finding of ncA1 and C1 genes in horse A2152 further supports, but does not prove, that these are nonclassical MHC class I genes. Another gene, 7-51, was also considered a nonclassical gene based on sequence similarity to putative nonclassical class I gene B3 in group D of a published paper (22). Gene 7-7 resembled classical genes with a transmembrane domain of 35 aa; however, the open reading frame extended 52 aa past the stop codon of the classical genes.…”

“…There is evidence for a third classical MHC class I locus (24), and four putative nonclassical MHC class I molecules have been described (22). Serologic reagents identify 17 MHC class I ELA-A haplotypes, and 11 of these were available to type horses (25,26).…”

Structural Illumination of Equine MHC Class I Molecules Highlights Unconventional Epitope Presentation Manner That Is Evolved in Equine Leukocyte Antigen Alleles

“…The unique disease pathogenesis of EIAV infection in horses, the distinguishing characteristics of the anti-EIAV CTL immunity in an equine MHC I-restricted manner (26,27), the anti-EIAV vaccine, which has been used in China since the 1970s, and the successful clearing of the EIA disease (EIAD) by the 1980s (28) all make it worthwhile to determine an in-depth structure of the preferences of equine MHC I molecule. In this study, we chose a structural approach to explore the mechanism of the successful anti-lentivirus immunity.…”