A Specialist Macaque MHC Class I Molecule with HLA-B*27-like Peptide-Binding Characteristics.

In different macaque species, the MHC gene is present in abundance, and its gene products are characterized by low cell-surface expression and a highly conserved peptide-binding cleft. We have characterized the peptide-binding motif of Mamu-A205:01, and elucidated the binding capacity for virus-derived peptides. The macaque A205 allotype prefers the basic amino acid arginine at the second position of the peptide, and hydrophobic and polar amino acids at the C-terminal end. These preferences are shared with HLA-B27 and Mamu-B008, molecules shown to be involved in elite control in human HIV type 1 and macaque SIV infections, respectively. In contrast, however, Mamu-A205 preferentially binds 8-mer peptides. Retention in the endoplasmic reticulum seems to be the cause of the lower cell-surface expression. Subsequent peptide-binding studies have illustrated that Mamu-A205:01 is able to bind SIV-epitopes known to evoke a strong CD8 T cell response in the context of the Mamu-B*008 allotype in SIV-infected rhesus macaques. Thus, the macaque gene encodes a specialized MHC class I molecule, and is most likely transported to the cell surface only when suitable peptides become available.