The effect of human beta2-microglobulin on major histocompatibility complex I peptide loading and the engineering of a high affinity variant. Implications for peptide-based vaccines.
The ability to directly load cell surface major histocompatibility complex (MHC) class I molecules with peptides provides a potentially powerful approach toward the development of vaccines to generate cell-mediated immunity. We demonstrate that exogenous beta2-microglobulin (beta2m) stabilizes human cell surface MHC I molecules and facilitates their loading with exogenous peptides. Additionally, using three-dimensional crystal structures and known interaction sites between MHC I heavy chains and beta2m, we engineered variants of human beta2m (hbeta2m) with a single serine substitution at residue 55. This alteration was predicted to promote hydrophobic interactions at the MHC I heavy chain/beta2m interface and displace an ordered water molecule. Compared with hbeta2m, the serine to valine substitution at residue 55 had improved ability to bind to cell surface HLA-A1, HLA-A2, and HLA-A3 molecules, facilitate exogenous peptide loading, and promote recognition by peptide-specific T cells. The inclusion of hbeta2m or higher affinity variants when pulsing cells with MHC-restricted peptides increases the efficiency of peptide loading 50-80-fold. Therefore, the inclusion of hbeta2m in peptide-based vaccines may increase cell surface antigen densities above thresholds that allow recognition of peptide antigens by the immune system, particularly for cryptic, subdominant, or marginally antigenic peptides.
Shields
M J
MJ
Laboratory of Immune Cell Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892-1152, USA.
Kubota
R
R
Hodgson
W
W
Jacobson
S
S
Biddison
W E
WE
Ribaudo
R K
RK
D017951:Antigen Presentation; D015195:Drug Design; D014644:Genetic Variation; D015234:HLA-A Antigens / Q000378:metabolism*; D006801:Humans; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000378:metabolism*; D011485:Protein Binding; D015202:Protein Engineering; D013602:T-Lymphocytes, Cytotoxic; D014612:Vaccines / Q000276:immunology; D001613:beta 2-Microglobulin / Q000235:genetics* / Q000378:metabolism*
D015234:HLA-A Antigens; D010455:Peptides; D014612:Vaccines; D001613:beta 2-Microglobulin