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.
Laboratory of Immune Cell Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892-1152, USA.
M J
MJ
Shields
R
R
Kubota
W
W
Hodgson
S
S
Jacobson
W E
WE
Biddison
R K
RK
Ribaudo
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