J Immunol 2014[Jun]; 192 (11): 4967-76 PMID24790147show ga
Major histocompatibility complex (MHC) class I polymorphisms are known to influence outcomes in a number of infectious diseases, cancers and inflammatory diseases. Human MHC class I heavy chains are encoded by the HLA-A, HLA-B and HLA-C genes. These genes are highly polymorphic, with the HLA-B locus being the most variable. Each HLA class I protein binds to distinct set of peptide antigens, which are presented to CD8+ T cells. HLA-disease associations have been shown in some cases to link to the peptide binding characteristics of individual HLA class I molecules. Here we show that polymorphisms at the HLA-B locus profoundly influence the assembly characteristics of HLA-B molecules and the stabilities of their peptide-deficient forms. In particular, dependence on the assembly factor tapasin is highly variable, with frequent occurrence of strongly tapasin-dependent or independent allotypes. Several polymorphic HLA-B residues located near the C-terminal end of the peptide are key determinants of tapasin-independent assembly. In vitro refolded forms of tapasin-independent allotypes assemble more readily with peptides compared to tapasin-dependent allotypes that belong to the same supertype, and during refolding, reduced aggregation of tapasin-independent allotypes is observed. Paradoxically, in HIV-infected individuals, greater tapasin-independent HLA-B assembly confers more rapid progression to death, consistent with previous findings that some HLA-B allotypes shown to be tapasin-independent are associated with rapid progression to multiple AIDS outcomes. Together, these findings demonstrate significant variations in the assembly of HLA-B molecules, and indicate influences of HLA-B folding patterns upon infectious disease outcomes.
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J+Immunol 2014 ; 192 (11): 4967-76
