Direct interaction between HLA-B and carbamazepine activates T cells in patients with Stevens-Johnson syndrome.
BACKGROUND
Increasing studies have revealed that HLA alleles are the major genetic determinants of drug hypersensitivity; however, the underlying molecular mechanism remains unclear.


OBJECTIVE
We adopted the HLA-B∗1502 genetic predisposition to carbamazepine (CBZ)-induced Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) as a model to study the pathologic role of HLA in delayed-type drug hypersensitivity.


METHODS
We in vitro expanded CBZ-specific cytotoxic T lymphocytes (CTLs) from patients with CBZ-induced SJS/TEN and analyzed the interaction between HLA-B and CBZ analogs based on CTL response, surface plasmon resonance, peptide-binding assay, site-directed mutagenesis, and computer modeling.


RESULTS
The endogenous peptide-loaded HLA-B∗1502 molecule presented CBZ to CTLs without the involvement of intracellular drug metabolism or antigen processing. The HLA-B∗1502/peptide/β(2)-microglobulin protein complex showed binding affinity toward chemicals sharing 5-carboxamide on the tricyclic ring, as with CBZ. However, modifications of the ring structure of CBZ altered HLA-B∗1502 binding and CTL response. In addition to HLA-B∗1502, other HLA-B75 family members could also present CBZ to activate CTLs, whereas members of the HLA-B62 and HLA-B72 families could not. Three residues (Asn63, Ile95, and Leu156) in the peptide-binding groove of HLA-B∗1502 were involved in CBZ presentation and CTL activation. In particular, Asn63 shared by members of the B75 family was the key residue. Computer simulations revealed a preferred molecular conformation of the 5-carboxamide group of CBZ and the side chain of Arg62 on the B pocket of HLA-B∗1502.


CONCLUSIONS
This study demonstrates a direct interaction of HLA with drugs, provides a detailed molecular mechanism of HLA-associated drug hypersensitivity, and has clinical correlations for CBZ-related drug-induced SJS/TEN.
Molecular Medicine Program, Taiwan International Graduate Program, Taipei, Taiwan.
Chun-Yu
CY
Wei
Wen-Hung
WH
Chung
Hsiao-Wen
HW
Huang
Yuan-Tsong
YT
Chen
Shuen-Iu
SI
Hung
D000293:Adolescent; D000328:Adult; D000368:Aged; D017951:Antigen Presentation / Q000276:immunology; D002220:Carbamazepine / Q000009:adverse effects* / Q000737:chemistry / Q000276:immunology*; D002460:Cell Line; D002648:Child; D004342:Drug Hypersensitivity / Q000235:genetics / Q000276:immunology*; D005260:Female; D059910:HLA-B15 Antigen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D008958:Models, Molecular; D010455:Peptides / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D013262:Stevens-Johnson Syndrome / Q000139:chemically induced / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D055815:Young Adult
C483536:HLA-B*15:02 antigen; D059910:HLA-B15 Antigen; D010455:Peptides; D002220:Carbamazepine