HLA Haplotype Determines Hapten or p-i T Cell Reactivity to Flucloxacillin

Abstract

Drug-induced liver injury (DILI) is a main cause of drug withdrawal. A particularly interesting example is flucloxacillin (FLUX)-DILI, which is associated with the HLA-B*57:01 allele. At present, the mechanism of FLUX-DILI is not understood, but the HLA association suggests a role for activated T cells in the pathomechanism of liver damage. To understand the interaction among FLUX, HLA molecules, and T cells, we generated FLUX-reacting T cells from FLUX-naive HLA-B*57:01+ and HLA-B*57:01− healthy donors and investigated the mechanism of T cell stimulation. We found that FLUX stimulates CD8+ T cells in two distinct manners. On one hand, FLUX was stably presented on various HLA molecules, resistant to extensive washing and dependent on proteasomal processing, suggesting a hapten mechanism. On the other hand, in HLA-B*57:01+ individuals, we observed a pharmacological interaction with immune receptors (p-i)–based T cell reactivity. FLUX was presented in a labile manner that was further characterized by independence of proteasomal processing and immediate T cell clone activation upon stimulation with FLUX in solution. This p-i–based T cell stimulation was restricted to the HLA-B*57:01 allele. We conclude that the presence of HLA-B*57:01 drives CD8+ T cell responses to the penicillin-derivative FLUX toward nonhapten mechanism.

Oxypurinol Directly and Immediately Activates the Drug-Specific T Cells via the Preferential Use of HLA-B*58:01

“…As our recent study (18) To understand how ALP or OXP stimulates T cells, we explored whether T cells could be activated by APCs preincubated with the drug, as is the case for abacavir-specific T cells and hapten-specific T cells (16,19,30,31). First, APCs were incubated with either the drug or the culture medium overnight.…”

“…Additionally, three ALP-allergic HLA-B*58:01 2 patients and eight HLA-B*58:01 2 healthy ALP-naive donors were recruited. Absence of the HLA-B*58:01 allele was determined in some cases by staining with anti-HLA class I B17 Ab (US Biological, Swampscott, MA) (16,20). The study was approved by the ethics committee of the Canton of Bern, and all participants gave informed consent.…”

“…Hapten-specific T cells normally require APCs to process haptenated proteins before they are loaded as haptenized peptides onto MHC molecules on the surface (16,32). Bortezomib is a proteasome inhibitor that can block the Ag-processing pathway of intracellular peptides (19).…”

“…Unlike HLA-B*57:01 and flucloxacillin (16), all ALP/OXP-specific T cells were activated via the p-i mechanism, regardless of their HLA-B*58:01 status. Unlike HLA-B*57:01 and abacavir (19), the drug binding was labile, and unlike HLA-B*15:02 and carbamazepine (15), there was no shared TCR usage within reactive T cells.…”

“…Furthermore, our group (16) recently showed that flucloxacillinspecific T cells restricted to HLA-B*57:01 recognize the drug via the p-i mechanism and not as a haptenized peptide. Therefore, it is not clear whether the altered peptide repertoire can be generalized to other HLA-associated drug hypersensitivity syndromes.…”