Characterizing immune responses in severe T-cell mediated adverse drug reactions

Severe immune-mediated adverse drug reactions (IM-ADRs) significantly impact patient outcome and inflict substantial cost on healthcare and drug development. Many of these T-cell mediated reactions are now known to be class I and/or class II HLA restricted, however, the minority of patients carrying an HLA risk allele will develop an IM-ADR. To help define the specific immunopathogenesis of these T-cell mediated drug reactions, a biobank of cryopreserved PBMCs and blister fluid/skin biopsies has been developed from HLA class I and II genotyped patients with IM-ADRs (Stevens-Johnson Syndrome/Toxic epidermal necrolysis (SJS/TEN), abacavir hypersensitivity, and drug reaction with eosinophilia and systemic symptoms (DRESS)) at various time points from their acute reaction. Causative drugs included antibiotics, antiretrovirals, anticonvulsants and allopurinol. Overnight gamma interferon ELISpot assay proved sensitive to identify dose-dependent drug responses at different time points during and following the acute IM-ADR. We used intracellular cytokine staining and cell sorting to identify drug specific CD137+/CD69+ activated CD8+ and CD4+ T cells. Single cell and bulk TCR sequencing was performed to compare activated and non-activated populations of T cells in the presence and absence of drug. Immune responses differed according to the drug, clinical phenotype/tissue specificity, time from drug reaction, CD4+ and/or CD8+ dependency, and the oligoclonality of drug specific T-cell populations.