Characterisation of HLA-restricted T-cell responses to abacavir using lymphocytes from drug-naïve volunteers



Bell, Catherine
Characterisation of HLA-restricted T-cell responses to abacavir using lymphocytes from drug-naïve volunteers. [Unspecified]

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Abstract

Immune-mediated adverse drug reactions are difficult to predict and can be severe in nature. Recently observed genetic associations highlight the importance of specific human leukocyte antigen alleles in the development of certain reactions. The mechanisms underlying antigen formation and subsequent T-cell activation require further investigation. The drugs abacavir (HLA-B*57:01) and ximelagatran (HLA-DRB*07:01 and HLA-DQA*02:01) represent compounds associated with skin and liver reactions respectively, for which a HLA association has been reported. In order to investigate the mechanism of HLA-restricted T-cell activation a cohort of 400 healthy volunteers was established. Both functional lymphocytes and DNA were isolated and stored. Following sequence-based HLA-typing twenty-six individuals expressing HLA-B*57:01 were identified (1 homozygote, 25 heterozygotes) and 101 individuals (10 homozygotes, 91 heterozygotes) expressing HLA-DRB*07:01 were identified. T-cells from these volunteers were utilised in in vitro assays. The first assays employed had low sensitivity and were unable to detect any drug-specific T-cells either by proliferation or cytokine secretion. Seventy-four CD8+ abacavir-specific T-cell clones however were generated from 3/3 volunteers expressing HLA-B*57:01. These clones secreted an array of cytokines and cytotoxic mediators (IFN-γ, Granzyme B, perforin, Fas ligand) in response to drug incubation. Chemically reactive metabolites are frequently associated with adverse drug reactions. The metabolism of abacavir in both liver and immune cell preparations was therefore assessed. In human liver cytosol, abacavir was metabolised to three isomeric carboxylic acids (48±15% turnover at 20h). This reaction proceeded via a reactive aldehyde metabolite that could be trapped with methoxylamine. Metabolism was blocked by the addition of 4-methylpyrazole, an alcohol dehydrogenase inhibitor (1000µM = 91.7±3.9% inhibition; p

Item Type: Unspecified
Additional Information: Date: 2012-09 (completed)
Subjects: ?? RM ??
Depositing User: Symplectic Admin
Date Deposited: 20 Aug 2013 15:05
Last Modified: 20 Aug 2021 07:10
URI: https://livrepository.liverpool.ac.uk/id/eprint/10595