CD4⁺ T cells prevent abacavir hypersensitivity reactions in HLA-B*57:01 transgenic mice

Abstract

Adverse drug reactions (ADR) are a major obstacle to drug development. Genome-wide association studies identified several human leukocyte antigens (HLA)-class I alleles as risk factors for ADR. The HLA-B*57:01 allele has been found to be associated with the development of abacavir (ABC) hypersensitivity syndrome (AHS) and with the induction of liver injury by the β-lactam antibiotic flucloxacillin. The nucleoside analog ABC, an inhibitor of the HIV reverse transcriptase, can induce severe multi-organ toxicity in >50% of HLA-B*57:01⁺ patients with HIV infection. In a previous study we showed that ABC induced binding to the HLA-B*57:01 of altered self-peptides containing predominantly isoleucine or leucine residues at the carboxyl terminus. Recognition of these self-peptides drives in vitro activation of cytotoxic CD8⁺ T cells. However, the early immune events/danger signals required to overcome the immune tolerance that otherwise suppress ADR are still unknown. In order to study HLA-linked drug hypersensitivity in vivo and to understand better drug immune tolerance, HLA-B transgenic mice were generated. Here, we show that ABC activates HLA-B*57:01 transgenic CD8⁺ T cells in vitro via CD8 and HLA. A systemic, but partial, early response to the drug is also observed in vivo, however, ABC fails to promote skin hypersensitivity in immunocompetent transgenic mice. Instead, depletion of CD4⁺ T cells breaks immune tolerance to ABC and promotes ADR in HLA-B*57:01 transgenic mice.

Supported by the Intramural Research Program of the NIAID, NIH, and CDER, FDA.