TARC/CCL17 Expression Is Associated with CD8⁺ T Cell Recruitment in Abacavir-Induced Skin Hypersensitivity in HLA-Transgenic Mice

Abacavir (ABC)-induced hypersensitivity (AHS) is strongly associated with human leukocyte antigen (HLA)-B*57 : 01 expression. Previous studies have demonstrated the feasibility of applying the HLA-transgenic mouse model in this context. ABC-induced adverse reactions were observed in HLA-B*57 : 01 transgenic (B*57 : 01-Tg) mice. Moreover, regulating immune tolerance could result in severe AHS that mimics symptoms observed in the clinical setting, which were modeled in CD4⁺ T cell-depleted programmed death-1 receptor (PD-1) knockout B*57 : 01-Tg (B*57 : 01-Tg/PD-1^-/-) mice. Here, we aimed to examine whether thymus and activation-regulated chemokine (TARC)/CCL17 level can be used as a biomarker for AHS. Serum TARC levels increased in HLA-B*57 : 01-transgenic mice following oral administration of ABC; this increase was associated with the severity of skin toxicity. In ABC-fed CD4⁺ T cell-depleted B*57 : 01-Tg/PD-1^-/- mice, TARC was detected in the epidermal keratinocytes of the ear. Skin toxicity was characterized by the infiltration of CD8⁺ T cells partially expressing C-C chemokine receptor type 4, which is the primary receptor for TARC. In vivo TARC neutralization effectively alleviated the symptoms of ear skin redness and blood vessel dilatation. Moreover, TARC neutralization suppressed the infiltration of CD8⁺ T cells to the ear skin but did not affect the ABC-induced adaptive immune response. Therefore, TARC was involved in ABC-induced skin toxicity and contributed to the recruitment of CD8⁺ T cells to skin. This evidence suggests that serum TARC level may be a functional biomarker for AHS.