Intracellular cytokines may model immunoregulation of abacavir hypersensitivity in HIV-infected subjects.

Background: The clinical treatment of patients with HIV and adverse drug events may be enhanced by an understanding of the underlying mechanisms. About 4% of patients with HIV receiving the potent antiretroviral drug abacavir develop a hypersensitivity reaction. This idiosyncratic reaction appears to have an immunologic component that has yet to be defined. Given that the T-cell type 2 cytokine IL-4 may be overproduced by patients with allergy or other immunologic dysregulation, an index cytokine profile could help elucidate the character of a drug-specific hypersensitivity reaction.
Objective: Quantitation of the production of the type 2 IL-4 and the counterregulatory type 1 cytokine IFN-gamma in patients with abacavir-related hypersensitivity.
Methods: Intracellular cytokines were enumerated in blood T cells by flow cytometry. Subjects were grouped for evaluation as patients with a hypersensitive response after abacavir treatment, patients initiating abacavir who also were evaluated again after 1 month on abacavir, patients on abacavir for 6 months without hypersensitivity, and HIV-naive control individuals.
Results: There was a significant association between increased IL-4 production by CD4 and CD8 T lymphocytes and hypersensitivity reactions to abacavir. Lymphocytes from hypersensitive subjects expressed CD28 and the anti-HIV chemokine macrophage inflammatory protein 1beta with a frequency comparable with HIV-naive control cells, suggesting the possibility that the activated T cells from patients with hypersensitivity are functional.
Conclusion: The expansion of type 0 and type 2 T cells phenotyped by IL-4 production may correlate with abacavir-associated hypersensitivity. The data suggest a cytokine bias that may facilitate B-cell differentiation and downregulate T-cell cytotoxic responses.