Isoniazid/rifampicin-specific t-cell responses in patients with anti-tuberculosis –induced dress syndrome

Background: Anti-tuberculosis drugs (ATDs) which are a combination of isoniazid, rifampicin, pyrazinamide and ethambutol are commonly used for the treatment of tuberculosis, but occasionally associated with drug- hypersensitive immune reactions such as drug rash with eosinophilia and systemic symptoms (DRESS) syndrome and hepatitis. The culprit drug and mechanistic basis of the hypersensitive reaction has not been defined. Objectives: The aim of this study was to find whether drug-responsive T cell response was detectable in patients with ATD-related DRESS and characterize the mechanistic features of the T-cell response. Methods: A lymphocyte transformation test (LTT) and IFNγ-ELISpot assay using ATDs were performed using peripheral blood mononuclear cells from the patient. Subsequently, drug-specific T-cell clones were generated by serial dilutions. Results: High proliferative responses to isoniazid or rifampicin were detectable in the patient with DRESS by LTT. Isoniazid/rifampicin- specific T-cell clones were generated from blood of the patients, but not pyrazinamide or ethambutol. The T cell clones proliferated and secreted IFNγ when stimulated with isoniazid or rifampicin. They did not cross-react with each other. Conclusion: These studies identify isoniazid/rifampicin- specific T-cells in peripheral blood of certain patients with ATD-induced DRESS. Further studies are needed to define the mechanisms of drug-responsive T cell activation.