Comparing immunopathogenesis of non-human immunodeficiency virus immune reconstitution inflammatory syndrome and immune-related adverse events: A prospective multicenter cohort study.

The concept of immune reconstitution inflammatory syndrome (IRIS) has recently been applied to patients with non-HIV infection with immune fluctuations. However, quantitative criteria to diagnose non-HIV IRIS have not been established. Similarly, immune-related adverse events (irAEs) caused by immune checkpoint inhibitors (ICIs) are also caused by immune fluctuations. No study has directly compared the immunological indicators of non-HIV IRIS and irAEs. Thus, we investigated whether irAEs can be included in non-HIV IRIS. We aimed to search for diagnostic biomarkers for non-HIV IRIS and to compare the immunopathogenesis of non-HIV IRIS and irAEs based on immunological indicators. We selected drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS) and dipeptidyl peptidase-4 inhibitor-associated bullous pemphigoid (DPP4i-BP) as underlying diseases of non-HIV IRIS. Blood cell counts, cytokines or chemokines, and herpesvirus-derived DNA in saliva were quantified and compared between IRIS/irAE-positive and -negative as well as non-HIV IRIS and irAEs groups. The DPP4i-BP group had a shorter incubation time to IRIS onset than the DIHS/DRESS group; the irAE group had a longer incubation time than the DIHS/DRESS group. A higher neutrophil-to-lymphocyte ratio and serum interferon gamma inducible protein 10 levels could be potential biomarkers of IRIS and irAEs onset; however, no useful cut-off values for diagnosis were indicated. Meanwhile, the transition of  regulatory T cells (Tregs) from the baseline to the onset of IRIS or irAEs differed between IRIS in DIHS/DRESS and irAEs. Only the DIHS/DRESS group showed an increase of Epstein-Bar virus (EBV) (p < 0.0001) and human herpesvirus 6 (p < 0.05) positivity in saliva at the onset of IRIS compared to that at baseline. Although non-HIV IRIS and irAEs have a small number of common immunological indicators, the dynamics of Tregs, cytokines, or chemokines and positivity of herpesvirus-derived DNA in saliva differ, suggesting that non-HIV IRIS and irAEs should remain as separate entities.