A case report of clonal EBV-like memory CD4+ T cell activation in fatal checkpoint inhibitor-induced encephalitis.
Checkpoint inhibitors produce durable responses in numerous metastatic cancers, but immune-related adverse events (irAEs) complicate and limit their benefit. IrAEs can affect organ systems idiosyncratically; presentations range from mild and self-limited to fulminant and fatal. The molecular mechanisms underlying irAEs are poorly understood. Here, we report a fatal case of encephalitis arising during anti-programmed cell death receptor 1 therapy in a patient with metastatic melanoma. Histologic analyses revealed robust T cell infiltration and prominent programmed death ligand 1 expression. We identified 209 reported cases in global pharmacovigilance databases (across multiple cancer types) of encephalitis associated with checkpoint inhibitor regimens, with a 19% fatality rate. We performed further analyses from the index case and two additional cases to shed light on this recurrent and fulminant irAE. Spatial and multi-omic analyses pinpointed activated memory CD4+ T cells as highly enriched in the inflamed, affected region. We identified a highly oligoclonal T cell receptor repertoire, which we localized to activated memory cytotoxic (CD45RO+GZMB+Ki67+) CD4 cells. We also identified Epstein-Barr virus-specific T cell receptors and EBV+ lymphocytes in the affected region, which we speculate contributed to neural inflammation in the index case. Collectively, the three cases studied here identify CD4+ and CD8+ T cells as culprits of checkpoint inhibitor-associated immune encephalitis.
Johnson, DB; McDonnell, WJ; Gonzalez-Ericsson, PI; Al-Rohil, RN; Mobley, BC; Salem, J-E; Wang, DY; Sanchez, V; Wang, Y; Chastain, CA; Barker, K; Liang, Y; Warren, S; Beechem, JM; Menzies, AM; Tio, M; Long, GV; Cohen, JV; Guidon, AC; O'Hare, M; Chandra, S; Chowdhary, A; Lebrun-Vignes, B; Goldinger, SM; Rushing, EJ; Buchbinder, EI; Mallal, SA; Shi, C; Xu, Y; Moslehi, JJ; Sanders, ME; Sosman, JA; Balko, JM
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