Case report describes severe encephalitis from HHV-6 after anti-CD19 CAR-T, suggesting clinical concern. Analysis found no HHV-6 in patient-derived transduced CAR-T cells.
We report a case of severe encephalitis caused by human herpes virus 6 (HHV-6) following CD19 chimeric antigen receptor T (CAR-T) cell therapy. Rapid expansion of circulating T-lymphocytes and high HHV-6 viral load (4,500,000 DNA copies/mL) early after CAR-T infusion suggested HHV-6 transferal from autologous CAR-T cells. To investigate this hypothesis, we retrospectively analyzed cryo-preserved patient samples for HHV-6. HHV-6 was undetectable in the apheresis product, transduced CAR-T cells, and in vitro activated CAR-T cells. In conclusion, despite strong clinical suspicion, we found no evidence to substantiate the infused CAR-T cells as the source of the severe HHV-6 infection.
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Birk et al. (2025) studied this question.
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