Human herpesvirus 6 and CAR T-cell toxicity

In this issue of Blood, , Kampouri et al report their findings on incidence of human herpesvirus 6B (HHV-6B) reactivation in patients receiving chimeric antigen receptor (CAR) T-cell therapies, both in a cohort of 89 patients monitored prospectively for up to 12 weeks following infusion and retrospectively in a larger group of 626 patients who had symptom-driven screening of plasma (n = 24) or cerebrospinal fluid (n = 34), concluding that HHV-6B reactivation and disease are infrequent in this setting and that routine monitoring is not warranted.1