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The following is a summary of “Human Herpesvirus-6 Reactivation and Disease Are Infrequent in Chimeric Antigen Receptor T-cell Therapy Recipients,” published in the April 2024 issue of Hematology by Kampouri et al.
Reactivation of human herpesvirus-6B (HHV-6B) and associated diseases have become more frequently reported following CAR-T-cell therapy (CARTx). Recent findings have even highlighted HHV-6 reactivation within the CAR-T-cell product itself, prompting inquiries into product and patient management. Diagnosing HHV-6B encephalitis poses challenges due to symptom overlap with immune effector cell-associated neurotoxicity syndrome.
Researchers made two lines of evidence to assess the incidence and outcomes of HHV-6B after CARTx. Firstly, in a prospective study involving weekly HHV-6B testing for up to 12 weeks post-infusion, 8 out of 89 participants experienced HHV-6B reactivation. Among them, three individuals had chromosomally integrated HHV-6 and were excluded, resulting in a cumulative HHV-6B reactivation of 6% (95% (CI), 2.2-12.5%). The detected HHV-6B levels were generally low (median peak, 435 copies/mL; IQR, 164-979) and did not necessitate therapy.
Secondly, a retrospective analysis was conducted on HHV-6B detection in blood and/or cerebrospinal fluid (CSF) within 12 weeks post-infusion in CARTx recipients. Among 626 patients, 24 underwent symptom-driven plasma testing, with only one positive detection. Among 34 patients who underwent CSF HHV-6 testing, one case of possible HHV-6 encephalitis was identified, resulting in a cumulative incidence of 0.17% (95% CI, 0.02-0.94%). Notably, the patient’s symptoms improved without requiring treatment.
Our findings indicate that HHV-6B reactivation and associated diseases are infrequent occurrences following CARTx. As such, routine HHV-6 monitoring is deemed unnecessary based on our data.
