ABSTRACT Background BK virus infection is a marker of poor immune recovery, especially after kidney or allogeneic cell transplantation. Because of the challenges associated with BK virus infection and the lack of effective treatments, there is a growing interest in novel approaches, such as adoptive cellular therapy, that aim to restore antiviral immunity and promote viral clearance. Methods Our clinical trial assessed the feasibility, safety, and efficacy of administering third‐party, BK virus‐specific cytotoxic T lymphocytes (CTLs) used to treat allogeneic HCT patients and kidney transplant patients with biopsy‐proven BK‐virus nephropathy. Comprehensive clinical assessments and correlative studies were performed. Results The study included six patients after kidney‐transplantation and five HCT recipients. Viremia declined in most evaluable patients by Day 45 after BKCTL infusion. No new instances of graft‐versus‐host disease, kidney‐transplant rejection, graft failure, or infusion‐related toxicities were attributed to the treatment. Antiviral activity (as assessed by interferon‐γ secretion) did not differ between infused BKV‐CTLs given to kidney‐transplant versus allogeneic SCT recipients. Conclusion In this study, we longitudinally tracked the in vivo persistence of adoptively transferred BKV‐CTLs and demonstrated their sustained functional activity. This therapy could be promising in KT and SCT patients with recent‐onset BK‐virus viremia. image
Olson et al. (2026) studied this question.