Ritz, JeromeMarty, Francisco M.Soiffer, Robert J.Antin, Joseph H.Koreth, JohnHo, Vincent T.Cutler, Corey S.Armand, PhilippeAlyea, Edwin P.Romee, RizwanGooptu, MahaswetaNikiforow, SarahLacerda, JoãoSoares, Maria VieiraForcade, EdouardAvigan, Jason I.Woolley, Ann E.Kim, Haesook T.Cheng, Matthew P.Espada, Eduardo2022-11-232022-11-232020Blood Adv. 2020 May 12;4(9):1881-18932473-9529http://hdl.handle.net/10451/55222© 2020 by The American Society of HematologyClinical disease caused by BK virus reactivation is a frequent complication of allogeneic hematopoietic cell transplantation (HCT). Because of the lack of effective antiviral agents, BK virus-specific T cells are emerging as a potential therapy for BK virus disease, but the immune response to BK virus after allogeneic HCT has not been well characterized. Our study describes reconstitution of BK virus-specific T-cell immunity in 77 adult patients after HCT. All patients had urinary symptoms, and urine was tested for BK virus replication; 33 patients were positive for BK virus (cases), and 44 were negative (controls). In BK virus cases, the median time to first positive test was 75 days (range, 2-511). BK virus cases had lower CD4 T-cell counts 3 to 9 months after transplant, but CD8 T-cell counts were similar in cases and controls. BK virus-specific T cells were identified by cytokine flow cytometry in cryopreserved samples collected prospectively. BK virus-specific CD4 T cells producing T helper 1 (Th1) cytokines recovered quickly after HCT. BK virus-specific T cells were detected more frequently in patients with BK virus reactivation at most time points, and CD4 T cells producing Th1 cytokines were more frequent than BK virus-specific cytolytic CD8 T cells. Early detection of interferon-γ+ and cytolytic BK virus-specific CD4 T cells was associated with lower rates of hematuria among cases. Overall, our study describes recovery of BK virus-specific T cells after HCT and the distinct roles for BK virus-specific T cells in the development and resolution of clinical symptoms.engjournal article10.1182/bloodadvances.20190011202473-9537