Clonal dynamics of adoptively transferred multi-virus specific T cells (MVST) in hematopoietic stem cell transplant patients

Abstract

Abstract Hematopoietic stem cell transplant (HCT) patients often risk complications from viral infection due to loss of protective antiviral immunity. One strategy to overcome this hurdle is to supplement the HCT with multi-virus specific T cells (MVST). In phase I trial (NCT02231853), MVSTs were generated using HLA-matched donor-derived dendritic cells pulsed with viral overlapping peptide libraries (cytomegalovirus (CMV), Epstein-Barr virus, Adenovirus, and BK polyomavirus) and then co-cultured with donor lymphocytes. These cells were infused into the patient in early post-SCT. Using T cell receptor CDR3 immnuosequencing, we investigated the fate of adoptively transferred donor derived MVST in four donor-patient pairs. Relative clonal frequencies were analyzed in the peripheral blood and bone marrow day 60, 100, 180, and 1 year post transplant. The top 10 most frequent clones in the MVST product did not necessarily survive in the patients, and only minor subsets of MVST clonal sequences survived at day 100 (2.92–7.75%). However, these minor MVST clones quickly expanded in all four patients to constitute over >20% of peripheral blood T cells even 6 months to 1 year later. Two patients analyzed had MVST antiviral clones peak during and after detectable viremia or viriuria, but were asymptomatic. One patient received steroids for treatment of GVHD, which was accompanied by the decline of MVST clones and subsequent CMV reactivation. These results suggest that adoptive transfer of viral-specific T cells can promote reconstitution of the anti-viral T cell repertoire and these cells persist in patients long-term post transplant. Furthermore, the fittest clones are dynamically selected to serve as long term sentinels against viral reactivation.