Polyomavirus-associated nephropathy (PVAN) after BK virus reactivation in kidney transplant recipients (KTR) can compromise graft survival. Lowering immunosuppression is the only established approach to prevent or treat PVAN but nonspecifically increasing host immune competence also augments rejection risk. Ex vivo T cell stimulation/expansion offers the possibility to generate BK-specific T cell lines for adoptive immunotherapy. The objective of this study was to develop and characterize a clinical-scale protocol to generate BK-specific T cell lines from viremic KTR. Peripheral blood mononuclear cells from healthy controls and viremic KTR were stimulated using BK virus peptide libraries loaded or not on monocytes-derived dendritic cells. Cell counts, flow cytometry, and next-generation sequencing were used to assess T cell expansion, differentiation, and clonal diversity. Enzyme-linked immunospots, cytotoxicity assays as well as adoptive transfer in NOD/SCID/IL2Rγnull mice were used to assess for pathogen-specificity and evidence of nonspecific alloreactivity. T cell lines from KTR and healthy control showed similar characteristics, implying that ongoing immunosuppression and chronic virus exposure do not compromise the differentiation, specificity, or clonal diversity of T cell lines after ex vivo production. Using antigen-loaded dendritic cells improved T cell expansion and favored central memory T cell differentiation. The T cell lines were antigen-specific and showed no nonspecific alloreactivity in vitro and in vivo. Using a rapid, clinically compliant culture system, we show that autologous BK virus-specific T cell lines can be reliably generated from viremic KTR. Our results pave the way for the treatment or prevention of PVAN with adoptive immunotherapy.

Summary: Since its first description by Evans in 1951, this syndrome has been linked to chronic immune thrombocytopenia with the concurrent or delayed onset of autoimmune haemolytic anaemia or neutropenia. For decades, the evolution of Evans syndrome (ES) has carried a poor prognosis and often resulted in chronic steroid exposure, multiple immune suppressing medications directed against T or B lymphocytes, and splenectomy. This paper presents a new view of ES based on recent advances in genomics which begin to classify patients based on their underlying molecular variants in previously described primary immune disorders. This has opened up new avenues of targeted therapy or bone marrow transplant at rather than broad long‐term immune suppression or splenectomy. Importantly, recent studies of the full lifespan of ES suggest that at least 80% of those paediatric patients will progress to various clinical or biological immunopathological manifestations with age despite the resolution of their cytopenias. Those patients merit long‐term follow‐up and monitoring in dedicated transition programs to improve outcome at the adult age.