BK Polyomavirus (BKPyV)-specific CD8 T-cell expansion in vitro using 27mer peptide antigens for developing adoptive T-cell transfer and vaccination.

BK polyomavirus (BKPyV) remains a significant cause of premature kidney transplant failure. In the absence of effective antivirals, current treatments rely on reducing immunosuppression to regain immune control over BKPyV replication. Increasing BKPyV-specific CD8 T-cells correlate with clearance of BKPyV-DNAemia in kidney transplant patients. We characterized a novel approach for expanding BKPyV-specific CD8 T-cells in vitro using 27mer-long synthetic BKPyV-peptides, different types of antigen-presenting cells (APCs) and CD4 T-cells.
Langerhans cells, immature, or mature monocytes-derived dendritic cells (Mo-DCs) were generated from peripheral blood mononuclear cells of healthy blood donors, pulsed with synthetic peptide pools consisting of 36 overlapping 27mers (27mP) or 180 15mers (15mP). BKPyV-specific CD8 T-cell responses were assessed by cytokine release assays using 15mP or immunodominant 9mers.
BKPyV-specific CD8 T-cells expanded using 27mP and required mature Mo-DCs (p=0.0312) and CD4 T-cells (p=0.0156) for highest responses. The resulting BKPyV-specific CD8 T-cells proliferated, secreted multiple cytokines including interferon-γ and TNF-α, were functional (CD107a+/PD1-) and cytotoxic.
Synthetic 27mP permit expanding BKPyV-specific CD8 T-cell responses when pulsing mature Mo-DC in presence of CD4 T-cells suggesting novel and safe approaches to vaccination and adoptive T-cell therapies for patients before and after kidney transplantation.

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