BKV replication and cellular immune responses in renal transplant recipients.

Hammer and colleagues report on BKV-specific T-cell responses in peripheral blood mononuclear cells (PBMC) of 15 viremic kidney transplant recipients (1). After stimulation with overlapping peptides spanning the viral capsid protein VP1, interferon-c (IFNc )-producing CD4+ T cells were observed in 7 patients (47%), including 2 patients (13%) with a CD8+ T-cell response. All patients with a detectable T-cell response had plasma BKV loads of >250 000 copies (c)/mL. Both patients with VP1-specific CD8+ T cells were the only ones to lose their grafts during follow-up. The authors concluded that high BKV load of >250 000 c/mL correlated with peripheral BKV-specific T-cell responses and that BKV-specific CD8+ responses indicated a risk for subsequent allograft loss (1).