Clinical Efficacy of BK Virus Specific T-Cells in Treatment of Severe Refractory Hemorrhagic Cystitis after HLA Haploidentical Transplantation

BK virus, a human polyomavirus is typically acquired in childhood and lies dormant in the endothelial cells of the kidney and urinary tract with 90% of healthy adults being seropositive. T-cells secreting interferon-gamma (IFNg) are thought to induce this latent state. Hemorrhagic cystitis caused by BK virus (BKV) is particularly common in the setting of HLA haploidentical transplantation and is often difficult to manage. Here we present a post-haploidentical HCT patient who developed severe BKV haemorrhagic cystitis resistant to standard therapy and who responded to adoptive transfer of donor T-cells enriched with anti-BKV specific cells.

A 40 year old man underwent haploidentical HCT for acute myeloid leukaemia with inv 3 and monosomy 7 while in first complete remission. The conditioning was myeloablative with thiotepa 10 mg/kg, intravenous busulfan 9.6 mg/kg and fludarabine 150 mg/m². Cyclophosphamide on days +3 and +4 (50 mg/kg) was used as graft versus host disease (GvHD) prophylaxis together with cyclosporine and mycophenolate mofetyl starting on day +5. On day +32 he developed haemorrhagic cystitis. Supportive treatment was initiated and cystoscopy showed diffuse bleeding from his bladder with blood clots. Urine PCR for BKV showed 5.2 billion copies/mL. Despite bladder irrigation, and intravenous hydration, he failed to improve, and treatment with weekly intravenous cidofovir was initiated on day +38. His symptoms improved, but on day +72 he again deteriorated despite on-going cidofovir. His immunosuppression was tapered without occurrence of GvHD but his hemorrhagic cystitis continued unabated. He underwent bladder diathermy, was treated with intravesicular hyaluronate, but continued to have frank haematuria with blood clots and significant lower abdominal pain. Although there was no evidence of obstruction his renal function deteriorated. Hence we elected to trial adoptive anti-BKV therapy.

Identification of anti-BKV T-cells in the original donor was performed using the research grade peptivators BKV LT and BKV VP1 and the rapid cytokine inspector (CD4/CD8 T cell) kit from Miltenyi biotec according to manufacturer's instructions. BKV-reactive CD4/CD8 T cells were identified by flow cytometry of intracellular IFNg. Lymphocytes were collected by pheresis and used to prepare an anti-BKV T-cell enriched product using the Clinimacs Prodigy and the cytokine capture system from Miltenyi Biotec. The eluted product contained 50% and 5% of CD4+ and CD8+ lymphocytes expressing IFNg+ respectively and the BK-enriched CD4+/CD8+ dose adoptively transferred on day +86 of transplantation was 0.34 x10⁴/Kg.

The presence of anti-BKV T-cells in the patient was checked weekly for the first month using the research grade peptivators BKV LT and BKV VP1 and the rapid cytokine inspector (CD4/CD8 T cell) kit. BK viral load was monitored by PCR in urine samples twice weekly. IFNg+ anti-BKV reactive T cells were undetectable in the patient for the first two weeks, but at 20 days post infusion an increase in the CD4+ IFNg+ population was observed. This observation temporally correlated with a substantial decrease of the urine BKV viremia from 3.3 million copies/mL to 1360 copies/mL and a complete resolution of symptoms. No GvHD, recurrence of urinary symptoms or any other problems have been observed to date (day +132 of transplantation, +46 days after the adoptive transfer).

We are not aware of any other reports of successful adoptive anti-BKV cellular therapy using this technology. Our experience suggests the use of anti-BKV T-cell enriched products generating using the Clinimacs Prodigy and the IFNg capture system is safe and efficient in HLA haploidentical HCT, where BKV cystitis constitutes a significant complication. This opens the possibility of further clinical trials.