First-time use of pathogen absorptive device in severe BK DNAemia/BK polyomavirus-associated nephropathy post kidney transplantation

Background: BK polyomavirus (BKPyV)-associated nephropathy in kidney transplant recipients is an important cause of allograft dysfunction and premature allograft failure. Treatment options for BKPyV-DNAemia following kidney transplantation remain limited. Adjunctive pathogen adsorption devices such as the Seraph® 100 Microbind® Affinity Blood Filter (Seraph® 100) have previously been used for clearance of viruses, bacteria, and toxins in critical illness under FDA Emergency Use Authorization. Case outline: An 18-year-old recipient of a deceased donor kidney transplant developed severe BKPyV-DNAemia and biopsy-proven BKPyV-nephropathy refractory to reduced immunosuppression, antiviral therapy, and adjunctive intravenous immunoglobulin (IVIG). Given progressive allograft dysfunction, consideration was given to adjunctive extracorporeal therapies targeting BKPyV-DNAemia removal. Complications: Despite multiple interventions including reduction of immunosuppression, cidofovir, leflunomide, and IVIG, BKPyV-DNAemia continued to worsen with levels reaching approximately 2 million copies/mL by 7 months post-transplant. The patient developed de novo donor-specific antibodies and biopsy-proven antibody-mediated rejection concurrent with BKPyV-nephropathy and rising serum creatinine. Within 8 weeks of Seraph® treatment, BKPyV-DNA levels resolved to < 5000 copies/mL. During the subsequent 12-month follow-up period, her graft function stabilized with serum creatinine of 1.2–1.3 mg/dL without proteinuria and stable class II DSA.