A CASE OF BK VIRUS NEPHROPATHY ASSOCIATED WITH PROLONGED IMMUNE EFFECTOR CELL-ASSOCIATED HEMATOTOXICITY FOLLOWING ANTI-CD19 CAR T-CELL THERAPY

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Abstract Title *

A CASE OF BK VIRUS NEPHROPATHY ASSOCIATED WITH PROLONGED IMMUNE EFFECTOR CELL-ASSOCIATED HEMATOTOXICITY FOLLOWING ANTI-CD19 CAR T-CELL THERAPY

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Co-author 1

Tsubasa Shinomiya raku10burnt@gmail.com Chiba University Hospital Nephrology Chiba Japan *

Co-author 2

Naoto Okubo onaoto@chiba-u.jp Chiba University Hospital Nephrology Chiba Japan -

Co-author 3

Yuuki Yoshioka yuukiy@chiba-u.jp Chiba University Hospital Nephrology Chiba Japan -

Co-author 4

Daisuke Honda dhonda@chiba-u.jp Chiba University Hospital Nephrology Chiba Japan -

Co-author 5

Hanae Wakabayashi hawakaba@chiba-u.jp Chiba University Hospital Nephrology Chiba Japan -

Co-author 6

Katsuhiko Asanuma kasanuma@chiba-u.jp Chiba University Hospital Nephrology Chiba Japan -

Co-author 7

Co-author 8

Co-author 9

Co-author 10

Co-author 11

Co-author 12

Co-author 13

Co-author 14

Co-author 15

Introduction

BK virus nephropathy (BKVN) is a complication primarily observed in immunosuppressed kidney transplant recipients but is rarely reported in non-transplant patients. We report a case of BKVN associated with prolonged myelosuppression following chimeric antigen receptor T-cell (CAR-T) therapy.

Methods

Case report; A 67-year-old woman was diagnosed with Diffuse Large B-cell Lymphoma, not Otherwise Specified (DLBCL-NOS) three years ago. However, due to difficulties in treatment, she underwent CAR-T therapy one year ago. While her DLBCL-NOS subsequently remained in remission following the CAR-T therapy, she experienced prolonged myelosuppression. As a result, she required periodic red blood cell transfusions and administration of granulocyte colony-stimulating factor preparations. Over the next six months, renal function deteriorated from Serum creatinine level 1.05 mg/dL to 2.75 mg/dL. Decoy cells were found in the urine cytology, and BKVN was suspected. The patient was referred to our department and admitted. Quantitative PCR testing showed high copy numbers of BKV DNA in both blood and urine. In addition, a renal biopsy revealed tubulointerstitial nephritis along the medullary radiation and multiple simian virus 40 (SV40) -positive tubular epithelial cells, confirming the diagnosis of BKVN. Serum Cre levels were in the range of 3 mg/dL at admission. She received high-dose intravenous immunoglobulin (IVIG) therapy (20 g/day for 5 days) as treatment for BKVN. However, the blood DNA copy number did not decrease, and her kidney function continued to decline.

Results

Discussion; BKV remains as a latent infection under normal immune function, but reactivates under immunosuppression. BKVN is known to be a cause of decline in transplant kidney function, but there have been no reports of its development due to immunosuppression after CAR-T therapy. As the use of CAR-T therapy is widespread, we should be aware of this emerging complication. Also, as no established treatment for BKVN in non-transplant patients is currently available, early detection is crucial.

Conclusion

Routine monitoring for BK virus infection should be considered in patients experiencing prolonged myelosuppression after CAR-T therapy to enable early detection and prompt management of BKVN.

This case report published in Kidney Medicine, October 10, 2025.

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