Kidney Week

Abstract: FR-PO1005

Characterization of the BKPyV-Specific Memory B Cell Response in KTx Recipients and Blood Donors

Session Information

• Transplantation: Basic
  October 25, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Transplantation

• 2101 Transplantation: Basic

Authors

• Affeldt, Patrick, Universitatsklinikum Koln, Koln, Nordrhein-Westfalen, Germany

Patrick Affeldt, MD

• Kreer, Christoph, Universitatsklinikum Koln, Koln, Nordrhein-Westfalen, Germany

Christoph Kreer

• Mueller, Roman-Ulrich, Universitatsklinikum Koln, Koln, Nordrhein-Westfalen, Germany

Roman-Ulrich Mueller, MD

• Steger, Gertrud, Universitatsklinikum Koln, Koln, Nordrhein-Westfalen, Germany

Gertrud Steger

• Klein, Florian, Universitatsklinikum Koln, Koln, Nordrhein-Westfalen, Germany

Florian Klein, MD, MSc

Background

While BK-Polyomavirus (BKPyV) infection is asymptomatic in immunocompetent individuals, it causes Polyomavirus-associated Nephropathy (PyVAN) in about 10% of all kidney transplant (KTx) recipients. PyVAN is one of the leading causes of premature graft function loss. Importantly, there is currently no virus-specific therapy available. Since the presence of BKPyV-directed antibodies has been associated with control of BKPyV infections, we set out to analyze the memory B-cell response against BKPyV on a single-cell level and isolate BKPyV neutralizing monoclonal antibodies (mAb).

Methods

Two cohorts of i.) 200 kidney transplant recipients (KTx) and ii.) 100 blood donors (BD) were screened for plasma neutralization against BKPyV genotypes Ib2 and IV using a pseudovirus neutralization assay. Based on plasma neutralizing activity, we selected the top 5 KTx and 5 BD neutralizers and isolated BKPyV-VP1-specific IgG+ memory B cells from peripheral blood mononuclear cells (PBMC) via Fluorescence activated cell sorting (FACS). Naturally paired heavy and light chain sequences were generated by total RNA reverse transcription and a BCR-specific nested PCR following sequence analysis. Clonality was inferred from IgBLAST annotated sequences and at least one antibody from each identified BKPyV-reactive B cell clone was selected for recombinant antibody production. Monoclonal antibodies were eventually evaluated for VP1-binding and neutralization against BKPyV genotypes (I-IV).

Results

Higher neutralization titers and BKPyV cross neutralizing activity against genotypes I-IV was observed in sera from KTX patients compared to the BD group. 1089 BKPyV specific memory B-cells from the top 5 neutralizers from each group were isolated and 768 memory B-cell receptor sequences analyzed. As a first proof of principle, 16 mAbs (5 BD, 11KTx) were produced and screened for neutralizing activity against all genotypes. Of those, mAb COR32_1_C2(KTx) showed a potent cross neutralizing activity (max. IC₅₀ <0.03 ug/ml) against all genotypes.

Conclusion

We established a pipeline to isolate BKPyV-Vp1-specific antibodies from human peripheral blood and found BKPyV-neutralizing antibodies in both the BD and the KTX group. Importantly, we identified COR32_1_C2 (KTx) as a promising candidate with highly potent neutralizing activity against all BKPyV genotypes.