BK polyomavirus-neutralizing activity of intravenous immunoglobulin products derived from donated blood in Japan

Background and Objectives BK polyomavirus (BKV) causes BKV-associated nephropathy and haemorrhagic cystitis, subsequent to BKV reactivation. Intravenous immunoglobulin products (IVIg), manufactured from the plasma of over ten thousand donors, may contain antibodies against BKV. However, the antibody titres and batch-to-batch variations in IVIg across the manufacturing year are unknown. This study aims to determine the BKV-neutralizing activity of IVIg from donated blood in Japan and its trend over the past several years. Materials and Methods A reliable measurement method was established to quantitatively determine neutralizing activity using the human lung (carcinoma) cell line, A549 and the Gardner strain of BKV. Six lots of IVIg and four lots of pooled plasma were used as the source material for this study. Results The mean neutralizing titre against BKV in pooled plasma was 3·4 ± 0·1 log10 and that in IVIg was 4·1 ± 0·1 log10. The titres of IVIg lots manufactured from 1999 to 2010 were stable. Conclusion IVIg derived from donated blood in Japan demonstrated high neutralizing activity against BKV, and its titre was maintained over the duration of 10 years, suggesting high prevalence of BKV among the donor population in Japan. Further studies are required to clarify the clinical implications of this neutralizing activity in IVIg.