Suppression of early and chronic BK polyoma virus replication by mycophenolic acid in Vero cells

Consensus is lacking about which immunosuppressant agents potentiate BK virus infection. The effects of mycophenolic acid (MPA) were investigated in BK virus (BKV)-infected Vero E6 cells. MPA (1-16 mg/l) exhibited a dose-dependent anti-viral effect (10¹-10⁴ fold reduction in BKV DNA copies/ml) in supernatant, similar to cidofovir (2.5-25 mg/l). This effect was observed for early and persistent infection, and infection with noncoding control region (NCCR) rearranged BKV. MPA reduced BKV DNA copies/ml by >1 log after day 14 in three patient isolates before and after NCCR rearrangement, and in cells. MPA reduced total cellular protein levels, consistent with an anti-metabolite effect without increased cytopathic activity. BKV infection was associated with a transient, significant reduction of collagen 1A1 on day 7 but not on days 14, 21, and 28 or in the presence of MPA. Reduction of alpha smooth muscle actin mRNA was observed only in the BKV + MPA group, and only on day 7. There was no significant alteration of heat shock protein 47 or transforming growth factor-β mRNA expression. These in vitro data suggest that MPA may have a protective, anti-viral effect in BKV-infected renal tubular cells with an anti-viral response. Maintaining, or even increasing, the MPA dose should be evaluated for reduction of BKV viremia levels.