Natalizumab has no direct biological effect on JC virus infectivity in permissive human neural cell lines

The human polyomavirus JC virus (JCV) infects 70-80% of humans and establishes latent infection in the kidney. In immunosuppressed patients, JCV reactivates and causes a fatal and progressive neurological disease known as progressive multifocal leukoencephalopathy (PML). Over the past three decades, PML has become an important neurological complication in acquired immunodeficiency syndrome (AIDS) patients. Recently, it was reported that patients treated with therapeutics that target the integrin receptor very late antigen (VLA)-4 are at increased risk of developing PML. However, the relationship between Natalizumab and this unexpected onset of PML has yet to be elucidated. Here, we investigated the effect of Natalizumab on the growth of JCV in the permissive human neural cell line IMR-32 following viral inoculation. Natalizumab had no effect either on the expression levels of viral proteins as determined by immunoblot analysis using specific antibodies or on the hemagglutination activity of cellular lysates from infected cells. These results suggest that there is no direct effect of Natalizumab on JCV infectivity in IMR-32 cells in vitro.