Polyomavirus JC microRNAs expression after infection in vitro.

The in vitro expression of the Polyomavirus JC (JCPyV) microRNAs, JC-miRNA-3p and -5p, at early time points post-infection was investigated. The expression of the JCPyV microRNAs was monitored in hematopoietic progenitor KG-1 cells and in kidney fibroblast-like COS-7 cells transformed with SV40 after infection with a JCPyV CY archetype viral clone. The JCPyV DNA viral load was low in KG-1 cells compared with that in COS-7 cells, which showed productive viral replication. The expression of the JCPyV microRNAs was observed from 12 h after the viral infection of both cell types and in the exosomes present in their cell supernatant. Additionally, this study verified that the JCPyV microRNAs in the exosomes present in the supernatants produced by the infected cells might be carried into uninfected cells. These findings suggest that additional investigations of the expression of JCPyV microRNAs and their presence in exosomes are necessary to shed light on their regulatory role during viral reactivation.