Rather, it is possible that a

productive Seliciclib nmr infection of MPyV may be blocked at a step after the generation of viral DNA in the infected cells. Previous studies have indicated that viral proteins and particles could be produced in oligodendrocytes and other cell types in the brain tissues of MPyV-inoculated mice (15, 16). Thus, it is speculated that MPyV temporarily replicates in brain cells, such as oligodendrocytes, and progeny virions may be retained in the infected cells without being released into the extracellular spaces in the brains of BALB/c and KSN mice, thereby leading to the lack of viral spread to the adjacent cells. Further analyses, such as immunoblotting, immunohistochemistry and electron microscopy, need to be conducted to better understand the mechanism of MPyV replication in the mouse brain. Previous investigations suggested that the intracranial injection of MPyV into the cerebrum led selleckchem to demyelination of the brain stem and spinal cord, thereby

causing paralysis and wasting in adult nude mice bearing human tumors (15, 16). In the current study, KSN nude mice did not exhibit any clinical symptoms after MPyV inoculation. This discrepancy in results can be explained by the differences in the inoculation procedure. Because extremely small amounts of virus inoculum were stereotaxically microinfused into the striatum of KSN mice, it is thought that the brain stem and spinal cord were less affected or not affected by MPyV infection; however, in the preliminary

experiment, stereotaxic inoculation of MPyV into the brain stem did not lead to paralysis in KSN mice (Nakamichi K, 2010, unpublished data). Thus, a severe immunodeficient state and/or tumor products may be associated with the MPyV-mediated demyelination in nude mice following transplantation Mephenoxalone with human tumors. When examining the spatial and temporal patterns of MPyV infection in the brain, the low but significant levels of viral DNA were observed in regions away from the inoculation site in the perfused brains of KSN mice between 8 and 30 days p.i. The onsets of the increase in viral DNA in these brain areas coincided with those in the spleen, blood, and liver; thus, it is probable that MPyV may be transported from the inoculation site to other areas of the brain and peripheral organs. It is also of interest to note that detectable amounts of MPyV DNA were present in the brains not only of KSN nude mice but also of BALB/c mice even at 30 days p.i. These observations indicate that MPyV infects the brains of immunocompetent mice without being completely cleared by immune responses. The characterization of viruses retained in the brain needs to be conducted to clarify long-term MPyV infection. In conclusion, MPyV established an asymptomatic long-term infection in the mouse brain after stereotaxic inoculation into the brain tissue.