Cytomegalovirus cell tropism, replication, and gene transfer in brain

Cytomegalovirus (CMV) infects a majority of adult humans. During early deve lopment and in the immunocompromised adult, CMV causes neurological deficit s. We used recombinant murine cytomegalovirus (mCMV) expressing either gree n fluorescent protein (GFP) or beta-galactosidase under control of human el ongation factor 1 promoter or CMV immediate early-1 promoter as reporter ge nes for infected brain cells. In vivo and in vitro studies revealed that ne urons and glial cells supported strong reporter gene expression after CMV e xposure. Brain cultures selectively enriched in either glia or neurons supp orted viral replication, leading to process degeneration and cell death wit hin 2 d of viral exposure. In addition, endothelial cells, tanycytes, radia l glia, ependymal cells, microglia, and cells from the meninges and choroid were infected. Although mCMV showed no absolute brain cell preference, rel ative cell preferences were detected. Radial glia cells play an important r ole in guiding migrating neurons; these were viral targets in the developin g brain, suggesting that cortical problems including microgyria that are a consequence of CMV may be caused by compromised radial glia. Although CMV i s a species-specific virus, recombinant mCMV entered and expressed reporter genes in both rat and human brain cells, suggesting that mCMV might serve as a vector for gene transfer into brain cells of non-murine species. GFP e xpression was sufficiently strong that long axons, dendrites, and their ass ociated spines were readily detected in both living and fixed tissue, indic ating that mCMV reporter gene constructs may be useful for labeling neurons and their pathways.