Murine cytomegalovirus infection of reaggregate cultures of fetal mouse brain

We used cultures of reaggregate embryonic mouse brain cells to study murine cytomegalovirus (MCMV) infection of neural tissues. After 21 to 28 days in culture, aggregates were infected with MCMV and studied sequentially for 14 days using virus assay, electron microscopy and indirect immunofluorescence. Infectious virus could be recovered from aggregate cultures beginning three days after infection, and peak virus titers were observed on day 7 in aggregate tissues and on day 14 in culture fluids. By transmission electron microscopy, intranuclear viral nucleocapsids were identified in neural cells at the periphery of the aggregates on day 3. Infection then spread centripetally into aggregate tissues so that by day 14 the majority of neural cells contained intranuclear inclusions, numerous nucleocapsids, and mature virus particles. Virion production in neural cells was the result of a sequence of events that included budding of nucleocapsids from the nucleus and envelopment of cytoplasmic virus particles by membranes of the Golgi apparatus. These studies indicate that MCMV infection of murine brain aggregate cultures is a potentially useful in vitro system for the study of CMV infections of neural tissue.