Mouse cytomegalovirus in developing brain tissue: Analysis of 11 species with GFP-expressing recombinant virus

Abstract

Cytomegaloviruses (CMVs) are species-specific large double-stranded DNA viruses. Mouse and human CMVs have a similar morphology, similar gene sequence, and exert similar cellular effects, but the replication of the virus outside its primary host species is limited. This may confer upon CMV certain advantages for expression of foreign genes or cellular labels in brain cells of nonhost species. We examined the ability of recombinant mouse (m)CMV expressing green fluorescent protein (GFP) to serve as a vector for transgene expression in developing neurons and glia outside the normal host species. For comparative purposes, 11 species were examined. Mouse CMV reporter gene expression was particularly strong in the developing brain of its normal host species, mouse, where it replicated in cultures and brain slices, leading to cell death. All mammalian species tested (human, rat, gerbil, hamster, mouse) showed reporter gene expression after mCMV infection. High levels of mCMV infection were also found in chicken central nervous system cells in vitro, and a low level of mCMV expression was found after an initial delay in turtle neurons and glia. No mCMV reporter gene expression was found in frog cells or aplysia neurons or glia or in drosophila or fungal cells. Infection of nonmouse neurons by low concentrations of mCMV led to strong expression of GFP in dendrites and axons with normal morphology. Despite the lack of replication, high doses of mCMV induced morphologic changes in neurons and glia from hamster and rat brain slices, leading to cells rounding up, and to the formation of giant cells consisting of an aggregate of many cells fused together into a syncytium. In contrast, in human hippocampal slices, GFP-expressing cells infected with mCMV had a relatively normal appearance 12 days after inoculation. To determine whether a CMV from another species could serve as a vector for gene transfer, a recombinant human CMV-expressing GFP was used for transgene expression in rat brain cells in vitro. Cytomegaloviruses thus have potential as useful vectors for gene transfer and labeling central nervous system cells, with the actions of CMV being dependent on a number of factors.

The Amount of Immature Glial Cells in Organotypic Brain Slices Determines the Susceptibility to Murine Cytomegalovirus Infection

“…In a previous report, we showed that the susceptibility to MCMV infection decreased in brain slice cultures with development of the brain , and this was confirmed by van den Pol et al (2000). It has been reported that resistance to MCMV infection is due to the development of host defense mechanisms such as NK cells (Brutkiewicz and Welsh, 1995).…”

“…Similarly, the rate of viral replication in glial cultures was significantly higher than that in neuronal cultures (van den Pol et al, 1999). Although the brain slice culture contains cells susceptible to MCMV infection, such as glial cells and endothelial cells, in addition to neural progenitor cells, the susceptibility to CMV tends to be confined to the SVZ and marginal area in the brain slice cultures.…”

“…૽ p Ͻ 0.05 and ૽૽ p Ͻ 0.01. walls, including the ventricular zone and SVZ (Becroft, 1981;Kosugi et al, 2000;Li and Tsutsui, 2000;Perlman and Argyle, 1992;Shinmura et al, 1997aShinmura et al, , 1997bvan den Pol et al, 2000).…”

Cytomegalovirus InducesInterferon-Stimulated Gene Expression and Is Attenuated by Interferon in the DevelopingBrain

“…Human CMV (hCMV) infections in the developing brain can lead to mental retardation, epilepsy, microcephaly, microgyria, hydrocephalus, and deafness (4, 21, 37). The developing brain is particularly sensitive to CMV infection (6,29,54,55,58) due to both the immature state of the systemic immune system and a preference of CMV for developing glia and neurons (61). CMV in the mature brain is less of a concern, except in immunocompromised individuals (22,23,32).…”

CD4+T-Cell Reconstitution Reduces Cytomegalovirus in the Immunocompromised Brain

“…Ϫ GFP ϩ ) strongly and rapidly expresses green fluorescent protein under control of the human elongation factor 1a promoter inserted at the immediateearly gene 2 (IE2) site (63). Expression of GFP enables the direct detection of MCMV in living and fixed, unstained tissue.…”