ABSTRACT
Infection with cytomegalovirus (CMV) shows a worldwide high prevalence with only immunocompromised individuals or newborns to become symptomatic. The host's constitution and the pathogen's virulence determine whether disease occurs after infection. Mouse CMV (MCMV) is an appreciated pathogen for in vivo investigation of host-pathogen interactions. It has recently been reported that a single base pair deletion can spontaneously occur in the open reading frame of MCMV-encoded chemokine 2 (MCK2), preventing the expression of the full-length gene product. To study the consequences of this mutation, we compared the Mck2-defective reporter virus MCMV-3D with the newly generated repaired Mck2(+) mutant MCMV-3DR. Compared with MCMV-3D, neonatal mice infected with MCMV-3DR showed severe viral disease after lung infection. Viral disease coincided with high viral activity in multiple organs and increased virus replication in previously described nodular inflammatory foci (NIF) in the lung. Notably, MCMV-3DR showed tropism for alveolar macrophages in vitro and in vivo, whereas MCMV-3D did not infect this cell type. Moreover, in vivo depletion of alveolar macrophages reduced MCMV-3DR replication in the lung. We proposed an Mck2-mediated mechanism by which MCMV exploits alveolar macrophages to increase replication upon first encounter with the host's lung mucosa.
Subject(s)
Chemokines, CC/metabolism , Herpesviridae Infections/virology , Inflammation/virology , Lung Diseases/virology , Lung/pathology , Macrophages, Alveolar/virology , Muromegalovirus/physiology , Solitary Pulmonary Nodule/virology , Viral Proteins/metabolism , Animals , Animals, Newborn , Cells, Cultured , Chemokines, CC/genetics , Macrophages, Alveolar/immunology , Mice , Mice, Inbred C57BL , Mice, Knockout , Muromegalovirus/pathogenicity , Sequence Deletion/genetics , Viral Proteins/genetics , Viral Tropism/genetics , Virulence/genetics , Virus Replication/geneticsABSTRACT
BACKGROUND: There is ongoing controversy about the transdifferentiation of hematopoietic stem cells (HSC) into different tissues such as mesenchymal cells. This transdifferentiation or 'plasticity' would be an appealing concept for many therapeutic strategies. While studies in the murine model show encouraging results, reports from clinical allogeneic stem cell transplantations do not support the concept of HSC plasticity. Our aim was to determine whether transplantation of transduced autologous marrow CD34+ cells leads to long-term engraftment of gene-marked cells with mesenchymal characteristics in the baboon. METHODS: We analyzed marrow of two baboons that had received green fluorescence protein (GFP)-marked CD34+ autologous marrow cells after myeloablative conditioning. Marrow was obtained 1 and 2.5 years after transplantation and adherent CD11a- (pan-leukocyte Ab) cells were cultured for 3 weeks. Cultures were then analyzed by flow cytometry and fluorescence microscopy for the presence of GFP+ cells. For further analysis fresh and cultured cells were also labeled with multiple Ab and functional analysis was performed. RESULTS: Both animals showed persistent and stable GFP marking by flow cytometry in peripheral blood leukocytes as well as in CD34+ marrow cells at 1 and 2.5 years after transplantation. There was no evidence of GFP+ mesenchymal cells by either flow cytometry or fluorescence microscopy, while functional and phenotypical analysis identified mesenchymal stem cells in these cultures. DISCUSSION: We conclude that genetically modified CD34+ cells do not contribute to the adherent marrow-derived mesenchymal cell population after autologous transplantation.
