Single cell detection of latent cytomegalovirus reactivation in host tissue
The molecular mechanisms leading to reactivation of latent cytomegalovirus are not well understood. To study reactivation, the few cells in an organ tissue that give rise to reactivated virus need to be identified, ideally at the earliest possible time point in the process. To this end, mouse cytomegalovirus (MCMV) reporter mutants were designed to simultaneously express the red fluorescent protein mCherry and the secreted Gaussia luciferase (Gluc). Whereas Gluc can serve to assess infection at the level of individual mice by measuring luminescence in blood samples or by in vivo imaging, mCherry fluorescence offers the advatage of detection of infection at the single cell level. To visualiz…
Ablation of the Regulatory IE1 Protein of Murine Cytomegalovirus Alters In Vivo Pro-inflammatory TNF-alpha Production during Acute Infection
Little is known about the role of viral genes in modulating host cytokine responses. Here we report a new functional role of the viral encoded IE1 protein of the murine cytomegalovirus in sculpting the inflammatory response in an acute infection. In time course experiments of infected primary macrophages (MΦs) measuring cytokine production levels, genetic ablation of the immediate-early 1 (ie1) gene results in a significant increase in TNFα production. Intracellular staining for cytokine production and viral early gene expression shows that TNFα production is highly associated with the productively infected MΦ population of cells. The ie1- dependent phenotype of enhanced MΦ TNFα production …
The Mouse Cytomegalovirus Gene m42 Targets Surface Expression of the Protein Tyrosine Phosphatase CD45 in Infected Macrophages
The receptor-like protein tyrosine phosphatase CD45 is expressed on the surface of cells of hematopoietic origin and has a pivotal role for the function of these cells in the immune response. Here we report that following infection of macrophages with mouse cytomegalovirus (MCMV) the cell surface expression of CD45 is drastically diminished. Screening of a set of MCMV deletion mutants allowed us to identify the viral gene m42 of being responsible for CD45 down-modulation. Moreover, expression of m42 independent of viral infection upon retroviral transduction of the RAW264.7 macrophage cell line led to comparable regulation of CD45 expression. In immunocompetent mice infected with an m42 del…
Superior induction and maintenance of protective CD8 T cells in mice infected with mouse cytomegalovirus vector expressing RAE-1γ.
Due to a unique pattern of CD8 T-cell response induced by cytomegaloviruses (CMVs), live attenuated CMVs are attractive candidates for vaccine vectors for a number of clinically relevant infections and tumors. NKG2D is one of the most important activating NK cell receptors that plays a role in costimulation of CD8 T cells. Here we demonstrate that the expression of CD8 T-cell epitope of Listeria monocytogenes by a recombinant mouse CMV (MCMV) expressing the NKG2D ligand retinoic acid early-inducible protein 1-gamma (RAE-1γ) dramatically enhanced the effectiveness and longevity of epitope-specific CD8 T-cell response and conferred protection against a subsequent challenge infection with List…
Frequent coinfection of cells explains functional in vivo complementation between cytomegalovirus variants in the multiply infected host.
In contrast to many other virus infections, primary cytomegalovirus (CMV) infection does not fully protect against reinfection. Accordingly, clinical data have revealed a coexistence of multiple human CMV variants/ strains in individual patients. Notably, the phenomenon of multiple infection was found to correlate with increased virus load and severity of CMV disease. Although of obvious medical relevance, the mechanism underlying this correlation is unknown. A weak immune response in an individual could be responsible for a more severe disease and for multiple infections. Alternatively, synergistic contributions of variants that differ in their biological properties can lead to qualitative…
Cytomegalovirus vector expressing RAE-1γ induces enhanced anti-tumor capacity of murine CD8+ T cells
Designing of CD8 T cell vaccines which would provide protection against tumors is still considered a great challenge in immunotherapy. Here we show a robust potential of a cytomegalovirus (CMV) vector expressing the NKG2D ligand RAE-1γ as CD8 T cell-based vaccine against malignant tumors. Immunization with the CMV vector expressing RAE-1γ delayed tumor growth or even provided complete protection against tumor challenge in both prophylactic and therapeutic settings. Moreover, a potent tumor control in mice vaccinated with this vector can be further enhanced by blocking the immune checkpoints TIGIT and PD-1. Expression of RAE-1γ by the CMV vector potentiated expansion of KLRG1+ CD8 T cells wi…