This project focuses on novel cytomegalovirus (CMV)-encoded immunomodulators and host defense pathways with which they intersect during initial stages of infection to affect outcomes in both immunocompetent and immunodeficient hosts. Human CMV remains the single most important vaccine preventable cause of congenital disease as well as a significant pathogen in individuals with immune deficit. Modulation of host innate and adaptive immunity contributes to increased disease risk. Myeloid lineage cells are important targets of viral escape and exploitation tactics, starting at the initial encounter and proceeding through latency. Murine CMV provides a tractable model yielding mechanistic insights into pathogenesis relevant to human CMV and host defense strategies broadly relevant to many human pathogens. The host defense value of programmed necrotic death has recently emerged along with the fascinating observation that extrinsic programmed cell death pathways are dispensable for core aspects of the virus-host interaction, including immune control of viral infection. In the next period, we will specifically investigate the contribution of extrinsic deathpathways in monocyte-derived cell function. The contribution programmed cell death pathways, as well as inflammation spawned by these pathways, will be dissected in three substantive and interlaced directions:
Specific Aim 1 Host control of viral infection in the absence of caspase 8-regulated death pathways. (1.a) Determine the role of caspase 8 and RIP3-regulated pathways to monocyte function. (1.b) Assess the impact of inflammatory monocyte suppression of antiviral T cell immunity. (1.c) Investigate cell death pathways control of viral dissemination by patrollingmonocytes.
Specific Aim 2 Viral control of apoptotic and programmed necrotic cell death pathways. (2.a) Differentiation of cell types subjected to extrinsic apoptosis or programmed necrosis. (2.b) Assess the regulation of cell death pathways in endothelial cells and monocytes.
Specific Aim 3 Defining the DAI-RIP3 pathway of programmed necrosis. (3.a) Determine the role of DAI as a pathogen sensor of infection via dsDNA. (3.b) Characterize DAI-RIP3 complex-dependent death. (3.c) Differentiate RIP1-RIP3 from DAI-RIP3 programmed necrosis in host defense. (3.d) Evaluate candidate RIP3 kinase inhibitors

Public Health Relevance

Murine cytomegalovirus (CMV) provides a tractable mammalian model that has unveiled overarching principles about human CMV pathogenesis. Key insights into viral immune modulation and host defense have consistently emerged in this genetically tractable rodent to be applicable to humans. In the past funding period, this virus system has unveiled novel functions of monocytes druing viral infection as well as new host defense pathways and viral escape mechanisms. These have had a broad impact on the general fields of viral pathogenesis, viral immunology and mammalian development. During the last funding period, we discovered that programmed necrosis is a bone fide host defense pathway that runs parallel to apoptosis, identified a novel viral inhibitor that prevents RIP1-RIP3 complex-dependent necroptosis as well as RIP3-DAI complex dependent programmed necrosis. We identified DAI as a RIP3 partner and candidate dsDNA sensor driving necrotic death. The project unveiled the fact that caspase 8-controlled pathways are dispensable for development, homeostasis and antiviral T cell immunity, and most likely evolved as components of host defense in response to viral immunomodulators.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
High Priority, Short Term Project Award (R56)
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Study Section
Virology - B Study Section (VIRB)
Program Officer
Beisel, Christopher E
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Emory University
Schools of Medicine
United States
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Crosby, Lynsey N; McCormick, A Louise; Mocarski, Edward S (2013) Gene products of the embedded m41/m41.1 locus of murine cytomegalovirus differentially influence replication and pathogenesis. Virology 436:274-83
Kaiser, William J; Upton, Jason W; Mocarski, Edward S (2013) Viral modulation of programmed necrosis. Curr Opin Virol 3:296-306
Upton, Jason W; Kaiser, William J; Mocarski, Edward S (2012) DAI/ZBP1/DLM-1 complexes with RIP3 to mediate virus-induced programmed necrosis that is targeted by murine cytomegalovirus vIRA. Cell Host Microbe 11:290-7
Daley-Bauer, Lisa P; Wynn, Grace M; Mocarski, Edward S (2012) Cytomegalovirus impairs antiviral CD8+ T cell immunity by recruiting inflammatory monocytes. Immunity 37:122-33
Mocarski, Edward S; Upton, Jason W; Kaiser, William J (2011) Viral infection and the evolution of caspase 8-regulated apoptotic and necrotic death pathways. Nat Rev Immunol 12:79-88
Kaiser, William J; Upton, Jason W; Long, Alyssa B et al. (2011) RIP3 mediates the embryonic lethality of caspase-8-deficient mice. Nature 471:368-72
Upton, Jason W; Kaiser, William J; Mocarski, Edward S (2010) Virus inhibition of RIP3-dependent necrosis. Cell Host Microbe 7:302-13