Periodic Reporting for period 4 - DissectCMV (Creating a comprehensive functional map of the viral and host factors in HCMV infection)
Período documentado: 2024-12-01 hasta 2025-11-30
Human cytomegalovirus (HCMV) is one of the most common human viruses, infecting most people worldwide. In healthy individuals, infection usually causes no symptoms. However, HCMV can cause severe disease in people with weakened immune systems, such as transplant recipients, and is a leading infectious cause of birth defects when transmitted during pregnancy. A key feature of HCMV is its ability to establish lifelong latent infection, during which the virus remains hidden in the body and can later reactivate. Despite its major medical importance, there is currently no approved vaccine against HCMV and no antiviral drugs that specifically target the latent phase of infection.
A major barrier to progress has been an incomplete understanding of HCMV biology. HCMV has the largest genome of any virus known to infect humans, encoding hundreds of potential proteins, many of which were poorly characterized. In addition, although HCMV can infect many cell types, the outcome of infection varies widely. Cells of the myeloid lineage play a central role in viral latency and reactivation, yet the molecular reasons why some cells support latent infection while others allow productive viral replication were largely unknown at the start of this project.
The overall objective of the DissectCMV project was to address these gaps by creating a comprehensive functional map of viral and host factors that control HCMV infection. The project aimed to identify previously unrecognized functional elements in the viral genome, to understand the molecular determinants that govern whether infection becomes latent or productive, and to develop new technologies that enable systematic analysis of virus–host interactions. By the end of the project, these goals were achieved, leading to a revised understanding of HCMV latency as a quantitative and dynamic state shaped by early infection events and host cell properties, rather than a strictly silent or inactive phase.
A major barrier to progress has been an incomplete understanding of HCMV biology. HCMV has the largest genome of any virus known to infect humans, encoding hundreds of potential proteins, many of which were poorly characterized. In addition, although HCMV can infect many cell types, the outcome of infection varies widely. Cells of the myeloid lineage play a central role in viral latency and reactivation, yet the molecular reasons why some cells support latent infection while others allow productive viral replication were largely unknown at the start of this project.
The overall objective of the DissectCMV project was to address these gaps by creating a comprehensive functional map of viral and host factors that control HCMV infection. The project aimed to identify previously unrecognized functional elements in the viral genome, to understand the molecular determinants that govern whether infection becomes latent or productive, and to develop new technologies that enable systematic analysis of virus–host interactions. By the end of the project, these goals were achieved, leading to a revised understanding of HCMV latency as a quantitative and dynamic state shaped by early infection events and host cell properties, rather than a strictly silent or inactive phase.
From the beginning of the project, we combined advanced genomic technologies with molecular and cellular experiments to study HCMV infection in unprecedented detail. We systematically analyzed viral gene expression and function across different stages of infection, uncovering important roles for previously overlooked viral RNA elements. These findings demonstrated that the viral genome contains many functional components beyond the classical genes that were originally annotated.
A major focus of the project was understanding why HCMV establishes latent infection in some cells but not in others. By applying single-cell analysis techniques, we showed that latency is not characterized by a complete shutdown of viral activity. Instead, latent infection reflects reduced levels of viral gene expression that are strongly influenced by the state of the host cell and by early events during infection. We further discovered that viral entry efficiency plays a critical role in determining infection outcome, identifying a previously unrecognized upstream determinant of latency establishment.
In parallel, we developed a novel virus-encoded CRISPR screening platform that allows high-resolution identification of viral and host genes required at different stages of the viral life cycle. This technology overcomes key limitations of existing approaches and provides a powerful, broadly applicable tool for studying complex virus–host interactions. The platform has already been adopted and adapted by other researchers, extending its impact beyond HCMV research.
The results of the project were disseminated through publications in leading peer-reviewed journals, presentations at international scientific conferences, and the sharing of methods and resources with the wider research community. Together, the scientific discoveries and technological advances generated by DissectCMV significantly advance understanding of persistent viral infections and provide a foundation for future therapeutic strategies aimed at preventing or controlling HCMV-associated disease.
A major focus of the project was understanding why HCMV establishes latent infection in some cells but not in others. By applying single-cell analysis techniques, we showed that latency is not characterized by a complete shutdown of viral activity. Instead, latent infection reflects reduced levels of viral gene expression that are strongly influenced by the state of the host cell and by early events during infection. We further discovered that viral entry efficiency plays a critical role in determining infection outcome, identifying a previously unrecognized upstream determinant of latency establishment.
In parallel, we developed a novel virus-encoded CRISPR screening platform that allows high-resolution identification of viral and host genes required at different stages of the viral life cycle. This technology overcomes key limitations of existing approaches and provides a powerful, broadly applicable tool for studying complex virus–host interactions. The platform has already been adopted and adapted by other researchers, extending its impact beyond HCMV research.
The results of the project were disseminated through publications in leading peer-reviewed journals, presentations at international scientific conferences, and the sharing of methods and resources with the wider research community. Together, the scientific discoveries and technological advances generated by DissectCMV significantly advance understanding of persistent viral infections and provide a foundation for future therapeutic strategies aimed at preventing or controlling HCMV-associated disease.
Before this project, research on HCMV was limited by an incomplete understanding of how the virus establishes lifelong latent infection and by a lack of tools to systematically study the many genes encoded by its large genome. Latency was commonly viewed as a silent and inactive state, and it remained unclear why infection outcomes differed so markedly between cell types.
By the end of the DissectCMV project, the field had progressed substantially beyond this state of the art. The project demonstrated that HCMV latency is not a strictly inactive state but a dynamic condition characterized by reduced, rather than absent, viral activity. It further showed that early events during infection, including viral entry efficiency and the intrinsic state of the infected cell, play a decisive role in shaping infection outcome. These findings led to a revised conceptual framework for understanding viral persistence.
In addition, the project delivered new experimental tools that enabled systematic analysis of viral and host gene function throughout the entire infection cycle. These technologies overcame long-standing technical limitations and provided capabilities that were previously unavailable to the research community. Together, the biological insights and technological advances achieved by the end of the project significantly advanced understanding of persistent viral infections and established a strong foundation for future research and therapeutic development aimed at controlling HCMV-associated disease.
By the end of the DissectCMV project, the field had progressed substantially beyond this state of the art. The project demonstrated that HCMV latency is not a strictly inactive state but a dynamic condition characterized by reduced, rather than absent, viral activity. It further showed that early events during infection, including viral entry efficiency and the intrinsic state of the infected cell, play a decisive role in shaping infection outcome. These findings led to a revised conceptual framework for understanding viral persistence.
In addition, the project delivered new experimental tools that enabled systematic analysis of viral and host gene function throughout the entire infection cycle. These technologies overcame long-standing technical limitations and provided capabilities that were previously unavailable to the research community. Together, the biological insights and technological advances achieved by the end of the project significantly advanced understanding of persistent viral infections and established a strong foundation for future research and therapeutic development aimed at controlling HCMV-associated disease.