Research Summary: Human cytomegalovirus (CMV) is a -herpesvirus that can cause morbidity and mortality in immuno- compromised individuals. Following primary infection, which is usually benign in immunocompetent individuals, CMV establishes latency and can periodically reactivate. CMV disease can manifest mild to severe disease condition in immunocompromised individuals. In newborns, CMV-associated neurological disorders represent the leading cause of birth defects affecting infants worldwide. Additionally, CMV causes gastrointestinal disorders, pneumonia, CMV syndrome, and end-organ disease in transplant recipients and is linked to early vascular damage resulting from infection of endothelial cells and macrophages. Ganciclovir is commonly used as an anti-CMV drug, but it has limitations including poor oral bioavailability, dose-related toxicity, selection of drug resistant viral mutants, and is precluded for use in pregnant women. The numerous shortcomings of the current treatment to prevent or treat CMV disease warrant the development of more potent and safer anti-CMV therapies. Immunoglobulin-based therapy is a promising pharmaceutical option for anti-CMV therapy based on its specificity, safety profile, and pharmacological activity. The overall objective of the grant is to evaluate the effectiveness of CMV neutralizing monoclonal antibodies (mAbs) to inhibit virus dissemination. We hypothesize that CMV neutralizing mAbs that block cell-free infections have the potential to effectively inhibit virus dissemination. To test this hypothesis, we will complete the following specific aims: 1) Delineate the inhibitory capacity of CMV neutralizing mAbs to determine the mechanism of action of neutralizing mAbs targeting the envelope proteins. And 2) Characterize neutralizing mAbs that effectively inhibit virus dissemination using in vitro and in vivo model systems. We plan to determine the mAbs that effectively inhibit viral dissemination using physiological-like assays including cell-associated spread of patient derived clinical strains, viral spread from latently infected cells, and an in vivo animal model. Importantly, we are expecting to define the critical steps of virus entry that are amenable to therapeutic intervention and identify mAbs as potential therapeutic to limit CMV-associated diseases.