Explaining the contagious nature of measles virus - PROJECT SUMMARY/ABSTRACT: Our goal is to understand why measles virus (MeV) is the most contagious human virus. MeV is a worldwide leading cause of vaccine-preventable deaths. Understanding what sets its mechanism of transmission apart from other viruses is important. Humans are the only natural reservoir for MeV. Thus, a critical challenge for MeV study is identification of representative model systems. Well-differentiated primary cultures of airways epithelial cells from human donors (HAE) provide a physiological relevant model of human airways. In HAE, direct cell-to-cell spread of MeV results in well-defined foci termed infectious centers that ultimately dislodge from the epithelial layer en masse. Of the many respiratory viruses screened to date, only MeV results in infectious center formation in HAE. We hypothesize that infectious center formation, release, and environmental contamination are vital steps for efficient host-to-host spread of MeV. In Aim 1, we address fundamental questions about the formation of infectious centers. We hypothesize that MeV targets mitochondria and induces mitophagy. Release of mitochondrial DNA into the cytoplasm is detected by the DNA sensing molecule cGAS which initiates a cascade that stimulates antiviral genes. Next, we ask where intracellular assembly of MeV occur in HAE. Again, preliminary data suggest that mitochondria may play an important role in this process. This model will challenge the currently accepted paradigm of how MeV replicates in airway epithelial cells. In Aim 2, we demonstrate that infectious center formation can be approximated by expression of only 2 MeV proteins: Fusion (F) and Hemagglutinin (H). We use replication deficient adenoviral vectors for delivery. Modular expression of adenoviral expressed viral proteins allows numerous advantages including: 1) rapid generation of recombinant expression vectors; 2) low risk that genetic manipulations of transgenes will impact vector titer; and 3) many combinations of viral protein comparisons are possible. This novel tool will allow for the substitution of proteins with known mutations that will alter complex formation; as well as, substitution of orthologous proteins from other viruses, such as respiratory syncytial virus, Nipah virus, and Sendai virus. In Aim 3 we determine how long aerosolized MeV remains viable under common environmental conditions. Dislodged infectious centers could protect the virus from desiccation and prolong the infectious period. We develop tools to aerosolize cell-associated or cell-free MeV. Subsequently, the infectivity will be compared following exposure to environmental conditions, (e.g., desiccation or temperature). Defining the stability of MeV across different environmental conditions could inform policy to reduce transmission. In summary, fundamental biological questions remain about the highly contagious MeV. Within airway epithelial cells, MeV undergoes its final amplification and prepares itself for spread to the next host. This final step is likely key to the contagious nature of MeV.
