Saliva Composition, Aerosolization and DRying Impact on Viral transmission – SCADRIV

Aerosols exchanged between asymptomatic carriers are the most significant transmission route for the SARS-CoV-2 virus, responsible for the COVID-19 pandemic. But successful transmission depends on the maintenance of viral infectivity during aerial transport. Understanding the coupling between the biology of a successful viral transmission and the physico-chemistry at play in aerosols airborne evaporation and viral delivery holds the keys to define the spatiotemporal aspects of transmission risk. Airborne transmission, from source to an infection site in a host, has never been studied as a whole because it comes with technical and conceptual challenges requiring strong transdisciplinary skills. SCADRIV goes well beyond the state of the art in virology and will decipher the link between viral infectivity and infection mechanisms on epithelial cells and the drying history at the scale of its transporting vessel, the droplet nucleus. Our interdisciplinary teams of biophysicists, virologists and biochemists will unravel this fundamental biological process via three specific aims. We will explore in a first phase of the project the extension dynamics of saliva filaments and its relationship to its composition, to determine droplet size and viral distribution. In a second phase, we will decipher how the drying history of a single droplet dictates its final structure and viral infectivity. Finally, we will interrogate how the rehydration of these droplet nuclei influences viral transport, aggregative state, and, successful host cell invasion. SCADRIV will address critical biological questions regarding the impact of the physicochemical history of the viral particles on the cell surface attachment, receptor engagement and endocytosis. This synergistic project, at the interface between physics and biology, shall open new conceptual understandings on the very first steps of virus-host interactions and be relevant to asymptomatic transmission of other airborne pathogens.