Abstract: Filoviruses such as Ebola virus (EBOV) are found on the skin's surface at late times of infection when viremia is high. Evidence indicates that skin-associated virus is an important source of virus transmitted to others. Yet, how virus arrives at the surface is not well understood. Our preliminary studies suggest that EBOV can traffic to the surface of the skin by infecting both dermal and epidermal cell populations within the skin and that this route of virus delivery to the skin's surface is important in vivo. Yet, which cells within the skin support filovirus replication and are principally responsible for virus load are unknown. Here, we seek to understand EBOV interactions with skin as it egresses from the body. We will also evaluate if EBOV is able to enter through the intact or abraded skin surface. We hypothesize that direct infection of cells within the skin serves as an important route of EBOV transmission. To examine this, we will test the following aims. Purified primary skin cells (e.g. keratinocytes, fibroblasts, and antigen presenting cells) will be examined for their support of EBOV infection and we will determine if these same populations are infected in skin explants. Further, we will determine if known cell surface receptors are expressed in permissive skin cells and explants and if inhibition of virus interactions with those receptors blocks EBOV infection. We will also assess the timing of skin involvement in EBOV infection in vivo in mice and in macaques. At the completion of these important studies, an understanding of EBOV interactions with skin will be developed and a new model platform will be established for studying filovirus infections of highly relevant human tissue.