Defining Marburg Virus interactions with skin

Project Summary/Abstract: Nearly one-third of all recorded Marburg virus (MARV) outbreaks have occurred in the last five years and the World Health Organization classifies MARV and related Filoviridae members, such as Ebola virus (EBOV) as pathogens that pose potential Public Health Emergencies of International Concern. With no licensed vaccine or therapeutics available, there is an urgent need to better understand the interactions of MARV with the human body. For instance, better elucidation of MARV's cellular tropism and transmission pathways is essential for understanding virus movement within the body and subsequent pathogenesis. Clinical reports indicate that MARV infection is more frequently associated with cutaneous rash than EBOV and MARV antigens and viral particles have been detected in bat skin and in skin from a human patient who succumbed to MARV infection, suggesting that skin, the largest organ in the human body, supports MARV infection. However, detailed examination of MARV interactions with skin has yet to be performed. Here, we propose to investigate MARV trafficking to and infection of skin using three different model systems. We hypothesize that direct MARV infection of skin cells is not only responsible for the viral load present in skin, but may also contribute to systemic infection, representing a potential conserved mechanism of filovirus pathogenesis. Further, infection of skin likely serves as a critical route of MARV trafficking to the surface of the skin where virus becomes available for host-to-host transmission. Finally, we propose that MARV infection of skin may be immunologically silent, with few proinflammatory responses elicited despite the production of significant viral loads within the skin. Through our studies investigating EBOV infection of skin, we have developed models and expertise that will be used to experimentally characterize MARV infection of skin for the first time through Aim 1 where we will determine viral load and innate immune responses within the skin during MARV infection and Aim 2 where we will identify skin populations contributing to MARV infection and determine the impact of phosphatidylserine receptors (PSR) loss on viral load. In these studies, we will employ nonhuman primates (NHPs), a low-containment mouse model, and human skin explants (HSE) to characterize MARV infection of the skin. Cellular tropism and infection dynamics will be defined by determining viral loads and titers, co-staining MARV-infected skin samples for viral antigen and cell markers and flow cytometric analysis of virally-infected cells within the skin over time. Additionally, the innate immune responses elicited by MARV infection will be explored in two different model systems. Finally, we will investigate virus trafficking to and infection of the skin of five PSR-deficient mouse lines using a low-containment virus model to explore host receptor utilization. These studies will provide the first comprehensive analysis of MARV interactions with skin and establish whether infection of this organ has virus- specific features. By addressing this urgent gap in MARV biology, this work will inform strategies for transmission control and potentially guide the development of antiviral therapeutics.