title: Investigating early events during enveloped RNA virus infection
title: understanding cell tropism, routes of infection and virus utilization of cellular receptors
titleType: Subtitle
Creators: name: Bohan, Dana
Publisher: name: University of Iowa
Year: 2025
Subjects: Dendritic cells
Ebola
Phosphatidylserine
SARS-CoV-2
Tropism
Viral Glycoprotein
public abstract

description: Enveloped viruses are the root of many issues in human society, with infections driving disease, stigma, financial burden, persistent sequelae, and death. Understanding the mechanisms by which viruses initiate human disease is critical to designing effective tools with which we can counter negative outcomes or prevent infection in the first place. In this work we describe three sets of novel observations regarding two major human pathogens: SARS-CoV-2 and Ebola virus (EBOV).
description: Chapter II details a previously undescribed mechanism of SARS-CoV-2 entry that relies on phosphatidylserine (PS) receptors and PS in the viral envelope. We show that 1) this class of host receptors serves to bind to viral PS and facilitate virion attachment and internalization, 2) AXL is the primary PS receptor enhancing SARS-CoV-2 entry in the absence of TMPRSS2, and 3) preventing AXL internalization therapeutically reduces infection, inhibits replication, and significantly lowers the amount of infectious virus produced in human lung cells. The implications of these data are manifold, from identifying an undescribed cofactor for SARS-CoV-2 infection with the potential to expand the range of infectable cells and the conditions under which such entry is possible, to the realization of a potential therapy for COVID-19 that has already shown some promise in clinical settings. The observations in this chapter serve to expand the number of pathogens that utilize PS receptors to enhance entry to include three betacoronaviruses and imply that future pandemic betacoronaviruses may be similarly susceptible to PS receptor-based inhibition of entry.
description: Chapter III centers around the novel observation that EBOV glycoprotein (GP) is sufficient to allow infection of mammalian skin. Previously supported only by post-hoc epidemiological studies, our data conclusively demonstrate that 1) EBOV GP can enable infection of keratinocytes in-vitro and in the context of the full epidermis, 2) EBOV GP is sufficient to penetrate the dermoepidermal junction and subsequently infect cells in the dermis, and 3) decornification and/or abrasion of the epidermis lower the barrier to EBOV GP-mediated infection. These data have major impacts on our understand of the readiness with which EBOV can transmit from person to person and to the potential avenues by which infection may be established. We thus provide insights for a route of infection that was previously uncharacterized with clear repercussions for public health and epidemiology for this highly lethal pathogen.
description: Chapter IV delineates the tropism of the EBOV GP with specific examination of dendritic cells (DCs). Long believed to be an indispensable cell type for EBOV replication and dissemination, we describe the first subset-level evidence of splenic DC infection in an EBOV GP-dependent manner. We show that 1) EBOV GP is sufficient to infect cDCs but does not confer an enhanced tropism for splenic conventional DCs (cDCs) relative to the broad tropism of Vesicular stomatitis virus glycoprotein (VSV G), 2) the presence of EBOV GP specifically elicits an accumulation of monocyte-origin DCs (moDC) in the murine spleen, and 3) this population of moDC is highly permissive to recombinant VSV-EBOV GP (rVSV/EBOV) infection, supporting high levels of viral replication virion production, and the depletion of these cells during infection significantly improves all disease and mortality readouts. These results show that EBOV infection of cDCs does not exceed the typical rates for broadly tropic viruses, and thus the importance of cDCs as early targets of infection may have been overestimated. We also demonstrate a novel role for moDC during EBOV GP-mediate infection, suggesting that this population of elicited antigen presenting cells (APCs) may play a pathogenic role during bona-fide EBOV infection and represent an interesting target for therapeutic abatement.
description: Altogether we present three complete sets of observations that lay groundwork for deployment of therapeutic and/or epidemiological modalities. By leveraging these observations we may be able to: develop PS receptor-targeting therapies to be better equipped should the next pandemic pathogen utilize these receptors during entry as EBOV and SARS-CoV-2 have; update public health messaging during EBOV outbreaks regarding the potential for skin-skin transmission and reduce the likelihood with which the virus can be transmitted; critically examine the role of cDC and moDC during EBOV infection, viewing them not as early footholds for the virus, but rather as elicited virus factories that should be targeted on a subset-specific level to reduce pathology.