Viruses cause diseases ranging from the common cold to the deadly and highly infectious Ebola disease. Their "modus operandi" is to enter healthy cells, often like a Trojan Horse, by hijacking normal physiological processes, tricking the cell to let them in. For this reason, a principal difficulty in designing therapies against viruses lies in the fact that attempts to stop them from entering a cell are also likely to affect normal physiological processes. For example, the Ebola virus infects healthy cells by disguising itself as debris (wastes or remains) from dead cells. Healthy cells whose normal function is to clear up this debris mistakenly take up Ebola and are thus infected. But there are always some differences between a virus and debris particles suggesting that, if studied carefully, it might be possible to design therapies that can block specific virus entry while leaving normal physiological processes essentially intact. In order to be successful in this attempt, it is necessary to understand virus uptake processes in quantitative detail both experimentally and theoretically, and particularly the latter, which is the main goal of this project. Building on separate studies that use microscope based technologies to measure binding forces between molecules, the focus of this project is to develop understanding of the behavior of collections of adhesion molecules (proteins on cell surfaces that cause cells to bind to other cells or particles), and ultimately to develop a predictive model for how an entire virus particle attaches to a cell prior to its uptake. An important part of this work is modeling the deformation of virus and cell particles in order to quantitatively measure their properties. If successful, this project will contribute to establishing an experimentally validated, quantitative connection between biology based models for virus entry into cells and the properties of the virus and the cell. The interdisciplinary nature of this research program will provide an excellent educational and research opportunity for graduate and undergraduate students. Working with the Da Vinci Science Center in Allentown, the investigators will design a new exhibit demonstrating the physical and mechanical details of virus uptake and how its study could lead to potential therapies or a cure. (The Da Vinci Science Center is an independent non-profit organization that promotes hands-on science learning through inquiry, highlights vibrant and important career opportunities in science available to every young person, and encourages all people to be curious and creative.)
The goal of this project is to establish an experimentally informed predictive and quantitative model of the Ebola Virus (EBOV)-host cell interactions at the molecular through single-virus levels. While EBOV-host cell attachment has been shown to depend critically on the molecular biophysics of interaction between receptors on the cell surface and the outer coat of the virus, the quantitative understanding essential for guiding the development of therapies that would prevent EBOV from attaching to, and thus from entering a cell, is completely lacking. Recent work has established the importance of TIM family proteins and the geometry and mechanical properties of its mucin-like stalk domain (MLD). Building on these recent findings, further progress can be made by using experimental and theoretical molecular biophysics to uncover a quantitative understanding of the molecular, cellular, and biophysical mechanisms of EBOV attachment to a host cell. Building on separate studies that utilize single-molecule force spectroscopy to characterize experimentally how TIM family proteins interact with EBOV, this project will develop biophysical models that show how single-molecule biomechanical properties, and how the properties of the MLD, such as its length, rigidity, and charge density, control TIM mediated cellular/viral membrane adhesion and engulfment. The model will be developed in three phases. 1) At the Intermolecular Scale, the adhesion between a single TIM-1 and the viral membrane is studied using coarse-grained Brownian Dynamics Models to predict interaction potentials. 2) At the Intermediate Scale, the glycocalyx will be added to the cell surface and glycoproteins will be added on the virus surface to establish the role of the mechanical properties of the MLD stalk, using a course grained model solved with Brownian Dynamics at 300K. 3) At the Mechanics of Whole Virus and Internalization Scale, findings at the Intermolecular and Intermediate Scales will be incorporated at the scale of the viral particles and deformable membranes will be added, with the goal of describing the virus adhesion process, including effects due to membrane bending and tension, using a combination of semi-analytic models and coarse-grained models. The project will thus elucidate quantitatively - for the first time - the biophysical mechanism of EBOV-host cell interaction, providing potential new targets for antiviral drug development. While the focus of the focus of this project is on the EBOV, the approach taken will be applicable to other related virus-host cell interactions.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
