Projects Experimental Virology

Fifty to 90 percent of all HCV infections are chronic. The association of virus with lipoproteins contributes to the persistence by directly influencing virus entry into the liver cell and also by protecting it from neutralizing antibodies.
We are investigating host factors and viral factors that influence the association of the virus with lipoproteins to elucidate their role in viral persistence. The interaction of HCV with lipoproteins begins during virus assembly. This occurs in the so-called lipid droplets, cellular organelles that store lipids (Figure 1: Vieyres et al. PLoS Pathogens 2016). HCV uses cellular lipases such as ATGL to mobilize lipids for the formation of HCV lipoviroparticles (Vieyres et al. PLoS Pathogens 2020). 

Following the release of HCV particles, circulating lipoproteins are incorporated into these particles (Bankwitz et al. J Hepatol 2017). This maturation process promotes both viral attachment to liver cells as well as antibody protection (Figure 2 and Bankwitz et al. J Hepatol 2017). Supported by SFB900, we are investigating the cellular and viral proteins that mediate the interaction between HCV and lipoproteins. Ultimately, the insights gained into how HCV escapes the antibody response with the help of lipoproteins will guide the development of a vaccine against HCV

Publications

In a small number of all HCV patients, strong immune responses lead to control and eventual elimination of the viral infection. However, the properties of this natural immune protection are not well understood. Most importantly, the role of antibodies in HCV protection is not clearly defined. Therefore, supported by the DZIF HCV vaccine project, we are investigating how antibodies protect against HCV infection. What are the properties of the antibodies that are generated during HCV infection that heals? How do these antibodies differ from those produced when the infection becomes chronic? Are different areas of the viral envelope proteins attacked? What factors influence the formation of particularly good antibodies, and how good are the antibodies that induce vaccine candidates? We are investigating these questions in order to develop a vaccine that induces particularly good protective antibodies.

To develop a precise measure of protective immunity, we first isolated antibodies from the blood of 104 HCV-positive patients and then screened them for their neutralizing properties against as many different HCV variants as possible. Using bioinformatics methods, we learned that variants respond differently to antibodies regardless of their genetic background. Our results may help to develop a broadly effective vaccine in the future and to assess the efficacy of vaccine candidates. 

Tour to HCV neutralization space. Final stop: B-cell vaccine | Nature Portfolio Webcasts

Publications

HCV has a narrow species tropism and naturally infects only humans. The factors that drive this tropism are not yet fully understood. Therefore, the lack of immunocompetent small animal models for HCV is a major obstacle to vaccine development, as it prevents prioritization of vaccine candidates in advance of costly clinical development. The inability of HCV to replicate in non-human cells could be due to the absence or incompatibility of essential co-factors for viral replication and/or antiviral restriction mechanisms in non-human cells that effectively prevent viral replication. Under these assumptions, we are applying various genetic screening systems to generate a comprehensive profile of all relevant factors for the species barrier to HCV infection in mouse cells. Using this information, we aim to develop in vivo models for HCV vaccine research. This project was funded by an ERC Starting Grant (VIRAFRONT, 2012-2017) and is now being pursued with support from the German Center for Infection Research (DZIF) and a grant from the National Institutes of Health (NIH, USA).Using a genome-wide cDNA screen, we identified two novel murine restriction factors that suppress HCV infection of murine liver cells. The lectin Cd302 and the complement receptor Cr1l cooperate with each other, interfering with cell entry of HCV and triggering transcriptional changes that block HCV infection (Brown et al. 2020). Knockout of Cd302 increases the susceptibility to HCV infection of transgenic animals expressing the HCV receptor. These results reveal a new facet of liver-intrinsic immunity and point to new avenues for the development of animal models to further qualify HCV vaccines.

Publications

We develop and use high-throughput screening assays to identify molecules with antiviral activity against, RSV and SARS-CoV-2. For this purpose, we use luminescence- or reporter-based systems and make use of substance libraries of the HZI, the MHH and other external cooperation partners. For example, we cooperate with the Scripps Institute and use the ReFRAME repurposing compound library. ReFRAME is the world's largest collection of already approved or clinically proven compounds. The collections we use include a wide range of basic chemical structures and complex molecules from natural sources (secondary metabolites from bacteria, fungi or plants) as well as already approved drugs. Our expertise in basic virological research enables us to elucidate the modes of action of these substances and viral resistance mechanisms. In doing so, we pursue the goal of developing new therapeutic options. 

In collaboration with experts at the HZI, we have analyzed the mode of action of labyrinthopeptins against different viruses. Labyrinthopeptins bind certain lipids and lead to the destruction of the membranes of viruses. This makes them very broadly antiviral molecules against which viruses have difficulty developing resistance (Blockus et al. 2020).
Funded by the Helmholtz International Laboratory and as part of an international consortium, we have uncovered a new mode of action for the treatment of RSV infection. RSV concentrates its components for RNA propagation in so-called "inculsion bodies". These fluid organelles play a crucial role in genome replication and viral transcription. The new compound hardens these replication organelles of the virus and disrupts in this way the infection (Risso-Ballester et al. Nature 2021).
 

Publications