Host factor interactions during early steps of Hepatitis C Virus cell entry and their inter-individual modulation by genetic and pharmacological perturbations
Red-fluorescent sensor that detects HCV infection of cultivated liver cells. In uninfected cells (upper panel) all signal is in the cytoplasm. In an infected culture (lower panel) the signal has moved to the nucleus in most cells – these are infected by HCV.
The hepatitis C virus causes chronic infection of the liver. In the long term this leads to scarring of the liver (cirrhosis), liver failure and liver cancer. About 120 million people are chronically infected with the hepatitis C.
An unusual trait of hepatitis C is that the virus particles are present at very high numbers in the blood of chronically infected individuals for decades and continuously mange to escape the immune system. To achieve this, the virus employs a number of tricks. On the one hand the virus has a very high mutation rate. This means that its genes and hence its form evolve very quickly, so that the immune system cannot fight it effectively. Moreover, the virus particles interact with lipid particles that normally exist in human blood to form so called lipoviral particles. This way the virus hides from the immune system and also uses receptor molecules that are found on the surface of liver cells to bind lipids from the blood to infect liver cells and thus maintain chronic infection.
The group around Thomas von Hahn investigates how variation in a human gene that plays an important role both in human lipid metabolism and in hepatitis C virus infection of liver cells affects growth and propagation of hepatitis C virus and the course of chrnic hepatitis C in infected individuals. Thus, they hope to gain a better understanding of how the hepatitis C virus functions, new diagnostic tools and – in the long term – new treatments.
The HCV replication cycle and the clinical course of chronic hepatitis C are modulated by genetic and non-genetic variation of the host. SR-BI – physiologically the main hepatic receptor for high density lipoproteins (HDL) – serves as a key host factor for HCV since it is critical for viral entry. Numerous genetic variants exist in the SCARB1 gene that encodes SR-BI and several of these have a clinical phenotype in that they alter the serum lipid profile. However, their effect on chronic HCV infection is unknown. To what extent variation in serum levels of SR-BI ligands affects HCV infection is also unclear. This project is intended to clarify how variation in the SCARB1 gene and in endogenous SR-BI ligands affects the HCV replication cycle and the ability of the virus to establish and maintain chronic infection.
The project has four parts: :
known coding non-synonymous SR-BI variants will be expressed in cell lines where endogenous SR-BI expression has been eliminated and then tested for their ability to function as HCV receptors.
Known SR-BI variants, coding or non-coding, with a minor allele frequency of at least 5% will be tested for their effect on the development, progression and treatment response of chronic HCV infection in cohorts of acutely and chronically HCV infected individuals. This genetic analysis will also include the definition and clinical characterization of haplotype blocks in the SCARB1 gene using father-mother-child trios.
In the same cohorts we will assess the impact of SR-BI ligand levels in the individuals’ serum on the course of chronic HCV infection, i.e. establishment, progression and treatment response of chronic hepatitis C.
Finally, sequencing of the HCV glycoprotein genes E1E2 in patients with known genotypes of interest will be performed to probe for evidence of genetic adaption of the viral population to the host environment during chronic infection. To be able to compare E1E2 sequences and identify characteristic mutations we will use samples from a cohort of women infected in a single source outbreak of chronic HCV infection due to a contaminated anti-D an immunoglobulin. Any viral variants thus identified will then be characterized in detail regarding their usage of SR-BI and its.
Representation of the gene structure of SCARB1. Genetic variants of interest are indicated.
Thomas von Hahn is talking about his research at CRC 900
Thomas von Hahn joined the CRC at the start of the second funding period in 2014. Gisa Gerold jointed the project at the start of the third funding period in 2018. Their project C7 addresses how various variants of a gene with a central role in fat metabolism influence the course of infection with hepatitis C virus.
Publications of the project C7
A screening assay for the identification of host cell requirements and antiviral targets for hepatitis D virus infection. Buchmann B, Döhner K, Schirdewahn T, Sodeik B, Manns MP, Wedemeyer H, Ciesek S, von Hahn T. Antiviral Res. 2017 May;141:116-123.
Scavenger receptor class B member 1 (SCARB1) variants modulate hepatitis C virus replication cycle and viral load. Westhaus S, Deest M, Nguyen ATX, Stanke F, Heckl D, Costa R, Schambach A, Manns MP, Berg T, Vondran FWR, Sarrazin C, Ciesek S, von Hahn T. J Hepatol. 2017 Mar 29. pii: S0168-8278(17)30184-8.
Cyclophilin polymorphism and virus infection. von Hahn T, Ciesek S. Curr Opin Virol. 2015 Oct;14:47-9. Review.
Primary biliary acids inhibit hepatitis D virus (HDV) entry into human hepatoma cells expressing the sodium-taurocholate cotransporting polypeptide (NTCP). Veloso Alves Pereira I, Buchmann B, Sandmann L, Sprinzl K, Schlaphoff V, Döhner K, Vondran F, Sarrazin C, Manns MP, Pinto Marques Souza de Oliveira C, Sodeik B, Ciesek S, von Hahn T. PLoS One. 2015 Feb 3;10(2):e0117152.
Impact of single nucleotide polymorphisms in the essential HCV entry factor CD81 on HCV infectivity and neutralization. Deest M, Westhaus S, Steinmann E, Manns MP, von Hahn T, Ciesek S. Antiviral Res. 2014 Jan;101:37-44.
Characterization of the inhibition of hepatitis C virus entry by in vitro-generated and patient-derived oxidized low-density lipoprotein. Westhaus S, Bankwitz D, Ernst S, Rohrmann K, Wappler I, Agné C, Luchtefeld M, Schieffer B, Sarrazin C, Manns MP, Pietschmann T, Ciesek S, von Hahn T. Hepatology. 2013 May;57(5):1716-24.