Viral Sequence Variation in Chronic Carriers of Hepatitis C Virus Has a Low Impact on Liver Steatosis

Abstract

Most clinical studies suggest that the prevalence and severity of liver steatosis are higher in patients infected with hepatitis C virus (HCV) genotype 3 than in patients infected with other genotypes. This may reflect the diversity and specific intrinsic properties of genotype 3 virus proteins. We analyzed the possible association of particular residues of the HCV core and NS5A proteins known to dysregulate lipid metabolism with steatosis severity in the livers of patients chronically infected with HCV. We used transmission electron microscopy to quantify liver steatosis precisely in a group of 27 patients, 12 of whom were infected with a genotype 3 virus, the other 15 being infected with viruses of other genotypes. We determined the area covered by lipid droplets in liver tissues and analyzed the diversity of the core and NS5A regions encoded by the viral variants circulating in these patients. The area covered by lipid droplets did not differ significantly between patients infected with genotype 3 viruses and those infected with other genotypes. The core and NS5A protein sequences of the viral variants circulating in patients with mild or severe steatosis were evenly distributed throughout the phylogenic trees established from all the collected sequences. Thus, individual host factors seem to play a much greater role than viral factors in the development of severe steatosis in patients chronically infected with HCV, including those infected with genotype 3 viruses.

Hepatitis C virus diversity and hepatic steatosis

“…). Nevertheless, an F residue was never detected in position 164 in any of the genotype 1 strains associated with severe steatosis .…”

“…However, in two other independent studies, analyses of the sequences of various clinical isolates failed to implicate the FV and LI residues in positions 182 and 186, or any other genetic differences between genotype 3 core proteins from patients with and without steatosis, suggesting a possible role for other factors in the development of steatosis in patients infected with genotype 3 viruses . In all these bioclinical studies, it was difficult to evaluate the role of the F164 residue in liver steatosis, because this residue was present in all genotype 3 isolates, even those from patients without steatosis (Fig. ).…”

Nuclear lipid droplets identified by electron microscopy of serial sections

“…This patient was infected with a HCV 1b genotype and was classified as having steatosis of intermediate severity, characterized by a median cumulative LD area of 275 μm 2 per 5000 μm 2 of liver tissue [8]. Routine histological diagnosis demonstrated a minimally active chronic hepatitis graded A1-F1 with the METAVIR score.…”

Quantifying hepatic steatosis by electron microscopy

“…More recently, we applied this method to the analysis of liver biopsy specimens from chronic HCV carriers, allowing us to quantify precisely the accumulation of LDs in liver tissues, even when the LDs are small (Figure 1). 3 In this method, LD diameter is determined on the computer screen for five consecutive squares (5000 μm 2 each) of two independent TEM grids (i.e. 10 different areas of 5000 μm 2 of hepatic tissue, for each biopsy).…”

“…For each biopsy, the areas in the 10 squares analysed are then summed, allowing the precise quantification of steatosis in the liver tissues of the patients. The analysis of the number and the mean diameter of the LDs encountered in 50 000 μm 2 of liver tissue can be also performed with this approach 3 …”