Abstract

Background & Aims

Hepatitis C virus (HCV) particles detected in sera from infected patients display heterogeneous forms of low-buoyant densities (<1.08), underscoring their lipidation via association with apoB-containing lipoproteins, which was proposed to occur during assembly or secretion from infected hepatocytes. However, the mechanisms inducing this association remain poorly-defined and, intriguingly, most HCVcc particles secreted from cultured cells exhibit higher density (>1.08) and are not/poorly apoB-associated.

Methods

We produced HCVcc particles of Jc1 or H77 strains from Huh-7.5 hepatoma cells cultured in 10%-fetal calf serum (FCS) standard conditions vs. in serum-free or human serum (HS) conditions before analyzing their density profiles comparatively to patient-derived virus. We also characterized serum-free medium-produced wild-type and Jc1/H77 HVR1-swapped mutant HCVcc particles incubated with either serum type or with purified lipoproteins.

Results

Compared to serum-free or FCS conditions, production with HS redistributed most HCVcc infectious particles to low-density (<1.08) or very-low-density (<1.04) ranges. In addition, short-time incubation with HS was sufficient to shift HCVcc physical particles to low-density fractions, in time- and dose-dependent manners, which increased their specific infectivity, promoted apoB-association and induced neutralization-resistance. Moreover, compared to Jc1, we detected higher levels of H77 HCVcc infectious particles in very-low-density fractions, which could unambiguously be attributed to strain-specific features of HVRI sequence. Finally, all three lipoprotein classes, i.e., very-low-density, low-density and high-density lipoproteins, could synergistically induce low-density shift of HCV particles; yet, this required additional non-lipid serum factor(s) that include albumin.

Conclusions

The association of HCV particles with lipids may occur in the extracellular milieu. The lipidation level depends on serum composition as well as on HVRI-specific properties. These simple culture conditions allow production of infectious HCV particles resembling those of chronically-infected patients.

Source: A serum protein factor mediates maturation and apoB-association of HCV particles in the extracellular milieu. Solène Denolly, Christelle Granier, Nelly Fontaine, Bruno Pozzetto, Thomas Bourlet, Maryse Guérin, François-Loïc Cosset. Science direct, “Epub ahead of print”, December 2018.