Transmitted/Founder Hepatitis C Viruses Induce Cell-Type- and Genotype-Specific Differences in Innate Signaling within the Liver

Abstract

Hepatitis C virus (HCV) infection leads to persistence in the majority of cases despite triggering complex innate immune responses within the liver. Although hepatocytes are the preferred site for HCV replication, nonparenchymal cells (NPCs) can also contribute to antiviral immunity. Recent innovations involving single-genome amplification (SGA), direct amplicon sequencing, and phylogenetic inference have identified full-length transmitted/founder (T/F) viruses. Here, we tested the effect of HCV T/F viral RNA (vRNA) on innate immune signaling within hepatocytes and NPCs, including the HepG2 and Huh 7.5.1 cell lines, a human liver endothelial cell line (TMNK-1), a plasmacytoid dendritic cell line (GEN2.2), and a monocytic cell line (THP-1). Transfection with hepatitis C T/F vRNA induced robust transcriptional upregulation of type I and III interferons (IFNs) within HepG2 and TMNK-1 cells. Both the THP-1 and GEN2.2 lines demonstrated higher type I and III IFN transcription with genotype 3a compared to genotype 1a or 1b. Supernatants from HCV T/F vRNA-transfected TMNK-1 cells demonstrated superior viral control. Primary human hepatocytes (PHH) transfected with genotype 3a induced canonical pathways that included chemokine and IFN genes, as well as overrepresentation of RIG-I (DDX58), STAT1, and a Toll-like receptor 3 (TLR3) network. Full-length molecular clones of HCV induce broad IFN responses within hepatocytes and NPCs, highlighting that signals imparted by the various cell types within the liver may lead to divergent outcomes of infection. In particular, the finding that HCV genotypes differentially induce antiviral responses in NPCs and PHH might account for relevant clinical-epidemiological observations (higher clearance but greater necroinflammation in persistence with genotype 3).

Hepatitis C Virus Sensing by Human Trophoblasts Induces Innate Immune Responses and Recruitment of Maternal NK Cells: Potential Implications for Limiting Vertical Transmission

“…Also, in this case we detected significant up-regulation of Type I and Type III IFN genes, similar to the immune response we observed after HCV-PAMP RNA transfection (Figure 3D). Moreover, when villous explants were cultured with supernatant containing sucrose-purified JFH-1 viral particles (41) (Figure 3E) and viral-RNA of a full-length infectious molecular clone of HCV known to efficiently transmit infection [transmitted founder (T/F) virus (42, 43)] (Supplemental Figure 2) for 48 hours, we found significant transcription of multiple Type I and Type III IFN genes. These data indicate that HCV is taken up directly by human trophoblasts and induces innate immune responses.…”

HCV genotype 3: a wolf in sheep’s clothing

“…[24,25] Another possible explanation for the high presence of steatosis could be that HCV G3 steatosis induces the liberation of proinflammatory chemokines that increase the recruitment of inflammatory cells to the liver. [14] In support of this idea, the depletion of liver Kupffer cells prevents the development of dietinduced hepatic steatosis and insulin resistance. [26] It is important to bear in mind that there is a significant correlation between the steatosis score and the titer of intrahepatic HCV RNA in patients with HCV G3, providing virological and some clinical evidence that steatosis is the morphological expression of a viral cytopathic effect in patients infected with this genotype.…”

“…[13] One of the possible reasons could be that in monocytic cell and plasmacytoid dendritic cell lines and in macrophages differentiated from monocytes with macrophage colonystimulating factor, HCV G3 induces greater interferon transcription than either genotype 1a or 1b. [14] However, this apparent benefit may backfire because of the increased rate of fibrosis progression of HCV G3, probably because of the higher non-parenchymal cell transcription of IFN genes following intracellular HCV G3 sensing. [14] It has been reported previously that HCV G3 is associated with a significantly increased risk of developing cirrhosis and HCC compared with HCV G1 and association that is independent of the patients' age, diabetes, body mass index, or antiviral treatment.…”

“…[14] However, this apparent benefit may backfire because of the increased rate of fibrosis progression of HCV G3, probably because of the higher non-parenchymal cell transcription of IFN genes following intracellular HCV G3 sensing. [14] It has been reported previously that HCV G3 is associated with a significantly increased risk of developing cirrhosis and HCC compared with HCV G1 and association that is independent of the patients' age, diabetes, body mass index, or antiviral treatment. [8] The high viremia observed in HCV G3-infected patients may be a marker of rapid disease damage, reflecting either the inability of the immune system to control the infection or the existence of some escape mechanisms in HCV G3 which prevents the immune system response from being effective.…”

Translating RNA sequencing into clinical diagnostics: opportunities and challenges

“…Host response, in the form of mRNA signatures, is also likely to become useful for monitoring specific infections. For example, upregulation of specific host immune factors (interferon beta 1 (IFNB1) interferon lambda 2 (IFNL2) and interferon lambda 3 (IFNL3)) was recently demonstrated for geno type 3 HCV infection, which is associated with accelerated liver fibrosis and is an independent risk factor for hepatocellular carcinoma, compared to nongenotype 3 HCV infection 86,87 . Host microRNA-gene interactions during the infection response are also proving to be a fruitful source of potential diagnostic biomarkers for specific infections, as well as distinguishing between active and latent infections; for example, the use of such markers to discriminate between latent infection and active disease with M. tuberculosis 88 .…”