IL-28B Genetic Variants Determine the Extent of Monocyte-Induced Activation of NK Cells in Hepatitis C

Peripheral blood correlates of virologic relapse after Sofosbuvir and Ribavirin treatment of Genotype-1 HCV infection

Background

Treatment of chronic hepatitis C virus infection with direct acting antiviral therapy results in viral elimination in over 90% of cases. The duration of treatment required to achieve cure differs between individuals and relapse can occur. We asked whether cellular and transcriptional profiling of peripheral blood collected during treatment could identify biomarkers predictive of treatment outcome.

Methods

We analyzed peripheral blood collected during treatment of genotype 1 HCV with 24 weeks of sofosbuvir and weight-based or low dose ribavirin in a trial in which 29% of patients relapsed. Changes in host immunity during treatment were assessed by flow cytometry and whole blood gene expression profiling. Differences in expression of immune-relevant transcripts based on treatment outcome were analyzed using the Nanostring Human Immunology V2 panel.

Results

Multiple cellular populations changed during treatment, but pre-treatment neutrophil counts were lower and natural post-treatment killer cell counts were higher in patients who relapsed. Pre-treatment expression of genes associated with interferon-signaling, T-cell dysfunction, and T-cell co-stimulation differed by treatment outcome. We identified a pre- and post-treatment gene expression signature with high predictive capacity for distinguishing treatment outcome, but neither signature was sufficiently robust to suggest viability for clinical use.

Conclusions

Patients who relapse after hepatitis C virus therapy differ immunologically from non-relapsers based on expression of transcripts related to interferon signaling and T-cell dysfunction, as well as by peripheral neutrophil and NK-cell concentrations. These data provide insight into the host immunologic basis of relapse after DAA therapy for HCV and suggests mechanisms which may be relevant for understanding outcomes with currently approved regimens.

Hepatitis C virus-induced natural killer cell proliferation involves monocyte-derived cells and the OX40/OX40L axis

BACKGROUND & AIMS

Natural killer (NK) cells are found at increased frequencies in patients with hepatitis C virus (HCV). NK cell activation has been shown to correlate with HCV clearance and to predict a favourable treatment response. The aim of our study was to dissect mechanisms leading to NK cell activation and proliferation in response to HCV.

METHODS

NK cell phenotype, proliferation, and function were assessed after the 6-day co-culture of human peripheral blood mononuclear cells with either HCV replicon-containing HuH6 hepatoblastoma cells or HCV-infected HuH7.5 cells. The results obtained were confirmed by immunohistochemistry of liver biopsies from patients with HCV and from HCV-negative controls.

RESULTS

In HCV-containing co-cultures, a higher frequency of NK cells upregulated the expression of the high-affinity IL-2 receptor chain CD25, proliferated more rapidly, and produced higher amounts of interferon γ compared with NK cells from control co-cultures. This NK cell activation was dependent on IL-2, cell-cell contact-mediated signals, and HCV replicon-exposed monocytes. The tumour necrosis factor-receptor superfamily member OX40 was induced on the activated CD25^± NK cell subset and this induction was abrogated by the depletion of CD14⁺ monocytes. Moreover, OX40L was upregulated on CD14^± monocyte-derived cells co-cultured with HCV-containing cells and also observed in liver biopsies from patients with HCV. Importantly, blocking of the OX40/OX40L interaction abolished both NK cell activation and proliferation.

CONCLUSIONS

Our results uncover a previously unappreciated cell-cell contact-mediated mechanism of NK cell activation and proliferation in response to HCV, mediated by monocyte-derived cells and the OX40/OX40L axis. These results reveal a novel mode of crosstalk between innate immune cells during viral infection.

LAY SUMMARY

Using a cell-culture model of hepatitis C virus (HCV) infection, our study revealed that natural killer (NK) cells become activated and proliferate when they are co-cultured with HCV-containing liver cells. The mechanism of this activation involves crosstalk with other innate immune cells and a cell-cell contact interaction mediated by the cell surface molecules OX40 and OX40L. Our study reveals a novel pathway leading to NK cell proliferation and activation against virus-infected cells that might be of relevance in antiviral immunity.

HLA-Bw4 80(T) and multiple HLA-Bw4 copies combined with KIR3DL1 associate with spontaneous clearance of HCV infection in people who inject drugs

BACKGROUND & AIMS

Natural killer (NK) cell function is regulated by inhibitory and activating receptors including killer cell immunoglobulin-like receptors (KIRs). Here, we analyzed the impact of different KIR/KIR-ligand genotypes on the outcome of hepatitis C virus (HCV) infection in people who inject drugs (PWID).

METHODS

KIR/KIR-ligand genotypes associated with spontaneous clearance of HCV infection were identified in a cohort of PWID from Germany (n=266) and further validated in a second anti-HCV positive cohort of PWID recruited in North America (n=342). NK cells of PWID and healthy donors were functionally characterized according to their KIR/KIR-ligand genotype by flow cytometry.

RESULTS

Multivariate logistic regression analysis revealed that KIR3DL1/HLA-Bw4 80(T) was associated with spontaneous clearance of HCV infection in PWID, which was confirmed in the PWID cohort from North America. Compared with PWID with detectable HCV RNA, the frequency of individuals with multiple HLA-Bw4 alleles was significantly higher in anti-HCV positive PWID with resolved HCV infection (29.7% vs. 15.2%; p=0.0229) and in anti-HCV seronegative PWID (39.2%; p=0.0006). KIR3DL1+ NK cells from HLA-Bw4 80(T)-positive PWID showed superior functionality compared to HLA-Bw4 80(I)-positive PWID. This differential impact was not observed in healthy donors; however, the HLA-Bw4 copy number strongly correlated with the functionality of KIR3DL1+ NK cells.

CONCLUSIONS

HLA-Bw4-80(T) and multiple HLA-Bw4 copies in combination with KIR3DL1 are associated with protection against chronic hepatitis C in PWID by distinct mechanisms. Better licensing of KIR3DL1+ NK cells in the presence of multiple HLA-Bw4 copies is beneficial prior to seroconversion whereas HLA-Bw4 80(T) may be beneficial during acute hepatitis C. Lay summary: Natural killer (NK) cells are part of the innate immune system and are regulated by a complex network of activating and inhibiting receptors. The regulating receptor-ligand pairs of an individual are genetically determined. Here, we identified a particular set of ligand and receptor genes that are associated with better functionality of NK cells and better outcome upon exposure to HCV in a high-risk group.

Type III Interferons in Hepatitis C Virus Infection

The interferon (IFN)-λ family of type III cytokines includes the closely related interleukin (IL)-28A (IFN-λ2), IL-28B (IFN-λ3), and IL-29 (IFN-λ1). They signal through the Janus kinases (JAK)-signal transducers and activators of transcription pathway and promote an antiviral state by the induction of expression of several interferon-stimulated genes (ISGs). Contrary to type I IFNs, the effect of IFN-λ cytokines is largely limited to epithelial cells due to the restricted pattern of expression of their specific receptor. Several genome-wide association studies have established a strong correlation between polymorphism in the region of IL-28B gene (encoding for IFN-λ3) and both spontaneous and therapeutic IFN-mediated clearance of hepatitis C virus (HCV) infection, but the mechanism(s) underlying this enhanced viral clearance are not fully understood. IFN-λ3 directly inhibits HCV replication, and in vitro studies suggest that polymorphism in the IFN-λ3 and its recently identified overlapping IFN-λ4 govern the pattern of ISGs induced upon HCV infection of hepatocytes. IFN-λ can also be produced by dendritic cells, and apart from its antiviral action on hepatocytes, it can regulate the inflammatory response of monocytes/macrophages, thus acting at the interface between innate and adaptive immunity. Here, we review the current state of knowledge about the role of IFN-λ cytokines in mediating and regulating the immune response during acute and chronic HCV infections.