Virus-Specific Cellular Response in Hepatitis C Virus Infection

Low Mannose Binding Lectin, but Not L-Ficolin, Is Associated With Spontaneous Clearance of Hepatitis C Virus After Infection

Some individuals can spontaneously clear the hepatitis C virus (HCV) after infection, whereas others develop a chronic infection. The exact mechanism of this phenomenon is unknown. We aimed to evaluate the association of plasma levels of MBL, L-ficolin, and cytokines with outcome of HCV infections in two groups of patients who cleared HCV spontaneously (CHS), and who developed chronic HCV infections (CHC). Altogether, 86 patients and 183 healthy controls were included. Of 86 patients, 36 had CHS and 50 had CHC. Concentrations of plasma MBL and L-ficolin were measured in patients and controls. Twenty plasma cytokines and adhesion molecules, including GM-CSF, ICAM-1, IFN-γ, IFN-α, IL-1α, IL-1β, IL-10, IL-12p70, IL-13, IL-17A, IL-4, IL-8, IP-10, MCP-1, IL-6, MIP-1α, MIP-1β, sE-Selectin, sP-Selectin, and TNF-α, were determined in all patients and randomly selected 45 controls. The level of MBL was significantly lower in subjects with CHS than in healthy controls (median: 293.10 vs. 482.64 ng/ml, p = 0.008), whereas the level of MBL was significantly higher in patients with CHC than in controls (median: 681.32 vs. 482.64 ng/ml, p = 0.001). No such differences in plasma L-ficolin were observed. Plasma levels of all cytokines and adhesion molecules, except ICAM-1, were significantly higher in patients than in controls. Moreover, patients with CHC had significantly higher levels of IFN-γ, IFN-α, IL-1α, IL-10, IL-13, IL-4, IL-6, and TNF-α than those with CHS. These findings implicate that lower levels of plasma MBL, together with lower levels of above mentioned cytokines may play a part in virus clearance of HCV infection.

Seronegative hepatitis C virus infection in Polish blood donors-Virological characteristics of index donations and follow-up observations

Nucleic acid testing (NAT) was implemented in Poland in 1999 for screening of plasma for fractionation and for all blood donors in 2002. To analyze seronegative NAT-positive samples representing hepatitis C virus (HCV) window-period (WP) in the years 2000 to 2016 and to determine infection outcome. We analyzed results of 17 502 739 donations screened in minipools (6-48) or individually. Index samples underwent viral load (VL) quantification, genotyping and Ag, and anti-HCV re-testing using chemiluminescence (CMIA), electrochemiluminescence (ECLIA), and fourth-generation enzyme-linked immunosorbent assay (IV EIA) assays. HCV-seronegative infections were identified in 126 donations (7.2/mln donations; 95% confidential intervals, 6.0-8.6). Frequency of NAT yields was decreasing over time. Of the initial 126 seronegative index cases 106 were retested: 32.1% were reactive in IV EIA, 11.3% in ECLIA, and 1.9% in CMIA. The lowest VL correlated with absent anti-HCV and HCV Ag, while VL was highest when the antigen was detectable and then it decreased when anti-HCV appeared at a level detectable by sensitive third generation tests while retesting. The proportion of genotype 1 was 38.9% in samples positive only for HCV RNA and 71.4% in samples that were anti-HCV reactive in re-testing. In parallel, genotype 3 frequency was 50% in the former group and 21% in the latter. NAT is an effective measure to limit HCV transmission by transfusion and IV EIA seems to have higher clinical sensitivity than ECLIA. Samples representing likely successive phases of early HCV infection were characterized by different genotype distribution probably due to very early elimination of genotype 3.

Immunopathogenesis of Liver Injury During Hepatitis C Virus Infection

The present report describes current concepts about the mechanism of liver cell injury caused by host immune response against hepatitis C virus (HCV) infection in human beings. This report is based on the observations from experimental studies and follow-up actions on human liver diseases. The results from different investigations suggest that liver injury depends on the presentation of viral antigen and the level of host immune response raised against HCV-related peptides. Both innate and adaptive immunity are triggered to counter the viral onset. During development of host immunity, the cell-mediated immune response involving CD4⁺ Th1 cells and CD8⁺ cytotoxic T-lymphocyte (CTL) cells were found to play a major role in causing liver damage. The hepatic Innate lymphoid cells (ILCs) subsets are involved in the immune regulation of different liver diseases: viral hepatitis, mechanical liver injury, and fibrosis. Humoral immunity and natural killer (NK) cell action also contributed in liver cell injury by antibody-dependent cellular cytotoxicity (ADCC). In fact, immunopathogenesis of HCV infection is a complex phenomenon where regulation of immune response at several steps decides the possibility of viral elimination or persistence. Regulation of immune response was noted starting from viral-host interaction to immune reaction cascade engaged in cell damage. The activation or suppression of interferon-stimulated genes, NK cell action, CTL inducement by regulatory T cells (Treg), B cell proliferation, and so on was demonstrated during HCV infection. Involvement of HLA in antigen presentation, as well as types of viral genotypes, also influenced host immune response against HCV peptides. The combined effect of all these effector mechanisms ultimately decides the progression of viral onset to acute or chronic infection. In conclusion, immunopathogenesis of liver injury after HCV infection may be ascribed mainly to host immune response. Second, it is cell-mediated immunity that plays a predominant role in liver cell damage.

Cytokine profile in chronic hepatitis C: An observation

The data addressing cytokine profile in chronically infected HCV patients are conflicting, ranging from Th1 or Th2 cytokine prevalence to the expression of both types of cytokines. Therefore, the aim of this study was to evaluate cytokine profile in these patients. Cytokine sera levels in HCV patients and healthy controls were evaluated using 13plex FlowCytomix Multiplex. Median values of both proinflammatory and anti-inflammatory cytokines were lower in HCV patients then in controls. In addition, the number of subjects producing detectable quantities of cytokines was significantly lower in the group of HCV patients. Yet, cytokine levels in those patients were remarkably heterogeneous ranging from low to extremely high, much higher than the maximal values in control group. Similarly, grouping data according to HCV genotype, HCV RNA load, ALT/AST ratio and the stage of fibrosis showed marked standard deviations, reflecting high intragroup diversity. No correlation was found between each disease-related factor and cytokine levels. Patients investigated in our and similar studies were disparate pursuant to characteristics of the hosts, pathogen and course of the disease. Therefore, the inconsistency of the literature data regarding cytokine pattern in chronic HCV patients may be a consequence of the disregarded/overlooked heterogeneity of these patients.

Critical roles of conventional dendritic cells in promoting T cell-dependent hepatitis through regulating natural killer T cells

Dendritic cells (DCs) play critical roles in initiating and regulating innate immunity as well as adaptive immune responses. However, the role of conventional dendritic cells (cDCs) in concanavalin A (ConA)-induced fulminant hepatitis is unknown. In this study, we demonstrated that depletion of cDCs using either CD11c-diphtheria toxin receptor transgenic mice (DTR Tg) mice or anti-CD11c antibody reduced the severity of liver injury significantly, indicating a detrimental role of cDCs in ConA-induced hepatitis. We elucidated further the pathological role of cDCs as being the critical source of interleukin (IL)-12, which induced the secretion of interferon (IFN)-γ by natural killer (NK) T cells. Reconstitution of cDCs-depleted mice with IL-12 restored ConA-induced hepatitis significantly. Furthermore, we determined that NK T cells were the target of DC-derived IL-12, and NK T cells contributed to liver inflammation and injury through production of IFN-γ. In summary, our study demonstrated a novel function of cDCs in mediating ConA-induced hepatitis through regulating IFN-γ secretion of NK T cells in an IL-12-dependent fashion. Targeting cDCs might provide potentially therapeutic applications in treating autoimmune related liver diseases.

Spontaneous Elimination of Hepatitis C Virus Infection

Hepatitis C virus (HCV) is the etiological agent of chronic hepatitis C and a major cause of liver cirrhosis and hepatocellular carcinoma. Only a minority of infected individuals can clear the virus spontaneously. The knowledge of the determinants of virus clearance would allow the development of effective methods preventing its further spread and optimizing treatment regimens. Viral factors associated with spontaneous virus clearance in the acute phase of infection, such as HCV genotype, virus heterogeneity, and the impact of viral proteins on the immune system have been characterized. Likewise, host genetic markers, such as the interleukin genotypes, HLA alleles, and factors affecting the T lymphocyte response appear to play an important role. Studies have revealed that natural clearance of HCV infection in the chronic phase is rare and its mechanisms are not well understood. In this review, we present the state-of-the art knowledge on the viral and host factors affecting the spontaneous elimination of HCV infection.