Impaired Toll-Like Receptor 3-Mediated Immune Responses from Macrophages of Patients Chronically Infected with Hepatitis C Virus

Abstract

Hepatitis C virus (HCV) is the most common chronic blood-borne infection in the UnitedStates, with the majority of patients becoming chronically infected and a subset (20%) progressing to cirrhosis and hepatocellular carcinoma. Individual variations in immune responses may help define successful resistance to infection with HCV. We have compared the immune response in primary macrophages from patients who have spontaneously cleared HCV (viral load negative [VL؊], n ‫؍‬ 37) to that of primary macrophages from HCV genotype 1 chronically infected (VL؉) subjects (n ‫؍‬ 32) and found that macrophages from VL؊ subjects have an elevated baseline expression of Toll-like receptor 3 (TLR3). Macrophages from HCV patients were stimulated ex vivo through the TLR3 pathway and assessed using gene expression arrays and pathway analysis. We found elevated TLR3 response genes and pathway activity from VL؊ subjects. Furthermore, macrophages from VL؊ subjects showed higher produc- Approximately 3.9 million individuals in the United States, or 1.8% of the general population, are infected with HCV, and 170 million people worldwide are estimated to be infected with HCV (1). Chronic HCV infection occurs in 50 to 80% of cases, with a subset (20%) progressing to cirrhosis (2). Patients with cirrhosis are at high risk of developing hepatocellular carcinoma, which is a fatal complication of chronic HCV infection. The current combination antiviral therapy (protease inhibitor, pegylated interferon, and ribavirin) for HCV genotype 1 infection is associated with significant toxicity and results in overall viral clearance in only 66 to 75% of patients depending on other important determinants of HCV viral clearance (e.g., HIV coinfection, interleukin 28B [IL28B] status, viral load, and stage of fibrosis). Recently, inhibitors of HCV proteases have become available as a new treatment regimen and show great promise in reducing viral load in treatment-naïve genotype 1 HCV-infected patients (3).The high prevalence of chronic HCV infection indicates that for most patients, neither the innate nor the adaptive immune system is successful at eliminating the virus. While studies ex vivo of chronically infected patients show elevated levels of cytokines in the serum (4) and elevations in immune markers (Toll-like receptors [TLRs] and cytokines) in monocytes and dendritic cells (DCs) (5-7), these increased levels correlate with liver disease, which is believed to be driven by the ongoing inflammatory response, and do not correlate with reduced viral loads (8). HCV persists in part through multiple viral mechanisms employed to evade immunologic control and facilitate infection, including HCV nonstructural protease proteins NS3/4A cleavage of immune signaling adapters (9-11). Some control of HCV infection is associated with an increase in T cell responses (both CD4 ϩ and CD8 ϩ T cells), although the persistence of viremia-despite the presence of HCV-specific CD8 ϩ T cells in the liver of chronically infected patients for years-suggests they are not effecti...

Immune Markers Associated with Host Susceptibility to Infection with West Nile Virus

“…No significant difference in antibody levels was observed between subjects with a history of asymptomatic or severe WNV infection, suggesting that susceptibility was not a consequence of an inability to mount a humoral response. This has been noted previously from comparisons of asymptomatic and mild WNV patients (20) and in patients infected with the related hepatitis C virus, for which antibody levels do not correlate with viral clearance (2,29). In our subjects, anti-E antibody serum levels were relatively constant for up to 8 years after infection, consistent with previous reports of persistence of anti-WNV antibodies for > 1 year (3,28).…”

“…1A), showing that both severe and asymptomatic subjects induce a humoral response. Our data suggest that the level of the antiviral titers is not a driving feature of disease severity, which is similar to findings of antibody levels in human subjects infected with the related flavivirus hepatitis C virus, for which antibody responses do not predict clearance of infecting virus (2,29). Notably, the kinetics of antibody development during infection may play a role in response to infection and this was not assessed in our cohort.…”

Neutralizing antibodies against West Nile virus identified directly from human B cells by single-cell analysis and next generation sequencing

“…These findings show that, although WNV infection induces a humoral response, the level of the anti-viral antibody titers is not a distinguishing feature of disease severity. This observation has also been noted for antibody levels in humans infected with a related hepacivirus, hepatitis C virus, for which antibody responses also fail to predict the clearance of infecting virus 42,43 . Our data suggest that the pathways needed to mount a successful antibody response remain intact and that the mechanisms leading to severe disease are independent of these pathways.…”

Systems Immunology Reveals Markers of Susceptibility to West Nile Virus Infection

“…Notably, our study also highlights the importance of production of CXCL10, which leads to the control of WNV in the murine model (41). CXCL10 is decreased in dendritic cells from older donors in response to WNV infection ex vivo (14) and is lower in macrophages of a cohort of subjects who fail to clear infection with the related flavivirus hepatitis C virus (29).…”