title: Chronic hepatitis C and persistent occult hepatitis C virus infection are characterized by distinct immune cell cytokine expression profiles.
abstract: Hepatitis C virus (HCV) replicates in immune cells in both chronic hepatitis C (CHC) and occult HCV infection, but the extent of virus replication in this compartment in these opposing infection forms varies greatly. It was unknown whether this could be linked to HCV genotype or to differences in host gene expression shaping the immune response, and whether HCV replication in immune cells is sensitive to endogenous antiviral cytokines. In this study, we uncovered that significantly greater HCV load in peripheral blood mononuclear cells (PBMC), but not in plasma, coincided with HCV genotypes 2 and 3 in CHC, but with genotype 1 in residual occult infection after clinical resolution of hepatitis C. Moreover, PBMC from individuals with occult infection transcribed significantly greater levels of IFN-alpha, IFN-gamma and TNF-alpha, but less interleukin (IL)-10 than those from CHC. In CHC, PBMC with low HCV load expressed significantly more IFN-gamma but less IL-12 than did cells with high virus content. In occult infection, HCV RNA detection in PBMC was associated with much lower IFN-alpha and IL-12 expression. Further, HCV replication in T lymphocytes could be completely eliminated by activation of endogenous IFN-gamma in CHC, but of IFN-alpha in occult infection. In conclusion, CHC and persistent occult HCV infection are characterized by clearly different profiles of antiviral cytokine response in circulating immune cells which are also different from those of healthy individuals. Higher expression of IL-10, combined with lower transcription of IFN-alpha, IFN-gamma and TNF-alpha, is associated with a more robust HCV replication in immune cells.
authors.affiliation: Molecular Virology and Hepatology Research Group, Division of BioMedical Sciences, Faculty of Medicine, Health Sciences Centre, Memorial University, St. John's, NF, Canada A1B3V6.
authors.forename: T N Q
authors.initials: TN
authors.lastname: Pham
authors.forename: S E
authors.initials: SE
authors.lastname: Mercer
authors.forename: T I
authors.initials: TI
authors.lastname: Michalak
mesh_terms: D000328:Adult; D000368:Aged; D001769:Blood / Q000276:immunology* / Q000821:virology*; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D005838:Genotype; D006515:Hepatitis B virus / Q000145:classification / Q000235:genetics / Q000276:immunology; D019698:Hepatitis C, Chronic / Q000276:immunology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000276:immunology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D016207:Cytokines