Activation of brain macrophages/microglia cells in hepatitis C infection

Hepatitis C virus (HCV) infection is commonly associated with cognitive dysfunction. Viral sequences and proteins were previously found in brain macrophage/microglia cells. The aim of the current study was to determine whether HCV infection affects the expression of key cytokines and chemokines in these cells.

Autopsy brain tissue from 15 patients was studied; 7 patients were HCV positive and 8 were HCV negative. Cryostat sections of frontal cortex and subcortical white matter were stained with monoclonal antibodies specific for microglia/macrophages (anti-CD68) and separated by laser capture microscopy. Transcripts representing 25 various cytokines and chemokines were measured by real-time quantitative PCR.

Compared with HCV-negative controls, HCV-positive patients demonstrated significantly higher levels of proinflammatory cytokines interleukin 1α (IL-1α), IL-1β, tumour necrosis factor α (TNFα), IL-12 and IL-18. HCV infection was also associated with increased transcription of chemokines IL-8, IL-16 and interferon-inducible protein 10 (IP-10). Type 1 interferon (IFN) activation was suggested by increased concentrations of IFNβ and myxovirus resistance protein A (MxA) transcripts. Similar results were obtained when CD68-positive/HCV-positive cells were compared with CD68-positive/HCV-negative cells in each of the 7 HCV-infected patients.

Evidence was found for activation of brain macrophages/microglia cells in autopsy brain tissue from HCV-positive patients. These findings could relate to the common presence of neurocognitive dysfunction among patients with chronic hepatitis C.