Viral factors associated with cytokine expression during HCV/HIV co-infection

Abstract

Co-infection with human immunodeficiency virus (HIV) is associated with reduced hepatitis C virus (HCV) treatment response and accelerated HCV disease. Cytokines, as mediators of immune responses, inflammation, and fibrogenesis, may underlie important differences in HCV pathogenesis during HIV co-infection. We previously found that serum interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-alpha) increased after HCV therapy with interferon (IFN) in HCV/HIV co-infected patients; however, cytokine levels were not predictive of HCV therapeutic response. Here, we examined viral factors associated with expression of IL-8, TNF-alpha, and transforming growth factor-beta1 (TGF-beta1) in uninfected, HCV mono-infected, HIV mono-infected, and HCV/HIV co-infected persons. HIV co-infection was associated with decreased IL-8 detection but not TNF-alpha detection. A significant interaction effect demonstrated that HIV infection was associated with elevated TGF-beta1 in HCV-positive individuals but not in HCV-negative individuals. The induction of a sustained profibrotic signal, such as TGF-beta1, by HIV may cause accelerated liver fibrosis during HCV/HIV co-infection and may hinder the host's ability to mount an effective HCV-specific immune response. Further studies are warranted to identify noninvasive markers of liver disease for the clinical management of HCV disease, particularly when liver biopsies have not been performed or are contraindicated.

FIG. 1

IL-8 (A), TNF-α (B), and TGF-β1 (C) levels by viral infection status. Serum levels of IL-8, TNF-α, and TGF-β1 were quantified using standard enzyme-linked immunoassays and normalized to a standard curve. The lower limit of detection (LLD) for each assay was 3.5 pg/mL for IL-8, 1.6 pg/mL for TNF-α, and 7.0 pg/mL for TGF-α1. Sample measurements below the LLD were assigned a value of 0. Values are expressed as log₁₀ transformed values (pg/mL). Lines in C denote mean TGF-β1 levels.