FOXP3 Expression in Hepatitis C Virus–Specific CD4⁺ T Cells During Acute Hepatitis C

Background & Aims

Down-regulation of hepatitis C virus (HCV)-specific CD4⁺ T-cell responses is a hallmark of chronic viral persistence in acute hepatitis C. FOXP3⁺CD25⁺CD4⁺ regulatory T cells can modulate HCV-specific immune responses in vitro, but the role of virus-specific regulatory T cells in the pathogenesis of chronic viral persistence is unknown.

Methods

Two novel HLA-DR15 tetramers were synthesized to study the kinetics and phenotype of FOXP3⁺-expressing HCV-specific CD4⁺ T cells from 10 patients with acute hepatitis C and 15 patients with chronic hepatitis C.

Results

In acute hepatitis C, generally only a low percentage of HCV-specific CD4⁺ T cells expressed FOXP3⁺ (mean of 2.5% in patients with self-limited acute hepatitis C vs 2.4% in patients with evolving chronic hepatitis C). Although distinct but short-lived increases in virus-specific FOXP3⁺CD4⁺ T cells occurred in 3 patients (30%, 26%, and 7% of tet⁺ CD4⁺ T cells, respectively), these did not correlate with the evolution of chronic hepatitis C. HCV-specific FOXP3⁺CD4⁺ T cells displayed a distinct phenotype, with only 10% expressing CD25 and 40% being CD127low. Interestingly, this phenotype of FOXP3⁺CD4⁺ T cells was already expanded in bulk CD4⁺ T cells in patients with chronic hepatitis C.

Conclusions

Although short-lived increases in HCV-specific FOXP3⁺CD4⁺ T cells occur during the course of acute hepatitis C, we could not demonstrate an association of HCV-specific regulatory T cells and persistent viremia.

Abbreviations used in this paper: PBMC, peripheral blood mononuclear cell, PE, phycoerythrin, Treg, regulatory T cell