T-Cell immune activation in children with vertically transmitted hepatitis C virus infection

Little is known concerning the clinical features, the histological outcome, and the effects on the maturation of immune system of children with vertically-transmitted hepatitis C virus (HCV) infection. Specifically, no data are available on the peripheral distribution of T-cell subsets. The frequency of naive and memory cells, activated T cells, and cytokine-producing T cells was analyzed in nine HCV-infected children born to HCV-positive mothers. In HCV-infected children, the distribution of naive and memory cells was not significantly altered in the CD4 subset whereas within the CD8 subset, an increase of memory and a decrease of naive cells was observed. The frequency of HLA-DR-positive and Fas-positive T cells was increased in HCV-infected children in both CD4 and CD8 subsets. The distribution of Fas-expressing T cells was directly related to that of HLA-DR cells and inversely related to the frequency of naive T cells. In regard with cytokine production we found increased levels of both CD4 and CD8 interferon-gamma (IFN-gamma)-producing cells whereas no difference in the percentage of interleukin-2 (IL-2)-producing T cells was observed. No meaningful correlation was observed between individual T cell subsets and ALT levels or HCV viral load. In conclusion, our results indicate an increased T-cell activation and a shift to a T(H)1 pattern of cytokine production in children with vertically transmitted HCV infection. The cause of this kind of immune response could reside in the persistent antigenic stimulation by chronic HCV infection.