Foxp3CD4CD25T cells control virus-specific memory T cells in chimpanzees that recovered from hepatitis C

regulatory T cells (TRegs) and the extent of suppression was as high in spontane- ously HCV-recovered chimpanzees as in persistently HCV-infected chimpanzees. Foxp3CD4CD25 TRegs suppressed IFN- production, expansion, and activation- induced cell death of HCV-specific T cells after recovery from HCV infection and in persistent HCV infection. Thus, TReg cells control HCV-specific T cells not only in persistent infection but also after recov- ery, where they may regulate memory T-cell responses by controlling their acti- vation and preventing apoptosis. However, Foxp3CD4CD25 TReg cells of both HCV- recovered and HCV-infected chimpanzees differed from Foxp3CD4CD25TReg cells of HCV-naive chimpanzees in increased IL-2 responsiveness and lower T-cell receptor excision circle content, implying a history of in vivo proliferation. This result suggests that HCV infection alters the population of Foxp3CD4CD25TReg cells. (Blood. 2006; 107:4424-4432)