8, 9 Studies in viral and bacterial infections, tumor rejection and autoimmunity demonstrated that Tregs suppress proliferation, cytokine production and cytotoxic activity of naïve and antigen-specific CD4+ and CD8+ effector T cells and are able to interfere with the activity of antigen-presenting cells as well as B cells.3

Studies addressing the role of Tregs in HBV infection mostly rely on correlation of Treg frequencies in peripheral blood of patients with different disease stages and have been somewhat contradictory.10-12 Therefore, we aimed at defining the overall effect that Tregs impose on the adaptive and innate immune response against HBV and at determining how they selleckchem may influence the outcome of infection. For our study, we used DEREG mice. DEREG mice are transgenic C57BL/6 mice that express an enhanced green

fluorescent protein-human diphtheria toxin receptor fusion protein under control of the foxp3-promotor.13 Foxp3+ Tregs can be depleted in DEREG Z VAD FMK mice by injecting diphtheria toxin (DTX) systemically and specifically, albeit only transiently.13 Because HBV cannot infect murine hepatocytes, we used an adenoviral vector transferring a 1.3-fold overlength HBV-genome (AdHBV) across the species barrier.14 Following Ad-HBV infection, HBV replicates in hepatocytes and infectious HBV virions are secreted into the bloodstream. Depending on the dose of the inoculum, induction of T cell responses leads to an acute, self-limiting or a persistent HBV infection.14, 15 This study investigates the regulatory effects of Tregs on the intrahepatic HBV-specific T cell and innate immune response, and on the B cell response in the early phase of HBV infection. ALT, alanine aminotransferase; BFA, brefeldin 上海皓元医药股份有限公司 A; DC, dendritic cell; DTX, diphtheria toxin; HBc, HBV core protein; HBeAg, hepatitis B e antigen; HBs, HBV small

surface protein; HBsAg, hepatitis B surface antigen; HBV, hepatitis B virus; IFNγ, interferon-γ; i.u., infectious units; k/o, knockout; LAL, liver-associated lymphocyte; MHC, major histocompatibility complex; NK, natural killer; PCR, polymerase chain reaction; RPMI 1640, Roswell Park Memorial Institute 1640; TNF, tumor necrosis factor; Tregs, regulatory T cells. AdHBV and AdHBV knockout (k/o) were constructed, produced, purified, and titrated as described.14, 15 All animal experiments were approved by the local authorities and animals received human care in accordance to the National Institutes of Health guidelines. Eight-week-old female DEREG mice received a single injection of 109 i.u. AdHBV intravenously. For depletion of Tregs, 1 μg diphtheria toxin (Merck, Darmstadt, Germany) was injected intraperitoneally on 3 consecutive days. Mice were sacrificed at indicated time points.