Tim-3 expression on PD-1+ HCV-specific human CTLs is associated with viral persistence, and its blockade restores hepatocyte-directed in vitro cytotoxicity
Rachel H. McMahan, Lucy Golden-Mason, Michael I. Nishimura, Brian J. McMahon, Michael Kemper, Todd M. Allen, David R. Gretch, Hugo R. Rosen
Rachel H. McMahan, Lucy Golden-Mason, Michael I. Nishimura, Brian J. McMahon, Michael Kemper, Todd M. Allen, David R. Gretch, Hugo R. Rosen
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Research Article Virology

Tim-3 expression on PD-1+ HCV-specific human CTLs is associated with viral persistence, and its blockade restores hepatocyte-directed in vitro cytotoxicity

Abstract

Having successfully developed mechanisms to evade immune clearance, hepatitis C virus (HCV) establishes persistent infection in approximately 75%–80% of patients. In these individuals, the function of HCV-specific CD8+ T cells is impaired by ligation of inhibitory receptors, the repertoire of which has expanded considerably in the past few years. We hypothesized that the coexpression of the negative regulatory receptors T cell immunoglobulin and mucin domain–containing molecule 3 (Tim-3) and programmed death 1 (PD-1) in HCV infection would identify patients at risk of developing viral persistence during and after acute HCV infection. The frequency of PD-1–Tim-3– HCV-specific CTLs greatly outnumbered PD-1+Tim-3+ CTLs in patients with acute resolving infection. Moreover, the population of PD-1+Tim-3+ T cells was enriched for within the central memory T cell subset and within the liver. Blockade of either PD-1 or Tim-3 enhanced in vitro proliferation of HCV-specific CTLs to a similar extent, whereas cytotoxicity against a hepatocyte cell line that expressed cognate HCV epitopes was increased exclusively by Tim-3 blockade. These results indicate that the coexpression of these inhibitory molecules tracks with defective T cell responses and that anatomical differences might account for lack of immune control of persistent pathogens, which suggests their manipulation may represent a rational target for novel immunotherapeutic approaches.

Authors

Rachel H. McMahan, Lucy Golden-Mason, Michael I. Nishimura, Brian J. McMahon, Michael Kemper, Todd M. Allen, David R. Gretch, Hugo R. Rosen

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Figure 8

Tim-3 blockade enhances antigen-specific CTL killing of hepatocytes.

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Tim-3 blockade enhances antigen-specific CTL killing of hepatocytes. (A)...
(A) Experimental design to assess how Tim-3 and/or PD-1 blockade affects cytotoxicity of HCV-specific CTLs against a hepatocyte cell line expressing an NS3 epitope. Cytotoxicity of NS31406-specific T cells against HepG2 cells transduced with a NS31406–1415 minigene was determined using a variation of the VITAL assay. (B) Intrahepatic lymphocytes were stimulated for 5 days with NS31406 peptide and the indicated blocking antibodies, followed by CD8+ T cell bead isolation. HCV-specific T cells were then cocultured with HepG2 cells expressing the NS31406 minigene at a 0.5:1 effector/target ratio. Percent specific lysis was calculated (see Methods). Values denote mean ± SEM of 6 patients; P values were determined using paired 2-tailed t test. (C) AST levels in the supernatants from B demonstrated an increase in cultures containing the Tim-3–blocking antibody. Values denote mean ± SEM of triplicate samples.