Combining regulatory T cell depletion and inhibitory receptor blockade improves reactivation of exhausted virus-specific CD8+ T cells and efficiently reduces chronic retroviral loads

PLoS Pathog. 2013;9(12):e1003798. doi: 10.1371/journal.ppat.1003798. Epub 2013 Dec 5.

Abstract

Chronic infections with human viruses, such as HIV and HCV, or mouse viruses, such as LCMV or Friend Virus (FV), result in functional exhaustion of CD8(+) T cells. Two main mechanisms have been described that mediate this exhaustion: expression of inhibitory receptors on CD8(+) T cells and expansion of regulatory T cells (Tregs) that suppress CD8(+) T cell activity. Several studies show that blockage of one of these pathways results in reactivation of CD8(+) T cells and partial reduction in chronic viral loads. Using blocking antibodies against PD-1 ligand and Tim-3 and transgenic mice in which Tregs can be selectively ablated, we compared these two treatment strategies and combined them for the first time in a model of chronic retrovirus infection. Blocking inhibitory receptors was more efficient than transient depletion of Tregs in reactivating exhausted CD8(+) T cells and reducing viral set points. However, a combination therapy was superior to any single treatment and further augmented CD8(+) T cell responses and resulted in a sustained reduction in chronic viral loads. These results demonstrate that Tregs and inhibitory receptors are non-overlapping factors in the maintenance of chronic viral infections and that immunotherapies targeting both pathways may be a promising strategy to treat chronic infectious diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies / immunology
  • CD8-Positive T-Lymphocytes / immunology*
  • Chronic Disease
  • Costimulatory and Inhibitory T-Cell Receptors / antagonists & inhibitors*
  • Costimulatory and Inhibitory T-Cell Receptors / immunology
  • Female
  • Hepatitis A Virus Cellular Receptor 2
  • Lymphocyte Activation*
  • Lymphocyte Depletion*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Programmed Cell Death 1 Receptor / immunology
  • Receptors, Virus / antagonists & inhibitors
  • Receptors, Virus / immunology
  • Retroviridae / immunology
  • Retroviridae Infections / therapy*
  • T-Lymphocytes, Regulatory / immunology*
  • Viral Load
  • Viruses / drug effects
  • Viruses / immunology

Substances

  • Antibodies
  • Costimulatory and Inhibitory T-Cell Receptors
  • Havcr2 protein, mouse
  • Hepatitis A Virus Cellular Receptor 2
  • Pdcd1 protein, mouse
  • Programmed Cell Death 1 Receptor
  • Receptors, Virus

Grants and funding

This work was supported by the German Research Association (DFG) Transregio 60 project B4 and DI 1914/1-1. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.