Highly competent, non-exhausted CD8+ T cells continue to tightly control pathogen load throughout chronic Trypanosoma cruzi infection

PLoS Pathog. 2018 Nov 12;14(11):e1007410. doi: 10.1371/journal.ppat.1007410. eCollection 2018 Nov.

Abstract

Trypanosoma cruzi infection is characterized by chronic parasitism of non-lymphoid tissues and is rarely eliminated despite potent adaptive immune responses. This failure to cure has frequently been attributed to a loss or impairment of anti-T. cruzi T cell responses over time, analogous to the T cell dysfunction described for other persistent infections. In this study, we have evaluated the role of CD8+ T cells during chronic T. cruzi infection (>100 dpi), with a focus on sites of pathogen persistence. Consistent with repetitive antigen exposure during chronic infection, parasite-specific CD8+ T cells from multiple organs expressed high levels of KLRG1, but exhibit a preferential accumulation of CD69+ cells in skeletal muscle, indicating recent antigen encounter in a niche for T. cruzi persistence. A significant proportion of CD8+ T cells in the muscle also produced IFNγ, TNFα and granzyme B in situ, an indication of their detection of and functional response to T. cruzi in vivo. CD8+ T cell function was crucial for the control of parasite burden during chronic infection as exacerbation of parasite load was observed upon depletion of this population. Attempts to improve T cell function by blocking PD-1 or IL-10, potential negative regulators of T cells, failed to increase IFNγ and TNFα production or to enhance T. cruzi clearance. These results highlight the capacity of the CD8+ T cell population to retain essential in vivo function despite chronic antigen stimulation and support a model in which CD8+ T cell dysfunction plays a negligible role in the ability of Trypanosoma cruzi to persist in mice.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • CD8-Positive T-Lymphocytes / immunology*
  • CD8-Positive T-Lymphocytes / metabolism*
  • CD8-Positive T-Lymphocytes / physiology
  • Chagas Disease / immunology*
  • Chagas Disease / metabolism
  • Lectins, C-Type / genetics
  • Lectins, C-Type / metabolism
  • Longitudinal Studies
  • Mice
  • Mice, Inbred C57BL
  • Muscle, Skeletal / immunology
  • Receptors, Immunologic
  • Trans-Activators / genetics
  • Trans-Activators / metabolism
  • Trypanosoma cruzi / immunology
  • Trypanosoma cruzi / pathogenicity
  • Tumor Necrosis Factor-alpha

Substances

  • KLRG1 protein, human
  • Lectins, C-Type
  • Receptors, Immunologic
  • Trans-Activators
  • Tumor Necrosis Factor-alpha