Control of Toxoplasma reactivation by rescue of dysfunctional CD8 + T-cell response via PD-1-PDL-1 blockade

Rajarshi Bhadra, Jason P. Gigley, Louis M. Weiss, Imtiaz A. Khan

Research output: Contribution to journalArticle

80 Scopus citations


In this study, we document that Toxoplasma gondii differentiation and reactivation are mediated by systemic CD8 T-cell dysfunction during chronic infection. We demonstrate that CD8+ T-cell exhaustion occurs despite control of parasitemia during early-chronic toxoplasmosis. During later phases, these cells become exhausted, leading to parasite reactivation and mortality. Concomitant with increased CD8+ T-cell apoptosis and decreased effector response, this dysfunction is characterized by a graded elevation in expression of inhibitory receptor PD-1 on these cells in both lymphoid and nonlymphoid tissue. Blockade of the PD-1-PDL-1 pathway reinvigorates this suboptimal CD8+ T-cell response, resulting in control of parasite reactivation and prevention of mortality in chronically infected animals. To the best of our knowledge, this report is unique in showing that exposure to a persistent pathogen despite initial control of parasitemia can lead to CD8 + T-cell dysfunction and parasite reactivation.

Original languageEnglish (US)
Pages (from-to)9196-9201
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number22
StatePublished - May 31 2011



  • Adaptive immunity
  • Recrudescence
  • Toxoplasma gondii

ASJC Scopus subject areas

  • General

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