Accumulating evidence implicates inflammation and immune responses in the pathophysiology of stroke. Immunomodulation has therefore emerged as a promising therapy for stroke. Regulatory lymphocytes, including CD4+CD25+ regulatory T cells (CD4+ Treg) and IL-10+ regulatory B cells (Bregs) are established modulators of immune responses in the injured brain. We recently discovered that another specialized T cell subpopulation?the CD8+CD122+CD49dhigh regulatory T cell?is among the first to enter the ischemic brain, even preceding the infiltration of CD4+ Tregs and Bregs. The primary function of CD8+ Tregs is to modulate the activities of other immune cells, especially effector T lymphocytes, and to maintain immune homeostasis. We found that selective depletion of circulating CD8+ Tregs exacerbated brain injury and functional outcomes at 3 and 7 days after stroke, and this could be reversed by the reconstitution of CD8+ Tregs. These exciting results suggest that CD8+ Tregs are natural defenders against ischemic brain injury. Further pilot studies discovered that: 1) CD8+ Treg-afforded early protection relies on their infiltration into the ischemic brain, as CD8+ Tregs lacking the ?brain targeting signal? CXCR3 do not infiltrate into the ischemic brain and lose their capacity to reduce brain infarction in CD8+ Treg-depleted mice. 2) The infiltrated CD8+ Tregs undergo genomic reprogramming upon brain infiltration and transcriptional upregulation of a group of genes that possess inflammation-resolving and/or neurorestorative functions, including the leukemia inhibitory factor (LIF) receptor and epidermal growth factor-like transforming growth factor (ETGF). 3) Post-stroke adoptive transfer of CD8+ Tregs significantly reduces brain infarct, enhances white matter integrity, and improves neurological functions up to 14d after tMCAO. 4) Adoptive transfer of ETGF-deficient CD8+ Treg fails to protect against tMCAO. The current proposal will further explore the effects of CD8+ Tregs in ischemic stroke and develop CD8+ Treg adoptive transfer as an immune therapeutic therapy for stroke. The novel central hypothesis to be tested is that brain infiltration of CD8+ Tregs promotes long-term neurological recovery after stroke through LIF/LIFR/ETGF-mediated neuroprotection, resolution of neuroinflammation, and neurorestorative mechanisms.
Three specific aims are proposed.
Aim 1. Establish post-stroke adoptive transfer of CD8+ Tregs as a clinically relevant treatment against acute ischemic brain infarct.
Aim 2. Test the hypothesis that post-stroke adoptive transfer of CD8+ Tregs promotes long-term neurological recovery and neurorestoration after ischemic stroke.
Aim 3. Test the hypothesis that LIF/LIFR-mediated release of ETGF is essential for CD8+ Treg-afforded neuroprotection and neurorestoration. This study will be the first to rigorously investigate the role of CD8+ Tregs in ischemic brain injury. The results will improve our understanding of stroke immunomodulation and shed light on CD8+ Treg transfer as a potential therapeutic strategy.

Public Health Relevance

Immunological responses may play important roles in both brain injury and recovery after ischemic stroke. This proposal will investigate the role of a novel population of anti-inflammatory immune cells, named CD8+CD122+ regulatory T cells (CD8+Tregs), in improving both short-term and long-term stroke outcomes using rodent models of cerebral ischemia. The proposed studies will also elucidate the mechanisms underlying CD8+Treg- afforded beneficial effects against stroke, which likely involve neuroprotection, resolution of post-stroke brain inflammation, and enhancement of brain repair. This research may pave the road for the development of novel therapeutic strategies for the treatment of ischemic stroke.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Bosetti, Francesca
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University of Pittsburgh
Schools of Medicine
United States
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Zhang, Haiyue; Xia, Yuguo; Ye, Qing et al. (2018) In Vivo Expansion of Regulatory T Cells with IL-2/IL-2 Antibody Complex Protects against Transient Ischemic Stroke. J Neurosci 38:10168-10179
Hu, Xiaoming; Leak, Rehana K; Thomson, Angus W et al. (2018) Promises and limitations of immune cell-based therapies in neurological disorders. Nat Rev Neurol 14:559-568
Yang, Tuo; Sun, Yang; Mao, Leilei et al. (2018) Brain ischemic preconditioning protects against ischemic injury and preserves the blood-brain barrier via oxidative signaling and Nrf2 activation. Redox Biol 17:323-337