CD8<sup>+</sup> T cell infiltration and proliferation in the brainstem during experimental cerebral malaria
Jun Wang, Qinghao Zhu, Yan Shen, Jiao Liang, Yi Wang, Yuxiao Huang, Guodong Tong, Xu Wang, Ningning Zhang, Kangjie Yu, Yinghui Li, Ya Zhao
Abstract
Abstract Introduction Cerebral malaria (CM) is a lethal neuroinflammatory disease caused by Plasmodium infection. Immune cells and brain parenchyma cells contribute to the pathogenesis of CM. However, a systematic examination of the changes that occur in the brain parenchyma region during CM at the single‐cell resolution is still poorly studied. Aims To explore cell composition and CD8 + T cell infiltration, single‐cell RNA sequencing (scRNA‐seq) was performed on the brainstems of healthy and experimental cerebral malaria (ECM) mice. Then CD8 + T cell infiltration was confirmed by flow cytometry and immunofluorescence assays. Subsequently, the characteristics of the brain‐infiltrated CD8 + T cells were analyzed. Finally, the interactions between parenchyma cells and brain‐infiltrated CD8 + T cells were studied with an astrocytes‐CD8 + T cell cocultured model. Results The brainstem is the most severely damaged site during ECM. ScRNA‐seq revealed a large number of CD8 + T cells infiltrating into the brainstem in ECM mice. Brain‐infiltrated CD8 + T cells were highly activated according to scRNA‐seq, immunofluorescence, and flow cytometry assays. Further analysis found a subset of ki‐67 + CD8 + T cells that have a higher transcriptional level of genes related to T cell function, activation, and proliferation, suggesting that they were exposed to specific antigens presented by brain parenchyma cells. Brain‐infiltrated CD8 + T cells were the only prominent source of IFN‐γ in this single‐cell analysis. Astrocytes, which have a high interferon response, act as cross‐presenting cells to recruit and re‐activate brain‐infiltrated CD8 + T cells. We also found that brain‐infiltrated CD8 + T cells were highly expressed immune checkpoint molecule PD‐1, while parenchyma cells showed up‐regulation of PD‐L1 after infection. Conclusions These findings reveal a novel interaction between brain‐infiltrated CD8 + T cells and parenchyma cells in the ECM brainstem, suggesting that the PD‐1/PD‐L1 signal pathway is a promising adjunctive therapeutic strategy for ECM targeting over‐activated CD8 + T cells.