Expression of negative immune regulatory molecules, pro-inflammatory chemokine and cytokines in immunopathology of ECM developing mice

Abstract

The pathological events in human cerebral malaria are mimicked in the experimental cerebral malaria (ECM) in Plasmodium berghei ANKA (PBA)-infected C57BL/6 mice. Although previously implied in ECM, the kinetics of cytokines and chemokines expression-an essential functional feature for defining causality in ECM development-remained untested. Herein, we characterized the immunopathological changes and the expression of negative immune regulatory molecules, cytokines and chemokines through asymptomatic (3days after infection, 3dpi), symptomatic (5dpi) and ECM (7dpi) stages in PBA-infected C57BL/6 mice. Parasitized RBCs were first detected in brain on 3dpi, edema and tissue alterations on 5dpi, and hemorrhages in different areas of brain on 7dpi. Increased cerebellar PD-1, CTLA-4 and LAG-3 expression and reduced hippocampal CXCL-4 expression on 3dpi were the first observed immunological changes. The negative immune regulatory molecules (PD-L1, CTLA-4), cytokines (TNF-α, sFAS-L), and chemokines (CXCL-10, MIP-1β) transcript levels varied in different brain areas in symptomatic and ECM phases. By 5dpi, TNF-α, CXCL10 and MIP-1β significantly increased in all brain parts studied; IL-1RA in whole brain, whereas CXCL4 reduced in hippocampus and cerebrum. By 7dpi, the hippocampal PD-1, CXCL4 and CTLA-4 expression decreased but the cerebral, cerebellar and hippocampal PD-L1 expression were elevated. TNF-α, CXCL10, MIP-1β, PD-1, CTLA-4 and PD-L1 expression were up-regulated in different brain areas. The TNFR2, IFN-gamma receptor, Lymphotoxin-β receptor and sFAS-L transcripts significantly increased in brain in ECM. Our data characterize key dynamic immunopathological changes in brain to imply relationship to ECM development.

Keywords: Blood-brain barrier; Cerebral malaria; Chemokines; Cytokines; Immunopathology.