Sequestration of infected red blood cells and reduced venous efflux precede excessive inflammatory responses in experimental cerebral malaria

Abstract

Cerebral malaria (CM) is a complex neurological complication of severe malaria caused by Plasmodium falciparum. Sequestration of infected red blood cells to the brain vasculature and excessive inflammatory responses in the brain are the key features of CM pathogenesis. Recent imaging studies have established edema development with rise in intracranial pressure as an indicator of fatal CM outcome. However, the link between sequestration of infected red blood cells, excessive inflammation and edema development remains elusive till date. In the present study, in vivo neuroimaging techniques, SPECT/CT and MRI, followed by immunohistochemistry stainings and quantitative reverse transcription-PCR measurements were performed on the mouse model of experimental cerebral malaria (ECM) investigating the rapid progression of the disease starting from an early stage. Sequestration of infected red blood cells, especially in the regions of large draining veins, was observed as the primary event of ECM pathogenesis, present already at a neurologically asymptomatic stage. Reduction of cerebral venous efflux and impaired perfusion in the territories of large draining veins and sinuses ensued, also from the early stage, which worsened with disease progression. In comparison, activation of astrocytes, microglia, endothelial cells and accumulation of leukocytes like CD8+ T cells were observed mostly at a later stage in the neurologically sick mice. Simultaneously, a pro-inflammatory storm of cytokines and chemokines could be detected at this late phase of ECM. Also, a disturbance in rostral migratory stream was observed, from an early stage, which could lead to an impairment in neurogenesis. Severe bilateral edema developed in the white matter tracts of the fatally sick mice. Collectively, the present study suggests direct effect of infected RBC sequestration on the spatiotemporal patterns of edema development by venous efflux reduction while excessive inflammation appears at a later stage