Experimental Cerebral Malaria Spreads along the Rostral Migratory Stream

PLoS Pathog. 2016 Mar 10;12(3):e1005470. doi: 10.1371/journal.ppat.1005470. eCollection 2016 Mar.

Abstract

It is poorly understood how progressive brain swelling in experimental cerebral malaria (ECM) evolves in space and over time, and whether mechanisms of inflammation or microvascular sequestration/obstruction dominate the underlying pathophysiology. We therefore monitored in the Plasmodium berghei ANKA-C57BL/6 murine ECM model, disease manifestation and progression clinically, assessed by the Rapid-Murine-Coma-and-Behavioral-Scale (RMCBS), and by high-resolution in vivo MRI, including sensitive assessment of early blood-brain-barrier-disruption (BBBD), brain edema and microvascular pathology. For histological correlation HE and immunohistochemical staining for microglia and neuroblasts were obtained. Our results demonstrate that BBBD and edema initiated in the olfactory bulb (OB) and spread along the rostral-migratory-stream (RMS) to the subventricular zone of the lateral ventricles, the dorsal-migratory-stream (DMS), and finally to the external capsule (EC) and brainstem (BS). Before clinical symptoms (mean RMCBS = 18.5±1) became evident, a slight, non-significant increase of quantitative T2 and ADC values was observed in OB+RMS. With clinical manifestation (mean RMCBS = 14.2±0.4), T2 and ADC values significantly increased along the OB+RMS (p = 0.049/p = 0.01). Severe ECM (mean RMCBS = 5±2.9) was defined by further spread into more posterior and deeper brain structures until reaching the BS (significant T2 elevation in DMS+EC+BS (p = 0.034)). Quantitative automated histological analyses confirmed microglial activation in areas of BBBD and edema. Activated microglia were closely associated with the RMS and neuroblasts within the RMS were severely misaligned with respect to their physiological linear migration pattern. Microvascular pathology and ischemic brain injury occurred only secondarily, after vasogenic edema formation and were both associated less with clinical severity and the temporal course of ECM. Altogether, we identified a distinct spatiotemporal pattern of microglial activation in ECM involving primarily the OB+RMS axis, a distinct pathway utilized by neuroblasts and immune cells. Our data suggest significant crosstalk between these two cell populations to be operative in deeper brain infiltration and further imply that the manifestation and progression of cerebral malaria may depend on brain areas otherwise serving neurogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anopheles / parasitology*
  • Brain / diagnostic imaging
  • Disease Models, Animal
  • Female
  • Follow-Up Studies
  • Longitudinal Studies
  • Magnetic Resonance Imaging
  • Malaria, Cerebral / diagnostic imaging*
  • Malaria, Cerebral / parasitology
  • Male
  • Mice, Inbred C57BL
  • Microglia / diagnostic imaging
  • Neural Stem Cells / diagnostic imaging
  • Olfactory Bulb / diagnostic imaging
  • Plasmodium berghei / physiology*
  • Radiography

Grants and funding

This work was supported by an award from the German Society of Pediatric Infectious Diseases (Deutsche Gesellschaft fuer Paediatrische Infektiologie, DGPI) to JP. AH, FTK and FS receive funding from a postdoctoral stipend of the Medical Faculty of the University of Heidelberg. JP received funding from the German Centre for Infection Research (Deutsches Zentrum fuer Infektionsforschung, DZIF) (grant no. 80006013). MP is supported by a memorial stipend from the Else-Kröner-Fresenius-Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.