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Francois Paquet-Durand, Susanne Beck, Soumyaparna Das, Timm Schubert, Naoyuki Tanimoto, Marina Garcia-Garrido, Regine Muehlfriedel, Sylvia Bolz, Benjamin Mordmueller, Mathias W Seeliger; Experimental malarial retinopathy reveals vascular alterations, parasite neuroretina infiltration, and neuronal cell death. Invest. Ophthalmol. Vis. Sci. 2018;59(9):716.
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© ARVO (1962-2015); The Authors (2016-present)
Malaria is one of the most important infectious diseases affecting mankind. Cerebral malaria is a particularly severe form of the disease, associated with high mortality and an ocular phenotype termed malarial retinopathy. Because of the connection between infection and retinopathy, ophthalmological examinations may allow for an early diagnosis of cerebral malaria.
We used Plasmodium berghei malaria parasites, transgenically labelled with GFP, to infect C57Bl6 mice. Experimental animals were studiedusing both in vivo imaging (scanning-laser-ophthalmoscopy, optical-coherence-tomography) and ex vivo histology. Ex vivo retinal preparations were stained for gliosis using GFAP immunofluorescence and cell death using the TUNEL assay, calpain activity assay, and caspase-3 immunofluorescence.
We followed the circulation of labelled malarial parasites via non-invasive in vivo retinal imaging. Ex vivo examinations showed that malarial parasites cross the blood-retinal-barrier and infiltrate the neuroretina, as assessed by GFAP co-labelling. This was concomitant with an extensive, irreversible, and long-lasting retinal neurodegeneration, as assessed by the TUNEL assay. Malarial infection was associated with increased retinal calpain activity (uninfected: 0.11%±0.02 SEM; infected: 0.39±0.08 SEM, n=5-6, p<0.001), but not caspase-3 activity. Anti-malarial treatment with dihydroartemisinin decreased the number of infected erythrocytes (from 2.8%±0.7 SEM to 0.04%±0.01 SEM, n=5-12), while the numbers of dying, TUNEL positive cells in the retina were reduced (from 0.41%±0.15 SEM to 0.15%±0.05 SEM, n=5). However, cell death was still significantly higher than in uninfected control (0.01%±0.00 SEM, n=5-6, p>0.001) and vascular symptoms were resolved only partly.
We show that murine malarial retinopathy reproduces the hallmarks of the human disease and introduce a novel preclinical model that is directly accessible, allows longitudinal measurements, and may enable future studies into disease pathogenesis and drug screening. In vivo retinal imaging may furthermore serve as a valuable tool for the early diagnosis of cerebral malaria in humans.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Malarial parasites infiltrate the neuroretina: A GFP-labelled malarial parasite (green) is shown within a GFAP-labelled Müller glial cell (red). Nuclear counterstain with DAPI (blue); photoreceptors below; scale bar=10 µm.
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