PARASITOLOGY

Infection in Real Time

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Science  10 Jun 2005:
Vol. 308, Issue 5728, pp. 1519
DOI: 10.1126/science.308.5728.1519a

Malaria parasites (Plasmodium) are injected into the mammalian bloodstream by mosquitoes, and the sporozoites travel to the liver, where they elude host immune responses and grow. Frevert et al. have taken a technically sophisticated approach to visualizing parasite infiltration of the liver in real time. Mosquitoes, infected with red fluorescent protein-labeled parasites, were continuously fed on a mouse engineered to express green fluorescent protein in cells of the liver sinusoids. Simultaneously, the mouse was held on the stage of a fluorescence microscope, and a lobe of the liver was exposed through the abdominal wall so that the route of the parasites could be monitored. The sporozoites could be seen to glide across the surface of the sinusoidal epithelial cells, to slow down and enter the Kupffer cells, and to use these as a bridge into the liver parenchyma. For up to 15 min, sporozoites traversed destructively through hepatocytes, leaving a trail of necrosis, until finally halting within a hepatocyte and replicating. During these journeys, parasites leave a trail of surface proteins, which tolerize the already immunologically lax Kupffer cells and hence help to shield the invader from host responses. — CA

PloS Biol. 3, e192 (2005).

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