Urinary neopterin in volunteers experimentally infected with Plasmodium falciparum.

To investigate the kinetics of monocyte/macrophage activation in falciparum malaria we determined urinary neopterin values serially in experimentally infected volunteers. Three subjects who had been immunized with irradiated sporozoites via mosquito bites served as controls. These individuals remained aparasitaemic, afebrile and without a rise in neopterin after challenge by infective mosquitoes. Four non-immune subjects developed Plasmodium falciparum parasitaemia, fever (3 of 4) and sharp rises in neopterin. Parasite densities reached 10-100 parasitized erythrocytes per microliter before elevations in temperature or neopterin levels were detected. Onset of fever preceded the rise in neopterin excretion by one day. Prompt chemotherapy was associated with the clearance of parasites from the blood and the return of temperature and neopterin levels to normal.