Concentration of Plasmodium ovale- and Plasmodium vivax-infected erythrocytes from nonhuman primate blood using Percoll gradients.

Plasmodium vivax and Plasmodium ovale schizont-infected erythrocytes were separated from peripheral blood by centrifugation using discontinuous Percoll (colloidal silica) gradients. Infected Aotus monkey or chimpanzee blood was diluted and placed on a discontinuous gradient containing 30%, 40%, 45%, and 50% Percoll (v/v in media) layers before centrifugation at 1,450 X g. Parasitized erythrocytes were concentrated to greater than 95% schizont-infected cells in two bands that contained an average of one leukocyte per 500 infected cells. Mononuclear cells and trophozoites were isolated in another band and noninfected red cells, ring-infected cells, and granulocytes were pelleted to the bottom. The yield of parasitized erythrocytes ranged from 50% to close to 100% of the estimated number of infected cells in the original whole blood. Use of this Percoll procedure results in a high yield of concentrated parasitized erythrocytes and separation of these cells from host white blood cells.