Enrichment of immunoglobulin binding Plasmodium falciparum-infected erythrocytes using anti-immunoglobulin-coated magnetic beads.

It has been shown that nonimmune, human immunoglobulins are bound to the surface of certain strains of Plasmodium falciparum-infected erythrocytes. We describe a novel way of enriching parasitized red blood cells (pRBC) for immunoglobulin binding/rosette formation using Dynabeads coated with antibodies raised against human immunoglobulins. Whole P. falciparum cultures were mixed with the precoated beads for approximately 120 min at room temperature, and the bound pRBC were isolated by magnetic force. The nonbound cell fraction contained ring-infected pRBC, immunoglobulin-negative, trophozoite-infected pRBC, and uninfected erythrocytes. A consistent elevation in the immunofluorescence and rosette formation rates of 100% and 86% respectively, was detected after the first enrichment and subcultivation. Protein A or G were also found to support binding of pRBC through surface-expressed immunoglobulin. The Dynabead technique is a novel way of enriching pRBC based on the immunoglobulin-binding capacity of the infected erythrocyte.