The clinical symptoms of the parasitic disease malaria are caused by the intraerythrocytic stage of the Plasmodium spp life cycle. The invasive form of the malarial parasite for erythrocytes is the merozoite. Erythrocyte invasion is a multistep process and proteins required for this event are transcribed during the schizont stage and subsequently expressed at the merozoite stage. The merozoite is able to invade erythrocytes using a wide range of invasion pathways. Invasion pathways are determined by erythrocyte and merozoite properties. Erythrocyte characteristics and availability of erythrocyte receptors are crucial criteria for successful invasion. Each parasite clone possesses unique invasion properties: firstly the parasite clone does not necessarily express all homologues of the invasion protein family; secondly, the amount of a particular protein being expressed may vary; and thirdly some proteins are predominantly expressed over others.

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