Resistance of Melanesian elliptocytes (ovalocytes) to invasion by Plasmodium knowlesi and Plasmodium falciparum malaria parasites in vitro.

Erythrocytes from humans with Melanesian elliptocytosis are resistant to invasion by Plasmodium falciparum in vitro and epidemiological evidence suggests they may be resistant to P. vivax and P. malariae. We have examined the ability of P. knowlesi merozoites to invade Melanesian elliptocytes in vitro as a definitive means of examining these cells for resistance to invasion by malarial species with different receptor requirements. The Melanesian elliptocytes were highly resistant to invasion by P. knowlesi merozoites showing that the resistance associated with this erythrocyte variant lies at a level common to the invasion pathway(s) of P. falciparum and P. knowlesi. This makes Melanesian elliptocytosis unique as no other human erythrocyte variant has been shown to be resistant to invasion by both species.