PLASMODIUM-FALCIPARUM LACKS SIALIDASE AND TRANS-SIALIDASE ACTIVITY

Sialic acid on the red cell surface plays a major role in invasion by the malaria parasite Plasmodium falciparum. The NeuAc(alpha 2,3) Gal m otif on the O-linked tetrasaccharides of the red cell glycophorins is a recognition site for the parasite erythrocyte-binding antigen (EBA-1 75). Consequently, the interaction of P. falciparum and the red cell m ight share homology with that of the influenza virus. The cellular int eractions of P. falciparum were examined for their sensitivity to 4-gu anidino-2,3-didehydro-D-N-acetyl neuraminic acid (4-guanidino Neu5Ac2e n), a potent inhibitor of influenza virus sialidase. Parasite invasion and subsequent development was unaffected by the sialidase inhibitor. The inhibitor did not affect rosette formation of parasite-infected e rythrocytes with uninfected cells nor their cytoadherence to C32 melan oma cells. Furthermore, we were unable to confirm the presence of a pr eviously reported parasite sialidase using sensitive fluorometric or h aemagglutination assays, neither was any malarial trans-sialidase iden tified. We conclude that P. falciparum possesses neither sialidase nor trans-sialidase activity and that an inhibitor of influenza virus sia lidase has no effect on important cellular interactions of this parasi te.