Abstract
During malaria [in humans] and other infections, the plasma concentration of .alpha.1-acid glycoprotein (AGP) increases 3- to 4-fold, but the function of this glycoprotein has been unknown. In vitro culture of the malaria parasite Plasmodium falciparum showed that AGP concentration achieved during malaria is sufficient to inhibit parasite multiplication by 80%. It was found that the inhibitory activity of AGP depends on and is a function of its sialic acid complement (12-16 mol/mol) and its higher-order structure. AGP acts by blocking parasite-erythrocyte interaction during the invasion process. A function for AGP with definite in vivo significance was indicated. They reveal an important protective response to malaria and perhaps other infectious diseases.