Protection of mice infected with Plasmodium berghei by Bacillus thuringiensis crystal proteins.

Eight Bacillus thuringiensis strains were used to test their activity against Plasmodium berghei. When crystal proteins extracted from strains 007, 017, 020, 021, 030, 032, and 037 were injected into plasmodium-infected mice through the tail vein at a rate of 0.45-1.5 mg per mouse, the lengths of survival for the mice were extended up to 5 days (from 8.5 days to 13.5-15 days). Blood-cell staining demonstrated that normal erythrocytes were lightly stained and regularly shaped while the erythrocytes from plasmodia-infected mice swelled, lost shape and even lysed. This means that the crystal proteins could protect erythrocytes from the plasmodium's attack. Proteins analysis revealed that most of the proteins are homologues of classic crystal proteins, with the exception of the 120-kDa protein of strain 020, a surface-layer protein. This study suggested a novel way to control plasmodial infections and even malaria.