|MC ELWAIN, T.|
Submitted to: Molecular and Biochemical Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/1999
Publication Date: N/A
Interpretive Summary: In this work we examine lipid composition and metabolisms of bovine red blood cells infected with B. bovis parasites. Lipid composition and metabolism in Babesia parasites remained uncharacterized. These analysis are important to understand the mechanisms of erythrocyte invasion by the parasite and for the design of improved methods of bovine babesiosis. The results in this manuscript show that the phospholipid phosphatidylcholine is the predominant lipid biosynthetic event in B. bovis. The striking differences in the contents of phosphatidylcholine between host erythrocytes and the parasite suggests that it may be a useful target for both chemotherapy and immunoprophylaxis against bovine babesiosis.
Technical Abstract: This work examines the lipid composition and metabolism of bovine red blood cells infected by apicomplexan Babesia parasites.Erythrocytes infected with Babesia bovis and B.bigemina(i-RBC)accumulate lipids and show increases in phosphatidylcholine,phosphatidic acid,diacylglycerol and cholesteryl esters as compared to uninfected erythrocytes cultured under the same conditions (n-RBC).In B.bovis merozoites phosphatidylcholine is the most abundant phospholipid while in bovine n-RBC it is only a minor component.B.Bovis cultures incorporate radiolabed choline mainly into phosphatidylcholine, with minor amounts recovered in sphingomyelin and lysophosphatidylcholine. When[14C]stearate was used as precursor,the labeling pattern again gave the highest incorporation into phosphatidylcholine.Diacylglycerol and small amounts of cholesteryl esters were the only labeled neutral lipids found. B.bovis also incorporates[3H]myo-inositol into phosphatidylinosital.Incuba- -tions with n-RBC as a control yielded no incorporation into either polar o neutral lipids with any precursor.The results indicate that the lipid changes observed in i-RBC are due to the lipid biosynthetic activities of the parasite.Gas chromotography-mass spectrometry(GC-MS)analysis of fatty acid methyl esters from phospholipids of i-RBC and n-RBC showed the same qualitative composition in both.However,i-RBC had higher ratios of saturated fatty acids and B.bovis cultures did not desaturate[14C]stearate. Cholesterol was the only sterol detected by GC-MS.This study provides the first data on B.bovis lipid constitution and biosynthesis.The differences in the contents of phosphatidylcholine between host erythrocytes and the parasite suggests that it may be a useful target for controlling bovine babesiosis.