Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2000
Publication Date: N/A
Interpretive Summary: Babesia bovis causes a persistent blood disease of cattle in tropical and sub-tropical regions worldwide. This manuscript describes the presence of conserved regions of parasite proteins among distinct B.bovis strains that may be the important interaction with the bovine red blood cell. If these regions are involved in important parasite functins such as bovine erythrocyte recognition, then they may be employed for development of improved methods of control of bovine babesiosis.
Technical Abstract: The Babesia bovis merozoite surface antigen-1 (MSA-1), a member of the Vari Merozoite Surface Antigen (VMSA) family, is an immunodominant glycoprotein which elicits antibodies that inhibit erythrocyte invasion. While While antigenic polymorphism is a general feature of vmsa genes, the molecular basis and extent of msa-1 sequene polymorphism have not been well lcharacterized. In this study we defined the msa-1 locus in the biologically cloned Mexico Mo7 strain of B.bovis, and identified the sequence differences between MSA-1 antigenically dissimilar strains. We then determined whethersequences conserved between distinct msa-1 alleles would induce cross-reactive CD4+ T lymphocytes or inhibitory antibodies. The msa-1 locus in Mo7 contains a single msa-1 gene flanked by transcribed genes with no sequence homology to members of the vmsa family. Argentina B. bovis strains R1A and S2P have msa-1 genes with amino acid sequences that are 98.8% identical to each other, and antibodies against S2P MSA-1 cross-react with native R1A MSA-1. In contrast, identity between the Argentina and Mexico Mo7 msa-1 alleles is only 52%, with no continuous stretch of identity longer than 16 amino acids. Despite limited sequence conservation, antibodies against R1A MSA-1 were able to inhibit invasion of erythrocytes by Mo7 merozoites. The results indicate that inhibition sensitive epitope(s) are conserved despite significant sequence divergence between Mexico and Argentina strain alleles, and support a conserved functional role for polymorphic MSA-1 in erythrocyte invasion.