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United States Department of Agriculture

Agricultural Research Service

Title: Babesia Bovis Merozoite Surface Protein-2c (Msa-2c) Contains Highly Immunogenic, Conserved B-Cell Epitopes That Elicit Neutralization-Sensitive Antibodies in Cattle

Authors
item Wilkowsky, S - CNIA,INTA-CASTELAR,ARGENT
item Farber, M - CNIA,INTA-CASTELAR,ARGENT
item Echaide, I - INTA,EEA RAFAELA, ARGENTI
item Torioni DE Echaide, S - INTA,EEA RAFAELA, ARGENTI
item Zamorano, P - CNIA,INTA-CASTELAR, ARGEN
item Dominguez, M - CNIA, INTA-CASTELAR, ARGE
item SUAREZ, CARLOS
item Florin-Christensen, M - CNIA, INTA-CASTELAR, ARGE

Submitted to: Molecular and Biochemical Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 26, 2002
Publication Date: N/A

Interpretive Summary: Bovine babesiosis caused by B. bovis is an important tick-borne hemoparasitic disease. The search for vaccine candidates against bovine babesiosis caused by Babesia bovis is greatly focused on the identification of merozoite surface-exposed antigens that are widely conserved, functionally relevant and immunodominant in cattle protected against B. bovis infections. We have recently identified msa-2c, a member of the B. bovis VMSA gene family, which in contrast to other members, appears to be highly conserved among geographically distant B. bovis strains. In this study, we further investigated the potential of the msa-2c gene product as diagnostic and vaccine candidate for bovine babesiosis. MSA-2c is expressed in the surface of merozoites, appears to be widely conserved among distinct strains and it is recognized by antibodies in sera from cattle either naturally or experimentally infected with Argentine strains of B. bovis. Experimental vaccination of bovines with recombinant MSA-2c (rMSA-2c) resulted in elicitation of high specific anti-rMSA-2c IgG titers, with similar amounts of IgG1 and IgG2 produced. Importantly, bovine anti-rMSA-2c antibodies were able to neutralize in vitro bovine erythrocyte invasion by R1A merozoites suggesting a significant functional role for MSA-2c. Taken together these results postulate MSA-2c as a candidate for the development of novel tools for improved control of bovine babesiosis.

Technical Abstract: The search for vaccine candidates against bovine babesiosis caused by Babesia bovis is greatly focused on the identification of merozoite surface-exposed antigens that are widely conserved, functionally relevant and immunodominant in cattle protected against B. bovis infections. We have recently identified msa-2c, a member of the B. bovis VMSA gene family, which in contrast to other members, appears to be highly conserved among geographically distant B. bovis strains. In this study, we further investigated the potential of the msa-2c gene product as diagnostic and vaccine candidate for bovine babesiosis. RT-PCR studies demonstrated that MSA-2c is transcribed in merozoites of the Argentine R1A strain. In addition, antibodies against R1A recombinant MSA-2c reacted in immunoblots with a single protein of approximately 30 kD in B. bovis merozoite extracts from both R1A and Australian ¿S¿ strains, demonstrating translation of this protein in these two strains and conservation of B-cell epitopes between them. These antibodies reacted with the cell surface of R1A merozoites in fixed immunofluorescence assays, indicating the surface localization of MSA-2c. This localization was confirmed by live immunofluorescence studies in two different strains, R1A and S2P. These results also demonstrate the conservation of MSA-2c surface-exposed B-cell epitopes between these two strains. Sera from cattle either naturally or experimentally infected with Argentine strains of B. bovis specifically recognized rMSA-2c in immunoblots, reinforcing the idea that B-cell epitopes in rMSA-2c are widely conserved among field strains of B. bovis. Furthermore, our results show that these B-cell epitopes are highly immunogenic, suggesting that MSA-2c may be a useful diagnostic tool for the detection of bovine babesiosis by B. bovis. Experimental vaccination of 5 bovines with rMSA-2c resulted in elicitation of high specific anti-rMSA-2c IgG titers, with similar amounts of IgG1 and IgG2 produced. Importantly, bovine anti-rMSA-2c antibodies were able to neutralize in vitro bovine erythrocyte invasion by R1A merozoites suggesting a significant functional role for MSA-2c. Taken together these results postulate MSA-2c as a candidate for the development of novel tools for improved control of bovine babesiosis.

Last Modified: 7/25/2014
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