Immunomolecular characterization of MIC-1, a novel antigen in babesia bigemina, which contains conserved and immunodominant B-cell epitopes that induce neutralizing antibodies

Authors: HERNÁNDEZ-SILVA, DIEGO JOSIMAR - Autonomous University Of Queretaro; VALDEZ-ESPINOZA, URIEL MAURICIO - Universidad Nacional Autonoma De Mexico; MERCADO URIOSTEGUI, MIGUEL ANGEL - Autonomous University Of Querétaro; AGUILAR-TIPACAMÚ, GABRIELA - Autonomous University Of Querétaro; RAMOS-ARAGÓN, JUAN ALBERTO - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP); HERNÁNDEZ-ORTIZ, RUBEN - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP); Ueti, Massaro; MOSQUEDA, JUAN - Autonomous University Of Querétaro

Submitted to: Journal of Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2018
Publication Date: 4/1/2018
Citation: Hernández-Silva, D., Valdez-Espinoza, U., Mercado Uriostegui, M., Aguilar-Tipacamú, G., Ramos-Aragón, J., Hernández-Ortiz, R., Ueti, M.W., Mosqueda, J. 2018. Immunomolecular characterization of MIC-1, a novel antigen in babesia bigemina, which contains conserved and immunodominant B-cell epitopes that induce neutralizing antibodies. Journal of Veterinary Science. https://doi.org/10.3390/vetsci5020032.
DOI: https://doi.org/10.3390/vetsci5020032

Interpretive Summary: Bovine babesiosis is widespread in tropical and subtropical regions and a large portion of cattle populations live in endemic areas. Currently, there are no effective strategies that control infection or disease. In this study, the conserved protein domain MIC-1 was found in the B. bigemina genome. Transcript was detected in B. bigemina blood stages by RT-PCR. Antibodies against peptides containing conserved B-cell epitopes were generated and confirmed the expression of the protein during blood stage development by immunoblot and indirect immunofluorescence assays. The presence of antibodies against this conserved protein in cattle naturally infected with B. bigemina was determined by indirect ELISA. The results showed up to 97.4% of cattle sera (113 out of 116) reacted with MIC-1. Finally, antibodies specific against MIC-1 were able to block 70% merozoite red blood cell invasion in vitro. In conclusion, B. bigemina MIC-1 is a novel antigen expressed in merozoites that induces neutralizing antibodies and contains conserved peptides.

Technical Abstract: Babesia bigemina in one the most prevalent species causing bovine babesiosis around the world. Antigens involved in host cell invasion are vaccine targets for this disease but are largely unknown for this species. The invasion process of Babesia spp. into erythrocytes involves various membrane proteins and organelles from the apical complex. A protein stored in the micronemes, called Micronemal Protein 1 (MIC-1), is a protein that contains a sialic acid binding domain (MAR); it participates in the invasion process of host cells and is a vaccine candidate in other apicomplexan parasites. It is not known if there is a homologous gene for mic-1 in B. bigemina. Therefore, the aim of this study was to characterize the MIC-1 gene homologue in B. bigemina. A gene was found with a MAR domain in the predicted amino acid sequence. Transcription was determined by RT-PCR. Subsequently, antibodies against peptides containing conserved B-cell epitopes were generated and were used to confirm the expression of MIC-1 in intraerythrocytic merozoites by immunoblotting and indirect immunofluorescence. The presence of anti-MIC-1 antibodies in cattle naturally infected with B. bigemina was determined by indirect ELISA, where up to 97.4% of the cattle sera (113 out of 116) reacted specifically MIC-1. Finally, antibodies specific against MIC-1 were able to block 70% merozoite red blood cell invasion in vitro. In conclusion, B. bigemina MIC-1 is a novel antigen expressed by merozoites that induces neutralizing antibodies and contains conserved peptides.