The translationally controlled tumor protein (TCTP), a novel antigen of Babesia bovis, participates in the establishment of acute infection and contains neutralizing B-cell epitopes

Authors: PÉREZ-ALMEIDA, CYMTHIA - Autonomous University Of Queretaro; HERNÁNDEZ-SILVA, DIEGO - Autonomous University Of Queretaro; HERNÁNDEZ-ARVIZU, EDWIN - Autonomous University Of Queretaro; ASADA, MASAHITO - Obihiro University Of Agriculture And Veterinary Medicine; KAWAZU, SHIN-ICHIRO - Obihiro University Of Agriculture And Veterinary Medicine; Ueti, Massaro; GOMEZ-SOTO, JOSÉ - Autonomous University Of Queretaro; DÁVILA-MONTERO, URSO - Autonomous University Of Queretaro; VEGA Y MURGUIA, CARLOS - Autonomous University Of Queretaro; MOSQUEDA, JUAN - Autonomous University Of Queretaro

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2025
Publication Date: 5/20/2025
Citation: Pérez-Almeida, C., Hernández-Silva, D.J., Hernández-Arvizu, E.E., Asada, M., Kawazu, S., Ueti, M.W., Gomez-Soto, J., Dávila-Montero, U.M., Vega y Murguia, C.A., Mosqueda, J. 2025. The translationally controlled tumor protein (TCTP), a novel antigen of Babesia bovis, participates in the establishment of acute infection and contains neutralizing B-cell epitopes. Pathogens. 14(5). Article 502. https://doi.org/10.3390/pathogens14050502.
DOI: https://doi.org/10.3390/pathogens14050502

Interpretive Summary: Babesia bovis is the causative agent of bovine babesiosis. The Translationally Controlled Tumor Protein (TCTP) is believed to interfere with the immune response by inhibiting the activation and proliferation of B-cell lymphocytes. In this study, we identified the tctp gene in the genome of B. bovis and confirmed its critical role in the infection process. We amplified and sequenced the gene from five different isolates, revealing over 99% conservation among them. TCTP expression was detected in intra-erythrocytic parasites through western blotting and confocal microscopy. Cattle immunized with TCTP peptides and subsequently challenged with a virulent strain exhibited milder clinical symptoms compared to the control group. In contrast, unvaccinated animals showed significantly lower total antibody levels after the challenge, suggesting that TCTP interferes with the immune response. Serum from immunized cattle demonstrated an ability to reduce infection in neutralization assays. In summary, the tctp gene produces conserved B-cell epitopes that stimulate the production of effective neutralizing antibodies, thereby enhancing the immune response and diminishing clinical symptoms in infected cattle.

Technical Abstract: Babesia bovis is a protozoan causing bovine babesiosis. It has been postulated that, in Apicomplexa parasites, the Translationally Controlled Tumor Protein (TCTP) interferes with the immune response by blocking the activation and proliferation of B-cell lymphocytes. Here, we identified the tctp gene in the B. bovis genome, identified peptides with predicted B-cell epitopes, generated specific antibodies, evaluated their potential to block erythrocyte invasion and assessed the role of TCTP in the establishment of an acute B. bovis infection. The complete tctp gene was amplified and sequenced in five B. bovis isolates; the gene and the predicted protein sequences were >99% conserved. Expression was confirmed in intra erythrocytic parasites by western blot and confocal microscopy. Peptides containing predicted B-cell epitopes were predicted, synthesized, and used in immunization assays, demonstrating their immunogenic capacity by inducing specific antibodies. Cattle were immunized with the mix of TCTP peptides, and they were challenged with a virulent strain of B. bovis. Clinical signs and parasitemia were monitored for 15 days. Less severe clinical signs were observed in immunized animals compared with controls. A lower amount (p<0.05) of total antibodies was observed in the serum of unvaccinated animals after challenge, indicating an interference of B. bovis TCTP with the bovine immune response. A neutralization assay was carried out using in vitro cultured B. bovis and serum against TCTP peptide. A reduction of >32% was observed with the sera from immunized cattle compared with control cattle sera. It is concluded that B. bovis has a tctp gene that is expressed in erythrocytic stages. The protein contains peptides with conserved B-cell epitopes, which induce neutralizing antibodies in immunized animals. Anti-TCTP antibodies help reduce the clinical signs and improve the humoral immune response of infected cattle.