Vaccination in cattle against Babesia bovis combining a modified vaccinia Ankara vector and protein ? adjuvant formulation based on a recombinant multi ? antigen

JARAMILLO ORTIZ, JOSÉ MANUEL; GRAVISACO MJ; PAOLETTA M; MONTENEGRO, VALERIA NOELY; DE LA FOURNIERE S; LOPEZ ARIAS L; VALENZANO M; GUILLEMI E; FARBER M; WILKOWSKY S. E

Banff

Simposio; Keystone Symposia: Emerging Technologies in Vaccine Discovery and Development; 2018

Keystone Symposia on Molecular and Cellular Biology

The immune control against the intraerythrocytic protozoan parasite Babesia bovis requires both cellular and humoral immune response. Therefore, tailored combinations of immunogens targeted at both arms of the immune system are strategies of choice to pursue sterilizing immunity. In this study, 13 ? 15 month - old and highly susceptible male Holstein steers (n=5 per group) were immunized with a subcutaneous dose (sc) of the currently live attenuated vaccine used in Argentina (R1A) or with a subunit vaccine as a prime (sc) and an intramuscular dose (im) of a modified vaccinia Ankara vector (MVA) as a boost, both expressing a multi-antigen (rMABbo ? rMVA). This chimeric protein includes the immunodominant B and T cell epitopes of three B. bovis proteins: Merozoite Surface Antigen ? 2c (MSA-2c), Rhoptry Associated Protein ? 1 (RAP-1) and Heat Shock Protein 20 (HSP20). A prime of a heterologous recombinant protein and a boost of wild type MVA group was used as control. Eleven weeks after the first immunization, all animals were challenged (sc) with an injection of parasite-infected erythrocytes containing 107 virulent B. bovis merozoites. All groups were monitored daily for fever and reduction of packed cell volume. Both the rMABbo ? rMVA and R1A vaccinated animals showed an antigen - specific T cellular and antibodies immune response. However, all rMABbo ? rMVA cattle shown clinical symptoms of disease upon challenge. These results confirm previous findings in murine model, but also demonstrate the limitation of the current formulation. This is the first report in which a novel vaccine candidate against Babesia bovis was constructed based on a recombinant and rationally designed viral vector and evaluated in the biological model.