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; ECHAIDE I; PAOLETTA M; MONTENEGRO, VALERIA NOELY; DE LA FOURNIERE S; LOPEZ ARIAS L; VALENZANO M; GUILLEMI, ELIANA C.; FARBER M; WILKOWSKY S. E

Londres

Congreso; The UK & International Veterinary Vaccinology Network Conference 2019; 2019

UK Veterinary Vaccinology Network (VVN) and the International Veterinary Vaccinology Network (IVVN)

The immune control against the intraerythrocytic parasite Babesia bovis requires both cellular and humoral immune responses. Therefore, combinations of immunogens targeted at both arms of the immune system are required 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) of B. bovis. 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. After challenge, 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 response and high titers of IgG antibodies, although the latter were not neutralizing. However, all rMABbo ? rMVA cattle shown clinical symptoms of disease upon challenge, although no treatment was required for any of them.All together, these findings show that although the novel recombinant vaccine rMABbo - rMVA exhibited a strong humoral and cellular response compared to the control groups, these responses did not correlate with protection. A detailed immune characterization of the protective response obtained by the attenuated R1A strain would be of great importance to understand the biological traits involved in the high level of efficacy of this vaccine.