Vaccine strategies against Babesia bigemina based on prime-boost immunizations in mice with recombinant proteins and modified vaccinia Ankara vector

MONTENEGRO, VALERIA NOELY; JARAMILLO ORTIZ, JOSÉ MANUEL; PAOLETTA, MARTINA SOLEDAD; GRAVISACO, MARÍA JOSÉ; DE LA FOURNIÈRE, SOFÍA ANA MARÍA; VALENZANO, MAGALÍ NICOLE; DEL MEDICO PAULA; CALAMANTE, GABRIELA; WILKOWSKY, SILVINA ELIZABETH

Mar del Plata

Congreso; Reunión Sociedad Argentina de Protozoología 2019; 2019

Babesia bigemina is an apicomplexan tick-borne parasite that infects RBC causing cattle morbidity and mortality in vast world areas. Vaccination with attenuated strains is effective but they have inherent disadvantages. Immunity to Babesia sp. requires both innate and adaptive responses including CD4+ T cells and neutralizing antibodies. The aim of this study was to evaluate prime-boost heterologous schemes in mice using immunogens that activate both humoral and cellular responses.Three recombinant proteins and two modified vaccinia virus Ankara (MVA) expressing a chimeric multi-antigen were obtained and evaluated as vaccines. The multi-antigen comprises B and T cell epitopes of the B. bigemina proteins: AMA-1, RAP-1 and TRAP-1. Epitope prediction was performed by bioinformatics using the B. bigemina genome. Mice were immunized at day 0 with recombinant proteins and at day 30 with each MVA. One group received a prime of AMA-1, RAP-1 and TRAP-1 in equal amounts and 30 days after alpha- MVA (containing epitopes of AMA-1 and RAP-1) and beta-MVA (containing epitopes of TRAP-1). A second group received a prime of AMA-1 and RAP-1 and a boost of alpha-MVA. A third group was immunized with recombinant TRAP-1 and then with beta-MVA. Two control groups received either a heterologous protein and wt-MVA or vehicle only. Serum samples were collected for antibody analysis and spleen cells were obtained at day 60 for cellular and cytokines assays. Priming with a cocktail of the 3 antigens and a boost with alpha-MVA and beta-MVA induced the highest level of specific IgG antibodies and activation of IFN+ CD4+ and CD8+ specific T cells. This group also showed a high ratio (>1) of IgG2a to IgG1 for the recombinant proteins AMA-1 and RAP-1 suggesting a strong induction of Th1-biased response. In summary, we have shown that a three-protein cocktail and both MVA used in prime-boost regimes are immunogenic for both antibodies and CD8+ /CD4+ T cells generating promising levels of B and T cell mediated immunity.