Abstract
Background Babesia bovis is a tick-transmitted protozoan hemoparasite and the causative agent of bovine babesiosis, a potential risk to more than 500 million cattle worldwide. The vaccines currently available are based on attenuated parasites, which are difficult to produce, and are only recommended for use in bovines under one year of age. When used in older animals, these vaccines may cause life-threatening clinical symptoms and eventually death. The development of a multi-subunit recombinant vaccine against B. bovis would be attractive from an economic standpoint and, most importantly, could be recommended for animals of any age. In the present study, recombinant ectodomains of MSA-2a1, MSA-2b and MSA-2c antigens were expressed in Pichia pastoris yeast as secreted soluble peptides.ResultsThe antigens were purified to homogeneity, and biochemically and immunologically characterized. A vaccine formulation was obtained by emulsifying a mixture of the three peptides with the adjuvant Montanide ISA 720, which elicited high IgG antibody titers against each of the above antigens. IgG antibodies generated against each MSA-antigen recognized merozoites and significantly inhibited the invasion of bovine erythrocytes. Cellular immune responses were also detected, which were characterized by splenic and lymph node CD4+ T cells producing IFN-γ and TNF-α upon stimulation with the antigens MSA-2a1 or MSA-2c.ConclusionsThese data strongly suggest the high protective potential of the presented formulation, and we propose that it could be tested in vaccination trials of bovines challenged with B. bovis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1862-1) contains supplementary material, which is available to authorized users.
Highlights
Babesia bovis is a tick-transmitted protozoan hemoparasite and the causative agent of bovine babesiosis, a potential risk to more than 500 million cattle worldwide
Expression, purification, and biochemical characterization of rMSA-2a1, rMSA-2b, and rMSA-2c For secreted expression in the methylotrophic yeast Pichia pastoris, constructs based on the codon-optimized gene sequences of Merozoite Surface Antigen (MSA)-2a1, MSA-2b and MSA-2c were used
Babesia bovis merozoite recognition and ability to inhibit parasite invasion with rMSA-2a1, rMSA-2b and rMSA-2c immune sera As a step, we investigated if antibodies against the three recombinant proteins reacted with B. bovis merozoites using immunofluorescence assays
Summary
Babesia bovis is a tick-transmitted protozoan hemoparasite and the causative agent of bovine babesiosis, a potential risk to more than 500 million cattle worldwide. When used in older animals, these vaccines may cause life-threatening clinical symptoms and eventually death. The development of a multi-subunit recombinant vaccine against B. bovis would be attractive from an economic standpoint and, most importantly, could be recommended for animals of any age. Calves become infected at a young age with B. bovis parasites and due to protective mechanisms of innate immunity, they do not develop clinical symptoms either upon infection or as adults. If the first exposure to the parasite occurs in animals older than 1 year of age, an immune imbalance is observed, which is characterized by pro-inflammatory cytokine release and the development of serious clinical symptoms, such as high temperature, sensory depression, anemia and uremia. The infection can rapidly lead to abortions and death [2, 3]
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