Vaccination against babesiosis using recombinant GPI-anchored proteins

The increase in human babesiosis is of major concern to health authorities. In the USA, most of these cases are due to infections with Babesia microti, whereas in Europe B. divergens is the major cause of clinical disease in humans. Here we review the immunological and biological literature of glycosylphosphatidylinositol (GPI)-anchored merozoite proteins of human Babesia parasites with emphasis on their role in immunity, and provide some new bioinformatical information on B. microti GPI-Anchored Proteins (GPI-AP). Cattle can be vaccinated with soluble parasite antigens (SPA) of Babesia divergens that are released by the parasite during proliferation. The major component in SPA preparations appeared to be a 37?kDa merozoite surface protein that is anchored in the merozoite membrane by a GPI anchor. Animals could be protected by vaccination with the recombinant 37?kDa protein expressed in Escherichia coli, provided the protein had a hydrophobic terminal sequence. Based on this knowledge, a recombinant vaccine was developed against Babesia canis infection in dogs, successfully. In order to identify similar GPI-AP in B. microti, the genome was analysed. Here it is shown that B. microti encodes all proteins necessary for GPI assembly and its subsequent protein transfer. In addition, in total 21 genes encoding for GPI-AP were detected, some of which reacted particularly strongly with sera from B. microti-infected human patients. Reactivity of antibodies with GPI-anchored merozoite proteins appears to be dependent on the structural conformation of the molecule. It is suggested that the three-dimensional structure of the protein that is anchored in the membrane is different from that of the protein that has been shed from the merozoite surface. The significance of this protein’s dynamics in parasite biology and immune evasion is discussed. Finally, we discuss developments in tick and Babesia vaccine research, and the role such vaccines could play in the control of human babesiosis.     

Comparative safety study of two commercialised vaccines against canine babesiosis induced by Babesia canis

The safety of two vaccines available on the French market against canine babesiosis – Nobivac Piro^® (NP) and Pirodog^® (P) – have been evaluated. Their local, general and biochemical impacts have been compared in a controlled experimental study. Three groups were used: a control group (T) and two groups vaccinated twice at 21 days interval. All dogs presented moderate local reaction. However, either clinical and biological parameters showed that the NP group presented a significantly more intense reaction at the injection site compared to the P group. No statistical difference has been revealed between the groups P and T evolutions.     

Vaccines against babesiosis using soluble parasite antigens

Babesiosis in cattle and dogs causes severe economical and emotional loss. Although effective chemotherapeutic treatment of infected animals is available, the prevention of babesiosis by vaccination would be preferable. Attenuated parasite lines of Babesia bovis have been used successfully to control tropical babesiosis in cattle. However, among other drawbacks associated with live vaccines, such vaccines bear the risk of variable infectivity and morbidity requiring veterinary surveillance. Soluble parasite antigens derived from different Babesia species have proven to induce immune responses that do not necessarily affect the parasite, per se, but reduce the manifestations of clinical disease upon infection. In this review, Theo Schetters and Sonia Montenegro-James present an overview of the results obtained with vaccines based on soluble parasite antigens and their characterization, and discuss the possible immune effector mechanisms of such vaccines.