Vaccine model based on recombinant hydrophobic protein and saponin

The Bd37 is an erythrocyte binding protein anchored at the surface of the parasite Babesia divergens. B. divergens is an Apicomplexa parasite, mostly of veterinary importance but able to infect humans after tick-bites. The lab model of bovine and human babesiosis is provided by the gerbils Meriones unguiculatus infected by Babesia divergens. Recombinant hydrophobic Bd37 is able to induce complete protective immune response when mixed with saponin, in contrast to hydrophilic Bd37 which only induce non-protective antibodies.

Interest / Relevance: Vaccine based on recombinant proteins, as well as efficient adjuvants, are challenging to develop. Interestingly, combination of hydrophobic recombinant protein and saponin has been successfully used in CoVID-19 vaccine from NOVAVAX and in the R21 vaccine against malaria.
The Bd37 vaccine model allows shifting from an inefficient to a fully protective immune response using hydrophobic peptide sequence and saponin. So this model is ideal to study protective and unprotective immune responses from basic point of view, to try correlate of protection discovery pipeline etc...
Ranging from in vitro to in vivo experiments, this vaccine model can also be used in the development of new vaccine formulation and efficient adjuvant.
Keywords: POC in vivo, vaccine, Apicomplexa, parasite, adjuvant,
Scientist's name: Stéphane DELBECQ
Schetters TPM
Detailed technology overview: This vaccine model use gerbils (Meriones unguiculatus) as host, which are immunized with positive and negative Bd37 vaccines. Immunization schedule consists in two injections at 3 weeks intervals, then infectious challenge is performed. Living parasites from in vitro culture are injected by IP route in gerbils. The infection develops in 3-10 days and clinical signs are monitored daily (parasitemia and haematocrit) by blood sampling at the tail. The positive Bd37 vaccine induce a complete protection, both against parasites (no infection) and diseases (no clinical signs). So any modification of the antigen Bd37 (either new hydrophobic sequence, lipids, etc…) could be tested, as well as new adjuvants or even new vaccine technologies (mRNA, nanoparticles…).

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