In line with the ELISA results measuring the reactivity against the recombinant proteins, we found that the antibody reactivity against native VAR2CSA on the surface of the IE differed both with respect to animal species, and with antigen type. For mice and rabbits (Figure 2A and Figure 2C ), the reactivity against native VAR2CSA on the IE surface was higher in sera from animals immunized with DBL5e and DBL6e, the reactivity against DBL1X, DBL2X, DBL3X and DBL4e was low. In general, it appeared that rats acquired higher levels of antibodies specific to the native protein compared to mice and rabbits, the difference being especially marked for DBL4e. However, as for mice and rabbits, the FV2, DBL5e and DBL6e immunizations resulted in high specific reactivity towards native VAR2CSA expressed on the IE ( Figure 2B ).