Protective Immunity in Mice Immunized With MSP1-Based Formulations and Challenged With Expressing MSP1.

The lack of continuous cultures has been an obstacle delaying pre-clinical testing of vaccine formulations based on known antigens. In this study, we generated a model to test available formulations based on the MSP1 antigen. The strains ANKA and NK65 were modified to express MSP1 instead of the endogenous MSP1. The hybrid parasites were used to challenge C57BL/6 or BALB/c mice immunized with MSP1-based vaccine formulations. The MSP1 was correctly expressed in the hybrid mutant lines as confirmed by immunofluorescence using anti-MSP1 monoclonal antibodies and by Western blot. Replacement of the MSP1 by the MSP1 had no impact on asexual growth . High titers of specific antibodies to MSP1 were not sufficient to control initial parasitemia in the immunized mice, but late parasitemia control and a balanced inflammatory process protected these mice from dying, suggesting that an established immune response to MSP1 in this model can help immunity mounted later during infection.