Immunization with parasite-derived apical membrane antigen 1 or passive immunization with a specific monoclonal antibody protects BALB/c mice againstlethal Plasmodium yoelii yoelii YM blood-stage infection

We have purified apical merozoite antigen 1 (AMA-1) from extracts of red bl ood cells infected with the rodent malaria parasite Plasmodium yoelii yoeli i YM. When used to immunize mice, the protein induced a strong protective r esponse against a challenge with the parasite. Monoclonal antibodies specif ic for P. yoelii yoelii AMA-1 were prepared, and one was very effective aga inst the parasite on passive immunization. A second protein that appears to be located in the apical rhoptry organelles and associated with AMA-1 was identified.