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Chapter 8 : Hunting for Protective Blood Stage Antigens
William Trager realized that malaria parasites grown in vitro or in monkeys were structurally and antigenically more complex than poliovirus and that the immune responses to these two parasites were so vastly different that a malaria vaccine was not on the horizon. Trager, to his credit, clearly recognized that a chemically defined parasite antigen would never be obtained by fractionation of intact infected red blood cells by using his beloved cultures. Instead, he felt that their main use in relation to the development of malaria vaccines would come from the identification of target antigens for both the asexual erythrocytic stages and the sexual stages by using the advances being made in biotechnology (monoclonal antibodies and recombinant DNA), areas in which he had no expertise. The concept of a blood stage vaccine is based on a fundamental principle: mimic the immunity that occurs in nature. The majority of blood stage vaccines are clustered around two hypothesized mechanisms of protection: block red blood cell entry by the merozoite and/or attack the development of the malaria parasite within the red blood cell, directly or indirectly. Leading blood stage vaccines include the merozoite surface protein 1 (MSP-1) and apical membrane antigen 1 (AMA-1).