Induction of protective immunity to malaria

Assessment of whether a particular antigen is a target of protective immune responses depends on the availability of purified antigens and/or monospecific antibodies to those antigens. In their work with Plasmodium falciparum the authors have attempted to clone and express in Escherichia coli as many as possible of the antigens of the asexual blood-stages of P. falciparum. These antigens, produced in E. coli, have been used to produce antisera with which the corresponding parasite antigens have been identified and characterized using the strategies outlined below. Fragments of one of the antigens, produced in E. coli as β-galactosidase fusion polypeptides, have been tested for their ability to immunize Aotus monkeys against infection with P. falciparum. This vaccine trial demonstrated that the ring-infected erythrocyte surface antigen (RESA) could induce protective immune responses and that protection correlated with antibody responses to either of two different repetitive sequences in RESA.