1. Field of the Invention
Plasmodium falciparum Merozoite Surface Protein 3 (MSP3) C-terminal polypeptides, including immunogenic and antigenic peptides which contain B cell epitopes and T helper epitopes and which inhibit the growth of Plasmodium falciparum. 
2. Description of Related Art
The asexual blood-stage multiplication of the malarial parasite is responsible for the acute symptoms of malaria in humans. Epidemiological observations have shown that adults living in endemic areas, although they are constantly reinfected and frequently carry parasites, control their levels of parasitemia and show substantial clinical resistance, compared with children [1].
Repeated infections and continued exposure to the malarial parasite are required to reach this level of immunity against disease [2]. This state of naturally acquired immunity against disease, a phenomenon that is called premonition [3], is not a sterile immunity and is marked by chronic lowgrade parasitemia without clinical symptoms.
The passive transfer of serum IgG from clinically immune individuals has been shown to be able to control disease and the level of parasitemia in nonprotected individuals who are exposed to geographically diverse parasite strains [4-6].
The present inventors previously showed that the protection afforded by IgG has no major direct effect on parasite invasion and growth in red blood cells (RBCs)—rather, it acts in association with blood monocytes through an antibody-dependent cellular inhibition (ADCI) mechanism that inhibits parasite development [7].
The cytophilic nature of protective IgG has been established [8, 9], and the importance of these antibodies in protection against malaria has also been demonstrated in other independent studies [10, 11].
The inventors' search for the targets of the protective antibodies, using ADCI (antibody-dependent cellular inhibition) as a functional assay, led them to identify merozoite surface protein 3 (MSP3) as one such target [12]. MSP3 is associated with merozoite surface molecules, possibly through the coiled-coil structures that have been predicted to be formed by the heptad repeats and the C-terminal leucine zipper domain [13]. The N-terminal part of the molecule consists of regions that are polymorphic among different strains.
In contrast, the C-terminal part of the molecule is highly conserved among the various isolates of the parasite [14, 15], and it is this region that was earlier identified by screening of a Plasmodium falciparum expression library by use of functional ADCI assays [12]. However, previous studies of MSP3 have focused only on a 27-aa region (aa 184-210, corresponding to the 3D7 strain, MSP3b) of the C-terminal part, which was earlier identified as a target of protective antibody response in hyperimmune serum samples [12].
USPTO Backgrounds
USPTO Backgrounds