title: Antigenic characterization of an intrinsically unstructured protein, Plasmodium falciparum merozoite surface protein 2.
abstract: Merozoite surface protein 2 (MSP2) is an abundant glycosylphosphatidylinositol (GPI)-anchored protein of Plasmodium falciparum, which is a potential component of a malaria vaccine. As all forms of MSP2 can be categorized into two allelic families, a vaccine containing two representative forms of MSP2 may overcome the problem of diversity in this highly polymorphic protein. Monomeric recombinant MSP2 is an intrinsically unstructured protein, but its conformational properties on the merozoite surface are unknown. This question is addressed here by analyzing the 3D7 and FC27 forms of recombinant and parasite MSP2 using a panel of monoclonal antibodies raised against recombinant MSP2. The epitopes of all antibodies, mapped using both a peptide array and by nuclear magnetic resonance (NMR) spectroscopy on full-length recombinant MSP2, were shown to be linear. The antibodies revealed antigenic differences, which indicate that the conserved N- and C-terminal regions, but not the central variable region, are less accessible in the parasite antigen. This appears to be an intrinsic property of parasite MSP2 and is not dependent on interactions with other merozoite surface proteins as the loss of some conserved-region epitopes seen using the immunofluorescence assay (IFA) on parasite smears was also seen on Western blot analyses of parasite lysates. Further studies of the structural basis of these antigenic differences are required in order to optimize recombinant MSP2 constructs being evaluated as potential vaccine components.
authors.affiliation: Department of Biochemistry, La Trobe University, Victoria, Australia.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Adda
authors.forename: Christopher A
authors.initials: CA
authors.lastname: MacRaild
authors.forename: Linda
authors.initials: L
authors.lastname: Reiling
authors.forename: Kaye
authors.initials: K
authors.lastname: Wycherley
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Boyle
authors.forename: Vivian
authors.initials: V
authors.lastname: Kienzle
authors.forename: Paul
authors.initials: P
authors.lastname: Masendycz
authors.forename: Michael
authors.initials: M
authors.lastname: Foley
authors.forename: James G
authors.initials: JG
authors.lastname: Beeson
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Norton
authors.forename: Robin F
authors.initials: RF
authors.lastname: Anders
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000953:Antigens, Protozoan / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D018604:Epitope Mapping; D005260:Female; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008808:Mice, Inbred CBA; D010963:Plasmodium falciparum / Q000235:genetics / Q000276:immunology*; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C065974:merozoite surface protein 2, Plasmodium