Differential ability of specific regions of Plasmodium falciparum sexual‐stage antigen, Pfs230, to induce malaria transmission‐blocking immunity

Abstract

Antibodies raised against an Escherichia coli-produced recombinant protein encoding a 76-kDa section (region C) of malaria transmission-blocking vaccine candidate, Pfs230, have previously been shown to significantly reduce the ability of Plasmodium falciparum parasites to infect mosquitoes (71.2-89.8%). To further define the region of the Pfs230 required for transmission-blocking activity, four recombinant proteins each encoding a section of region C (Pfs230 amino acids 443-1132) were produced using the same E. coli expression system and tested for immunogenicity in mice: (i) r230/MBP.C5' encodes the first half of region C (amino acids 443-791, six cysteines); (ii) r230/MBP.CM1 encodes only cysteine motif (CM) 1 (amino acids 583-913, eight cysteines); (iii) r230/MBP.C1.6 (amino acids 453-913, eight cysteines) also includes all of CM1; and (iv) r230/MBP.C2 encodes only CM2 (amino acids 914-1268, 11 cysteines). All the recombinant proteins induced antibodies that recognized parasite-produced Pfs230, but the titre of the Pfs230 specific-antibodies generated varied, C = C1.6 = C5' > CM1 > CM2. Two recombinants, r230/MBP.C5' and r230/MBP.C1.6, induced antibody titres that were equivalent to or greater than the titre generated by r230/MBP.C. However, in contrast to r230/MBP.C, none of the recombinants induced antibodies that effectively blocked parasite infectivity to mosquitoes. This suggests that the inclusion of amino acids 914-1132 is important for the production of the transmission-blocking epitope present in region C.

A Plant-Produced Pfs230 Vaccine Candidate Blocks Transmission of Plasmodium falciparum

“…In this study, we expressed, purified, and characterized 230CMB (aa 444 to 730). The 230CMB antigen described here is similar to r230/MBP.C5 (aa 443 to 791) produced by Bustamante et al (2), which comprises the region of Pfs230 positioned just after the N-terminal cleaved domain until midway through the first cysteine motif domain and contains four cysteine residues. However, unlike the MBP fusion, 230CMB is a stand-alone soluble antigen which is recognized in both Western blot assays and ELISA by two different anti-Pfs230 MAbs possessing TB activity.…”

N-Terminal Prodomain of Pfs230 Synthesized Using a Cell-Free System Is Sufficient To Induce Complement-Dependent Malaria Transmission-Blocking Activity

“…In previous studies (4,43), transmission-blocking antibodies against Pfs230C were effective only at a higher concentration (i.e., a 1:2 dilution).…”

Geographical Distribution of Selected and Putatively Neutral SNPs in Southeast Asian Malaria Parasites

“…An oligo microarray study on Chr 2 of Plasmodium showed that 69% of all polymorphisms detected were in membrane-associated genes in telomeric and subtelomeric regions and that polymorphism is rather rare elsewhere in the genome (Volkman et al 2002). The highly polymorphic genes included Var genes involved in antigenic variation (Bull et al 1998;Newbold 1999), vaccine targets such as pfs230 (Bustamante et al 2000;Williamson 2003), and merozoite antigens (M. K. Hughes and A. L. Hughes 1995) for which there is independent evidence of positive selection from sequence comparisons. Furthermore, many other polymorphisms were found in unknown genes that may also be surface expressed and exposed to immune selection (Volkman et al 2002).…”