Characterization of a novel merozoite surface protein of Plasmodium vivax, Pv41

• Expression of Pv41 during the mature schizont stages of the parasite's intra-erythrocytic cycle.
• Antigenicity of Pv41 in humans infected with vivax malaria parasites.
• Specific reaction of recombinant Pv41 protein with anti-mouse.
• Localization of Pv41 in the merozoite surface.
• High titer of Pv41 immune mouse serum.

Since the genome of Plasmodium vivax was sequenced, few proteins have been characterized as highly immunogenic and candidates for inclusion in a vivax malaria vaccine. The P. vivax 41 (Pv41) protein has a signal peptide, one glutamate-rich domain in its central region, and two sexual stage s48/45 domains, and is characterized as a gametocyte surface protein; however, this protein may be expressed principally on the merozoite surface of parasites. The previous study reported the transcription, blood-stage expression, and subcellular localization of Pv41 within the parasite. In this study, the recombinant Pv41 protein was expressed as a soluble form, of a molecular mass ~44 kDa, by a cell-free expression system and was specifically recognized by animal immune sera and vivax patient sera. Evaluation of the human humoral immune response to Pv41 indicated a high immunogenicity, with 62.5% sensitivity and 95% specificity, by protein array. Immunofluorescence assays (IFA) using polyclonal anti-Pv41 antibodies showed that Pv41 was localized on the merozoite surface. The high immunogenicity of Pv41 indicates its potential as a vivax malaria vaccine candidate antigen, particularly in light of its location on the merozoite surface of the parasite.

The high immunogenicity of Pv41 indicates its potential as a vivax malaria vaccine candidate antigen, particularly in light of its location on the merozoite surface of the parasite. Localization of Pv41 is on the surface of merozoite parasites. Schizont-stage parasites were dual-labeled with antisera against Pv41 (red color) and either PvMSP1-19 (merozoite surface marker, green color) (a) or Pv12 (apical protein, green color) (b). Nuclei were visualized by DAPI staining in merged images.Figure optionsDownload as PowerPoint slide