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.

Graphical abstractThe 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 full-size imageDownload as PowerPoint slide