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Open Access Research

A member of the CPW-WPC protein family is expressed in and localized to the surface of developing ookinetes

Niwat Kangwanrangsan15, Mayumi Tachibana12, Rachaneeporn Jenwithisuk16, Takafumi Tsuboi3, Suda Riengrojpitak4, Motomi Torii12 and Tomoko Ishino12*

Author Affiliations

1 Department of Molecular Parasitology, Graduate School of Medicine, Ehime University, Shitsukawa, Toon, Matsuyama, Ehime, 791-0295, Japan

2 Division of Molecular Parasitology, Proteo-Science Center, Ehime University, Shitsukawa, Toon, Matsuyama, Ehime, 791-0295, Japan

3 Division of Malaria Research, Proteo-Science Center, Ehime University, Matsuyama, Ehime, 790-8577, Japan

4 Department of Pathobiology, Faculty of Science, Mahidol University, Rachathevi, Bangkok, 10400, Thailand

5 Present address: Department of Pathobiology, Faculty of Science, Mahidol University, Rachathevi, Bangkok, 10400, Thailand

6 Present address: Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Rachathevi, Bangkok, 10400, Thailand

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Malaria Journal 2013, 12:129  doi:10.1186/1475-2875-12-129

Published: 15 April 2013

Abstract

Background

Despite the development of malaria control programs, billions of people are still at risk for this infectious disease. Recently, the idea of the transmission-blocking vaccine, which works by interrupting the infection of mosquitoes by parasites, has gained attention as a promising strategy for malaria control and eradication. To date, a limited number of surface proteins have been identified in mosquito-stage parasites and investigated as potential targets for transmission-blocking vaccines. Therefore, for the development of effective transmission-blocking strategies in epidemic areas, it is necessary to identify novel zygote/ookinete surface proteins as candidate antigens.

Methods

Since the expression of many zygote/ookinete proteins is regulated post-transcriptionally, proteins that are regulated by well-known translational mediators were focused. Through in silico screening, CPW-WPC family proteins were selected as potential zygote/ookinete surface proteins. All experiments were performed in the rodent malaria parasite, Plasmodium yoelii XNL. mRNA and protein expression profiles were examined by RT-PCR and western blotting, respectively, over the course of the life cycle of the malaria parasite. Protein function was also investigated by the generation of gene-disrupted transgenic parasites.

Results

The CPW-WPC protein family, named after the unique WxC repeat domains, is highly conserved among Plasmodium species. It is revealed that CPW-WPC mRNA transcripts are transcribed in gametocytes, while CPW-WPC proteins are expressed in zygote/ookinete-stage parasites. Localization analysis reveals that one of the CPW-WPC family members, designated as PyCPW-WPC-1, is a novel zygote/ookinete stage-specific surface protein. Targeted disruption of the pycpw-wpc-1 gene caused no obvious defects during ookinete and oocyst formation, suggesting that PyCPW-WPC-1 is not essential for mosquito-stage parasite development.

Conclusions

It is demonstrated that PyCPW-WPC-1 can be classified as a novel, post-transcriptionally regulated zygote/ookinete surface protein. Additional studies are required to determine whether all CPW-WPC family members are also present on the ookinete surface and share similar biological roles during mosquito-stage parasite development. Further investigations of CPW-WPC family proteins may facilitate understanding of parasite biology in the mosquito stage and development of transmission-blocking vaccines.

Keywords:
Malaria; Transmission-blocking vaccine; Mosquito; Post-transcriptional regulation; CPW-WPC protein