Cloning, expression and transmission-blocking activity of anti-PvWARP, malaria vaccine candidate, in Anopheles stephensi mysorensis.

Background: Notwithstanding progress in recent years, a safe, an effective and affordable malaria vaccine is not available yet. Ookinete-secreted protein, Plasmodium vivax von Willebrand factor A domain-related protein (PvWARP), is a candidate for malaria transmission-blocking vaccines (TBVs).

Methods: The PvWARP was expressed in Escherichia coli BL21 using the pET-23a vector and was purified using Ni-NTA affinity chromatography from a soluble fraction. Polyclonal antibody was raised against rPvWARP and transmission blocking activity was carried out in an Anopheles stephensi-P. vivax model.

Results: Expression of full length of PvWARP (minus signal peptide) expression showed a 35-kDa protein. The purified protein was recognized by mouse polyclonal antibody directed against rPvWARP. Sera from the animals displayed significantly a blocking activity in the membrane feeding assay of An. stephensi mysorensis.

Conclusions: This is the first report on P. vivax WARP expression in E. coli that provides an essential base for development of the malaria TBV against P. vivax. This may greatly assist in malaria elimination, especially in the oriental corner of WHO Eastern Mediterranean Regional Office (WHO/EMRO) including Afghanistan, Iran and Pakistan.