Navid Dinparast Djadid

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.

Background: The identification of key molecules is crucial for designing transmission-blocking vaccines (TBVs), among those ookinete micronemal proteins are candidate as a general class of malaria transmission-blocking targets. Here, the sequence analysis of an extra-cellular malaria protein expressed in ookinetes, named von Willebrand factor A domain-related protein (WARP), is reported in 91Plasmodium vivaxisolates circulating in different regions of Iran.Methods: Clinical isolates were collected from north temperate and southern tropical regions in Iran. Primers have been designed based onP. vivaxsequence (ctg_6991) which amplified a fragment of about 1044 bp with no size variation. Direct sequencing of PCR products was used to determine polymorphism and further bioinformatics analysis inP. vivaxsexual stage antigen,pvwarp.Results: Amplifiedpvwarpgene showed 886 bp in size, with no intron. BLAST analysis showed a similarity of 98–100% toP. vivaxSal-I strain; however, Iranian isolates had 2 bp mismatches in 247 and 531 positions that were non-synonymous substitution [T (ACT) to A (GCT) and R (AGA) to S (AGT)] in comparison with the Sal-I sequence.Conclusion: This study presents the first large-scale survey onpvwarppolymorphism in the world, which provides baseline data for developing WARP-based TBV against both temperate and tropicalP. vivaxisolates.