Genetic Diversity of Plasmodium vivax Circumsporozoite Protein and Sexual Stage Antigens 25 in Malaria-Endemic Areas in Asia, Africa, and America during the Period 2004-2020: A Systematic Review

The knowledge of genetic diversity and transmission dynamics of Plasmodium vivax is essential in predicting the emergence of drug resistance and control of malaria, relapse patterns, and vaccine development. Plasmodium vivax circumsporozoite protein (pvcsp) is involved in sporozoite binding to liver cells. Moreover, the circumsporozoite proteins are essential in parasite transformation in mosquito development. It comprises the domain of tandem repeated sequenced flanked by three non-repeated conserved sequenced. Three types of repeat elements, either VK210, VK247, or P. vivax-like types, are detected in clinical isolates of P. vivax. Thus, pvcsp serves as a tool for genotyping P. vivax variants.The VK210 pattern is a major pvcsp genetic diversity distributed worldwide, demonstrating vivax variation. Apart from pvcsp, P. vivax sexual stage antigen also plays a crucial role in various transformation processes in the mosquito's midgut. Among various P. vivax sexual stage antigens, pvs25 is the most extensively studied transmission-blocking vaccine (TBV) candidate antigen of P. vivax. Considering the genetic diversity of P. vivax, it is necessary to accurately evaluate the transmission dynamics of vivax malaria. This systemic review focuses on analysing current information on the genetic diversity of pvcsp and pvs25 in P. vivax isolates from different malaria-endemic areas from 2004 to 2020. The prevalence and patterns of pvcsp and pvs25 reported from various studies depend on geographical distribution and the time of sample collection. This information would help understand the host immune response mechanism to identify potential vaccine candidates. The results of this study will be used as a baseline for future investigations.