A systematic review on genetic diversity of var gene DBL1α domain from different geographical regions in Plasmodium falciparum isolates

Background The major variant surface antigen (VSA) in Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) encoded by var gene family has an important role in cytoadhesion/sequestration and rosetting by adhesion of uninfected erythrocytes to infected erythrocytes leading to disease severity. DBL1 alpha domain in the PfEMP-1, protein is crucial in the cytoadhesion phenomena in P. falciparum infections and this review aims to analyse the genetic diversity of DBL1 alpha domain sequences in PfEMP-1 from different geographical regions globally. Methods All available DBL1 alpha sequence data was reviewed by using the electronic database PubMed, ResearchGate, Google, Google scholar, MEDLINE with the following Keywords -Plasmodium falciparum", "var gene", "DBL1 alpha", "field isolate", "diversity", "polymorphism", "Africa", "America", "Asia" and "Caribbean" from different geographical regions across the world. Results A total of 240 studies were identified initially but only 20 studies qualified for this systematic review. The overall ratio of distinct sequences DBL1 alpha domain was 24.62/1167 the highest in African region (33.59/766 isolates) and lowest in South America (5.6/215 isolates). In the 18 included studies, the presence of distinct DBL1 alpha sequences was the highest in Oceania 55.32% (1186/2144) followed by Africa (38.43%), Asia (22.45%) and South America (16.48%), though the sample size in Oceania was comparatively smaller to that of Africa and South America. Conclusion This review highlights the ratio and percentage of distinct sequences of DBL1 alpha domain of var gene in different geographical regions giving an idea of the existing diversity prevalent in this potential vaccine target gene which may contribute to designing the preventive measures towards disease severity.