Genetic diversity of PfEMP1-DBL 1-α and its association with severe malaria in a hyperendemic state of India

ObjectiveTo find out the extent of duffy-binding-like (DBL) αgene diversity and the rosetting potential of the parasite population in association with severe malaria.MethodsGenotyping of DBLα domain was done by PCR using three sets of primers (FR, F1R2 and F2R2) and the rosetting frequency was assessed by parasite culture followed by ethidium bromide staining and visualization under a fluorescent microscope.ResultsThe significant association of high parasite density with severe malaria and the positive correlation between rosetting frequency and parasite density in vivo (ρ = 0.613, P< 0.0001) were observed. Moreover, the parasite strains having multiple fragments of F2R2 region and ‘b’ variant of FR region of DBL 1-α showed increased rosetting frequency and supported the strain specific association of disease severity.ConclusionsThe findings suggest that rosetting mediated higher parasitemia might have contributed to the development of severe disease. As the rosetting domain of Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), the DBLα binds to multiple host receptors; the significant association of multiple fragments of F2R2 region with severe malaria suggests several receptor-ligand interactions as the possible mechanisms of pathogenesis. Alternatively, the high percentage distribution of smaller fragments with mild malaria suggests the lack of adequate rosetting epitopes that might have contributed to low rosetting frequency in mild malaria.