Limited genetic diversity and expression profile of Plasmodium falciparum haem detoxification protein: a possible diagnostic target.

Abstract

Haem detoxification protein (HDP) is a significant protein in the erythrocytic stage of the Plasmodium lifecycle. HDP could be of paramount interest as a diagnostic biomarker for accurate diagnosis of malaria. We thus explored HDP genetic variation, expression levels of HDP and immune response. Phylogenetic analysis was carried out using Pfhdp orthologues sequences of various Plasmodium species. Blood samples were collected from patients in central India. Pfhdp gene was amplified, and sequenced by sanger DNA sequencing. B-cell epitopes were identified in PfHDP using Bepipred Linear Epitope Prediction 2.0, and median-joining network was constructed using global PfHDP sequences. Pfhdp expression levels during erythrocytic stage were assessed using real-time qPCR at 4-h intervals. An IgG immune response against synthetic PfHDP peptides was analysed using ELISA. Phylogenetic analysis revealed the conserved nature of Pfhdp gene. Diversity analysis revealed one non-synonymous mutation (F91L) among all isolates. Neutrality tests indicated negative selection for Pfhdp gene. HDP was expressed throughout the erythrocytic cycle, and comparatively, high expression was observed in the late trophozoite and schizont stages. High IgG response against both peptides was observed, and no polymorphism was seen in any of the seven predicted B-cell epitopes. Findings of the present study indicate the possibility of HDP being exploited as a diagnostic biomarker for Plasmodium falciparum malaria after proteomic validation studies.