Genetic variability of histidine-rich protein 2 repeat sequences: Misleading factor in true determination of Plasmodium falciparum in different population

Genetically diverse parasites enhances resistance against antimalarials, vaccines and host immune responses. The present study was designed to evaluate the role played by Plasmodium falciparum genetic diversity in predicting the real world malarial population.

Initially, the incidence pattern of all four northern Indian malarial species was examined using 18S rRNA gene and performed principal component analysis (PCA) based on frequencies of Plasmodium species. Consequently, genetic variance of Plasmodium falciparum histidine-rich protein-2 (Pfhrp2) gene among different malarial populations were compared using phylogenetic analysis. Multi-dimensional scaling was performed to assess genetic similarities and distances among studied populations.

Of total 2168 patients screened, 561 patients with fever of unknown origin were included. 18S rRNA and Pfhrp2 genes were amplified in 78 and 45 samples, respectively. Among them 13.9%(78/561) patients had Plasmodium infection. Infections by P. falciparum, P. vivax and mixed infections were diagnosed among 47(60.2%) and 28(35.9%) and 3(3.8%) patients, respectively. We found eight types of Pfhrp2 amino acid sequence repeats among northern Indian population. The PCA findings were in line with genetic diversity and phylogenetic data. Temporal analysis showed the proportion of total diversity present in total subpopulation (ΔS/ΔT) was maximum for P. falciparum.

Higher incidence of Pfhrp2 sequence variation through genetic recombination among multiple strains during sexual reproduction is potentially correlated with high transmission activity. This sequence variation might alter RDT detection sensitivities for different parasites by modulating the structure and frequency of antigenic epitopes.