Monitoring artemisinin resistance in Plasmodium falciparum: comparison of parasite clearance time by microscopy and real-time PCR and evaluation of mutations in Pfatpase6 gene in Odisha state of India

The activity of methylene blue against asexual and sexual stages of Plasmodium vivax

Methylene blue (MB) is an alternative for combating drug-resistant malaria parasites. Its transmission-blocking potential has been demonstrated in vivo in murine models, in vitro, and in clinical trials. MB shows high efficacy against Plasmodium vivax asexual stages; however, its efficacy in sexual stages is unknown. In this study, we evaluated the potential of MB against asexual and sexual forms of P. vivax isolated from the blood of patients residing in the Brazilian Amazon. An ex vivo schizont maturation assay, zygote to ookinete transformation assay, direct membrane feed assay (DMFA), and standard membrane feed assay (SMFA) using P. vivax gametocytes with MB exposure were performed. A cytotoxicity assay was also performed on freshly collected peripheral blood mononuclear cells (PBMCs) and the hepatocyte carcinoma cell line HepG2. MB inhibited the P. vivax schizont maturation and demonstrated an IC₅₀ lower than that of chloroquine (control drug). In the sexual forms, the MB demonstrated a high level of inhibition in the transformation of the zygotes into ookinetes. In the DMFA, MB did not considerably affect the infection rate and showed low inhibition, but it demonstrated a slight decrease in the infection intensity in all tested concentrations. In contrast, in the SMFA, MB was able to completely block the transmission at the highest concentration (20 µM). MB demonstrated low cytotoxicity to fresh PBMCs but demonstrated higher cytotoxicity to the hepatocyte carcinoma cell line HepG2. These results show that MB may be a potential drug for vivax malaria treatment.

Geographic Plasmodium falciparum sarcoplasmic reticulum Ca2+ ATPase (PfSERCA) genotype diversity in India

Plasmodium falciparum sarcoplasmic reticulum Ca²⁺ ATPase (PfSERCA) is sarcoplasmic reticulum membrane bound transporter to regulate cytosol Ca²⁺ ions. Ca²⁺ act as secondary messenger and play important role in differentiation of parasite during its life cycle. Present study is epidemiological surveillance of PfSERCA (Pf3D7_0106300) gene fragment harboring 263, 402, 431 codon to look for its single nucleotide polymorphism which is well documented to be associated with Artemisinin tolerance. Filter paper with finger pricked blood samples for Plasmodium falciparum infected uncomplicated malaria patients were obtained for region as diverse as down the longitude from east to west of India i.e. Mizoram, Tripura, Meghalaya, Jharkhand, Odhisa. There observed no mutation for codon 263 at all study sites. Mizoram showed highest PfSERCA diversity with well known SNPs of L402 V, E431 K, A438 V and novel mutations as well i.e. A338 V, S357Y, S379Y. Tripura reported highest proportion of Plasmodium isolates (18.5%) with E431 K single nucleotide polymorphism. Moving towards the west i.e. Meghalaya, Jharkhand, Odhisa showed no occurrence of most prevalent PfSERCA 431, 402 polymorphism worldwide but some novel mutations and its haplotypes. In present study, significantly increased proportion of novel PfSERCA polymorphism among children suggests the susceptibility of these Plasmodium falciparum strains to acquired immunity. Mizoram, sharing open international border with south east asia, demonstrated highest PfSERCA diversity. Spatial PfSERCA diversity from far north east India to moving towards west implies its association with antimalarial susceptibility.