AUTHOR=Fabbri Camila , Quaresma Ramos Glenda , Clarys Baia-da-Silva Djane , Oliveira Trindade Alexandre , Carlos Salazar-Alvarez Luis , Costa Ferreira Neves Juliana , Santos Bastos Ivanildes dos , Guimarães Costa Allyson , Vinicius Guimarães Lacerda Marcus , Marcelo Monteiro Wuelton , Trindade Maranhão Costa Fabio , Costa Pinto Lopes Stefanie 

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

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=Volume 13 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2023.1108366

DOI=10.3389/fcimb.2023.1108366

ISSN=2235-2988

ABSTRACT=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 on peripheral blood mononuclear cells (PBMCs) freshly collected and on the hepatocyte carcinoma cell line HepG2 was also performed. MB inhibited the P. vivax schizont maturation and demonstrated a 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 freshly PBMCs but higher to the hepatocyte carcinoma cell line HepG2. These results show that MB may be a potential drug for vivax malaria treatment.