title: Morphological Characteristics of Schistosoma mansoni PZQ-Resistant and -Susceptible Strains Are Different in Presence of Praziquantel.
abstract: Schistosomiasis is one of the most common human parasitic diseases whose socioeconomic impact is only surpassed by malaria. Praziquantel (PZQ) is the only drug commercially available for the treatment of all schistosome species causing disease in humans. However, there has been stronger evidences of PZQ-resistance on Schistosoma mansoni and thus it is very important to study the phenotypic characteristics associated with it. The aim of this study was to evaluate morphological alterations in S. mansoni PZQ-resistant adult worms and eggs, by comparing a PZQ- resistant strain obtained under PZQ drug pressure with a PZQ-susceptible strain. For this, scanning electronic microscopy was used to assess tegumental responsiveness of both strains under PZQ exposure, and optical microscopy allowed the monitoring of worms and eggs in the presence of the drug. Those assays showed that PZQ-susceptible worms exposed to the drug had more severe tegumental damages than the resistant one, which had only minor alterations. Moreover, contrary to what occurred in the susceptible strain, resistant worms were viable after PZQ exposure and gradually regaining full motility after removal of the drug. Eggs from resistant strain parasites are considerably smaller than those from susceptible strain. Our results suggest that there might be a difference in the tegument composition of the resistant strain and that worms are less responsive to PZQ. Changes observed in egg morphology might imply alterations in the biology of schistosomes associated to PZQ-resistance, which could impact on transmission and pathology of the disease. Moreover, we propose a hypothetical scenario where there is a different egg tropism of the S. mansoni resistant strain. This study is the first comparing two strains that only differ in their resistance characteristics, which makes it a relevant step in the search for resistance determinants.
authors.affiliation: Graduate Program in Areas of Basic and Applied Biology, Instituto de Ciências Biomédicas Abel Salazar, Universidade do PortoPorto, Portugal; Medical Parasitology Unit, Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de LisboaLisbon, Portugal; Bioanalytical, Microfabrication, and Separations Group, Instituto de Química de São Carlos, Universidade de São PauloSão Carlos, Brazil.
authors.forename: António
authors.initials: A
authors.lastname: Pinto-Almeida
authors.affiliation: Medical Parasitology Unit, Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de LisboaLisbon, Portugal; Departamento De Biologia Animal, Instituto de Biologia, Universidade Estadual de CampinasCampinas, Brazil.
authors.forename: Tiago
authors.initials: T
authors.lastname: Mendes
authors.affiliation: Departamento De Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil.
authors.forename: Rosimeire Nunes
authors.initials: RN
authors.lastname: de Oliveira
authors.affiliation: Departamento De Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil.
authors.forename: Sheila de Andrade Penteado
authors.initials: Sde A
authors.lastname: Corrêa
authors.affiliation: Departamento De Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil.
authors.forename: Silmara Marques
authors.initials: SM
authors.lastname: Allegretti
authors.affiliation: Medical Parasitology Unit, Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa Lisbon, Portugal.
authors.forename: Silvana
authors.initials: S
authors.lastname: Belo
authors.affiliation: Graduate Program in Areas of Basic and Applied Biology, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto Porto, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Tomás
authors.affiliation: Laboratory of Parasitology, Department of Morphology and Pathology, Universidade Federal de São Carlos São Carlos, Brazil.
authors.forename: Fernanda de Freitas
authors.initials: Fde F
authors.lastname: Anibal
authors.affiliation: Bioanalytical, Microfabrication, and Separations Group, Instituto de Química de São Carlos, Universidade de São Paulo São Carlos, Brazil.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Carrilho
authors.affiliation: Medical Parasitology Unit, Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de LisboaLisbon, Portugal; Bioanalytical, Microfabrication, and Separations Group, Instituto de Química de São Carlos, Universidade de São PauloSão Carlos, Brazil; Laboratory of Parasitology, Department of Morphology and Pathology, Universidade Federal de São CarlosSão Carlos, Brazil.
authors.forename: Ana
authors.initials: A
authors.lastname: Afonso
keywords: Praziquantel; Schistosoma mansoni; eggs; morphology; resistance; schistosomiasis; tegument