PfCap380 as a marker for Plasmodium falciparum oocyst development in vivo and in vitro

• Published in: Malaria Journal
• Main Authors: Leslie S. Itsara, Yaxian Zhou, Julie Do, Samrita Dungel, Matthew E. Fishbaugher, Will W. Betz, Thao Nguyen, Mary Jane Navarro, Erika L. Flannery, Ashley M. Vaughan, Stefan H. I. Kappe, Anil K. Ghosh
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2018
• Subjects: Plasmodium falciparum; Ookinete; Oocyst; Capsule; PfCap380; Malaria vaccines; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-018-2277-6; https://doaj.org/article/6f4b2269acd6441080313f82bdc857a3

Abstract Background Despite the importance of the Plasmodium berghei oocyst capsule protein (PbCap380) in parasite survival, very little is known about the orthologous Plasmodium falciparum capsule protein (PfCap380). The goal of this work was to study the growth of P. falciparum oocysts using PfCap380 as a developmental marker. Methods To study P. falciparum oocyst development using both in vivo (mosquito-derived) and in vitro (culture-derived) growth conditions, antibodies (polyclonal antisera) were raised against PfCap380. For studies on in vivo oocysts, mature P. falciparum gametocytes were fed to Anopheles stephensi mosquitoes. For studies on in vitro parasites, P. falciparum gametocytes were induced and matured for subsequent ookinete production. Ookinetes were purified and then tested for binding affinity to basal lamina components and transformation into early oocysts, which were grown on reconstituted basal lamia coated wells with novel oocyst media. To monitor in vivo oocyst development, immunofluorescence assays (IFA) were performed using anti-PfCap380 antisera on Pf-infected mosquito midguts. IFA were also performed on culture-derived oocysts to follow in vitro oocyst development. Results The anti-PfCap380 antisera allowed detection of early midgut oocysts starting at 2 days after gametocyte infection, while circumsporozoite protein was definitively observed on day 6. For in vitro culture, significant transformation of gametocytes to ookinetes (24%) and of ookinetes to early oocysts (85%) was observed. After screening several basal lamina components, collagen IV provided greatest binding of ookinetes and transformation into early oocysts. Finally, PfCap380 expression was observed on the surface of culture-derived oocysts but not on gametocytes or ookinetes. Conclusions This study presents developmental monitoring of P. falciparum oocysts produced in vivo and in vitro. The anti-PfCap380 antisera serves as an important reagent for developmental studies of oocysts from the mosquito midgut and also from ...