title: Plasmodium yoelii sporozoites with simultaneous deletion of P52 and P36 are completely attenuated and confer sterile immunity against infection.
abstract: Malaria infection starts when sporozoites are transmitted to the mammalian host during a mosquito bite. Sporozoites enter the blood circulation, reach the liver, and infect hepatocytes. The formation of a parasitophorous vacuole (PV) establishes their intracellular niche. Recently, two members of the 6-Cys domain protein family, P52 and P36, were each shown to play an important albeit nonessential role in Plasmodium berghei sporozoite infectivity for the rodent host. Here, we generated p52/p36-deficient Plasmodium yoelii parasites by the simultaneous deletion of both genes using a single genetic manipulation. p52/p36-deficient parasites exhibited normal progression through the life cycle during blood-stage infection, transmission to mosquitoes, mosquito-stage development, and sporozoite infection of the salivary glands. p52/p36-deficient sporozoites also showed normal motility and cell traversal activity. However, immunofluorescence analysis and electron microscopic observations revealed that p52/p36-deficient parasites did not form a PV within hepatocytes in vitro and in vivo. The p52/p36-deficient parasites localized as free entities in the host cell cytoplasm or the host cell nucleoplasm and did not develop as liver stages. Consequently, they did not cause blood-stage infections even at high sporozoite inoculation doses. Mice immunized with p52/p36-deficient sporozoites were completely protected against infectious sporozoite challenge. Our results demonstrate for the first time the generation of two-locus gene deletion-attenuated parasites that infect the liver but do not progress to blood-stage infection. The study will critically guide the design of Plasmodium falciparum live attenuated malaria vaccines.
authors.affiliation: Seattle Biomedical Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA 98109-5219, USA.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Labaied
authors.forename: Anke
authors.initials: A
authors.lastname: Harupa
authors.forename: Ronald F
authors.initials: RF
authors.lastname: Dumpit
authors.forename: Isabelle
authors.initials: I
authors.lastname: Coppens
authors.forename: Sebastian A
authors.initials: SA
authors.lastname: Mikolajczak
authors.forename: Stefan H I
authors.initials: SH
authors.lastname: Kappe
mesh_terms: D000818:Animals; D009033:Culicidae / Q000469:parasitology; D003593:Cytoplasm / Q000469:parasitology; D004195:Disease Models, Animal; D005260:Female; D017353:Gene Deletion; D018390:Gene Targeting; D022781:Hepatocytes / Q000469:parasitology / Q000648:ultrastructure; D008288:Malaria / Q000276:immunology / Q000517:prevention & control*; D051379:Mice; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D010967:Plasmodium yoelii / Q000235:genetics / Q000254:growth & development / Q000276:immunology* / Q000472:pathogenicity*; D015800:Protozoan Proteins / Q000235:genetics* / Q000276:immunology; D051381:Rats; D017208:Rats, Wistar; D034101:Sporozoites / Q000276:immunology*; D014617:Vacuoles / Q000469:parasitology
chemical_list: D015800:Protozoan Proteins