Back to Search
Start Over
Safety, infectivity and immunogenicity of a genetically attenuated blood-stage malaria vaccine.
- Source :
-
BMC medicine [BMC Med] 2021 Nov 22; Vol. 19 (1), pp. 293. Date of Electronic Publication: 2021 Nov 22. - Publication Year :
- 2021
-
Abstract
- Background: There is a clear need for novel approaches to malaria vaccine development. We aimed to develop a genetically attenuated blood-stage vaccine and test its safety, infectivity, and immunogenicity in healthy volunteers. Our approach was to target the gene encoding the knob-associated histidine-rich protein (KAHRP), which is responsible for the assembly of knob structures at the infected erythrocyte surface. Knobs are required for correct display of the polymorphic adhesion ligand P. falciparum erythrocyte membrane protein 1 (PfEMP1), a key virulence determinant encoded by a repertoire of var genes.<br />Methods: The gene encoding KAHRP was deleted from P. falciparum 3D7 and a master cell bank was produced in accordance with Good Manufacturing Practice. Eight malaria naïve males were intravenously inoculated (day 0) with 1800 (2 subjects), 1.8 × 10 <superscript>5</superscript> (2 subjects), or 3 × 10 <superscript>6</superscript> viable parasites (4 subjects). Parasitemia was measured using qPCR; immunogenicity was determined using standard assays. Parasites were rescued into culture for in vitro analyses (genome sequencing, cytoadhesion assays, scanning electron microscopy, var gene expression).<br />Results: None of the subjects who were administered with 1800 or 1.8 × 10 <superscript>5</superscript> parasites developed parasitemia; 3/4 subjects administered 3× 10 <superscript>6</superscript> parasites developed significant parasitemia, first detected on days 13, 18, and 22. One of these three subjects developed symptoms of malaria simultaneously with influenza B (day 17; 14,022 parasites/mL); one subject developed mild symptoms on day 28 (19,956 parasites/mL); and one subject remained asymptomatic up to day 35 (5046 parasites/mL). Parasitemia rapidly cleared with artemether/lumefantrine. Parasitemia induced a parasite-specific antibody and cell-mediated immune response. Parasites cultured ex vivo exhibited genotypic and phenotypic properties similar to inoculated parasites, although the var gene expression profile changed during growth in vivo.<br />Conclusions: This study represents the first clinical investigation of a genetically attenuated blood-stage human malaria vaccine. A P. falciparum 3D7 kahrp- strain was tested in vivo and found to be immunogenic but can lead to patent parasitemia at high doses.<br />Trial Registration: Australian New Zealand Clinical Trials Registry (number: ACTRN12617000824369 ; date: 06 June 2017).<br /> (© 2021. The Author(s).)
- Subjects :
- Artemether therapeutic use
Artemether, Lumefantrine Drug Combination therapeutic use
Australia
Humans
Male
Plasmodium falciparum genetics
Protozoan Proteins genetics
Vaccine Development
Vaccines, Attenuated adverse effects
Antimalarials therapeutic use
Malaria drug therapy
Malaria Vaccines adverse effects
Malaria, Falciparum drug therapy
Malaria, Falciparum prevention & control
Subjects
Details
- Language :
- English
- ISSN :
- 1741-7015
- Volume :
- 19
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- BMC medicine
- Publication Type :
- Academic Journal
- Accession number :
- 34802442
- Full Text :
- https://doi.org/10.1186/s12916-021-02150-x