A next-generation genetically attenuated Plasmodium falciparum parasite created by triple gene deletion.
Immunization with live-attenuated Plasmodium sporozoites completely protects against malaria infection. Genetic engineering offers a versatile platform to create live-attenuated sporozoite vaccine candidates. We previously generated a genetically attenuated parasite (GAP) by deleting the P52 and P36 genes in the NF54 wild-type (WT) strain of Plasmodium falciparum (Pf p52(-)/p36(-) GAP). Preclinical assessment of p52(-)/p36(-) GAP in a humanized mouse model indicated an early and severe liver stage growth defect. However, human exposure to >200 Pf p52(-)/p36(-) GAP-infected mosquito bites in a safety trial resulted in peripheral parasitemia in one of six volunteers, revealing that this GAP was incompletely attenuated. We have now created a triple gene deleted GAP by additionally removing the SAP1 gene (Pf p52(-)/p36(-)/sap1(-) GAP) and employed flippase (FLP)/flippase recognition target (FRT) recombination for drug selectable marker cassette removal. This next-generation GAP was indistinguishable from WT parasites in blood stage and mosquito stage development. Using an improved humanized mouse model transplanted with human hepatocytes and human red blood cells, we show that despite a high-dose sporozoite challenge, Pf p52(-)/p36(-)/sap1(-) GAP did not transition to blood stage infection and appeared to be completely attenuated. Thus, clinical testing of Pf p52(-)/p36(-)/sap1(-) GAP assessing safety, immunogenicity, and efficacy against sporozoite challenge is warranted.
Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA.
Sebastian A
SA
Mikolajczak
Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA.
Viswanathan
V
Lakshmanan
Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA.
Matthew
M
Fishbaugher
Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA.
Nelly
N
Camargo
Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA.
Anke
A
Harupa
Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA.
Alexis
A
Kaushansky
Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA.
Alyse N
AN
Douglass
Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA.
Michael
M
Baldwin
The Walter and Eliza Hall Institute of Medical Research, Victoria, Australia.
Julie
J
Healer
The Walter and Eliza Hall Institute of Medical Research, Victoria, Australia.
Matthew
M
O'Neill
The Walter and Eliza Hall Institute of Medical Research, Victoria, Australia.
Thuan
T
Phuong
The Walter and Eliza Hall Institute of Medical Research, Victoria, Australia.
Alan
A
Cowman
1] Seattle Biomedical Research Institute (Seattle BioMed), Seattle, Washington, USA [2] Department of Global Health, University of Washington, Seattle, Washington, USA.
Stefan H I
SH
Kappe
D000818:Animals; D000852:Anopheles / Q000469:parasitology*; D004195:Disease Models, Animal; D017353:Gene Deletion; D055786:Gene Knockout Techniques; D006801:Humans; D016778:Malaria, Falciparum / Q000097:blood* / Q000469:parasitology; D010963:Plasmodium falciparum / Q000502:physiology*; D015800:Protozoan Proteins / Q000235:genetics*; D014613:Vaccines, Attenuated / Q000235:genetics
D015800:Protozoan Proteins; D014613:Vaccines, Attenuated