title: A full-length Plasmodium falciparum recombinant circumsporozoite protein expressed by Pseudomonas fluorescens platform as a malaria vaccine candidate.
abstract: The circumsporozoite protein (CSP) of Plasmodium falciparum is a major surface protein, which forms a dense coat on the sporozoite's surface. Preclinical research on CSP and clinical evaluation of a CSP fragment-based RTS, S/AS01 vaccine have demonstrated a modest degree of protection against P. falciparum, mediated in part by humoral immunity and in part by cell-mediated immunity. Given the partial protective efficacy of the RTS, S/AS01 vaccine in a recent Phase 3 trial, further improvement of CSP-based vaccines is crucial. In this report, we describe the preclinical development of a full-length, recombinant CSP (rCSP)-based vaccine candidate against P. falciparum malaria suitable for current Good Manufacturing Practice (cGMP) production. Utilizing a novel high-throughput Pseudomonas fluorescens expression platform, we demonstrated greater efficacy of full-length rCSP as compared to N-terminally truncated versions, rapidly down-selected a promising lead vaccine candidate, and developed a high-yield purification process to express immunologically active, intact antigen for clinical trial material production. The rCSP, when formulated with various adjuvants, induced antigen-specific antibody responses as measured by enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay (IFA), as well as CD4+ T-cell responses as determined by ELISpot. The adjuvanted rCSP vaccine conferred protection in mice when challenged with transgenic P. berghei sporozoites containing the P. falciparum repeat region of CSP. Furthermore, heterologous prime/boost regimens with adjuvanted rCSP and an adenovirus type 35-vectored CSP (Ad35CS) showed modest improvements in eliciting CSP-specific T-cell responses and anti-malarial protection, depending on the order of vaccine delivery. Collectively, these data support the importance of further clinical development of adjuvanted rCSP, either as a stand-alone product or as one of the components in a heterologous prime/boost strategy, ultimately acting as an effective vaccine candidate for the mitigation of P. falciparum-induced malaria.
authors.affiliation: Leidos Inc., Frederick, Maryland, United States of America.
authors.forename: Amy R
authors.initials: AR
authors.lastname: Noe
authors.affiliation: Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Diego
authors.initials: D
authors.lastname: Espinosa
authors.affiliation: HIV and Malaria Vaccine Program, Aaron Diamond AIDS Research Center, Affiliate of The Rockefeller University, New York, New York, United States of America.
authors.forename: Xiangming
authors.initials: X
authors.lastname: Li
authors.affiliation: HIV and Malaria Vaccine Program, Aaron Diamond AIDS Research Center, Affiliate of The Rockefeller University, New York, New York, United States of America.
authors.forename: Jordana G A
authors.initials: JG
authors.lastname: Coelho-Dos-Reis
authors.affiliation: HIV and Malaria Vaccine Program, Aaron Diamond AIDS Research Center, Affiliate of The Rockefeller University, New York, New York, United States of America.
authors.forename: Ryota
authors.initials: R
authors.lastname: Funakoshi
authors.affiliation: Leidos Inc., Frederick, Maryland, United States of America.
authors.forename: Steve
authors.initials: S
authors.lastname: Giardina
authors.affiliation: Pfenex Inc., San Diego, California, United States of America.
authors.forename: Hongfan
authors.initials: H
authors.lastname: Jin
authors.affiliation: Pfenex Inc., San Diego, California, United States of America.
authors.forename: Diane M
authors.initials: DM
authors.lastname: Retallack
authors.affiliation: Pfenex Inc., San Diego, California, United States of America.
authors.forename: Ryan
authors.initials: R
authors.lastname: Haverstock
authors.affiliation: Pfenex Inc., San Diego, California, United States of America.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Allen
authors.affiliation: Infectious Disease Research Institute, Seattle, Washington, United States of America.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Vedvick
authors.affiliation: Infectious Disease Research Institute, Seattle, Washington, United States of America.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Fox
authors.affiliation: Infectious Disease Research Institute, Seattle, Washington, United States of America.
authors.forename: Steven G
authors.initials: SG
authors.lastname: Reed
authors.affiliation: Leidos Inc., Frederick, Maryland, United States of America.
authors.forename: Ramses
authors.initials: R
authors.lastname: Ayala
authors.affiliation: Leidos Inc., Frederick, Maryland, United States of America.
authors.forename: Brian
authors.initials: B
authors.lastname: Roberts
authors.affiliation: Leidos Inc., Frederick, Maryland, United States of America.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Winram
authors.affiliation: Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Sacci
authors.affiliation: HIV and Malaria Vaccine Program, Aaron Diamond AIDS Research Center, Affiliate of The Rockefeller University, New York, New York, United States of America.
authors.forename: Moriya
authors.initials: M
authors.lastname: Tsuji
authors.affiliation: Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Fidel
authors.initials: F
authors.lastname: Zavala
authors.affiliation: Leidos Inc., Frederick, Maryland, United States of America.
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Gutierrez
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D056945:Hep G2 Cells; D006801:Humans; D017780:Malaria Vaccines / Q000008:administration & dosage* / Q000737:chemistry; D016778:Malaria, Falciparum / Q000276:immunology / Q000517:prevention & control*; D051379:Mice; D008810:Mice, Inbred C57BL; D030781:Organisms, Genetically Modified; D010963:Plasmodium falciparum / Q000276:immunology*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011551:Pseudomonas fluorescens / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014611:Vaccination / Q000379:methods
chemical_list: D000276:Adjuvants, Immunologic; D017780:Malaria Vaccines; D015800:Protozoan Proteins; D011994:Recombinant Proteins