title: Enhanced immunity to Plasmodium falciparum circumsporozoite protein (PfCSP) by using Salmonella enterica serovar Typhi expressing PfCSP and a PfCSP-encoding DNA vaccine in a heterologous prime-boost strategy.
abstract: Two Salmonella enterica serovar Typhi strains that express and export a truncated version of Plasmodium falciparum circumsporozoite surface protein (tCSP) fused to Salmonella serovar Typhi cytolysin A (ClyA) were constructed as a first step in the development of a preerythrocytic malaria vaccine. Synthetic codon-optimized genes (t-csp1 and t-csp2), containing immunodominant B- and T-cell epitopes present in native P. falciparum circumsporozoite surface protein (PfCSP), were fused in frame to the carboxyl terminus of the ClyA gene (clyA::t-csp) in genetically stabilized expression plasmids. Expression and export of ClyA-tCSP1 and ClyA-tCSP2 by Salmonella serovar Typhi vaccine strain CVD 908-htrA were demonstrated by immunoblotting of whole-cell lysates and culture supernatants. The immunogenicity of these constructs was evaluated using a "heterologous prime-boost" approach consisting of mucosal priming with Salmonella serovar Typhi expressing ClyA-tCSP1 and ClyA-tCSP2, followed by parenteral boosting with PfCSP DNA vaccines pVR2510 and pVR2571. Mice primed intranasally on days 0 and 28 with CVD 908-htrA(pSEC10tcsp2) and boosted intradermally on day 56 with PfCSP DNA vaccine pVR2571 induced high titers of serum NANP immunoglobulin G (IgG) (predominantly IgG2a); no serological responses to DNA vaccination were observed in the absence of Salmonella serovar Typhi-PfCSP priming. Mice primed with Salmonella serovar Typhi expressing tCSP2 and boosted with PfCSP DNA also developed high frequencies of gamma interferon-secreting cells, which surpassed those produced by PfCSP DNA in the absence of priming. A prime-boost regimen consisting of mucosal delivery of PfCSP exported from a Salmonella-based live-vector vaccine followed by a parenteral PfCSP DNA boosting is a promising strategy for the development of a live-vector-based malaria vaccine.
authors.affiliation: Center for Vaccine Development, University of Maryland, 685 W. Baltimore Street, HSF I, Room 480, Baltimore, MD 21201, USA. .
authors.forename: Magaly
authors.initials: M
authors.lastname: Chinchilla
authors.forename: Marcela F
authors.initials: MF
authors.lastname: Pasetti
authors.forename: Sandra
authors.initials: S
authors.lastname: Medina-Moreno
authors.forename: Jin Yuan
authors.initials: JY
authors.lastname: Wang
authors.forename: Oscar G
authors.initials: OG
authors.lastname: Gomez-Duarte
authors.forename: Rick
authors.initials: R
authors.lastname: Stout
authors.forename: Myron M
authors.initials: MM
authors.lastname: Levine
authors.forename: James E
authors.initials: JE
authors.lastname: Galen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D002478:Cells, Cultured; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D005260:Female; D005822:Genetic Vectors; D006460:Hemolysin Proteins / Q000235:genetics; D018928:Immunity, Mucosal; D007117:Immunization, Secondary / Q000379:methods*; D007371:Interferon-gamma / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000276:immunology; D017780:Malaria Vaccines / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D023421:Models, Animal; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000276:immunology*; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D012485:Salmonella typhi / Q000235:genetics / Q000276:immunology*; D019444:Vaccines, DNA / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan; D001426:Bacterial Proteins; D000939:Epitopes; D006460:Hemolysin Proteins; D017780:Malaria Vaccines; C487838:PfCSP DNA vaccine; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D019444:Vaccines, DNA; C041595:circumsporozoite protein, Protozoan; D007371:Interferon-gamma