title: Immunogenic properties of a recombinant fusion protein containing the C-terminal 19 kDa of Plasmodium falciparum merozoite surface protein-1 and the innate immunity agonist FliC flagellin of Salmonella typhimurium.
abstract: In a recent study, we demonstrated the immunogenic properties of a new malaria vaccine polypeptide based on a 19 kDa C-terminal fragment of the merozoite surface protein-1 (MSP1(19)) from Plasmodium vivax and an innate immunity agonist, the Salmonella enterica serovar Typhimurium flagellin (FliC). Herein, we tested whether the same strategy, based on the MSP1(19) component of the deadly malaria parasite Plasmodium falciparum, could also generate a fusion polypeptide with enhanced immunogenicity. The His(6)FliC-MSP1(19) fusion protein was expressed from a recombinant Escherichia coli and showed preserved in vitro TLR5-binding activity. In contrast to animals injected with His(6)MSP1(19), mice subcutaneously immunised with the recombinant His(6)FliC-MSP1(19) developed strong MSP1(19)-specific systemic antibody responses with a prevailing IgG1 subclass. Incorporation of other adjuvants, such as CpG ODN 1826, complete and incomplete Freund's adjuvants or Quil-A, improved the IgG responses after the second, but not the third, immunising dose. It also resulted in a more balanced IgG subclass response, as evaluated by the IgG1/IgG2c ratio, and higher cell-mediated immune response, as determined by the detection of antigen-specific interferon-gamma secretion by immune spleen cells. MSP1(19)-specific antibodies recognised not only the recombinant protein, but also the native protein expressed on the surface of P. falciparum parasites. Finally, sera from rabbits immunised with the fusion protein alone inhibited the in vitro growth of three different P. falciparum strains. In summary, these results extend our previous observations and further demonstrate that fusion of the innate immunity agonist FliC to Plasmodium antigens is a promising alternative to improve their immunogenicity.
authors.affiliation: Centro Interdisciplinar de Terapia Gênica (CINTERGEN), Universidade Federal de São Paulo, Escola Paulista de Medicina, Brazil.
authors.forename: Daniel Y
authors.initials: DY
authors.lastname: Bargieri
authors.forename: Juliana A
authors.initials: JA
authors.lastname: Leite
authors.forename: Stefanie C P
authors.initials: SC
authors.lastname: Lopes
authors.forename: Maria Elisabete
authors.initials: ME
authors.lastname: Sbrogio-Almeida
authors.forename: Catarina J M
authors.initials: CJ
authors.lastname: Braga
authors.forename: Luis C S
authors.initials: LC
authors.lastname: Ferreira
authors.forename: Irene S
authors.initials: IS
authors.lastname: Soares
authors.forename: Fabio T M
authors.initials: FT
authors.lastname: Costa
authors.forename: Mauricio M
authors.initials: MM
authors.lastname: Rodrigues
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D005408:Flagellin / Q000235:genetics / Q000276:immunology*; D015870:Gene Expression; D007074:Immunoglobulin G / Q000097:blood; D007279:Injections, Subcutaneous; D007371:Interferon-gamma / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology; D017780:Malaria Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D020066:Merozoite Surface Protein 1 / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010963:Plasmodium falciparum / Q000235:genetics / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology*; D013154:Spleen / Q000276:immunology; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D000913:Antibodies, Protozoan; D001426:Bacterial Proteins; D007074:Immunoglobulin G; D017780:Malaria Vaccines; D020066:Merozoite Surface Protein 1; D011993:Recombinant Fusion Proteins; D014614:Vaccines, Synthetic; D005408:Flagellin; D007371:Interferon-gamma