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Immunogenic properties of a recombinant fusion protein containing the C-terminal 19 kDa ofPlasmodium falciparummerozoite surface protein-1 and the innate immunity agonist FliC flagellin ofSalmonellaTyphimurium

Authors
Journal
Vaccine
0264-410X
Publisher
Elsevier
Publication Date
Volume
28
Issue
16
Identifiers
DOI: 10.1016/j.vaccine.2010.02.004
Keywords
  • P. Falciparum
  • Vaccine
  • Flagellin
  • Tlr5
Disciplines
  • Biology

Abstract

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 6FliC-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 6MSP1 19, mice subcutaneously immunised with the recombinant His 6FliC-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-γ 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.

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