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.

Immunogenicity of Recombinant Proteins Consisting of Plasmodium vivax Circumsporozoite Protein Allelic Variant-Derived Epitopes Fused with Salmonella enterica Serovar Typhimurium Flagellin

“…On the basis of the results obtained with the P. falciparum CSP-derived vaccine, we generated recombinant polypeptides containing various immunodominant regions of the P. vivax CSP fused with a strong agonist of the innate immune system, the flagellin (FliC) protein of Salmonella enterica serovar Typhimurium. The enhanced immunogenicity of FliC-containing fusion proteins has been previously demonstrated in studies of P. vivax and P. falciparum merozoite-derived vaccines (8)(9)(10).…”

Immunization with the MAEBL M2 Domain Protects against Lethal Plasmodium yoelii Infection

“…The recombinant protein (rPyM2-MAEBL) was expressed and purified as previously described (31), with slight modifications. E. coli BL21(DE3) (Novagen) was transformed with the pET28aM2 plasmid and cultivated at 37°C in Luria-Bertani broth in the presence of 30 g/ml kanamycin (Sigma).…”

Salivary IgA enhancement strategy for development of a nasal-spray anti-caries mucosal vaccine

“…The fusion strategy can be achieved by inserting vaccine target antigen at the N-terminus or C-terminus or within the hypervariable region of the flagellin. A number of vaccine candidates with this strategy have reached early stage clinical studies, and this represents one of the most promising new directions in vaccine development [13,14,[17][18][19].…”

“…Flagellin as the ligand of toll-like receptor 5 (TLR5) has been proven to be an effective mucosal adjuvant and become promising for clinical use [13][14][15][16][17][18][19]. We applied the recombinant flagellin as mucosal adjuvant in anti-caries vaccines by nasal immunization, either using flagellin directly by simple mixing with antigen or using fusion strategy to combine flagellin and the target antigen in a single fusion protein, proved the efficacy for enhancement of specific IgA response in oral fluids and better protection against caries [11,20,21].…”