Synthetic antigen based on the ligand domain of the
The disclosure provides compositions that are useful for eliciting a strain-transcending immune response in an animal or human directed against the blood-stage of the malarial parasite Plasmodium vivax . The compositions are based on the ligand domain of Plasmodium vivax Duffy binding protein (PvDBPII). Polar charged polymorphic residues within the dominant strain-specific B-cell epitope were mutated to uncharged residues (e.g. serine, alanine and threonine). This DEKnull variant of PvDBPII produced in bacteria can be purified and refolded in vitro to mimic conformation and erythrocyte binding function of native DBPII. Immunogenicity of DEKnull was confirmed by administration to mice. Compared to the naturally-occurring, strain variant DBPII, DEKnull elicits antibodies that are more broadly reactive with different strain variants of DBPII and enhances production of functional inhibitory antibodies to the shared protective epitopes of native DBPII.
1. An engineered Plasmodium vivax Duffy Binding Protein (PvDBPII) having a modified dominant immunogenic polymorphic B-cell epitope region, wherein the modified region comprises the amino acid sequence SEQ ID NO: 4 (ASTAATSRTS) and wherein said modified region has reduced immunogenic dominance when compared to the region of a native PvDBPII comprising the amino acid sequence SEQ ID NO: 3 (DEKAQQRRKQWWNESK) and wherein the engineered PvDBPII can generate in a recipient animal or human subject an immune response having increased binding specificity for conserved Duffy binding epitopes of a Plasmodium Duffy Binding Protein when compared to an immune response generated by a natural PvDBPII.
2. The engineered P. vivax Duffy Binding Protein (PvDBPII) of claim 1 , wherein the modified region of the engineered PvDBPII consists essentially of the amino acid sequence SEQ ID NO: 4 (ASTAATSRTS).
3. The engineered P. vivax Duffy Binding Protein (PvDBPII) of claim 1 , having the amino sequence at least 95% sequence identity with the sequence SEQ ID NO: 2.
4. The engineered P. vivax Duffy Binding Protein (PvDBPII) of claim 1 , wherein the engineered PvDBPII is expressed from a recombinant nucleic acid inserted into an expression vector.
5. The engineered P. vivax Duffy Binding Protein (PvDBPII) of claim 4 , wherein the recombinant nucleic acid is codon optimized for expression of the PvDBPII in a genetically modified host cell.
6. A composition formulated for the generation in a recipient animal or human of an immune response, the composition comprising an engineered Plasmodium vivax Duffy Binding Protein (PvDBPII) having a modified dominant immunogenic polymorphic B-cell epitope region, wherein the modified region comprises the amino acid sequence SEQ ID NO: 4 (ASTAATSRTS) and wherein said modified region has reduced immunogenic dominance when compared to the region of a native PvDBPII having the amino acid sequence SEQ ID NO: 3 (DEKAQQRRKQWWNESK) and wherein the engineered PvDBPII can generate in a recipient animal or human subject an immune response having increased binding specificity for conserved Duffy binding epitopes of a Plasmodium Duffy Binding Protein when compared to an immune response generated by a natural PvDBPII variant, and further comprising a pharmaceutically acceptable carrier.
7. The composition of claim 6 , wherein the modified region of the engineered PvDBPII consists essentially of the amino acid sequence SEQ ID NO: 4 (ASTAATSRTS).
8. The composition of claim 6 , wherein the engineered PvDBPII has an amino sequence having at least 95% sequence identity with the sequence SEQ ID NO: 2.
9. The composition of claim 6 , wherein the engineered PvDBPII is expressed from a recombinant nucleic acid inserted into an expression vector.
10. The composition of claim 9 , wherein the recombinant nucleic acid is codon optimized for expression of the PvDBPII in a genetically modified host cell.
11. The engineered P. vivax Duffy Binding Protein (PvDBPII) of claim 1 , having the amino sequence SEQ ID NO: 2.
12. The composition of claim 6 , wherein the engineered PvDBPII has the amino sequence SEQ ID NO: 2.