Signal peptide fusion partners facilitating listerial expression of antigenic sequences and methods of preparation and use thereof
The present invention provides nucleic acids, expression systems, and vaccine strains which provide efficient expression and secretion of antigens of interest into the cytosol of host cells, and elicit effective CD4 and CD8 T cell responses by functionally linking Listerial or other bacterial signal peptides/secretion chaperones as N-terminal fusion partners in translational reading frame with selected recombinant encoded protein antigens. These N-terminal fusion partners are deleted (either by actual deletion, by mutation, or by a combination of these approaches) for any PEST sequences native to the sequence, and/or for certain hydrophobic residues.
1. A polynucleotide comprising:
(a) a promoter; and
(b) a nucleic acid operably linked to the promoter, wherein the nucleic acid encodes a fusion protein comprising:
a polypeptide derived by recombinant modification of a Listerial ActA protein sequence, the Listerial ActA protein sequence in its unmodified form comprising a signal sequence and one or more PEST motifs, the modification comprising removal of each of the PEST motifs by deletion or substitution by one or more residues such that the polypeptide lacks any PEST motif; and
a non-Listerial antigen.
2. The polynucleotide of claim 1 , wherein the modification comprises truncation of the unmodified Listerial ActA protein sequence at about residue 100 and the removal of each of the PEST motifs from the truncated Listerial ActA protein sequence by deletion or substitution by one or more residues such that the polypeptide lacks any PEST motif.
3. The polynucleotide of claim 1 , wherein the polypeptide retains the signal sequence of the Listerial ActA protein sequence in unmodified form.
4. The polynucleotide of claim 1 , wherein the modification further comprises:
removal of one or more hydrophobic domains which are not part of the signal sequence of the Listerial ActA protein sequence; and/or
substitution of one or more residues within one or more hydrophobic domains which are not part of the signal sequence of the Listerial ActA protein sequence with amino acids which are not hydrophobic.
5. The polynucleotide of claim 1 , wherein at least 75% of the sequence KTEEQPSEVNTGP (SEQ ID NO: 1) is deleted from the Listerial ActA protein sequence.
6. The polynucleotide of claim 1 , wherein the sequence KTEEQPSEVNTGP (SEQ ID NO: 1) or KTEEQPSEVNTGPR (SEQ ID NO: 2) is deleted from the Listerial ActA protein sequence.
7. The polynucleotide of claim 1 , wherein one or more P, E, S, and T residues in the sequence KTEEQPSEVNTGPR (SEQ ID NO: 2) in the Listerial ActA protein sequence is substituted with a residue other than P, E, S, and T.
8. The polynucleotide of claim 7 , wherein each P, E, S, and T residue in the sequence KTEEQPSEVNTGPR (SEQ ID NO: 2) is substituted with K or R.
9. The polynucleotide of claim 1 , wherein one or more hydrophobic residues within the sequence LIAML (SEQ ID NO: 8) in the Listerial ActA protein sequence are substituted with amino acids which are not hydrophobic.
10. The polynucleotide of claim 9 , wherein the sequence LIAML (SEQ ID NO: 8) is replaced with the sequence QDNKR (SEQ ID NO: 9).
11. The polynucleotide of claim 1 , wherein the polypeptide comprises SEQ ID NO: 30 or SEQ ID NO: 31.
12. The polynucleotide of claim 1 , wherein the promoter is an actA or hly promoter.
13. The polynucleotide of claim 1 , wherein the non-Listerial antigen is a cancer cell, tumor, or infectious agent antigen.
14. A plasmid comprising the polynucleotide of claim 1 .
15. A Listeria bacterium comprising the polynucleotide of claim 1 .
16. The Listeria bacterium of claim 15 , which is Listeria monocytogenes.
17. The Listeria bacterium of claim 15 , which is attenuated by a functional deletion of the bacterium's genomic actA gene.
18. The Listeria bacterium of claim 15 , wherein the polynucleotide is inserted into the bacterium's genomic actA or inlB gene.
19. A vaccine comprising the Listeria bacterium of claim 15 and a pharmacologically acceptable excipient.
20. A method of producing a Listeria bacterium for use in a vaccine, comprising:
integrating a polynucleotide of claim 1 into the genome of the Listeria bacterium.
21. The method of claim 20 , wherein the polynucleotide of claim 1 is inserted into the bacterium's genomic actA or inlB gene.