Live
The present invention provides compositions and methods of inducing an immune response in a subject in need thereof, comprising administering to the subject an immunologically-effective amount of a live Salmonella typhi vector comprising a heterologous antigen from a pathogen, wherein the heterologous antigen comprises an outer membrane protein, an antigenic fragment thereof or a variant thereof, wherein the antigen is delivered to a mucosal tissue of the subject by an outer membrane vesicle.
1. A live Salmonella typhi vector that has been engineered
i) to express one or more heterologous antigens; and
ii) to overexpress a lipid A deacylase PagL, wherein the Salmonella Typhi vector is capable of increased formation and delivery of immunogenic recombinant outer membrane vesicles (rOMVs) comprising the one or more heterologous antigens.
2. The Salmonella typhi vector of claim 1 , wherein the heterologous antigen is encoded by a nucleic acid sequence that is chromosomally integrated in S. typhi.
3. The Salmonella typhi vector of claim 2 , wherein the nucleic acid sequence encoding the heterologous antigen is inserted into an S. typhi locus selected from the group consisting of guaBA, rpoS, htrA, ssb, and combinations thereof.
4. The Salmonella typhi vector of claim 3 , wherein the nucleic acid sequence encoding the heterologous antigen is inserted into the rpoS locus of S. typhi.
5. The Salmonella typhi vector of claim 3 , wherein the nucleic acid sequence encoding the heterologous antigen is chromosomally integrated into the guaBA locus.
6. The Salmonella typhi vector of claim 1 , wherein the S. typhi overexpresses a cytolysin A (ClyA) protein to facilitate outer membrane vesicle formation.
7. The Salmonella typhi vector of claim 6 , wherein the ClyA is mutated to reduce hemolytic activity of ClyA.
8. The Salmonella typhi vector of claim 7 , wherein the ClyA mutant is selected from the group consisting of ClyA I198N, ClyA A199D, ClyA E204K, ClyA C285W and combinations thereof.
9. The Salmonella typhi vector of claim 6 , wherein the ClyA is a fusion protein.
10. The Salmonella typhi vector of claim 9 , wherein the ClyA comprises I198N, A199D, and E204K substitution mutations.
11. The Salmonella typhi vector of claim 1 , wherein the PagL amino acid sequence is selected from SEQ ID NO:2 and SEQ ID NO:4.
12. The Salmonella typhi vector of claim 6 , wherein the PagL and/or ClyA is expressed on a plasmid in S. typhi.
13. The Salmonella typhi vector of claim 12 , wherein the plasmid has a non-antibiotic based plasmid selection system.
14. The Salmonella typhi vector of claim 13 , wherein the plasmid expresses a gene that is essential for the growth of S. typhi and has been chromosomally mutated in the S. typhi vector.
15. The Salmonella typhi vector of claim 14 , wherein the gene encodes single stranded binding protein (SSB).
16. A composition comprising isolated recombinant outer membrane vesicles from the Salmonella typhi of claim 1 .
17. A method of inducing an immune response in a subject in need thereof, comprising administering to the subject an immunologically-effective amount of isolated recombinant outer membrane vesicles from the Salmonella typhi according to claim 1 .
18. The method of claim 17 , wherein the isolated recombinant outer membrane vesicles are administered parenterally.