Polycistronic expression system for bacteria

1. A recombinant nucleic acid comprising a polycistronic expression unit, wherein said polycistronic expression unit comprises:

a functional gene endogenous to a Gram-positive bacterium, and

one or more genes exogenous to said Gram-positive bacterium, which encode a therapeutic product,

wherein said endogenous gene and said one or more exogenous genes are transcriptionally controlled by a promoter endogenous to said Gram-positive bacterium, wherein said promoter is a ribosomal gene promoter or a glycolysis gene promoter, wherein said endogenous gene and said one or more exogenous genes are transcriptionally coupled by one or more intergenic regions active in said Gram-positive bacterium, and wherein said one or more intergenic regions are preceding rplW, rplP, rpmD, rplB, rpsG, rpsE, rplN, rplM, rplE, or rplF.

2. The recombinant nucleic acid of claim 1 , wherein said promoter is the promoter of pyk, eno, pgk, gap (gapA or gapB), tbp, fbaA, rpsD, rpsL, rpsG, rplR, rpsE, rpmD, rplS, rpsK, rplJ, rplL, rpmB, rplD, rplW, rplB, rp10, rplK, rpsH, rplU, rpsM, rpsS, rplU, rplV, rplP, rplN, rpsJ, or rplX of said Gram-positive bacterium.

3. The recombinant nucleic acid of claim 2 , wherein said promoter is the promoter of eno, gap, pyk, rpmB, or rplS of said Gram-positive bacterium.

4. The recombinant nucleic acid of claim 1 , wherein said one or more exogenous genes are transcriptionally coupled to the 3′ end of said endogenous gene.

5. The recombinant nucleic acid of claim 4 , wherein one of said one or more exogenous genes is the most 3′ gene of said polycistronic expression unit.

6. The recombinant nucleic acid of claim 1 , wherein said one or more intergenic regions are endogenous to said Gram-positive bacterium.

7. The recombinant nucleic acid of claim 1 , wherein said therapeutic product is:

(i) an antigen for inducing immunity or immunotolerance,

(ii) a non-vaccinogenic therapeutically active polypeptide,

(ii) an antibody or a functional fragment thereof, or

(iv) a fusion protein or a multimeric protein.

8. The recombinant nucleic acid of claim 7 , wherein said therapeutic product is an antibody or a functional fragment thereof.

9. The recombinant nucleic acid of claim 8 , wherein one exogenous gene encodes the light chain (V L ) of an antibody or of a functional fragment thereof, and another exogenous gene encodes the heavy chain (V H ) of the antibody or of a functional fragment thereof.

10. The recombinant nucleic acid of claim 8 , wherein said functional fragment is an Fab.

11. The recombinant nucleic acid of claim 9 , wherein the exogenous gene encoding said V L or functional fragment thereof is transcriptionally coupled to the 3′ end of the exogenous gene encoding said V H or functional fragment thereof.

12. The recombinant nucleic acid of claim 8 , wherein said one or more exogenous genes encode a single domain antibody.

13. The recombinant nucleic acid of claim 8 , wherein said one or more exogenous genes encode an anti-TNFα antibody, an anti-TNFα antibody fragment, or an anti-TNFα single antibody variable domain.

14. The recombinant nucleic acid of claim 1 , wherein said one or more exogenous genes encode:

(i) proinsulin;

(ii) cA2 anti-TNFα Fab;

(iii) CDP870 anti-hTNFα Fab;

(iv) trefoil factor;

(v) IL-10;

(vi) IL-27; or

(vii) an antibody against a toxin from Clostridium difficile.

15. The recombinant nucleic acid of claim 1 , wherein said Gram-positive bacterium is a lactic acid bacterium or a Bifidobacterium.

16. The recombinant nucleic acid of claim 15 , wherein said lactic acid bacterium is a Lactococcus , a Lactobacillus , or an Enterococcus.

17. The recombinant nucleic acid of claim 15 , wherein said lactic acid bacterium is Lactococcus lactis or Enterococcus faecium.

18. A vector comprising the recombinant nucleic acid of claim 1 .

19. The recombinant nucleic acid of claim 1 , wherein the polycistronic expression unit comprises, in 5′ to 3′ order, (i) an eno promoter as said endogenous promoter, (ii) eno as said functional endogenous gene, and (iii) said one or more exogenous genes.

20. The recombinant nucleic acid of claim 19 , wherein said eno and said one or more exogenous genes are transcriptionally coupled by an intergenic region preceding rpmD.

21. The recombinant nucleic acid of claim 1 , wherein said Gram-positive bacterium is Lactococcus lactis.

22. The recombinant nucleic acid of claim 2 , wherein said Gram-positive bacterium is Lactococcus lactis.

23. The recombinant nucleic acid of claim 3 , wherein said Gram-positive bacterium is Lactococcus lactis.

24. The recombinant nucleic acid of claim 4 , wherein said Gram-positive bacterium is Lactococcus lactis.

25. The recombinant nucleic acid of claim 5 , wherein said Gram-positive bacterium is Lactococcus lactis.

26. The recombinant nucleic acid of claim 6 , wherein said Gram-positive bacterium is Lactococcus lactis.

27. The recombinant nucleic acid of claim 7 , wherein said Gram-positive bacterium is Lactococcus lactis.

28. The recombinant nucleic acid of claim 8 , wherein said Gram-positive bacterium is Lactococcus lactis.

29. The recombinant nucleic acid of claim 9 , wherein said Gram-positive bacterium is Lactococcus lactis.

30. The recombinant nucleic acid of claim 10 , wherein said Gram-positive bacterium is Lactococcus lactis.

31. The recombinant nucleic acid of claim 11 , wherein said Gram-positive bacterium is Lactococcus lactis.

32. The recombinant nucleic acid of claim 12 , wherein said Gram-positive bacterium is Lactococcus lactis.

33. The recombinant nucleic acid of claim 13 , wherein said Gram-positive bacterium is Lactococcus lactis.

34. The recombinant nucleic acid of claim 14 , wherein said Gram-positive bacterium is Lactococcus lactis.

35. The recombinant nucleic acid of claim 15 , wherein said Gram-positive bacterium is Lactococcus lactis.

36. The recombinant nucleic acid of claim 16 , wherein said lactic acid bacterium is Lactococcus lactis.

37. The recombinant nucleic acid of claim 17 , wherein said lactic acid bacterium is Lactococcus lactis.

38. The vector of claim 18 , wherein said Gram-positive bacterium is Lactococcus lactis.

39. The recombinant nucleic acid of claim 19 , wherein said Gram-positive bacterium is Lactococcus lactis.

40. The recombinant nucleic acid of claim 20 , wherein said Gram-positive bacterium is Lactococcus lactis.

41. The recombinant nucleic acid of claim 1 , wherein said one or more intergenic regions are:

a) a nucleic sequence comprising or consisting of any one of SEQ ID NOs: 1-13;

b) a nucleic sequence comprising one mismatch, or a deletion or an insertion of one nucleotide as compared to either SEQ ID NO: 2 or SEQ ID NO: 8;

c) a nucleic sequence comprising one, two, or three mismatches, or a deletion or an insertion of one, two, or three nucleotides as compared to any one of SEQ ID NOs: 3-4 and SEQ ID NOs: 9-10; or

d) a nucleic sequence comprising one, two, three, or four mismatches, or a deletion or an insertion of one, two, three, or four nucleotides as compared to any one of SEQ ID NOs:

5-7 and SEQ ID NOs: 11-13.

42. The recombinant nucleic acid of claim 41 , wherein said one or more intergenic regions are endogenous to said Gram-positive bacterium.

43. A vector comprising said recombinant nucleic acid of claim 42 .

44. The vector of claim 43 , wherein said Gram-positive bacterium is Lactococcus lactis.