Antimicrobial theta defensins and methods of using same

1. A method of reducing or inhibiting growth or survival of a microorganism in an environment capable of sustaining the growth or survival of the microorganism, comprising administering an effective amount of a theta defensin to said environment, thereby reducing or inhibiting the growth or survival of the microorganism.

2. The method of claim 1 , which has antimicrobial activity against a microorganism selected from the group consisting of a gram positive bacterium, a gram negative bacterium, a yeast and a fungus.

3. The method of claim 2 , wherein said microorganism is selected from the group consisting of Staphylococcus sp., Listeria sp., Escherichia sp., Salmonella sp., Candida sp., and Cryptococcus sp.

4. The method of claim 3 , wherein said microorganism is selected from the group consisting of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium, Candida albicans , and Cryptococcus neoformans.

5. The method of claim 1 , which has antimicrobial activity against a protozoan.

6. The method of claim 5 , wherein said protozoan is selected from the group consisting of Giardia sp. and Acanthamoeba sp.

7. The method of claim 1 , which has antimicrobial activity against a virus.

8. The method of claim 7 , wherein said virus is human immunodeficiency virus-1.

9. The method of claim 1 , wherein said environment is a food or food product.

10. The method of claim 1 , wherein said environment is a solution.

11. The method of claim 10 , wherein said solution is a contact lens solution.

12. The method of claim 10 , wherein said solution is an eye wash solution.

13. The method of claim 1 , wherein said environment is an inanimate object comprising a surface.

14. The method of claim 1 , wherein said environment is a mammal.

15. The method of claim 1 , wherein said administration is topical.

16. The method of claim 1 , wherein said administration is by injection.

17. The method of claim 1 , wherein said administration is oral.

18. The method of claim 1 , wherein said theta defensin, or a functional fragment thereof, is a cationic, arginine-rich cyclic peptide having each amino acid linked by a peptide bond and having one or more intrachain crosslinks, said intrachain crosslink formed between two amino acids, said theta defensin peptide or functional fragment lacks a free amino or carboxyl terminus, has less than 29 amino acids, and possesses antimicrobial activity.

19. The method of claim 1 , wherein said theta defensin has the amino acid sequence:

Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa1-Xaa6-Xaa4-Xaa4-Xaa1-

Xaa1-Xaa6-Xaa4-Xaa5-Xaa1-Xaa3-Xaa7-Xaa8,

wherein:

Xaa1 independently is an aliphatic amino acid;

Xaa2 is an aromatic amino acid;

Xaa3 is Cys or Trp;

Xaa4 independently is Mg or Lys;

Xaa5 is Cys or Trp;

Xaa6 is Cys or Trp;

Xaa7 is Thr or Ser; and

Xaa8 is Mg or Lys.

20. The method of claim 1 , wherein said theta defensin has the amino acid sequence:

Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa1-Xaa6-Xaa4-Xaa4-Xaa1-

Xaa1-Xaa6-Xaa4-Xaa5-Xaa1-Xaa3-Xaa7-Xaa8,

wherein:

Xaa1 independently is Gly, Ile, Leu, Val or Ala;

Xaa2 is Phe, Trp or Tyr;

Xaa3 is Cys or Trp;

Xaa4 independently is Arg or Lys;

Xaa5 is Cys or Trp;

Xaa6 is Cys or Trp;

Xaa7 is Thr or Ser; and

Xaa8 is Arg or Lys.

21. The method of claim 20 , wherein said theta defensin has the amino acid sequence:

Gly-Phe-Cys-Arg-Cys-Leu-Cys-Arg-Arg-Gly-Val-Cys-Arg-Cys-Ile-Cys-Thr-Arg.

(SEQ ID NO:1)

22. The method of claim 20 , wherein Xaa1 is linked through a peptide bond to Xaa8.

23. The method of claim 20 , wherein an intrachain crosslink is formed between two amino acids selected from the group consisting of:

Xaa3 at position 3 and Xaa3 at position 16;

Xaa5 at position 5 and Xaa5 at position 14; and

Xaa6 at position 7 and Xaa6 at position 12.

24. The method of claim 23 , wherein Xaa1 is linked through a peptide bond to Xaa8.

25. The method of claim 23 , wherein said intrachain crosslink is a disulfide crosslink.

26. The method of claim 23 , wherein said intrachain crosslink is a di-tryptophan crosslink.

27. The method of claim 23 , wherein said intrachain crosslink is a lanthionine crosslink.

28. The method of claim 24 , wherein said theta defensin has the amino acid sequence:

Gly-Phe-Cys-Arg-Cys-Leu-Cys-Arg-Arg-Gly-Val-Cys-Arg-Cys-Ile-Cys-Thr-Arg.

(SEQ ID NO:1)

29. The method of claim 28 , said theta defensin comprising three disulfide crosslinks consisting of

Xaa3 at position 3 and Xaa3 at position 16;

Xaa5 at position 5 and Xaa5 at position 14; and

Xaa6 at position 7 and Xaa6 at position 12.

30. The method of claim 1 , wherein said theta defensin has the amino acid sequence:

Xaa1-Xaa2-Xaa9-Xaa4-Xaa10-Xaa1-Xaa11-Xaa4-Xaa4-

Xaa1-Xaa1-Xaa12-Xaa4-Xaa13-Xaa1-Xaa14-Xaa7-Xaa8,

wherein:

Xaa1 independently is an aliphatic amino acid;

Xaa2 is an aromatic amino acid;

Xaa4 independently is Arg or Lys;

Xaa7 is Thr or Ser;

Xaa8 is Arg or Lys;

Xaa9 is Glu, Asp, Lys or Ser;

Xaa10 is Glu, Asp, Lys or Ser;

Xaa11 is Glu, Asp, Lys or Ser;

Xaa12 is Glu, Asp, Lys or Ser;

Xaa13 is Glu, Asp, Lys or Ser;

Xaa14 is Glu, Asp, Lys or Ser.

31. The method of claim 30 , wherein an intrachain crosslink is formed between two amino acids selected from the group consisting of

Xaa9 and Xaa14;

Xaa10 and Xaa13; and

Xaa11 and Xaa12.

32. The method of claim 31 , wherein said crosslink is selected from the group consisting of lactam and lactone.

33. The method of claim 1 , wherein said theta defensin, or a functional fragment thereof, has the amino acid sequence:

Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa1-Xaa6-Xaa4-Xaa4-Xaa1-

Xaa1-Xaa6-Xaa4-Xaa5-Xaa1-Xaa3-Xaa7-Xaa8,

wherein:

Xaa1 independently is an aliphatic amino acid;

Xaa2 is an aromatic amino acid;

Xaa3 is Cys or Trp;

Xaa4 independently is Arg or Lys;

Xaa5 is Cys or Trp;

Xaa6 is Cys or Trp;

Xaa7 is Thr or Ser; and

Xaa8 is Arg or Lys, said theta defensin or functional fragment having an intrachain crosslink formed between two amino acids selected from the group consisting of:

Xaa3 at position 3 and Xaa3 at position 16;

Xaa5 at position 5 and Xaa5 at position 14; and

Xaa6 at position 7 and Xaa6 at position 12.

34. The method of claim 33 , wherein said theta defensin, or a functional fragment thereof, has the amino acid sequence:

Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa1-Xaa6-Xaa4-Xaa4-Xaa1-

Xaa1-Xaa6-Xaa4-Xaa5-Xaa1-Xaa3-Xaa7-Xaa8,

wherein:

Xaa1 independently is Gly, Ile, Leu, Val or Ala;

Xaa2 is Phe, Trp or Tyr;

Xaa3 is Cys or Trp;

Xaa4 independently is Arg or Lys;

Xaa5 is Cys or Trp;

Xaa6 is Cys or Trp;

Xaa7 is Thr or Ser; and

Xaa8 is Arg or Lys, said theta defensin or functional fragment having an intrachain crosslink formed between two amino acids selected from the group consisting of:

Xaa3 at position 3 and Xaa3 at position 16;

Xaa5 at position 5 and Xaa5 at position 14; and

Xaa6 at position 7 and Xaa6 at position 12.

35. The method of claim 1 , wherein said theta defensin, or a functional fragment thereof, has the amino acid sequence:

Xaa1-Xaa2-Xaa9-Xaa4-Xaa10-Xaa1-Xaa11-Xaa4-Xaa4-

Xaa1-Xaa1-Xaa12-Xaa4-Xaa13-Xaa1-Xaa14-Xaa7-Xaa8,

wherein:

Xaa1 independently is an aliphatic amino acid;

Xaa2 is an aromatic amino acid;

Xaa4 independently is Arg or Lys;

Xaa7 is Thr or Ser;

Xaa8 is Ag or Lys;

Xaa9 is Glu, Asp, Lys or Ser;

Xaa10 is Glu, Asp, Lys or Ser;

Xaa11 is Glu, Asp, Lys or Ser;

Xaa12 is Glu, Asp, Lys or Ser;

Xaa13 is Glu, Asp, Lys or Ser;

Xaa14 is Glu, Asp, Lys or Ser, wherein an intrachain crosslink is formed between two amino acids selected from the group consisting of

Xaa9 and Xaa14;

Xaa10 and Xaa13; and

Xaa11 and Xaa12.

36. The method of claim 1 , wherein said theta defensin comprises the amino acid sequence of SEQ ID NO:18, said peptide having antimicrobial activity.

37. The method of claim 1 , wherein said theta defensin comprises the amino acid sequence of SEQ ID NO:20, said peptide having antimicrobial activity.