Antigen screening system

1. A method of identifying a cancer or tumor antigen, the method comprising:

(a) providing a library comprising bacterial cells, wherein each bacterial cell of the library comprises a heterologous polypeptide expressed in a cancer or tumor cell;

(b) contacting the bacterial cells with a first plurality of human cells which comprises human antigen presenting cells that internalize the bacterial cells;

(c) contacting the first plurality of human cells with a second plurality of human cells which comprises human lymphocytes, under conditions in which lymphocytes are stimulated by polypeptides presented by the first plurality of human cells;

(d) determining whether a lymphocyte of the second plurality of human cells is stimulated by a heterologous polypeptide presented by a cell of the first plurality of human cells, wherein stimulation of a lymphocyte of the second plurality of human cells by a heterologous polypeptide presented by a cell of the first plurality of human cells indicates that the heterologous polypeptide is a cancer or tumor antigen,

wherein the first and second plurality of human cells come from the same human subject.

2. The method of claim 1 , wherein the first plurality of human cells is isolated from the human subject.

3. The method of claim 1 , wherein the bacterial cells further comprise a cytolysin polypeptide.

4. The method of claim 3 , wherein the cytolysin polypeptide is listeriolysin O (LLO).

5. The method of claim 1 , wherein the first plurality of human cells is provided in an array, and wherein cells in each location of the array are contacted with a set of bacterial cells, each set comprising a different heterologous polypeptide.

6. The method of claim 1 , wherein the first and second plurality of human cells comprise cells from peripheral blood.

7. The method of claim 1 , wherein the first plurality of human cells comprises dendritic cells.

8. The method of claim 1 , wherein the first plurality of human cells comprises immortalized cells.

9. The method of claim 1 , wherein the second plurality of human cells comprises human lymphocytes derived from a cancer or tumor.

10. The method of claim 1 , further comprising formulating the antigen or a nucleic acid encoding the antigen as an immunogenic composition.

11. The method of claim 1 , wherein the heterologous polypeptides comprise full length polypeptides encoding mutations, splice variants, or translocations present in a cancer or tumor.

12. The method of claim 1 , wherein the heterologous polypeptides comprise polypeptides which are fragments of full length polypeptides encoding mutations, splice variants, or translocations present in a cancer or tumor.

13. The method of claim 1 , wherein the heterologous polypeptides comprise full length polypeptides encoded by a virus or other infectious agent present in a cancer or tumor.

14. The method of claim 1 , wherein the heterologous polypeptides comprise polypeptides which are fragments of full length polypeptides encoded by a virus or other infectious agent present in a cancer or tumor.

15. The method of claim 1 , wherein the heterologous polypeptides comprise full length polypeptides encoding autoantigens associated with a cancer or tumor.

16. The method of claim 1 , wherein the heterologous polypeptides comprise polypeptides which are fragments of full length polypeptides encoding autoantigens associated with a cancer or tumor.

17. A method of identifying a cancer or tumor antigen, the method comprising:

(e) providing a library comprising bacterial cells, wherein each bacterial cell of the library comprises a heterologous polypeptide expressed in a cancer or tumor cell;

(f) contacting the bacterial cells with a first plurality of human cells from one or more initial human subjects which comprises human antigen presenting cells that internalize the bacterial cells;

(g) contacting the first plurality of human cells with a second plurality of human cells from the one or more initial human subjects which comprises human lymphocytes, under conditions in which lymphocytes are stimulated by polypeptides presented by the first plurality of human cells;

(h) determining whether a lymphocyte of the second plurality of human cells is stimulated by a heterologous polypeptide presented by a cell of the first plurality of human cells, wherein stimulation of a lymphocyte of the second plurality of human cells by a heterologous polypeptide presented by a cell of the first plurality of human cells indicates that the heterologous polypeptide is a cancer or tumor antigen; and

(i) repeating steps (b) to (d) with human cells isolated from one or more additional human subjects, wherein the additional human subjects have different clinical manifestations of a cancer or tumor than the one or more initial human subjects.

18. The method of claim 17 , wherein the first plurality of human cells is isolated from the human subject.

19. The method of claim 17 , wherein the bacterial cells further comprise a cytolysin polypeptide.

20. The method of claim 19 , wherein the cytolysin polypeptide is listeriolysin O (LLO).

21. The method of claim 17 , wherein the first plurality of human cells is provided in an array, and wherein cells in each location of the array are contacted with a set of bacterial cells, each set comprising a different heterologous polypeptide.

22. The method of claim 17 , wherein the first and second plurality of human cells comprise cells from peripheral blood.

23. The method of claim 17 , wherein the first plurality of human cells comprises dendritic cells.

24. The method of claim 17 , wherein the first plurality of human cells comprises immortalized cells.

25. The method of claim 17 , wherein the second plurality of human cells comprises human lymphocytes derived from a cancer or tumor.

26. The method of claim 17 , further comprising formulating the antigen or a nucleic acid encoding the antigen as an immunogenic composition.

27. The method of claim 17 , wherein the heterologous polypeptides comprise full length polypeptides encoding mutations, splice variants, or translocations present in a cancer or tumor.

28. The method of claim 17 , wherein the heterologous polypeptides comprise polypeptides which are fragments of full length polypeptides encoding mutations, splice variants, or translocations present in a cancer or tumor.

29. The method of claim 17 , wherein the heterologous polypeptides comprise full length polypeptides encoded by a virus or other infectious agent present in a cancer or tumor.

30. The method of claim 17 , wherein the heterologous polypeptides comprise polypeptides which are fragments of full length polypeptides encoded by a virus or other infectious agent present in a cancer or tumor.

31. The method of claim 17 , wherein the heterologous polypeptides comprise full length polypeptides encoding autoantigens associated with a cancer or tumor.

32. The method of claim 17 , wherein the heterologous polypeptides comprise polypeptides which are fragments of full length polypeptides encoding autoantigens associated with a cancer or tumor.

33. The method of claim 17 , wherein at least one human subject is an individual who suffers from a cancer or tumor.

34. The method of claim 17 , wherein at least one human subject is an individual who does not suffer from a cancer or tumor.

35. The method of claim 17 , wherein at least one human subject is an individual who responds, or has responded, to a cancer or tumor therapy.

36. The method of claim 17 , wherein at least one human subject is an individual who does not respond, or has not responded, to a cancer or tumor therapy.

37. The method of claim 17 , wherein at least one human subject is an individual who has cleared or regressed a cancer or tumor.

38. The method of claim 1 or 17 , wherein each bacterial cell of the library comprises a heterologous polypeptide differentially expressed in a cancer or tumor cell.