Intracellular Delivery Vehicles

A method of determining whether a library contains or encodes an immunogenic polypeptide, the method comprising:

• (a) providing a cell member library, which cell member library comprises a plurality of cell members, each cell member comprising a first polynucleotide encoding a polypeptide encoded by the genome of a pathogenic organism, the first polynucleotide operably linked to a promoter such that each cell member of the cell member library produces its respective polypeptide;
• (b) individually contacting each cell member of the cell member library with a second cell capable of (i) endocytosing the contacted cell member and (ii) displaying the polypeptide produced by the endocytosed cell member on its surface through the MHC class I pathway;
• (c) individually contacting each second cell of step (b) with a sample containing a least one cytotoxic T-lymphocyte derived from a mammal previously infected with the pathogenic organism;
• and
• (d) detecting whether a cytotoxic T-lymphocyte within the sample is activated, wherein activation of the cytotoxic T-lymphocyte indicates that the polypeptide is immunogenic, thereby determining whether the cell member library contains or encodes an immunogenic polypeptide.