Immunogenicity of a mycobacterial T-cell epitope expressed in outer membrane protein PhoE of Escherichia coli.

The outer membrane protein PhoE of Escherichia coli can be used for the expression of foreign antigenic determinants. Previously, a T-cell epitope of the 65 kDa heat shock protein (hsp65) of Mycobacterium tuberculosis, comprising amino acids 180 to 188, was expressed in PhoE. The hybrid protein induced proliferation of epitope-specific T-cell clones in vitro. In this report, the potential of the hybrid protein to induce an in vivo T-cell response against the 180-188 T-cell epitope was assessed. Popliteal lymph node cells, isolated from rats immunized with PhoE containing the hsp65 epitope, showed high proliferative responses to a synthetic peptide consisting of amino acids 180 to 188 of hsp65, indicating that the epitope is immunogenic in the PhoE-associated conformation.