Production of Vibrio cholerae ghosts (VCG) by expression of a cloned phage lysis gene: potential for vaccine development.

The protein E-specific lysis mechanism of the Escherichia coli-specific bacteriophage PhiX174 was employed to produce Vibrio cholerae ghosts (VCG). VCG consist of both rounded and collapsed cells that have lost their cytoplasmic contents through an E-specific hole in the cell envelope. These ghosts are proposed as non-living material for immunization against cholera. A specific membrane anchor sequence was used to insert the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) fusion protein into the cell envelope of V. cholerae. The identity of the expression products was confirmed by Western blot analysis employing an RT-specific monoclonal antibody. HIV-1 RT was chosen as a model for the purpose of evaluating heterologous gene expression in V. cholerae and the carrier potential of VCG. Intraperitoneal immunization of mice was used to evaluate the immunogenic potential of VCG. Preliminary results showed significant seroconversions to intact whole-cell vibrio antigens in mice immunized with VCG or a heat-killed whole-cell vibrio preparation.