EFFICIENT INDUCTION OF CYTOTOXIC CD8(-CELLS AGAINST EXOGENOUS PROTEINS - ESTABLISHMENT AND CHARACTERIZATION OF A T-CELL LINE SPECIFIC FOR THE MEMBRANE-PROTEIN ACTA OF LISTERIA-MONOCYTOGENES() T)

The property of listeriolysin (LLO) to introduce soluble passenger pro teins into the cytosol of antigen-presenting cells allows the inductio n of CD8(+) cytotoxic T cells against such antigens. To overcome the p otential problem of presentation of the immunodominant epitope LL091-9 9 by H-2K(d), a variant LLO92A was established in which Tyr 92 was rep laced by Ala. Immunization of BALB/c mice with purified LLO92A failed to stimulate cytotoxic T cells specific for either the epitope LL091-9 9 or for any other LLO-derived peptide. Injection of mixtures of purif ied LLO92A and soluble nucleoprotein (NP) of influenza virus into mice resulted in a strong cytotoxic T cell response exclusively directed a gainst NP. The LLO92A variant was successfully used to generate, propa gate and characterize a CD8(+) T cell line specific for the membrane-b ound virulence factor ActA of Listeria monocytogenes. Interestingly, w ildtype ActA bound to the surface of live L. monocytogenes was not pre sented by MHC class I molecules to the CD8(+) T cell line.