Stimulation of HIV gp120-specific cytolytic T lymphocyte responses in vitro and in vivo using a detoxified pertussis toxin vector

CD8(+) cytolytic T lymphocytes (CTL) are almost certainly an important comp onent of a potentially protective immune response to HIV. To test the abili ty of pertussis toxin (PT) to deliver an HIV-derived major histocompatibili ty complex (MHC) class I peptide for CTL stimulation, we constructed a fusi on of the gp120 P18-I10 CTL epitope with a genetically detoxified derivativ e of PT (PT9K/129G) and assayed this fusion for its ability to stimulate a gp120-specific CTL response in vitro and in vivo. Antigen-presenting cells incubated with this fusion protein were lysed by P18-I10-specific CTL in vi tro and this activity was shown to be MHC class I restricted. The activity was inhibited by brefeldin A but was not inhibited by proteasome inhibitors , possibly because PT undergoes retrograde intracellular transport through the Golgi apparatus to the endoplasmic reticulum and delivers epitopes dire ctly to nascent class I molecules. Mice immunized intraperitoneally with a single dose of the fusion protein without adjuvant raised a strong gp120-sp ecific CTL response in the spleen. This CTL response was dependent on (1) t he dose of fusion administered, (2) the fusion of the epitope with the toxi n (since coadministration of peptide and toxin gave no response), and (3) t he activity of CD8(+) cells. These data demonstrate that this detoxified de rivative to PT, which is already a component of a licensed vaccine for huma ns, could represent a useful vaccine vector molecule for stimulation of HIV -specific CTL responses.