 |
The cytolytic potential of SIV Gag specific CD8+ T cells predicts vaccine efficacy
Presented by Erik Rollman, Australia.
Rollman E.1, Smith M.Z.1, De Rose R.1, Zuber B.2, Kent S.1
1University of Melbourne, Department of Microbiology and Immunology, Melbourne, Australia, 2Mabtech AB, Nacka, Sweden
Objectives: To evaluate the cytolytic phenotype of SIV Gag CD8+ T cells in vaccinated/infected non-human primates using a combined tetramer/intracellular staining (Tet/ICS) assay. Further, to examine the kinetics of activation (IFN-g) and effector molecules (Granzyme B and the degranulation marker CD107a) in these CD8+ T cell populations and to analyse the relationship between cytolytic profiles of CTLs and disease progression.
Methods: Blood samples were drawn from vaccinated (vacinia/fowlpox or attenuated SIV) pigtail macaques (Macaca nemestrina) before and after intravenous challenge with pathogenic SIVmac251. Fresh blood was co-cultured with labelled anti-CD107a antibody following re-stimulation with the immunodominant CD8+ epitope (KP9, SIV Gag164-172). After 0, 0.5, 1, 3 and 5 hours of in vitro re-stimulation the cells were stained with the MHC class I specific tetramer (Mane-A*10-KP9) in combination with conjugated antibodies directed towards intracellular IFN-g and Granzyme B and analysed by flow cytometry.
Results: Vacinia/fowlpox vaccination induced tetramer positive (Tet+) CD8+ T cells capable of only slow production (after 3h) of IFN-g and with low frequency (<5% of Tet+ cells) of CD107a expression accompanied by poor Granzyme B release. In contrast, attenuated SIV infection (previously shown to protect from SIVmac251 challenge) showed very rapid (within 30 min) induction of cytolysis with high expression of CD107a (>40% of Tet+ cells). Upon acute SIV infection, of the VV/FPV immunised animals, the kinetics of the Tet+ CD8+ T cell cytolysis phenotype changed, with a rapid (within 30 min) antigen-specific up-regulation of IFN-g and with high frequencies (>50%) of Tet+ cells degranulating and releasing Granzyme B.
Conclusion: Live attenuated virus infection generates CD8+ T cells with much more rapid killing capacity compared to CD8+ T cells induced by prime/boost vaccination. The delayed killing kinetics exhibited by vector based vaccine-induced T cells may limit the ability of T cell-based HIV vaccines to control acute infection following a pathogenic lentiviral exposure.
Back to the session -
Back to the Programme-at-a-Glance
|
|