Synergism between active listeriolysin O and dimethyldioctadecylammonium bromide to activate CD8+ T cells

Purified recombinant listeriolysin O (LLO) was assessed for its ability to induce T cell responses in mice. Intraperitoneal immunisation with LLO, as a fusion with glutathione-S-transferase (GST), induced the production of LLO-specific CD8+ T cells, but not LLO-specific CD4+ T cells. The generation of this response could be blocked by pre-treatment with cholesterol, indicating a requirement for LLO pore formation. An increase in the LLO-specific response of both CD8+ and CD4+ T cells could be detected following the addition of dimethyldioctadecylammonium bromide (DDA), although the generation of this response was not dependent upon LLO pore formation, suggesting that DDA might change the presentation pathway of LLO leading to activation of the CD8+ T cells. However, this response was dependent upon the presence of structurally intact LLO, suggesting a requirement for the innate recognition of LLO in the activation of the CD4+ and CD8+ T cells. Therefore, DDA and LLO can act synergistically to induce the production of a CD8+ T cell response.