The effect of T1 and T2 cytokines on the cytotoxic T cell response to mannan-MUC1

MUC1 is a mucin over-expressed in breast cancer and a proposed target fbr i mmunotherapy. By immunising mice with MUC1 conjugated to mannan (M-FP), CD8 (+) MHC-class-I restricted cytotoxic T lymphocytes (CTL), of high CTL precu rsor (CTLp) frequency (1/8000) and with significant tumour protection, can be induced. The effect of various cytokines [interleukin-2 (IL-2), IL-4, IL -6, IL-7, interferon gamma (IFN gamma), and granulocyte/macrophage-colony-s timulating factor (GN-CSF)] on the MUC1 CTL immune response was investigate d (a) by measuring the frequencies of CTLp in mice immunised with vaccinia virus constructs containing recombinant cytokines and M-FP, or (b) by immun ising cytokine- or cytokine-receptor-knockout (-/-) mice with M-FP. Vaccini a virus (VV) constructs containing recombinant cytokines were used either i ndividually or in combination in vivo with M-FP immunisation. M-FP immunisa tions combined with VV-IL-2, VV-IL-7 and VV-GM-CSF, and combinations of VV- IFN gamma + VV-IL-2, VV-IFN gamma + VV-IL-4 or VV-GM-CSF + VV-IL-7 increase d CTLp frequencies up to threefold (1/17 666: M-FP + VV-GM-CSF + VV-IL-7) c ompared to M-FP (1/77 500) alone. By contrast, M-FP combined with VV-IL-4 d ecreased the CTLp frequency threefold whereas VV-IL-6 and VV-IFN gamma had no effect. Studies in cytokine- and cytokine-receptor-gene-knockout (-/-) m ice demonstrated that mice that are IL-2 -/- and IL-7 receptor -/- produce the same CTLp response to M-FP as do control mice, whereas responses in the IL-6 -/-, IL-IO -/- and IFN gamma -/- mice were marginally improved and re sponses to M-FP in IL-4 -/- and tumour necrosis factor receptor 2 -/- mice were weaker. In spite of the increase in CTLp frequency, this was not refle cted in an in vivo tumour model. Tumour challenges using MUC1(+) P815 cells , demonstrated that the addition of cytokines had little additive effect on the already effective tumour-regression capabilities of M-FP alone.