Heterogeneous interleukin-15 inducibilities in murine B16 melanoma and RM-1 prostate carcinoma by interferon-alpha treatment

Long-term treatment of mouse cancer cells with interferon-alpha (IFN-alpha) converts parental B16 melanoma cells to B16alpha vaccine cells. Inoculation of syngeneic mice with UV-irradiated B16alpha vaccine cells triggers immunity to the parental B16 tumor that is mediated by host macrophages, T cells, and NK cells. Lymph node cells from mice inoculated with irradiated B16alpha vaccine cells, but not with irradiated parental cells, proliferate when cultured in vitro, suggesting long-term in vivo activation of lymphoid cells. Both IL-15 mRNA and IL-15 protein are highly induced in B16alpha vaccine cells. The bulk of the induced IL-15 is shown to be cell-associated, either cytoplasmic or membranous. The current study investigated the feasibility of applying the B16alpha vaccination protocol to generate a cancer vaccine against murine RM-1 prostate carcinoma. In comparison to B16alpha vaccine cells, long-term IFN-alpha-treated RM-1 cells (RM-1alpha vaccine cells) showed significant IL-15 mRNA induction but relatively low IL-15 protein up-regulation. When UV-irradiated, a 3-fold increase in intracellular IL-15 was observed in RM-1alpha vaccine cells, suggesting UV damage may have negated a possible control mechanism for IL-15 synthesis. Efficacy of in vivo vaccination of syngeneic mice with UV-irradiated RM-1alpha and B16alpha vaccine cells showed correlation between high IL-15 level and high vaccine efficacy in B16alpha cells compared to low IL-15 level and low vaccine efficacy in RM-1alpha cells. This supports the concept that the induction of IL-15 in tumor cells can be useful for creating whole-cell cancer vaccines.

Proteasome activator and antigen-processing aminopeptidases are regulated by virus-induced type I interferon in the hepatitis C virus-infected liver

Many components of the class I antigen-processing pathway are thought to be regulated solely by interferon-gamma (IFN-gamma). Herein, we report type I IFN-mediated induction of proteasome activator (PA28) subunits alpha and beta, endoplasmic reticulum aminopeptidase 1 (ERAP1), ERAP2, and leucine aminopeptidase (LAP). This mechanism was initiated by either synthetic RNA (poly(I-C)) or by hepatitis C virus (HCV) RNA-mediated induction of type I IFN and abrogated by blocking of type I IFN. In serial liver biopsies of chimpanzees with acute HCV infection, increases in PA28 subunit and aminopeptidase mRNA levels correlated with intrahepatic type I IFN responses and preceded intrahepatic IFN-gamma responses by several weeks. Thus, viral RNA-induced type I IFN regulates the antigen-processing machinery early during viral infection and prior to IFN-gamma response. This mechanism may contribute to the high effectiveness of type I IFN-based therapies if administered early during acute HCV infection.