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Chronic HCV infection can lead to cirrhosis and is associated with increased mortality. Interleukin (IL)-10-producing B cells (B10 cells) are regulatory cells that suppress cellular immune responses. Here, we aimed to determine whether HCV induces B10 cells and assess the roles of the B10 cells during HCV infection. HCV-induced B10 cells were enriched in CD19hi and CD1dhi CD5+ cell populations. HCV predominantly triggered the TLR2-MyD88-NF-κB and AP-1 signaling pathways to drive IL-10 production by B cells. In a humanized murine model of persistent HCV infection, to neutralize IL-10 produced by B10 cells, mice were treated with pcCD19scFv-IL-10R, which contains the genes coding the anti-CD19 single-chain variable fragment (CD19scFv) and the extracellular domain of IL-10 receptor alpha chain (sIL-10Ra). This treatment resulted in significant reduction of B10 cells in spleen and liver, increase of cytotoxic CD8+ T-cell responses against HCV, and low viral loads in infected humanized mice. Our results indicate that targeting B10 cells via neutralization of IL-10 may offer a novel strategy to enhance anti-HCV immunotherapy.

We have previously reported that adoptive transfer of tumor-draining lymph node (TDLN) B cells confers tumor regression in a spontaneous pulmonary metastasis mouse model of breast cancer. In this study, we identified IL-10-producing cells within these B cells, and found that IL-10 removal, either by using IL-10−/− TDLN B cells or by systemic neutralization of IL-10, significantly augmented the therapeutic efficacy of adoptively transferred TDLN B cells. Depletion of IL-10 in B-cell adoptive transfers significantly increased cytotoxic lymphocytes (CTLs) and B-cell activity of peripheral blood mononuclear cells (PBMCs) and splenic cells in the recipient. Activated TDLN B cells express Fas ligand, which was further enhanced by co-culture of these TDLN B cells with 4T1 tumor cells. Effector B cells killed tumor cells directly in vitro in an antigen-specific and Fas ligand-dependent manner. Trafficking of TDLN B cells in vivo suggested that they were recruited to the tumor and lung as well as secondary lymphoid organs. These findings further define the biological function of antitumor effector B cells, which may offer alternative cellular therapies to cancer.

Salmonella are important intracellular pathogens in humans and other animal hosts. IL-24 is a novel tumour suppressor and can mediate induction of Th1-type cytokines from PBMC. However, the immunological consequences of this cytokine during intracellular pathogen infection in vivo remain unclear. In the present study, we used a virulent S. typhimurium C5 infected mouse model of typhoid fever to demonstrate that administration of exogenous IL-24 had a protective effect against the bacteria. The IL-24 glycosylation site mutant, in contrast, showed a decreased protective effect. Furthermore, the protective effect of IL-24 was abrogated in IFN-gamma KO mice. More importantly, we demonstrated that IL-24 predominately stimulated neutrophils to produce IFN-gamma and IL-12, subsequently activating CD8+ T cells both in vivo and in vitro. In addition, IL-24 could induce neutrophils to produce NO. These data indicate that the neutrophils activated by IL-24 may play important roles in host defence against Salmonella infection in vivo. Our findings support the development of a novel cytokine immunotherapy against Salmonella.

Salmonella are important intracellular pathogens in humans and other animal hosts. IL-24 is a novel tumour suppressor and can mediate induction of Th1-type cytokines from PBMC. However, the immunological consequences of this cytokine during intracellular pathogen infection in vivo remain unclear. In the present study, we used a virulent S. typhimurium C5 infected mouse model of typhoid fever to demonstrate that administration of exogenous IL-24 had a protective effect against the bacteria. The IL-24 glycosylation site mutant, in contrast, showed a decreased protective effect. Furthermore, the protective effect of IL-24 was abrogated in IFN-gamma KO mice. More importantly, we demonstrated that IL-24 predominately stimulated neutrophils to produce IFN-gamma and IL-12, subsequently activating CD8+ T cells both in vivo and in vitro. In addition, IL-24 could induce neutrophils to produce NO. These data indicate that the neutrophils activated by IL-24 may play important roles in host defence against Salmonella infection in vivo. Our findings support the development of a novel cytokine immunotherapy against Salmonella.