Comparison of viral replication and IFN response in alpaca and bovine cells following bovine viral diarrhea virus infection.

Alpacas develop diminished disease following bovine viral diarrhea virus (BVDV) infection compared to cattle. We hypothesized that alpaca and bovine cells have differential permissiveness and responses to BVDV infection. To characterize alpaca testicular (AT) and bovine turbinate (BT) cells BVDV infection permissiveness, viral replication and interferon (IFN) synthesis was evaluated. BVDV replicated 3-4 logs lower in AT cells with diminished antigen deposition compared to BT cells. BVDV infection inhibited IFN response in both AT and BT cells. Compared to BT cells, BVDV-infected AT cells had a 2-5 fold increase in IFN synthesis following dsRNA stimulation. The greater IFN response of AT cells compared to BT cells following poly I:C stimulation with or without ncp BVDV infection, may be the basis for the decreased BVDV permissiveness of AT cells and may contribute to the clinical differences following BVDV infection of alpacas and cattle.

Tumor- and organ-dependent infiltration by myeloid-derived suppressor cells.

Myeloid-derived suppressor cells (MDSCs) increase during tumor growth and following cytoreductive therapy resulting in immune dysfunction and tumor escape from host control. We report organ- and tumor-specific expansion of MDSCs, differences in their molecular and membrane phenotypes and T-cell suppressive activity. A significant increase in MDSCs was observed within the spleen, peripheral blood (PB), bone marrow (BM), lungs, and livers of mice bearing orthotopic 4T1, but not CI66 mammary tumors. The PB of 4T1 TB mice had the highest frequency of MDSCs (78.6±2.1%). Similarly, the non-parenchymal cells (NPCs) in the tumor tissue, livers and lungs of 4T1 tumor-bearing (TB) mice had an increased MDSCs frequency. Studies into Gr-1 and Ly-6C staining of MDSCs revealed significant increases in CD11b+Gr-1(dull)Ly-6C(high) and CD11b+Gr-1(bright)Ly-6C(low) subsets. The frequency of MDSCs inversely correlated with the CD3+ T-cell frequency in the spleen, and blood of 4T1 TB mice and was associated with a significant decrease in splenic and NPCs IFN-γ and IL-12 transcript levels, as well as significantly increased levels of granulocyte-macrophage colony-stimulating factor (GM-CSF), stem cell factor (SCF), granulocyte colony-stimulating factor (G-CSF), interleukin-10 (IL-10), interleukin-13 (IL-13), arginase-1 (ARG-1), nitric oxide synthase (NOS-2), vascular endothelial growth factor-A (VEGF-A) transcripts. In summary, MDSCs are significantly increased not only in lymphoid organs, but also in parenchymal organs including lungs and livers of TB mice, where they may facilitate metastasis to these organ sites.

Therapeutic activity of sunitinib for Her2/neu induced mammary cancer in FVB mice.

Mouse mammary tumor virus-Neu (MMTV/neu) transgenic mice on an FVB-background (FVB-neuN) have increased numbers of myeloid derived suppressor cells (MDSCs) and regulatory T-cells (T-regs) in the spleen during mammary tumor induction and progression. Using this transgenic tumor model, we assessed the therapeutic activity of sunitinib, a multi-targeted, tyrosine kinase (TK) inhibitor and its effects on immune-regulatory cells. Our preliminary results show that sunitinib at 40mg/kg/day, p.o. (per os), delayed the time to tumor induction and reduced the incidence and growth of tumors in FVB-neuN mice. In association with its therapeutic activity, sunitinib reduced the absolute number of splenic T-reg cells (CD4(+)CD25(+)CD62L(+)) and MDSCs (CD11b(+)Gr1(+)) that were increased during tumor progression with less activity in mice with gross tumors. A significant decrease in the absolute number of splenic T-regs, dendritic cells (DCs), MDSCs and hematopoietic progenitors (Lin(-)Sca1(+)CD90(dull)) was observed following sunitinib treatment. The frequency of splenic T-regs and hematopoietic progenitors, but not MDSCs was also reduced by sunitinib treatment. Additionally immune-regulatory cytokines and enzymes were down regulated by sunitinib treatment, including TGFbeta and NOS2 in the spleen cells of sunitinib treated mice as compared to untreated tumor bearing (TB) mice. We conclude that sunitinib has therapeutic activity, in association with the down regulation of MDSCs and T-regs and has a trend towards the normalization of the inflammatory cytokine levels induced by tumor progression and growth. Based on these results, we suggest that sunitinib reduction of immune suppressive cells is a critical part of its adjuvant immune therapeutic activity.