In mice, intravenous injections are commonly administered in the lateral tail vein. This technique is sometimes difficult to carry out and may cause stress to mice. Though injection through the retro-orbital venous sinus can provide certain advantages over lateral tail vein injection, this method is poorly defined and infrequently used. To compare the efficacy of these two routes of drug delivery, the authors injected MAFIA transgenic mice with the depletion agent AP20187, which selectively induces apoptosis in macrophages. Each mouse received five consecutive daily injections through either the lateral tail vein or the retro-orbital venous sinus. The authors then compared macrophage depletion in different tissues (lung, spleen, bone marrow and peritoneal exudate cells). Both routes of injection were similarly effective. A separate experiment using BALB/c mice indicated that retro-orbital venous sinus injection was the less stressful of the two methods.

Intranasal application of vesicular stomatitis virus (VSV) causes acute infection of the central nervous system (CNS). However, VSV encephalitis is not invariably fatal, suggesting that the CNS may contain a professional antigen-presenting cell (APC) capable of inducing or propagating a protective antiviral immune response. To examine this possibility, we first characterized the cellular elements that infiltrate the brain as well as the activation status of resident microglia in the brains of normal and transgenic mice acutely ablated of peripheral dendritic cells (DCs) in vivo. VSV encephalitis was characterized by a pronounced infiltrate of myeloid cells (CD45highCD11b+) and CD8+ T cells containing a subset that was specific for the immunodominant VSV nuclear protein epitope. This T cell response correlated temporally with a rapid and sustained upregulation of MHC class I expression on microglia, whereas class II expression was markedly delayed. Ablation of peripheral DCs profoundly inhibited the inflammatory response as well as infiltration of virus-specific CD8+ T cells. Unexpectedly, the VSV-induced interferon-gamma (IFN-γ) response in the CNS remained intact in DC-deficient mice. Thus, both the inflammatory and certain components of the adaptive primary antiviral immune response in the CNS are dependent on peripheral DCs in vivo.

Currently there are no curative therapies available for patients with metastatic prostate cancer. Thus, novel therapies are needed to treat this patient population. Immunotherapy represents one promising approach for the elimination of occult metastatic tumors. However, the prostate tumor microenvironment (TME) represents a hostile environment capable of suppressing anti-tumor immunity and effector cell function. In view of this immunosuppressive activity, we engineered murine prostate cancer cells with regulated expression (tet-on) of CCL21. Prostate tumor cells implanted orthotopically produced primary prostate tumors with predictable metastatic disease in draining lymph nodes and distant organs. Expression of CCL21 in the prostate TME enhanced survival, inhibited tumor growth and decreased the frequency of local (draining lymph node) and distant metastasis. Therefore, these studies provide a strong rationale for further evaluation of CCL21 in tumor immunity and its use in cancer immunotherapy.

TRAMPC2 (transgenic adenocarinoma of mouse prostate) tumors are heavily infiltrated with myeloid but not lymphoid (T and B) cells that may reflect the accumulation of immature dendritic cells (DCs) in TRAMPC2 tumors. Secondary lymphoid tissue chemokine (CCL21, SLC) is chemotactic for T cells and DCs and may serve as co‐localization signal for these cells during early phases of the cellular immune response to prostate tumors. We proposed in this study that modification of tumor microenvironment (TME) by expression of CCL21 in TRAMP tumor would induce infiltration of DCs and T cells and minimizes the myeloid cell infiltrate that appears to be responsible for disruption of T cell signaling complex. We generated TRAMPC2 cell lines with regulated expression of CCL21 using the tetracycline responsive promoter, so that we could activate the transgene at selected times during tumor progression (tet on system). Orthotopic tumor volumes were smaller in tetracycline treated mice and these mice lived longer than control mice. Lymph node (LN) metastasis was detected in all 3 control mice (1 found dead) whereas only 2 out of 4 treated mice had LN metastasis. 2 out of 3 untreated mice but only 1 out of 4 treated mice had lung metastasis. Our data indicates that expression of CCL21 in the prostate TME inhibits tumor growth and prevents metastasis and may represent a novel approach to modulate anti‐tumor immunity and tumor growth.