Sustained and NK/CD4+ T Cell-Dependent Efficient Prevention of Lung Metastasis Induced by Dendritic Cells Harboring Recombinant Sendai Virus

Abstract

We recently demonstrated efficient antitumor immunity against murine tumors using dendritic cells (DCs) activated by recombinant Sendai viruses (rSeVs), and proposed a new concept, “immunostimulatory virotherapy,” for cancer immunotherapy. However, there has been little information on the efficacy of this method in preventing metastatic diseases. In this study, we investigated the efficacy of vaccinating DCs activated by fusion gene-deleted nontransmissible rSeV (rSeV/dF) using a murine model of lung metastasis. Bolus and i.v. administration of DCs harboring rSeV/dF-expressing GFP without pulsation of tumor Ag (DC-rSeV/dF-GFP) 2 days before tumor inoculation showed efficient prevention against lung metastasis of c1300 neuroblastoma, but not of RM-9 prostatic cancer. We found that the timing of DC therapy was critical for the inhibition of pulmonary metastasis of RM-9, and that the optimal effect of DCs was seen 28 days before tumor inoculation. Interestingly, the antimetastatic effect was sustained for over 3 mo, even when administered DCs were already cleared from the lung and organs related to the immune system. Although NK cell activity had already declined to baseline at the time of tumor inoculation, Ab-mediated depletion studies revealed that CD4+ cells as well as the presence of, but not the activation of, NK cells were crucial to the prevention of lung metastasis. These results are the first demonstration of efficient inhibition of lung metastasis via bolus administration of virally activated DCs that was sustained and NK/CD4+ cell-dependent, and may suggest a potentially new mechanism of DC-based immunotherapy for advanced malignancies.

Validation of recombinant Sendai virus in a non-natural host model

“…The effect of SeV on immune modulation is further highlighted in a study by Komary et al, which showed that SeV-transduced dendritic cells can induce persistent NK and CD4-cell-dependent anti-tumor activity. 20 We have previously shown that SeV administration evokes cellular and humoral immune responses in an animal model and that the level of neutralising antibodies (as measured by in vitro assays) increases after virus re-administration. 7 However, there was no correlation between neutralising antibody levels and residual gene expression (r 2 ¼0.046, P¼0.16).…”

Antagonism of VEGF by Genetically Engineered Dendritic Cells Is Essential to Induce Antitumor Immunity against Malignant Ascites

“…Importantly, rSeVs lead DCs to highly activated/mature state via a DExD/Hbox RNA helicase, retinoic acid-inducible gene-I (RIG-I; refs. 13,14); therefore, we have been able to show that DCs activated by rSeVs (DC-rSeV) induced highly efficient antitumor immunity against various tumors (7)(8)(9).…”

“…Construction and recovery of rSeVs rSeVs were constructed as described previously (7)(8)(9). In brief, LLC-MK2 cells were transfected with a plasmid mixture containing each of the following plasmids: pSeV þ 18/dF-GFP (green fluorescent protein) or pSeV þ 18/dF-hsFLT-1 (16), pGEM-NP, pGEM-P, and pGEM-L in Superfect reagent (Qiagen).…”

“…Twenty-four hours later, cells were washed and incubated in MEM containing araC and trypsin. Virus yield is expressed in cell infection units, as previously described (7)(8)(9). Human cDNA of soluble flt-1, 2,064-bp encoding 6 of 7 extracellular domains (17), was amplified by PCR with primer set containing NotI site from total RNA of human umbilical vein endothelial cell.…”

“…To provide a possible solution, we recently proposed a new concept, "immunostimulatory virotherapy" (5,6), using a new DC-activating modality, the replication-competent (6) and fusion (F)-genedeleted nontransmissible (7)(8)(9) recombinant Sendai viruses (rSeV). SeV, a member of the family Paramyxoviridae, has a nonsegmented negative-strand RNA genome and shows a broad spectrum of gene transfer (10)(11)(12), including DCs (7)(8)(9). Importantly, rSeVs lead DCs to highly activated/mature state via a DExD/Hbox RNA helicase, retinoic acid-inducible gene-I (RIG-I; refs.…”