Multiple Administration Routes, Including Intramuscular Injection, of Oncolytic Tanapoxvirus Variants Significantly Regress Human Melanoma Xenografts in BALB/c Nude Mice Reconstituted with Splenocytes from Normal BALB/c Donors.

Human melanoma is the most aggressive form of skin cancer and is responsible for the most deaths of all skin cancers. Localized tumors, and those which have limited spread, have 5-year survival rates of over 90%, with those numbers steadily rising over the past decade. However, metastatic melanomas have a sharp decrease in 5-year survival rates and are still an area of need for new, successful therapies. Immuno-oncolytic viruses (OVs) have emerged as a promising class of immunovirotherapy that can potentially address this disease. The Food and Drug Administration in the United States has approved one oncolytic herpes simplex virus expressing granulocyte-macrophage colony-stimulating factor (Talimogene Laherparepvec) for the treatment of metastatic melanoma, and others could soon follow for this and other cancers. In previous studies, Tanapoxvirus (TPV) recombinants expressing mouse interleukin-2 (mIL-2) and another expressing bacterial flagellin from Salmonella typhimurium (FliC) have demonstrated anti-tumor efficacy in nude mouse models. TPV replicates only in humans and monkeys, including tumor cells, which makes the use of syngeneic tumor models impossible for the study of this OV in a standard immunocompetent system. In this study, TPV/Δ66R/mIL-2 and TPV/Δ2L/Δ66R/FliC were tested for their ability to treat human melanoma xenografts (SK-MEL3) in a BALB/c nude mouse model reconstituted with splenocytes from genetically compatible, normal BALB/c donor mice. Two SK-MEL3 tumors were transplanted into each flank of BALB/c nude mice, and the larger tumor was treated intratumorally (IT) with virus or mock injection. In one set of animals, mice received adoptive transfers of splenocytes from BALB/c mice on day 4 to reconstitute their immune systems and allow for adaptive immune responses to occur in a xenograft model. Direct IT injection of TPV/Δ66R/mIL-2 led to significantly greater rates of tumor regression compared to reconstituted control (RC) mice in the primary and distant tumor sites, whereas TPV/Δ2L/Δ66R/FliC treatment led to significantly greater rates of tumor regression in distant tumor sites only. A second experiment used TPV/Δ66R/mIL-2 to test whether TPV could be administered intravenously (IV), intramuscularly (IM), or both routes simultaneously to exert similar anti-tumor effects in an indirectly treated tumor. A single SK-MEL3 tumor was transplanted into one flank of BALB/c nude mice and was treated either into the tail vein, the nearest rear leg to the tumor, or both. All mice then received adoptive transfers of splenocytes in the same way as previously described on day 4 and received an additional TPV treatment on day 14. The results demonstrated that TPV/Δ66R/mIL-2 treatment IV or IM had significantly greater rates of tumor regression than RC-treated mice but failed to exert this effect when both routes were used simultaneously. Data obtained through these experiments support the continued development of Tanapoxvirus for the treatment of human melanoma and using immune reconstitution to create intact adaptive immunity in a xenograft context, which can allow other tropism-limited OVs to be studied against human cancers.

T-independent response mediated by oncolytic tanapoxvirus recombinants expressing interleukin-2 and monocyte chemoattractant protein-1 suppresses human triple negative breast tumors.

Human triple negative breast cancer (TNBC) is an aggressive disease, associated with a high rate of recurrence and metastasis. Current therapeutics for TNBC are limited, highly toxic and show inconsistent efficacy due to a high degree of intra-tumoral and inter-tumoral heterogeneity. Oncolytic viruses (OVs) are an emerging treatment option for cancers. Several OVs are currently under investigation in preclinical and clinical settings. Here, we examine the oncolytic potential of two tanapoxvirus (TPV) recombinants expressing mouse monocyte chemoattractant protein (mMCP)-1 [also known as mCCL2] and mouse interleukin (mIL)-2, in human TNBC, in vitro and in vivo. Both wild-type (wt) TPV and TPV recombinants demonstrated efficient replicability in human TNBC cells and killed cancer cell efficiently in a dose-dependent manner in vitro. TPV/∆66R/mCCL2 and TPV/∆66R/mIL-2 expressing mCCL2 and mIL-2, respectively, suppressed the growth of MDA-MB-231 tumor xenografts in nude mice significantly, as compared to the mock-injected tumors. Histological analysis of tumors showed areas of viable tumor cells, necrotic foci and immune cell accumulation in virus-treated tumors. Moreover, TPV/∆66R/mIL-2-treated tumors showed a deep infiltration of mononuclear immune cells into the tumor capsule and focal cell death in tumors. In conclusion, TPV recombinants expressing mCCL2 and mIL-2 showed a significant therapeutic effect in MDA-MB-231 tumor xenografts, in nude mice through induction of potent antitumor immune responses. Considering the oncolytic potency of armed oncolytic TPV recombinants expressing mCCL2 and mIL-2 in an experimental nude mouse model, these viruses merit further investigation as alternative treatment options for human breast cancer.

Oncolytic tanapoxvirus expressing FliC causes regression of human colorectal cancer xenografts in nude mice.

Colorectal cancers are significant causes of morbidity and mortality and existing therapies often perform poorly for individuals afflicted with advanced disease. Oncolytic virotherapy is an emerging therapeutic modality with great promise for addressing this medical need. Herein we describe the in vivo testing of recombinant variants of the tanapoxvirus (TPV). Recombinant viruses were made ablated for either the 66R gene (encoding a thymidine kinase), the 2L gene (encoding a TNF-binding protein), or both. Some of the recombinants were armed to express mouse chemotactic protein 1 (mCCL2/mMCP-1), mouse granulocyte-monocyte colony stimulating factor (mGM-CSF), or bacterial flagellin (FliC). Tumors were induced in athymic nude mice by implantation of HCT 116 cells and subsequently treated by a single intratumoral injection of one of the recombinant TPVs. Histological examination showed a common neoplastic cell type and a range of immune cell infiltration, necrosis, and tumor cell organization. Significant regression was seen in tumors treated with virus TPV/Δ2L/Δ66R/fliC, and to a lesser extent the recombinants TPV/Δ2L and TPV/Δ66R. Our results suggest that oncolytic recombinants of the TPV armed with activators of the innate immune response may be effective virotherapeutic agents for colorectal cancers in humans and should be explored further to fully realize their potential.

Evaluation of three experimental bovine viral diarrhea virus killed vaccines adjuvanted with combinations of Quil A cholesterol and dimethyldioctadecylammonium (DDA) bromide.

Bovine viral diarrhea virus (BVDV) infections cause respiratory, reproductive, and enteric disease in cattle. Vaccination raises herd resistance and limits the spread of BVDV among cattle. Both killed and modified live vaccines against BVDV are available. While modified live vaccines elicit an immune response with a broader range and a longer duration of immunity, killed vaccines are considered to be safer. One way to improve the performance of killed vaccines is to develop new adjuvants. The goal of this research was evaluate new adjuvants, consisting of combinations of Quil A cholesterol and dimethyldioctadecylammonium (DDA) bromide, for use in killed vaccines. Responses to three novel killed vaccines, using combinations of Quil A and DDA as adjuvants, were compared to responses to a commercial modified live and a commercial killed vaccine. Vaccination response was monitored by measuring viral neutralizing antibodies (VN) levels and by response to challenge. All three novel vaccines were efficacious based on reduction in virus isolation, pyrexia, and depression. Compared to a commercial killed vaccine, the three novel vaccines elicited higher VN levels and reduced injection site inflammation.

Myopathy related to administration of a cationic amphiphilic drug and the use of multidose drug distribution analysis to predict its occurrence.

Many cationic amphiphilic (phospholipidosis-inducing) drugs (CADs) accumulate in tissues following repeated dosing in preclinical models, and this is sometimes associated with dose-limiting toxicities. Plasma drug levels cannot be used to estimate tissue accumulation of CADs since it occurs in tissues despite stabilization of plasma levels. Severe myopathy was found in skeletal muscles of rats during the initial safety evaluation of a dopamine D3 receptor antagonist, PNU-177864, and was associated with phospholipidosis in numerous tissues. The myopathy was observed only when plasma levels of PNU-177864 remained essentially constant throughout the 24-hour dosing period. A repeat dose drug distribution study using whole body autoradiography demonstrated that drug-related material did not accumulate in skeletal muscle or other tissues following repeated doses at levels considered within the therapeutic range and showing toxicokinetic profiles acceptable for further development. These observations provided support for the continued development of and longer-term toxicity studies with this candidate compound.

Epididymal and systemic phospholipidosis in rats and dogs treated with the dopamine D3 selective antagonist PNU-177864.

Repeat dose oral toxicity studies were conducted in rat and dog to assess the safety for human clinical testing of the potent dopamine D3 receptor antagonist, PNU-177864. Systemic phospholipidosis was the principal treatment-related change with epididymal epithelial cell phospholipidosis being the most prominent finding in rats and dogs. Epididymal epithelial cells had no histologic evidence of degeneration; sperm density and morphology were normal histologically in both species; and sperm concentration, morphology, and motility in the dog were comparable to dogs given vehicle. Other sites with phospholipidosis included lymphoid tissues (lymph nodes, Peyer's patches, and/or spleen), pulmonary alveolar macrophages, and peripheral blood lymphocytes in rats and dogs and adrenal cortex, liver, pituitary, hair follicles, bone marrow lymphocytes and plasma cells, and skeletal muscle in rats only. The phospholipidosis was resolved after a 6-week recovery period in all tissues but epididymis. There was no evidence of cell injury in tissues that had phospholipid accumulations except in rat skeletal muscle that had multifocal myofiber degeneration and necrosis. For clinical trials, serum AST and CK and peripheral blood lymphocyte vacuolation were considered potential safety biomarkers for skeletal muscle degeneration and phospholipidosis, respectively.