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Histological evaluation of intratumoral myxoma virus treatment in an immunocompetent mouse model of melanoma.

ABSTRACT: Two recombinant myxoma viruses (MYXV expressing a fluorescent protein [MYXV-Tred] and MYXV-Tred encoding murine interleukin-15 [MYXV-IL15]) were evaluated for therapeutic effects in an aggressive B16F10 melanoma model in immunocompetent mice. It was hypothesized that continuous expression of IL-15 within a tumor would recruit cytotoxic effector cells to induce an antitumor immune response and improve treatment efficacy. Weekly intratumoral injections were given to evaluate the effect of treatment on the median survival time of C57BL/6 mice bearing established B16F10 melanomas. Mice that received MYXV-Tred or MYXV-IL15 lived significantly longer than mice given treatment controls. Unexpectedly, the median survival time of MYXV-IL15-treated mice was similar to that of MYXV-treated mice. At 1, 2, and 4 days postinoculation, viral plaque assays detected replicating MYXV-Tred and MYXV-IL15 within treated tumors. At these time points in MYXV-IL15-treated tumors, IL-15 concentration, lymphocyte grades, and cluster of differentiation-3+ cell counts were significantly increased when compared to other treatment groups. However, viral titers, recombinant protein expression, and lymphocyte numbers within the tumors diminished rapidly at 7 days postinoculation. These data indicate that treatment with recombinant MYXV should be repeated at least every 4 days to maintain recombinant protein expression within a murine tumor. Additionally, neutrophilic inflammation was significantly increased in MYXV-Tred- and MYXV-IL15-treated tumors at early time points. It is speculated that neutrophilic inflammation induced by intratumoral replication of recombinant MXYV contributes to the antitumoral effect of MYXV treatment in this melanoma model. These findings support the inclusion of neutrophil chemotaxins in recombinant poxvirus oncolytic virotherapy.

SUBMITTER: Doty RA

PROVIDER: S-EPMC4389688 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:UNLABELLED:With over 3.5 billion people at risk and approximately 390 million human infections per year, dengue virus (DENV) disease strains health care resources worldwide. Previously, we and others established models for DENV pathogenesis in mice that completely lack subunits of the receptors (Ifnar and Ifngr) for type I and type II interferon (IFN) signaling; however, the utility of these models is limited by the pleotropic effect of these cytokines on innate and adaptive immune system development and function. Here, we demonstrate that the specific deletion of Ifnar expression on subsets of murine myeloid cells (LysM Cre(+) Ifnar(flox/flox) [denoted as Ifnar(f/f) herein]) resulted in enhanced DENV replication in vivo. The administration of subneutralizing amounts of cross-reactive anti-DENV monoclonal antibodies to LysM Cre(+) Ifnar(f/f) mice prior to infection with DENV serotype 2 or 3 resulted in antibody-dependent enhancement (ADE) of infection with many of the characteristics associated with severe DENV disease in humans, including plasma leakage, hypercytokinemia, liver injury, hemoconcentration, and thrombocytopenia. Notably, the pathogenesis of severe DENV-2 or DENV-3 infection in LysM Cre(+) Ifnar(f/f) mice was blocked by pre- or postexposure administration of a bispecific dual-affinity retargeting molecule (DART) or an optimized RIG-I receptor agonist that stimulates innate immune responses. Our findings establish a more immunocompetent animal model of ADE of infection with multiple DENV serotypes in which disease is inhibited by treatment with broad-spectrum antibody derivatives or innate immune stimulatory agents. IMPORTANCE:Although dengue virus (DENV) infects hundreds of millions of people annually and results in morbidity and mortality on a global scale, there are no approved antiviral treatments or vaccines. Part of the difficulty in evaluating therapeutic candidates is the lack of small animal models that are permissive to DENV and recapitulate the clinical features of severe human disease. Using animals lacking the type I interferon receptor only on myeloid cell subsets, we developed a more immunocompetent mouse model of severe DENV infection with characteristics of the human disease, including vascular leakage, hemoconcentration, thrombocytopenia, and liver injury. Using this model, we demonstrate that pathogenesis by two different DENV serotypes is inhibited by therapeutic administration of a genetically modified antibody or a RIG-I receptor agonist that stimulates innate immunity.

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Histological evaluation of intratumoral myxoma virus treatment in an immunocompetent mouse model of melanoma.

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