Attenuated and Protease-Profile Modified Sendai Virus Vectors as a New Tool for Virotherapy of Solid Tumors

Peer reviewe

Evaluation of a novel immunogenic vaccine platform based on a genome replication-deficient Sendai vector

We developed a novel vaccine platform based on a paramyxoviral, genome replication-deficient Sendai virus vector that can express heterologous genes inserted into the genome. To validate the novel approach in vivo, we generated a combined vaccine candidate against human respiratory syncytial virus (RSV) and human parainfluenza virus type 3 (PIV3). The present study compares two different methods of displaying heterologous antigens: (i) the RSV fusion (F) protein, encoded as a secretable version in an additional transcription unit, serves as an antigen only after being expressed in infected cells; (ii) PIV3 fusion (F) and hemagglutinin-neuraminidase (HN) genes, replacing Sendai counterparts in the vector genome, are also expressed as structural components on the surface of vaccine particles. The efficacy of this prototype vaccine was assessed in a mouse model after mucosal administration. The vaccine candidate was able to elicit specific mucosal, humoral and T cell-mediated immune responses against RSV and PIV3. However, PIV3 antigen display on the vaccine particles' surface induced higher antibody titers than the RSV antigen, being expressed only after cell infection. Consequently, this construct induced an adequate neutralizing antibody response only to PIV3. Finally, replicating virus particles were not detected in the lungs of immunized mice, confirming the genome stability and replication deficiency of this vaccine vector in vivo. Both factors can contribute substantially to the safety profile of vaccine candidates. In conclusion, this replication-deficient Sendai vector represents an efficient platform that can be used for vaccine developments against various viral pathogens. (C) 2013 Elsevier Ltd. All rights reserved

A Novel Armed Oncolytic Measles Vaccine Virus for the Treatment of Cholangiocarcinoma

Cholangiocarcinoma (CC) is curable only in early stages by complete surgical resection. Thus, in advanced disease stages in which a complete removal of the tumor mass is no longer possible and palliative chemotherapy achieves only modest success, therapeutics employing new methods of action are desperately needed. Oncolytic viruses employed in clinical studies have been shown to spread preferentially in cancer cells. Beyond that, virotherapeutic cell killing can be enhanced by virus-based expression of suicide genes. We engineered a measles vaccine virus (MeV) vector expressing super cytosine deaminase (SCD), a fusion protein of yeast cytosine deaminase and uracil phosphoribosyltransferase, which converts the prodrug 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) and subsequently to 5-fluorouridine-monophosphate. This novel vector was evaluated using three different human-derived CC cell lines. In vitro, all CC cell lines were found to be permissive to MeV infection. Partial blocking of MeV-mediated oncolysis could be overcome by employment of the SCD transgene together with administration of 5-FC. In vivo, intratumoral application of SCD-armed MeV together with a systemic 5-FC treatment showed a significant reduction in tumor size in a TFK-1 xenograft mouse model when compared with virus-only treatment. In a second animal experiment employing a HuCCT1 xenograft tumor model, an enhanced SCD-armed MeV vector, in which the SCD transgene was expressed from a different genomic position, led not only to reduced tumor volumes, but also to a significant survival benefit. On the basis of these encouraging preclinical data on employment of SCD-armed MeV for the virotherapeutic treatment of chemotherapy-resistant CC, a clinical virotherapy trial is set up currently

Evaluation of a novel immunogenic vaccine platform based on a genome replication-deficient Sendai vector.

We developed a novel vaccine platform based on a paramyxoviral, genome replication-deficient Sendaivirus vector that can express heterologous genes inserted into the genome. To validate the novel approachin vivo, we generated a combined vaccine candidate against human respiratory syncytial virus (RSV)and human parainfluenza virus type 3 (PIV3). The present study compares two different methods ofdisplaying heterologous antigens: (i) the RSV fusion (F) protein, encoded as a secretable version in anadditional transcription unit, serves as an antigen only after being expressed in infected cells; (ii) PIV3fusion (F) and hemagglutinin-neuraminidase (HN) genes, replacing Sendai counterparts in the vectorgenome, are also expressed as structural components on the surface of vaccine particles. The efficacyof this prototype vaccine was assessed in a mouse model after mucosal administration. The vaccinecandidate was able to elicit specific mucosal, humoral and T cell-mediated immune responses againstRSV and PIV3. However, PIV3 antigen display on the vaccine particles’ surface induced higher antibodytiters than the RSV antigen, being expressed only after cell infection. Consequently, this construct inducedan adequate neutralizing antibody response only to PIV3. Finally, replicating virus particles were notdetected in the lungs of immunized mice, confirming the genome stability and replication deficiencyof this vaccine vector in vivo. Both factors can contribute substantially to the safety profile of vaccinecandidates. In conclusion, this replication-deficient Sendai vector represents an efficient platform thatcan be used for vaccine developments against various viral pathogens

An armed oncolytic measles vaccine virus eliminates human hepatoma cells independently of apoptosis

Due to late diagnosis and a pronounced chemoresistance, Most patients with hepatocellular carcinoma (HCC) have an overall poor prognosis. Measles vaccine viruses (MeV) have been shown to possess anti-tumor properties and their efficacy has been enhanced by arming with suicide genes. To test armed MeV for the treatment of HCC, we equipped it with the suicide gene Super-cytosine deaminase (SCD) and tested the efficacy in cell culture and in a mouse xenograft model of human HCC. Prodrug conversion was investigated in cell culture and quantified by high-performance liquid chromatography. We observed a strong oncolytic activity of MeV-SCD against human HCC in vitro and in vivo. The prodrug was efficiently converted in infected cells leading to a significant enhancement of the cytotoxic effect. Treatment of HCC xenografts with MeV caused long-term virus replication in tumor tissue. We show that the suicide gene therapy induces an apoptosis-like cell death but is not dependent on intact apoptosis pathways. These results demonstrate that MeV-based suicide gene therapy is a promising novel therapy regimen for HCC overcoming resistance towards conventional therapy. The independence from apoptosis raises hopes for the treatment of patients whose tumor cells exert defects in this cell death mechanism