Antitumor and immunostimulatory activities of a genotype V recombinant attenuated veterinary Newcastle disease virus vaccine

Antitumor conventional treatments including chemo/radiotherapy result in several side effects and non-specificity. Therapies including the use of oncolytic viruses, particularly the Newcastle disease virus (NDV), have emerged as an attractive alternative due to their capacity to kill cancer cells directly or through stimulation of the immune system. In the present study, a commercial vaccine composed of a recombinant attenuated NDV strain P05 (rNDV-P05) was assessed for antitumor and immunostimulatory activity. Firstly, hemagglutination activity was evaluated at different pH and temperature conditions. Then, cancer cell lines and peripheral blood mononuclear cells (PBMC) were co-cultured with or without rNDV-P05 and cytoplasmic nucleosomes were measured by enzyme-linked immunosorbent assay (ELISA) as an apoptosis indicator. Antitumor cytokines produced by PBMC in response to the virus were analyzed by ELISA and reverse transcription quantitative polymerase chain reaction. Characterization of rNDV-P05 indicates that the virus is slightly sensible to acid and basic pH, and stable at temperatures no greater than 42°C. The majority of cell lines developed apoptosis in co-culture with rNDV-P05 in a dose-time dependent manner. The highest level of HeLa, HCC1954 and HepG2 cell apoptosis was at 48 h/50 hemagglutination units (HU), and HL-60 was 24 h/50 HU. A549 cell line and PBMC did not show sensitivity to apoptosis by the virus. PBMC from healthy donors stimulated with the rNDV-P05 increased significantly the levels of interferon (IFN)-α, IFN-γ, tumor necrosis factor (TNF)-α and soluble TNF-related apoptosis-inducing ligand in culture supernatants, as well as their mRNA expression. These results demonstrate that the pro-apoptotic effect of rNDV-P05 and its magnitude is specific to particular tumor cell lines and is not induced on PBMC; and the virus stimulates the expression of several key antitumor cytokines. This study promotes the use of rNDV-P05 in an alternate application of different viral strains during virotherapy with NDV.

Cytotoxic effect of co-expression of human hepatitis A virus 3C protease and bifunctional suicide protein FCU1 genes in a bicistronic vector

Recent reports on various cancer models demonstrate a great potential of cytosine deaminase/5-fluorocytosine suicide system in cancer therapy. However, this approach has limited success and its application to patients has not reached the desirable clinical significance. Accordingly, the improvement of this suicide system is an actively developing trend in gene therapy. The purpose of this study was to explore the cytotoxic effect observed after co-expression of hepatitis A virus 3C protease (3C) and yeast cytosine deaminase/uracil phosphoribosyltransferase fusion protein (FCU1) in a bicistronic vector. A set of mono- and bicistronic plasmid constructs was generated to provide individual or combined expression of 3C and FCU1. The constructs were introduced into HEK293 and HeLa cells, and target protein synthesis as well as the effect of 5-fluorocytosine on cell death and the time course of the cytotoxic effect was studied. The obtained vectors provide for the synthesis of target proteins in human cells. The expression of the genes in a bicistronic construct provide for the cytotoxic effect comparable to that observed after the expression of genes in monocistronic constructs. At the same time, co-expression of FCU1 and 3C recapitulated their cytotoxic effects. The combined effect of the killer and suicide genes was studied for the first time on human cells in vitro. The integration of different gene therapy systems inducing cell death (FCU1 and 3C genes) in a bicistronic construct allowed us to demonstrate that it does not interfere with the cytotoxic effect of each of them. A combination of cytotoxic genes in multicistronic vectors can be used to develop pluripotent gene therapy agents.

Identification of Optimal Insertion Site in Recombinant Newcastle Disease Virus (rNDV) Vector Expressing Foreign Gene to Enhance Its Anti-Tumor Effect

Recombinant Newcastle disease virus (rNDV) is tumor selective and intrinsically oncolytic, which has been developed as a vector to express exogenous genes to enhance its oncolytic efficacy. Our previous studies found that insertion sites of foreign gene in rNDV vector affected its expression and anti-tumor activities. However, the optimal insertion site for foreign genes remains unknown. In this study, we inserted the enhanced green fluorescence protein (EGFP) and IL2 genes into four different intergenic regions of the rNDV using reverse genetics technology. Recombinants rNDV-EGFPs and rNDV-IL2s were successfully rescued, which displayed the similar growth kinetics with parental virus. Both EGFP mRNA and protein levels were most abundant in HepG2 cells, when EGFP gene was inserted between the NP/P site of the rNDV. Similarly, the IL-2 expressed by HepG2 cells infected with rNDV-IL2 was highest, when IL2 was inserted into NP/P site. To test whether these rNDVs that express higher foreign genes could induce stronger anti-tumor response, we treated the H22-oxter-tumor-bearing C57BL/6J mice with rNDV-IL2s and then examined the oncolytic efficacy. The results showed that rNDV-IL2-NP/P had the strongest inhibition of murine hepatoma carcinoma tumors. The splenocytes isolated from the mice treated with rNDV-IL2-NP/P reached the highest degrees of CD4+ T and CD8+ T cells. In addition, animals' survival rate in rNDV-IL2-NP/P-treated group was higher than that of other groups. Taken together, these results demonstrate that NP and P gene junction in rNDV is the optimal insertion site for foreign genes expression to enhance rNDV's anti-tumor effects.

Fifty Years of Clinical Application of Newcastle Disease Virus: Time to Celebrate!

This review provides an overview of 50 years of basic and clinical research on an oncolytic avian virus, Newcastle Disease Virus (NDV), which has particular anti-neoplastic and immune stimulatory properties. Of special interest is the fact that this biological agent induces immunogenic cell death and systemic anti-tumor immunity. Furthermore, localized oncolytic virotherapy with NDV was shown to overcome systemic tumor resistance to immune checkpoint blockade immunotherapy. Clinical experience attests to low side effects and a high safety profile. This is due among others to the strong virus-induced type I interferon response. Other viral characteristics are lack of interaction with host cell DNA, lack of genetic recombination and independence of virus replication from cell proliferation. In this millennium, new recombinant strains of viruses are being produced with improved therapeutic properties. Clinical applications include single case observations, case series studies and Phase I to III studies.

Oncolytic Newcastle disease virus expressing chimeric antibody enhanced anti-tumor efficacy in orthotopic hepatoma-bearing mice

Background

Oncolytic virus which arms the therapeutic gene to enhance anti-tumor activity is a prevalent strategy to improve oncovirotherapy of cancer. Newcastle disease virus (NDV) is a naturally oncolytic virus used for cancer therapy. Previously, we generated a mouse-human chimeric HAb18 antibody (cHAb18) against tumor-associated antigen CD147 and demonstrated the inhibition of invasion and migration of hepatocellular carcinoma (HCC) cells. Here, we constructed a recombinant NDV carrying intact cHAb18 gene (rNDV-18HL) based on Italien strain using a reverse genetics system.

Method

Recombinant rNDV-18HL was generated using reverse genetics technology. The characteristics of virally expressed cHAb18 antibody were identified by western blot, enzyme-linked immunosorbent assay, transwell invasion assay, and surface plasmon resonance technology. The biodistribution of recombinant rNDV-18HL using orthotopic xenograft mouse model was assessed with living imaging and immunohistochemistry. Kaplan-Meier survival curves and the log-rank test were performed to analyze the anti-tumor activity of rNDV-18HL.

Results

The cHAb18 was produced in rNDV-18HL-infected cells followed by releasing into the supernatant by cytolysis. The rNDV-18HL-encoded cHAb18 antibody kept affinity for CD147 and showed inhibiting the migration and invasion of HCC cells. Viral replication and virulence were not attenuated by the incorporation of cHAb18 gene which significantly enhanced the suppression of relict tumor cell migration. The rNDV-18HL selectively replicated in orthotopic HCC xenografts leading to cHAb18 expression in situ, which induced the tumor necrosis, reduced the intrahepatic metastasis, and prolonged the survival in mice.

Conclusions

This study provides a new strategy of arming oncolytic NDV with therapeutic antibody to enhance anti-tumor efficacy of cancer therapy.