Abstract
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.