The Cytotoxic Effect of the Wild-Type Newcastle Disease Virus Strain on Tumor Cells in vitro

Oncolytic Newcastle disease viruses (NDVs) make up a group of antitumor agents for the experimental treatment of oncological diseases that nonpathogenic for human beings. It is known that realization of the cytotoxic effect of NDV strains on the tumor cells depends on the peculiarities of viral genome structure, strain virulence, and tumor cell culture (National Institutes of Health, 2018). At the same time, the mechanism of NDV-induced death has been poorly studied. The aim of this work was to study the nature of morphological changes in HeLa and Hep-2 (HeLa derivative) human tumor cells after infection with the wild-type mesogenic NDV strain NDV/Altai/pigeon/770/2011. The calculation of living tumor cells using MTT test demonstrated that the cytotoxic activity of NDV/Altai/pigeon/770/2011 strain in 144 h after infection decreases the cell viability till 13.08 ± 8.29% (HeLa) and 4.74 ± 3.29% (Hep-2, HeLa derivative). A routine staining detected morphological traits of degradation of infected cells, while morphometric studies detected an increase in the value of the nuclear–cytoplasmic ratio (NCR). The presence of a virus in the tumor cells was visualized by the method of immunocytochemical staining (ICS) using antibodies to the HN glycoprotein of the NDV envelope. The results of immunodetection of tumor necrosis factor α (TNFα) suggest the activation of cell death along the apoptosis pathway against the background of viral infection. The results obtained indicate a pronounced cytotoxic activity of wild-type NDV/Altai/pigeon/770/2011 strain regarding HeLa and Hep-2 (HeLa derivative) adenocarcinoma cells and sensitivity of the studied cell lines to the oncolytic effect of NDV.