Selective oncolytic activity of newcastle disease virus in equine sarcoid primary cells: a preclinical investigation.

Equine sarcoids are the most common skin tumors in horses and are characterized by local invasiveness, high recurrence rates, and inconsistent responses to current therapies. Oncolytic virotherapy represents a promising alternative approach that exploits defects in antiviral signaling pathways in tumor cells. Newcastle disease virus (NDV), an avian paramyxovirus that is nonpathogenic in mammals, has demonstrated tumor-selective activity in several species; however, its effects on equine sarcoids have not been previously investigated. In this study, primary cell cultures derived from equine sarcoid tumors were established to evaluate the selective cytotoxicity of NDV. Sarcoid tissues from six horses generated thirteen primary sarcoid cultures, while three primary equine fibroblast cultures served as non-tumor controls. Bovine papillomavirus (BPV) DNA was assessed by quantitative polymerase chain reaction. Cells were infected with a green fluorescent protein-expressing Newcastle disease virus (NDV-GFP), and cell viability was measured after seventy-two hours using a metabolic viability assay. Sarcoid cultures exhibited significantly greater sensitivity to viral infection than normal fibroblasts, with substantially lower half-maximal inhibitory concentrations. Viral infectivity, quantified by fluorescence intensity, correlated with increased susceptibility to virus-induced cytotoxicity. Notably, the oncolytic activity of Newcastle disease virus was observed in both bovine papillomavirus-positive and bovine papillomavirus-negative sarcoid cultures. These findings demonstrate that NDV-GFP induces stronger cytotoxic effects in equine sarcoid cells than in normal fibroblasts, supporting its potential as a novel therapeutic strategy in equine oncology.