OPTIMIZATION AND VISUAL MONITORING OF SERUM-FREE CULTIVATION OF THE GFP-PRODUCING SHEEPPOX VIRUS STRAIN “SSPV (TK-) OMP16” IN VERO CELLS

Abstract

This study optimized cultivation conditions for a GFP-producing sheeppox virus strain used as a model analogue of the recombinant strain “SSPV (TK-) OMP16”. The virus was propagated in continuous Vero cell culture using serum-free OptiPRO medium supplemented with 1% L-glutamine. Cell monolayers were infected with virus doses of 0.01, 0.05, 0.1, and 0.3 TCID₅₀/cell and incubated at 37 °C for 120 h. Biological activity was assessed in the culture fluid and in virus-containing suspensions obtained after freeze–thaw treatment of the infected monolayer. Virus accumulation in the culture fluid was limited, whereas freeze–thaw treatment promoted more efficient release of infectious virus and clearer detection of cytopathic effect. The highest titer, 3.5 log TCID₅₀/cm³, was recorded at 0.3 TCID₅₀/cell after 72 h of cultivation. These findings confirm the usefulness of GFP for visual monitoring and optimization of serum-free recombinant sheeppox virus cultivation in Vero cells and future veterinary vaccine platform quality control.