Effects of fetal bovine serum concentration and vented flask conditions on E-11 cell growth and tilapia lake virus infection

Tilapia Lake Virus (TiLV) is an emerging pathogen threatening global tilapia aquaculture, causing high mortality and significant economic losses. The present study aimed to optimize E-11 cell culture conditions for improved growth and TiLV propagation under different serum and flask ventilation conditions. E-11 cells were cultured in Leibovitz’s L-15 medium supplemented with 10%, 15%, and 20% fetal bovine serum (FBS) and maintained at 25°C in a CO₂-free incubator. Cell viability was assessed over four days using the Trypan Blue exclusion assay, while TiLV propagation was evaluated in both seal-cap and vent-cap flasks through microscopic observation of cytopathic effects (CPE). Results showed that E-11 cells supplemented with 15% FBS exhibited the highest viability (85–90%) and optimal proliferation compared to cells grown in 10% or 20% FBS. Morphologically, all cultures displayed similar epithelial-like characteristics with polygonal cell shapes and intact monolayers under the microscope. No significant differences in viability were observed between open- and closed-vented flasks; however, CPE were detected only in infected E-11 cells maintained in vent-cap flasks by 10 days post-infection (dpi), while cells in seal-cap flasks remained morphologically intact. These findings suggest that a 15% FBS concentration and a vented culture environment support both healthy E-11 cell growth and effective TiLV propagation. This optimized culture system enhances the reliability of in vitro TiLV studies and supports efforts toward sustainable aquaculture and food security.