2.3. Determination of Tissue Culture Infectious Dose (50%) (TCID50)
96-well microtitre plates containing 100 μL of confluent FRhK-4 were infected with 100 μL of serial 10-fold of dilutions of stock virus in minimal essential medium with 1% FCS (maintenance medium) starting from 10−1 to 108. Titrations were done in quadruplicate. Infected cells were incubated for 4 days at 37°C. Appearance of CPE was recorded daily. TCID50 was determined according to Reed and the Muench method [19].