FMD is a transmissible viral disease of animals. It is causing very highly economical loses in Pakistan and all over the world. Through vaccination FMD is being controlled in Pakistan. Inactivated virus is used in vaccines. FMD virus grows on BHK-21 cell lines. FMDV show good adoptability on these cell lines. For good and high titer FMDV needs few physical factors to grow on BHK-21 cell lines. These factors include Temperature, Cell density and Multiplicity of infection (MOI)was considered in this research. The FMDV strain “O” was grown on BHK-21 cell line. The cells monolayer was propagated for conduction of effect of these factors on the virus. The mentioned factors were studied to get optimum level of virus titer in in vitro cell lines. The effect of 35°C, 37°C and 39°C was evaluated on the virus growth. Maximum virus propagation was noted at optimum temperature 37°C. The viral concentration at 37°C was significantly (P<0.05) higher than at 35°C and 39°C. The effect of cell density was studied on the virus concentration. Flask of three different densities 25cm2, 175cm2 and 275cm2were utilized in the current study. The virus concentration in all three different densities was not significantly different (P>0.05) from each other. Another factor Multiplicity of infection (MOI)was investigated in the study. Five different volumes 10ul, 20ul, 30ul, 40ul and 50ul of the FMDV strain “O” were used to investigate the effect of factor on the virus concentration. The results revealed highest viral harvest concretion at 50ul volume with MOI of 7.1, %age of cells infected with single virus and 6.3 × 1079. The MOI at 50ul was significantly higher (P<0.05) than the other four concentration of the virus. It was concluded from the study that the optimum temperature for the maximum FMDV concentration harvest is 37°C. The density of cell has no significant effect on the growth of virus that is flask of any density may be used to grow the FMDV. Multiplicity of infection (MOI) of 14.2 give maximum
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TCID50 Optimizing the conditions for the cell culture and virus cultivation helps in maximum virus harvest achievement. From the present study it may be suggested that the physical factors may be optimized for the remaining strains of FMD and other vaccine viruses to attain maximum virus grow.