Comparison of sensitivity of VERO cell line versus primary monkey kidney cells in the detection of residual live polio virus during and after inactivation.

Substitution of Primary Monkey Kidney (PMK) Cells by Monkey Cell Lines (MCL) for detection of residual live virus in poliovaccine control has been considered for various reasons. The sensitivity of VERO Cells versus PMK cells has been investigated. This study was done with poliovirus during and just after formalin inactivation. The amount of residual live virus was tested by TCID50 end-point titrations in roller-tubes and small bottles at different stages in the inactivation process. Just before or at the end of inactivation, a 1 000 doses vaccine equivalent volume was tested on Roux bottles. Thus far the results show that VERO cells seem to be less sensitive than PMK cells, especially for type 3 virus. Additional studies will be needed to investigate whether the sensitivity of the VERO cells can be improved to detect residual live poliovirus during and after inactivation with the same sensitivity as PMK cells.