Inhibitory Effect of Heated Vaccinia Virus on Growth of Vaccinia Virus in Earle's L Cells.

Heated vaccinia virus has been applied to cultures of L cells followed by active virus. Multiplicities, determined by electron microscope particle count, were 10 and 100 for heated virus and 10 for challenge, active virus. Delay times ranged from 0 to 21 1/2 hours. Substantial inhibition was observed with inoculation of heated virus at M = 10. At M = 100 the growth of a challenge inoculum applied 21 1/2 hours later was 94% suppressed. The consequences of these findings are discussed in connection with titration of residual virus in heat-treated virus preparations.