... 2Essentiality of A12L protein in VV replication. In order to determine the essentiality of A12L protein in virus replica-tion, T-REx 293 cells were infected with vvtetOA12L in the presence/absence ... virus infectivity, but not for core protein process-ing or for INV and EEV formation. Virol 19 94, 202:294-304. 10 . Wilcock D, Smith GL: Vaccinia virions lacking core protein VP8are deficient in ... the 21- kilodalton protein and a newlyidentified 15 -kilodalton envelope protein. J Virol 19 97, 71: 18 21- 1833. 18 . Rodriguez JR, Risco C, Carrascosa JL, Esteban M, Rodriguez D: Vac-cinia virus 15 -kilodalton...