MCL1 and infection: While the release of viral protein/particles were enhanced with decreased expression levels of Mcl-1, compared to that in Bak knockdown and control cells, IBV S and N protein expression levels in total cell lysates were only slightly higher in Mcl-1 knockdown cells at 20 hours post-infection, and largely comparable with siEGFP-transfected cells at 24 hours post-infection (Fig. 6A).