Figure 8. Current model/Working hypothesis.

Both wildtype virus (wt; black) and ORF4 mutant virus (ΔORF4; grey) initially activate – in an ORF4-independent manner – the Akt pathway (a). After being endocytosed, the wt virus is able to maintain the activation of Akt in an ORF4-dependent manner which aids to leave the endosome rather quickly (b). In contrast, due to the lack of ORF4, ORF4 mutant virus is trapped much longer in the endosome and escapes with delay, most likely by additional, ORF4-independent mechanisms (c).