APOA4 and infection: Among the large number of mammalian genes induced in infected cells compared to uninfected controls, one of the most upregulated genes at 12 and 24 hours post-infection was apolipoprotein A-IV (APOA4) [3.08 log2(FC) at 24 hours, P adj = 3.14E-09], an apolipoprotein primarily produced in the small intestine (Fig. 4A) (32).