Heterologous expression of adenovirus E3-gp19K in an E1a-deleted adenovirus vector inhibits MHC I expression in vitro, but does not prolong transgene expression in vivo.

An E1a-deleted adenovirus vector constitutively expressing native adenovirus E3-gp19K (Ad.RSV-gp19K) was constructed in order to determine whether or not E3-gp19K mediated interference with antigen presentation would result in prolonged transgene expression in vivo. Cultured fibroblasts infected with Ad.RSV-gp19K produced a native size gp19K protein and had decreased cell surface levels of MHC I as shown by immunoprecipitation and flow cytometry. The congenic mouse strains Balb/b (H-2b MHC I with high gp19K affinity), Balb/k (H-2k MHC I with no gp19K affinity), and Balb/c (H-2d MHC I with moderate gp19K affinity) were chosen for in vivo experiments because of their range of gp19K affinities. Following transduction of mice form each strain with Ad.RSV-gp19K and AD/RSV-hAAT (a reporter adenovirus), or Ad/RSV-cFIX (control adenovirus) and Ad/RSV-hAAT, the level and duration of serum hAAT protein were unrelated to gp19K protein expression. Evaluation of MHC I abundance on hepatocytes following in vivo transduction demonstrated that recombinant adenovirus rapidly increased the abundance of surface MHC I molecules on hepatocytes, and surface MHC I molecules were reduced earlier and to a greater extent following wild-type adenovirus infection compared with hepatocytes transduced with control or Ad.RSV-gp19K recombinant adenovirus. This difference in surface MHC I down-regulation may be related to the different promoters (RSV-LTR versus the native E3 promoter) and will be an important consideration in the development of newer generation adenovirus vectors designed to evade host immune responses.