ADENOVIRUS INFECTION STIMULATES THE RAF MAPK SIGNALING PATHWAY AND INDUCES INTERLEUKIN-8 EXPRESSION/

Previous studies have shown that airway administration of adenovirus o r adenovirus vectors results in a dose-dependent inflammatory response which limits the duration of transgene expression. We explored the po ssibility that adenovirus infection triggers signal transduction pathw ays that induce the synthesis of cytokines and thus contribute to the early inflammatory response. Since stimulation of the Raf/mitogen-acti vated protein kinase (MAPK) pathway activates transcription factors th at control the expression of inflammatory cytokines, we examined the a ctivation of this pathway following adenovirus infection. Adenovirus i nfection induced the rapid activation of Raf-l and a transient increas e in the tyrosine phosphorylation and activation of p42(mapk) at early times postinfection. Activation of the Raf/MAPK pathway by adenovirus is likely triggered by the infection process, since it occurred rapid ly and with various mutant adenoviruses and adenovirus vectors. Moreov er, interleukin-8 (IL-8) mRNA accumulation was evident at 20 min posti nfection and was induced even in the presence of cycloheximide. Both M APK activation and IL-g production were inhibited by forskolin, a pote nt inhibitor of Raf-l. These results suggest that adenovirus-induced R af/MAPK activation contributes to IL-8 production. Adenovirus-induced activation of the Raf/MAPK signaling pathway and IL-8 production may p lay critical roles in the inflammation observed following in vivo admi nistration of adenovirus vectors for gene therapy.