Potential involvement of IL-8 in the pathogenesis of human cytomegalovirus infection

The observations that several types of viruses induced interleukin (IL)-8 production prompted us to investigate the interrelationship between IL-8 and cytomegalovirus (CMV) infection. CMV infection caused IL-8 production in a human monocytic cell line, THP-1, in dose- and time-dependent manners. Moreover, CMV induced IL-8 gene expression by concurrently activating transcription factors, NF-kappaB and AP-1. Furthermore, CMV infection of human fibroblast cell lines increased gene expression of a specific receptor for IL-8, CXCR1. IL-8 in turn enhanced CMV replication in a human embryonic fibroblast, MRC-5, in dose- and time-dependent manners. Augmented replication eventually culminated in the increased production of infectious CMV virions. Moreover, IL-8 can attenuate the antiviral activity of interferon (IFN), particularly that of alpha-type against picornaviruses such as encephalomyocarditis virus and poliovirus. The inhibitory effects were associated with reduced 2',5'-A oligoadenylate synthetase activity. These results would imply that CMV can induce IL-8, which can augment CMV replication directly and indirectly by counteracting antiviral activity of IFN.