['The deciphering of intracellular signaling pathways that are activated by the interaction between viral fusion peptides and cellular membranes are important for the understanding of both viral replication strategies and host defense mechanisms.', 'Fusion peptides of several enveloped viruses belonging to different virus families were prepared by standard 9-fluorenylmethoxycarbonyl polyamine solid-phase synthesis and used to stimulate U937 cells in vitro to analyze the phosphorylation patterns of the signaling pathways (PKC, Src, Akt, and MAPK pathways). Immunoprecipitation and Western blotting were carried out by using phosphospecific antibodies. All samples were also assayed for the presence of IL-10 and IFN-beta by ELISA and activation of nuclear factors (AP-1 and NF-kappaB).', 'We have demonstrated that hydrophobic domains of fusion proteins are able to induce several transduction pathways that lead to cytokine (IFN-beta and IL-10) production, an event that appears to be dependent on early activation of AP-1 and NF-kappaB.'] Do viral fusion peptides induce several signal transduction pathway activations that are essential for interleukin-10 and beta-interferon production?