The leukocyte function-associated antigen-1 (LFA-1) is involved in the interferon-alpha response induced by herpes simplex virus in blood leukocytes

Role of tyrosine kinases, protein kinase C, and protein kinase A in the regulation of interferon-alpha production induced by herpes simplex virus type 1

Herpes simplex virus 1 (HSV-1) is able to induce interferon-alpha production by natural IFN-alpha-producing cells. In this study, signal transduction in this process was examined. It was found that sequestering of calcium by EGTA abolished IFN-alpha induction by HSV-infected cells. Stimulation of human PBMC by HSV-1-infected fibroblasts resulted in the production of inositol triphosphate (InsP3) and tyrosine phosphorylation of cellular proteins. The protein kinase C inhibitor, H7, and the tyrosine kinase inhibitor, herbimycin A, were able to suppress IFN-alpha gene expression as determined by IFN bioassay and RT-PCR. An IFN-alpha-specific ELISpot assay revealed that herbimycin A and H7 remarkably decreased the number of IFN-alpha-producing cells. PMA or calcium ionophore A23187 alone did not increase IFN-alpha production. However, PMA in conjugation with ionophores increased IFN-alpha production as early as 2 h. HA1004 and 2',5'-dideoxyadenosine, which are potent inhibitors of PKA pathway, had no effect on IFN-alpha production. In contrast, BrcAMP, a specific PKA activator, inhibited the IFN-alpha secretion and number of IFN-alpha-producing cells and to a lesser extent reduced the level of IFN-alpha mRNA. Our results indicate that protein kinase C, tyrosine kinases, and protein kinase A are involved in the regulation of IFN-alpha production in response to HSV-1.

Stimulation of natural interferon-alpha/beta-producing cells by Staphylococcus aureus

Human peripheral blood mononuclear cells (PBMCs) produced high levels of antiviral activity, as determined by bioassay, when stimulated by Staphylococcus aureus Cowan I (SAC) and E. coli. Specific immunoassays demonstrated the presence of both IFN-alpha and gamma and, for SAC, also low levels of IFN-beta. The frequencies of SAC-induced IF N-alpha-producing cells (IPCs) were up to 1-2 per 10(3) PBMCs. These IPCs expressed the HLA-DR and CD4 antigens but not CD3, CD14, or CD19, thus resembling the natural IFN-alpha-producing cells (NIPC). The SAC was more efficient as IFN inducer when heat killed than when streptomycin inhibited. The SAC was inhibitory to virally induced IFN-alpha responses, in particular when streptomycin inhibited. Both pronase treatment and mechanical disruption of SAC cells abolished their capacity to induce IFN-alpha production. Staphylococcal strains lacking or expressing low levels of protein A (SpA) showed a decreased ability to induce IFN-alpha production. However, purified SpA did not itself induce IFN-alpha. Possibly, SpA together with other bacterial surface proteins is important for the capacity of SAC to induce IFN-alpha production in NIPC.