Background:  We have previously identified that interleukin (IL) -27, a member of the IL-12 cytokine family, is a novel anti-HIV cytokine. Like interferon (IFN) -α, IL-27 inhibits HIV-1 replication in both CD4⁺ T cells and monocyte-derived macrophages (MDM). To elucidate the mechanism of the antiviral activity, we compared the antiviral effect and gene expression profile of IL-27-treated cells to those of IFN-α-treated cells.

Methods:  CD4⁺ T cells and monocytes were isolated from healthy donors’ peripheral blood mononuclear cells (PBMC). CD4⁺ T cells were stimulated with phytohemagglutinin (PHA), and MDM were induced from monocytes using macrophage-colony stimulating factor. CD4⁺ T cells and MDM were infected with HIV_NL4.3 and HIV_Ad8, respectively. HIV-1 replication was monitored by p24 antigen capture assay. Real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) were performed to quantitate the production of IFN-α, -β, and -γ. To determine the role of IFN in the IL-27-mediated HIV inhibition, a neutralization assay was performed using neutralization antibody. The gene expression profiles were analyzed using DNA microarray analysis. The gene expression was confirmed by the Quantigene plex assay.

Results:  Both IFN-α and IL-27 preferentially inhibited HIV-1 replication in MDM compared to CD4⁺ T cells. The IC₅₀ of IL-27 to CD4⁺ T cells and MDM was 15±10 ng/mL and 0.4±0.15 ng/mL, respectively. The quantitative RT-PCR and ELISA indicated that IL-27 had no effect on the induction of IFN from both cell types, and the neutralization assay demonstrated that IFN had no significant effect on the IL-27^–-mediated HIV inhibition in both cell types. DNA microarray analysis illustrated that IL-27 induced 28 IFN-inducible genes (IFIG) in MDM, and 5 IFIG in CD4⁺ T cells. The overall gene expression profile of IL-27-treated CD4⁺ T cells significantly differs from that of IL-27-treated MDM. The quantitative assay confirmed that IL-27 activated IFIG and genes encoding anti-viral proteins, e.g., RNA-dependent kinase, oligoadenylate synthetase, myxovirus protein, and APOBEC3G.

Conclusions:  IL-27 preferentially inhibited HIV-1 replication in MDM compared to CD4⁺ T cells. The cytokine differentially regulates the gene expression between CD4⁺ T cells and MDMs. IL-27 significantly induces IFIG and anti-viral genes in MDM as IFN-α does, suggesting that IL-27 inhibits HIV replication in MDM via mechanism(s) similar to that of IFN-α; however, the cytokine inhibits the viral replication in CD4⁺ T cells via different mechanism(s) compared to MDM.