Gene expression of IFN-γ-inducing factor (IL-18), RANTES and MIP-1α in HIV positive patients as compared to HIV seronegative individuals

Abstract

IL-18, a potent co-stimulator of IL-12 in inducing IFN-γ production, has been shown to enhance HIV replication in vitro. However, there is no clinical data of whether IL-18 is dysregulated in patients infected with HIV-1. The roles of β-chemokines, RANTES and MIP-1α, in blocking CCR-5 tropic virus and may also contribute in delayed disease progression have been recently reported. This study is to investigate the gene expression of IL-18, RANTES and MIP-1α in PBMCs of HIV-1 infected patients as compared to HIV seronegative healthy donors. Heparinized peripheral blood samples were obtained from 30 HIV-1-infected patients (1:1 of CD4+ T cell count < and ≥ 200 cells/mm³) with no active opportunistic infection and without previous antiretroviral and immunosuppressive treatments, and 15 HIV seronegative blood donors at Chulalongkorn hospital and Thai Red Cross National Blood Bank, respectively. Peripheral blood mononuclear cells (PBMCs) were separated from the blood samples by Ficoll-Hypaque gradient. RNA were extracted from PBMCs and then subjected for RT-PCR with specific primers of IL-18, RANTES and MIP-1α. β-actin RT-PCR was included as a housekeeping gene control. It was revealed that RANTES and MIP-1α mRNA were detected in PBMCs from all of the subjects either HIV-seropositive or seronegative. Almost all, i.e., 14 of 15 in group A (HIV seronegative blood donors), all of group B (HIV-infected with CD4+ T cell count ≥ 200 cells/mm³) and 14 of 15 in group C (HIV-infected with CD4+ T cell count <200 cells/mm³) showed mRNA expression of IL-18 in their PBMCs. This is the first report to show that IL-18, as similar to RANTES and MIP-1α, was constitutively expressed in PBMCs from both of HIV seronegative and seropositive individuals. The proportion of IL-18 mRNA expression was not statistically different in the advanced as compared to the less advanced HIV-infected patients. This finding may indicate the essential roles as well as the redundancy of these cytokine and chemokines in the immune system, and therefore were preserved even in advanced HIV infection. Nevertheless, as the RT-PCR used in this study was a qualitative method, for more precise comparative analysis, quantitative RT-PCR assay should be used for the further study. The clear-cut roles of IL-18 both in physiologic state and in HIV infection required further investigation.