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IL-16 represses HIV-1 promoter activity
J W Maciaszek1, N A Parada, W W Cruikshank
1The Program in Virology and Immunology, University of Massachusetts Medical Center, Worcester 01605, USA.
Insights
Interleukin-16 (IL-16) significantly represses HIV-1 promoter activity in CD4+ lymphoid cells. This finding suggests IL-16 may be a key factor in controlling HIV-1 replication.
Area of Science:
- Immunology
- Virology
- Molecular Biology
Background:
- Interleukin-16 (IL-16) is a cytokine produced by CD8+ lymphocytes.
- IL-16 is known to inhibit HIV-1 and SIV replication in peripheral blood mononuclear cells (PBMCs).
- CD4 acts as the receptor for IL-16, mediating signal transduction that influences cellular activation states.
Purpose of the Study:
- To investigate the mechanism by which IL-16 affects HIV-1 replication.
- To determine if IL-16's inhibitory effect on HIV-1 occurs at the level of viral gene expression.
Main Methods:
- Transient transfection studies utilizing HIV-1 long terminal repeat (LTR)-reporter gene constructs.
- Pretreatment of CD4+ lymphoid cells with recombinant IL-16.
Main Results:
- Recombinant IL-16 pretreatment repressed HIV-1 promoter activity by up to 60-fold.
- IL-16 effectively prevented both PMA and Tat-mediated activation of the HIV-1 promoter.
- The inhibitory effect of IL-16 was dependent on sequences within the core enhancer region, not solely on transcription factor binding.
Conclusions:
- IL-16 exerts a potent inhibitory effect on HIV-1 promoter activity.
- IL-16's mechanism of action involves the viral enhancer region and is independent of general transcription factor downregulation.
- IL-16 represents a potential therapeutic target for controlling HIV-1 expression.
Abstract:
IL-16 is produced by CD8+ lymphocytes and has been reported to inhibit HIV-1 and SIV replication in infected PBMCs. CD4 serves as a receptor for the secreted form of IL-16, and IL-16 binding to CD4 induces signal transduction, which affects the activation state of the cell. We hypothesized, therefore, that the effect of IL-16 on HIV-1 replication might occur at the level of virus expression. In transient transfection studies with HIV-1 LTR-reporter gene constructs we found that pretreatment of CD4+ lymphoid cells with recombinant IL-16 repressed HIV-1 promoter activity up to 60-fold, preventing both PMA and Tat activation. This effect of IL-16 required sequences contained within the core enhancer, but was not simply due to the down-regulation of transcription factors binding to this element.