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Inhibition of HIV type 1 Tat-mediated trans-activation by oncostatin M in HLtat cells
1Rega Institute for Medical Research, Katholieke Universiteit Leuven, Belgium.
Abstract:
We have tested the effect of oncostatin M (OSM) on the Tat-mediated trans-activation in a HeLa cell line (HLtat) expressing Tat, using a transfection assay with the LacZ gene under the control of the HIV-1 LTR. Oncostatin M reduced the LacZ expression by 50% at a concentration of 9.5 ng/ml (IC50), which was far below the 50% cytotoxic concentration (CC50 > 400 ng/ml). Although HLtat cells may represent an interesting model for the study of the signal transduction pathway of OSM, this cytokine did not inhibit the tumor necrosis factor (TNF)-dependent activation of the HIV LTR in Molt pNAZ cells or the Tat-mediated trans-activation in HeLa, HeLa-CD4, Hep-II, COS-7, or Jurkat-tat cells. Likewise, OSM did not show any anti-HIV-1 activity in the MT4 cell/MTT assay. Our findings with OSM indicate that, for the screening of HIV Tat inhibitors, care must be taken in selecting a system that not only emulates HIV Tat trans-activation, but is also representative for in vivo-infected cells.
Insights
Oncostatin M (OSM) inhibits HIV-1 Tat trans-activation in specific cell models but lacks broad anti-HIV activity. Careful selection of cell systems is crucial for screening effective HIV Tat inhibitors.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- The Human Immunodeficiency Virus type 1 (HIV-1) Tat protein is essential for viral replication.
- Identifying novel inhibitors of HIV-1 Tat is critical for developing new antiretroviral therapies.
Purpose of the Study:
- To investigate the effect of Oncostatin M (OSM) on HIV-1 Tat-mediated trans-activation.
- To evaluate OSM's potential as an inhibitor of HIV-1 replication.
Main Methods:
- Transfection assays using a LacZ reporter gene under the HIV-1 Long Terminal Repeat (LTR) promoter in a Tat-expressing HeLa cell line (HLtat).
- Cytotoxicity assays (CC50) and anti-HIV activity assays (MT4 cell/MTT assay).
- Testing OSM's effect on tumor necrosis factor (TNF)-dependent HIV-1 LTR activation and Tat-mediated trans-activation in various cell lines.
Main Results:
- OSM inhibited Tat-mediated trans-activation in HLtat cells with an IC50 of 9.5 ng/ml, showing minimal cytotoxicity (CC50 > 400 ng/ml).
- OSM did not inhibit TNF-dependent HIV-1 LTR activation or Tat-mediated trans-activation in other tested cell lines (Molt pNAZ, HeLa, HeLa-CD4, Hep-II, COS-7, Jurkat-tat).
- OSM demonstrated no anti-HIV-1 activity in the MT4 cell/MTT assay.
Conclusions:
- While OSM exhibits inhibitory effects on HIV-1 Tat trans-activation in specific cellular contexts, its activity is not broad-spectrum.
- The findings highlight the importance of selecting appropriate cell-based systems that accurately reflect in vivo HIV-1 infection for screening potential Tat inhibitors.
- OSM's limited efficacy suggests it may not be a viable candidate for direct anti-HIV therapy, but its mechanism warrants further investigation in specific signaling pathways.