Background: Progesterone levels are higher in placental barriers during pregnancy, but the effect of progesterone on human immunodeficiency virus type 1 (HIV-1) infection in placental cells has not been addressed. We hypothesize that progesterone may affect HIV infection.
Methods: Purified trophoblastic cells and trophoblastic cell lines were infected or transfected with HIV-1, and the effect of progesterone was analyzed. Viral replication was measured by viral p24 or viral load quantification. Nuclear factor kappa -B (NF- kappa B) or long terminal repeat (LTR)-dependent transcription was measured by luciferase assays. Expression of chemokine receptors was analyzed by flow cytometry. Tumor necrosis factor (TNF) messenger RNA was assessed by reverse-transcription polymerase chain reaction (RT-PCR) and quantitative RT-PCR.
Results: Progesterone inhibits HIV-1 replication in placental cells at the concentration found in the placental interface, at a postentry step, and does not affect cell surface expression of chemokine receptors. Progesterone did not inhibit basal or induced LTR transcription or NF- kappa B activation. TNF synthesis in placental cells is induced by HIV-1 infection that, in an autocrine manner, activates viral replication, because neutralizing anti-TNF antibodies block it. Progesterone inhibits the induction of TNF synthesis by viral infection and virus or gp-120-induced TNF transcription.
Conclusion: Our results demonstrate that progesterone inhibits HIV-1 replication in placental cells by reducing TNF levels, which are required for optimal viral replication.