Antiviral Effects of Mifepristone and its Analogs on HIV-1 Vpr-Induced Virus Replication
E Schafer*, M Wagner, and V Ayyavoo
Univ. of Pittsburgh, PA, USA
HAART regimens eventually fail to provide complete and long-term suppression of
virus replication due to the inability to fully clear virus replication in
non-dividing cellular reservoirs. The HIV-1 viral protein R, Vpr, increases
virus replication in T cells and is necessary for the infection of primary
monocytes/macrophages and other non-dividing cells. It has been shown that Vpr
interacts with the cellular glucocorticoid teceptor (GR) and transactivates the
HIV-1 LTR through GRE and that
this event can be blocked by the GR inhibitor, mifepristone. Based on these
observations, we believe that targeting Vpr-mediated virus transcription with
glucocorticoid antagonists can demonstrate a potent anti-retroviral therapy.
of HIV-1 Vpr-mediated GRE and LTR
transactivation was demonstrated in 293T, HeLa, and COS-1 cells. HIV-1 LTR-luciferase or GRE-luciferase reporter plasmids
were co-transfected with pVpr in 293T and HeLa cells and co-transfected with
both pVpr and pGR in COS-1 cells in the presence of mifepristone and its
analogs. Antiviral effects of mifepristone and analog compounds were determined
through infectivity assays using dual-tropic and macrophage-tropic viruses.
Normal donor PBMC and U1 cells were infected and compounds were added in a
dose-dependent and time-dependent manner and p24 was analyzed by ELISA.
Cytotoxicity assays were performed using PBMC following standard MTT
Results: Our results show that Vpr-induced
transactivation of both autologous and heterologous promoters was inhibited by
mifepristone and analogues in a dose-dependent manner. Three analogues
inhibited LTR or GRE
transactivation by as much as >90% at a 1 mM
concentration. Infectivity assays using dual-tropic and macrophage-tropic viruses,
demonstrated antiviral effects on a dose-dependent regimen of mifepristone
analogs. The effects of mifepristone analogs were also tested in HIV-1 latent
cells that could be activated with extracellular Vpr protein. Cytotoxic effects
of mifepristone and its analogs demonstrated that the CT50 of these compounds
range from 10 to 40 mM in normal human primary cells.
Conclusions: By utilizing the relationship between Vpr and
the glucocortoicoid receptor, glucocorticoid antagonists such as mifepristone
and mifepristone analogs hold promise for anti-retroviral therapy.
Keywords: Antiviral; Viral Inhibition; LTR-Induced Transactivation