Activation Of HIV-1 Expression Research Articles

Activation of HIV-1 expression in latently infected CD4+ T cells by the small molecule PKC412.

BackgroundHIV-1 latency is a major obstacle for HIV-1 eradication. Extensive efforts are being directed toward the reactivation of latent HIV reservoirs with the aim of eliminating latently infected cells via the host immune system and/or virus-mediated cell lysis.ResultsWe screened over 1,500 small molecules and kinase inhibitors and found that a small molecule, PKC412 (midostaurin, a broad-spectrum kinase inhibitor), can stimulate viral transcription and expression from the HIV-1 latently infected ACH2 cell line and primary resting CD4+ T cells. PKC412 reactivated HIV-1 expression in ACH2 cells in a dose- and time-dependent manner. Our results also suggest that the nuclear factor κB (NF-κB) signaling could be one of cellular pathways activated during PKC412-mediated activation of latent HIV-1 expression. Additionally, combining PKC412 with the HDAC inhibitor vorinostat (VOR) had an additive effect on HIV-1 reactivation in both ACH2 cells and infected resting CD4+ T cells.ConclusionsThese studies provide evidence that PKC412 is a new compound with the potential for optimization as a latency-reactivator to eradicate HIV-1 infection.

Role of regulatory proteins in HIV-1/HTLV-1 coinfection

In HTLV-1 endemic areas, 5 to 10% of HIV-1-infected individuals are also coinfected with HTLV-1/2. Several studies support the finding that dual infection of HIV-1 and HTLV-2 may confer delayed AIDS progression. In contrast, HTLV-1 has been concluded to have either no effect or to increase progression to AIDS in HIV-1-infected individuals. Although Tax-1 is known to influence HIV-1 replication in vitro, other HTLV-1 proteins likely have a role in retroviral coinfection. Here, we are investigating whether HTLV-1 proteins regulate activation of HIV-1 expression in latently-infected cells. In this study, we used B-cells infected with molecular clones that either express both p12 and p8, p12-only, p8-only, or contain knockouts to orf-I, orf-II, or hbz. The HTLV-1-infected B-cells were cocultured with KK1 T-cells latently-infected with HIV-1. Following coculture, cells and media were assayed for viral expression. Analyses of immunoblot and ELISA data suggest that HTLV-1-infected B-cells that express p8 enhanced activation of latent HIV-1 expression. We are currently examining whether cell-to-cell contact with p8 expressing cells is required to reactivate the latently-infected KK1 cells. Results from this study could have an impact on treatment of patients coinfected with HIV-1 and HTLV-1.

Heterogeneity of Signal Transducer and Activator of Transcription Binding Sites in the Long-Terminal Repeats of Distinct HIV-1 Subtypes

HIV-1 can be subdivided into distinct subtypes; the consequences of such a genomic variability remain largely speculative. The long terminal repeats (LTR) control HIV transcription and reflect the major differences of distinct viral subtypes. Three regions in the HIV-1 subtype B LTR are close matches to the Signal Transducer and Activator of Transcription (STAT) consensus sequence. Here, we show heterogeneity in these putative STAT binding sites among HIV-1 LTR subtypes A through G. Transfection of constitutively activated STAT5 lead to transcriptional activation of HIV-1 expression in 293T cells transfected with a reporter assay driven by HIV-1 LTR subtype B. Constitutively activated STAT5 transactivated the LTR of various subtypes in U937 cells with different potency. These findings support and expand the potential relevance of STAT5 activation in HIV infection and may bear relevance for a differential regulation of latency and expression of different subtypes of HIV-1.

Cutting edge: in vivo induction of integrated HIV-1 expression by mycobacteria is critically dependent on Toll-like receptor 2.

Mycobacterial infection has been implicated as a possible factor in AIDS progression in populations where HIV-1 and Mycobacterium tuberculosis are coendemic. In support of this concept, we have previously shown that HIV-1-transgenic (Tg) mice infected with mycobacteria display enhanced viral gene and protein expression. In this study, we demonstrate that the induction of HIV-1 observed in this model is dependent on Toll-like receptor 2 (TLR2), a pattern recognition receptor known to be involved in mycobacteria-host interaction. Spleen cells from HIV-1-Tg mice deficient in TLR2 (Tg/TLR2(-/-)) were found to be completely defective in p24 production induced in response to live M. tuberculosis or Mycobacterium avium as well as certain mycobacterial products. Importantly, following in vivo mycobacterial infection, Tg/TLR2(-/-) mice failed to display the enhanced HIV-1 gag/env mRNA and p24 protein synthesis exhibited by wild-type Tg animals. Together, these results argue that TLR2 plays a crucial role in the activation of HIV-1 expression by mycobacterial coinfections.

Influence of cell cycle on HIV-1 expression differs among various models of chronic infection.

Because of an inherent dependence on host cell second and third messenger signaling pathways for activation of HIV-1 expression, a potential exists for a relationship between the induction of latent HIV-1 and cell-cycle-related events. To investigate this potential relationship, cellular models of latent HIV-1 infection (OM-10.1 promyelocytes, ACH-2 T-lymphocytes, and U1 promonocytes) were chemically treated or gamma-irradiated to synchronize cultures at each cell cycle stage and then examined for constitutive and TNF-alpha-induced HIV-1 expression. Cell cycle synchronization alone had no effect on HIV-1 expression in OM-10.1 and U1 cultures; whereas enhanced constitutive HIV-1 expression was observed in ACH-2 cultures at G2 + M. A 2 hour TNF-alpha treatment of all synchronized OM-10.1 cultures activated HIV-1 expression to a similar extent as unsynchronized cultures. In contrast, the extent of TNF-alpha-induced HIV-1 expression in ACH-2 S and G2 + M cultures and in the U1 G0/G1 culture was greater than that in unsynchronized control cultures. However, no delay in the initial response was observed. Thus, the influence of cell cycle on constitutive and induced HIV-1 expression varied in each cellular model and, therefore, may further relate to the different molecular mechanisms maintaining viral latency.