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A major barrier to curing HIV-1 is the long-lived latent reservoir that supports re-emergence of HIV-1 upon treatment interruption. Targeting this reservoir will require mechanistic insights into the establishment and maintenance of HIV-1 latency. Whether T cell signaling at the time of HIV-1 infection influences productive replication or latency is not fully understood. We used a panel of chimeric antigen receptors (CARs) with different ligand binding affinities to induce a range of signaling strengths to model differential T cell receptor signaling at the time of HIV-1 infection. Stimulation of T cell lines or primary CD4+ T cells expressing chimeric antigen receptors supported HIV-1 infection regardless of affinity for ligand; however, only signaling by the highest affinity receptor facilitated HIV-1 expression. Activation of chimeric antigen receptors that had intermediate and low binding affinities did not support provirus transcription, suggesting that a minimal signal is required for optimal HIV-1 expression. In addition, strong signaling at the time of infection produced a latent population that was readily inducible, whereas latent cells generated in response to weaker signals were not easily reversed. Chromatin immunoprecipitation showed HIV-1 transcription was limited by transcriptional elongation and that robust signaling decreased the presence of negative elongation factor, a pausing factor, by more than 80%. These studies demonstrate that T cell signaling influences HIV-1 infection and the establishment of different subsets of latently infected cells, which may have implications for targeting the HIV-1 reservoir. [ABSTRACT FROM AUTHOR]

Long-lived latent HIV-infected cells lead to the rebound of virus replication following antiretroviral treatment interruption and present a major barrier to eliminating HIV infection. These latent reservoirs, which include quiescent memory T cells and tissueresident macrophages, represent a subset of cells with decreased or inactive proviral transcription. HIV proviral transcription is regulated at multiple levels including transcription initiation, polymerase recruitment, transcription elongation, and chromatin organization. How these biochemical processes are coordinated and their potential role in repressing HIV transcription along with establishing and maintaining latency are reviewed. [ABSTRACT FROM AUTHOR]

Treatment for HIV has relied on the use of antiretroviral agents that can be subject to the development of resistant viruses. The study of inhibitors directed against cellular proteins required for HIV replication is therefore of growing interest. Inducible T cell kinase (ITK) is a Tec family tyrosine kinase that regulates T cell receptor (TCR)-induced activation of PLCγ-1, Ca2+ mobilization and transcription factor activation, and actin rearrangement downstream of both TCR and chemokine receptors. Because productive infection of T cells with HIV requires T cell activation, chemokine receptors and actin reorganization, we asked whether ITK affects HIV infection using ITK-specific siRNA. a kinase-inactive ITK mutant or an ITK inhibitor. We demonstrate that loss of ITK function resulted in marked reductions in intracellular p24 levels upon HIV infection. Loss of ITK function after establishment of HIV infection also decreased virus spread within the culture. Inhibition of ITK did not affect expression of the HIV coreceptors CD4 or CXCR4 but partially blocked HIV viral entry, an effect that correlated with decreased actin polarization to gp120. Additionally, ITK was required for efficient HIV transcription, and overexpression of ITK increased both viral transcription and virus-like particle formation. Our data suggest that inhibition of ITK blocks HIV infection by affecting multiple steps of HIV replication. [ABSTRACT FROM AUTHOR]

Periodontal infections contribute to HIV-associated co-morbidities in the oral cavity and provide a model to interrogate the dysregulation of macrophage function, inflammatory disease progression, and HIV replication during co-infections. We investigated the effect of Porphyromonas gingivalis on the establishment of HIV infection in monocyte-derived macrophages. HIV replication in macrophages was significantly repressed in the presence of P. gingivalis . This diminished viral replication was due partly to a decrease in the expression of integrated HIV provirus. HIV repression depended upon signaling through TLR4 as knock-down of TLR4 with siRNA rescued HIV expression. Importantly, HIV expression was reactivated upon removal of P. gingivalis. Our observations suggest that exposure of macrophages to Gram-negative bacteria influence the establishment and maintenance of HIV persistence in macrophages through a TLR4-dependent mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Current drugs used for antiretroviral therapy against human immunodeficiency virus (HIV) have a narrow spectrum of activity and, more often, have associated toxicities and severe side effects in addition to developing resistance. Thus, there is a need to develop new therapeutic strategies against HIV/AIDS to complement the already existing ones. Surprisingly, transactivator of transcription (Tat), an early virus-encoded protein required for the efficient transcription of the HIV genome, has not been developed as a target for small molecular therapeutics. We have previously described the ability of an endogenous Michael acceptor electrophile (MAE), 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), to inhibit Tat-dependent transcription by targeting its cysteine (Cys)-rich domain. In an effort to identify other MAEs possessing inhibitory activity against HIV-1 Tat, we tested a collection of plant-derived compounds with electrophilic properties, including curcumin, rosmarinic acid, and gambogic acid, for their ability to inhibit Tat. Celastrol (Cel), a triterpenoid MAE isolated from Tripterygium wilfordii, exhibited the highest inhibitory activity against Tat. Using biochemical techniques, we demonstrate that Cel, by covalently modifying the cysteine thiols, inhibits Tat transactivation function. Using circular dichroism spectroscopy, we show that alkylation of Tat brought about a change in the secondary structure of Tat, which inhibited the transcription elongation of the HIV proviral genome by effecting mechanisms other than Tat–TAR (transactivation-responsive region) interaction. Our results demonstrate the underlying mechanism of antiretroviral activity of the plant-derived MAEs and suggest that Cel could serve as a lead compound to develop novel antiviral therapeutics. [Copyright &y& Elsevier]