Pertussis toxin B-oligomer suppresses IL-6 induced HIV-1 and chemokine expression in chronically infected U1 cells via inhibition of activator protein 1

U1 and OM10.1. Myeloid Cell Lines as Surrogate Models of Reversible Proviral Latency

As already discussed for T cell lines, also myeloid cell lines as served as the earliest models of chronic HIV infection. They were particularly relevant in the late 1980s and early 1990s when most experimental in vitro infections were based on laboratory-adapted "T-cell tropic" strains of HIV-1, such as LAI/IIIB or others, that later were found to rely upon CXCR4 as coreceptor for viral entry in addition to CD4 as primary receptor. Although primary macrophages do express CXCR4 together with CD4, virus replication is much less efficient than that observed with CCR5-using "macrophage-tropic" strains, as discussed separately in this book. Although different myeloid cell lines have been used to generate models of chronic HIV-1 infection that could be used to investigate features of proviral reactivation, as reviewed in (Cassol et al. J Leukoc Biol 80:1018-1030, 2006), two cell lines in particular have been broadly used and will be here discussed: the U937-derived U1 and HL-60-derived OM-10.1.

Integrated analysis of lncRNA, miRNA and mRNA profiles reveals potential lncRNA functions during early HIV infection

Background

Long noncoding RNAs (lncRNAs) can regulate gene expression in a cis-regulatory fashion or as “microRNA sponges”. However, the expression and functions of lncRNAs during early human immunodeficiency virus (HIV) infection (EHI) remain unclear.

Methods

3 HAART-naive EHI patients and 3 healthy controls (HCs) were recruited in this study to perform RNA sequencing and microRNA (miRNA) sequencing. The expression profiles of lncRNAs, mRNAs and miRNAs were obtained, and the potential roles of lncRNAs were analysed based on discovering lncRNA cis-regulatory target mRNAs and constructing lncRNA–miRNA–mRNA competing endogenous RNA (ceRNA) networks. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed on 175 lncRNA-associated differentially expressed (DE) mRNAs to investigate the potential functions of DE lncRNAs in ceRNA networks.

Results

A total of 242 lncRNAs, 1240 mRNAs and 21 mature known miRNAs were determined as differentially expressed genes in HAART-naive EHI patients compared to HCs. Among DE lncRNAs, 44 lncRNAs were predicted to overlap with 41 target mRNAs, and 107 lncRNAs might regulate their nearby DE mRNAs. Two DE lncRNAs might regulate their cis-regulatory target mRNAs BTLA and ZAP70, respectively, which were associated with immune activation. In addition, the ceRNA networks comprised 160 DE lncRNAs, 21 DE miRNAs and 175 DE mRNAs. Seventeen DE lncRNAs were predicted to regulate HIF1A and TCF7L2, which are involved in the process of HIV-1 replication. Twenty DE lncRNAs might share miRNA response elements (MREs) with FOS, FOSB and JUN, which are associated with both immune activation and HIV-1 replication.

Conclusions

This study revealed that lncRNAs might play a critical role in HIV-1 replication and immune activation during EHI. These novel findings are helpful for understanding of the pathogenesis of HIV infection and provide new insights into antiviral therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02802-9.

Immunomodulation as a Novel Strategy for Prevention and Treatment of Bordetella spp. Infections

Well-adapted pathogens have evolved to survive the many challenges of a robust immune response. Defending against all host antimicrobials simultaneously would be exceedingly difficult, if not impossible, so many co-evolved organisms utilize immunomodulatory tools to subvert, distract, and/or evade the host immune response. Bordetella spp. present many examples of the diversity of immunomodulators and an exceptional experimental system in which to study them. Recent advances in this experimental system suggest strategies for interventions that tweak immunity to disrupt bacterial immunomodulation, engaging more effective host immunity to better prevent and treat infections. Here we review advances in the understanding of respiratory pathogens, with special focus on Bordetella spp., and prospects for the use of immune-stimulatory interventions in the prevention and treatment of infection.

Soybean-derived Bowman-Birk inhibitor (BBI) blocks HIV entry into macrophages

Bowman-Birk inhibitor (BBI) is a soybean-derived protease inhibitor that has anti-inflammation and anti-HIV effect. Here, we further investigated the anti-HIV action of BBI in macrophages, focusing on its effect on viral entry. We found that BBI could significantly block HIV entry into macrophages. Investigation of the mechanism(s) of the BBI action on HIV inhibition showed that BBI down-regulated the expression of CD4 receptor (as much as 80%) and induced the production of the CC chemokines (up to 60 folds at protein level) in macrophages. This inhibitory effect of BBI on HIV entry could be blocked by the neutralization antibodies to CC chemokines. These findings indicate that BBI may have therapeutic potential as a viral entry inhibitor for the prevention and treatment of HIV infection.

Soybean-derived Bowman-Birk Inhibitor (BBI) Inhibits HIV Replication in Macrophages

The Bowman-Birk inhibitor (BBI), a soybean-derived protease inhibitor, is known to have anti-inflammatory effect in both in vitro and in vivo systems. Macrophages play a key role in inflammation and immune activation, which is implicated in HIV disease progression. Here, we investigated the effect of BBI on HIV infection of peripheral blood monocyte-derived macrophages. We demonstrated that BBI could potently inhibit HIV replication in macrophages without cytotoxicity. Investigation of the mechanism(s) of BBI action on HIV showed that BBI induced the expression of IFN-β and multiple IFN stimulated genes (ISGs), including Myxovirus resistance protein 2 (Mx2), 2',5'-oligoadenylate synthetase (OAS-1), Virus inhibitory protein (viperin), ISG15 and ISG56. BBI treatment of macrophages also increased the expression of several known HIV restriction factors, including APOBEC3F, APOBEC3G and tetherin. Furthermore, BBI enhanced the phosphorylation of IRF3, a key regulator of IFN-β. The inhibition of IFN-β pathway by the neutralization antibody to type I IFN receptor (Anti-IFNAR) abolished BBI-mediated induction of the anti-HIV factors and inhibition of HIV in macrophages. These findings that BBI could activate IFN-β-mediated signaling pathway, initialize the intracellular innate immunity in macrophages and potently inhibit HIV at multiple steps of viral replication cycle indicate the necessity to further investigate BBI as an alternative and cost-effective anti-HIV natural product.

Pulmonary inflammation induced by bacteria-free outer membrane vesicles from Pseudomonas aeruginosa

Pseudomonas aeruginosa is often involved in lung diseases such as cystic fibrosis. These bacteria can release outer membrane vesicles (OMVs), which are bilayered proteolipids with diameters of approximately 20 to 250 nm. In vitro, these OMVs activate macrophages and airway epithelial cells. The aim of this study was to determine whether OMVs from P. aeruginosa can induce pulmonary inflammation in vivo and to elucidate the mechanisms involved. Bacteria-free OMVs were isolated from P. aeruginosa cultures. Wild-type, Toll-like receptor (TLR)2 and TLR4 knockout mice were exposed to OMVs by the airway, and inflammation in the lung was assessed using differential counts, histology, and quantification of chemokines and cytokines. The involvement of the TLR2 and TLR4 pathways was studied in human cells using transfection. OMVs given to the mouse lung caused dose- and time-dependent pulmonary cellular inflammation. Furthermore, OMVs increased concentrations of several chemokines and cytokines in the mouse lungs and mouse alveolar macrophages. The inflammatory responses to OMVs were comparable to those of live bacteria and were only partly regulated by the TLR2 and TLR4 pathways, according to studies in knockout mice. This study shows that OMVs from P. aeruginosa cause pulmonary inflammation without live bacteria in vivo. This effect is only partly controlled by TLR2 and TLR4. The role of OMVs in clinical disease warrants further studies because targeting of OMVs in addition to live bacteria may add clinical benefit compared with treating with antibiotics alone.

Interplay between viral Tat protein and c-Jun transcription factor in controlling LTR promoter activity in different human immunodeficiency virus type I subtypes

HIV-1 transcription depends on cellular transcription factors that bind to sequences in the long-terminal repeat (LTR) promoter. Each HIV-1 subtype has a specific LTR promoter configuration, and minor sequence changes in transcription factor binding sites (TFBSs) or their arrangement can influence transcriptional activity, virus replication and latency properties. Previously, we investigated the proviral latency properties of different HIV-1 subtypes in the SupT1 T cell line. Here, subtype-specific latency and replication properties were studied in primary PHA-activated T lymphocytes. No major differences in latency and replication capacity were measured among the HIV-1 subtypes. Subtype B and AE LTRs were studied in more detail with regard to a putative AP-1 binding site using luciferase reporter constructs. c-Jun, a member of the AP-1 transcription factor family, can activate both subtype B and AE LTRs, but the latter showed a stronger response, reflecting a closer match with the consensus AP-1 binding site. c-Jun overexpression enhanced Tat-mediated transcription of the viral LTR, but in the absence of Tat inhibited basal promoter activity. Thus, c-Jun can exert a positive or negative effect via the AP-1 binding site in the HIV-1 LTR promoter, depending on the presence or absence of Tat.

Transcriptional regulation of the mouse CD11c promoter by AP-1 complex with JunD and Fra2 in dendritic cells

CD11c, a member of the β(2) integrin family of adhesion molecule, is expressed on the surface of myeloid lineages and activated lymphoid cells and forms a heterodimeric receptor with CD18. We analyzed the mouse CD11c promoter structure to elucidate the transcriptional regulation in dendritic cells (DCs). By reporter assay, the -84/-65 region was identified to be essential for activity of the mouse CD11c promoter in the mouse bone marrow-derived (BM) DCs and monocyte cell line RAW264.7. An electrophoretic mobility shift assay using a number of antibodies against transcription factors revealed that the target region was recognized by a complex including JunD and Fra2, which are transcription factors belonging to the AP-1 family. The direct interaction of JunD and Fra2 with the CD11c promoter was further confirmed by a chromatin immunoprecipitation assay using CD11c-positive cells purified from BMDCs. Finally, mouse JunD and/or Fra2 siRNA was introduced into BMDCs to evaluate the involvement of these factors against CD11c transcription and found that Fra2 siRNA reduced cell surface expression level of CD11c. These results indicate that AP-1 composed with JunD and Fra2 protein plays a primary role in enhancing the transcription level of the CD11c gene in DC.

TRIM22 inhibits HIV-1 transcription independently of its E3 ubiquitin ligase activity, Tat, and NF-kappaB-responsive long terminal repeat elements

Previous studies identified clones of the U937 promonocytic cell line that were either permissive or nonpermissive for human immunodeficiency virus type 1 (HIV-1) replication. These clones were investigated further in the search for host restriction factors that could explain their differential capacity to support HIV-1 replication. Among known HIV-1 restriction factors screened, tripartite motif-containing protein 22 (TRIM22) was the only factor constitutively expressed in nonpermissive and absent in permissive U937 cells. Stable TRIM22 knockdown (KD) rescued HIV-1 long-terminal-repeat (LTR)-driven transcription in KD-nonpermissive cells to the levels observed in permissive cells. Conversely, transduction-mediated expression of TRIM22 in permissive cells reduced LTR-driven luciferase expression by ∼7-fold, supporting a negative role of TRIM22 in HIV-1 transcription. This finding was further confirmed in the human T cell line A3.01 expressing TRIM22. Moreover, overexpression of TRIM22 in 293T cells significantly impaired basal and phorbol myristate acetate-ionomycin-induced HIV-1 LTR-driven gene expression, whereas inhibition of tumor necrosis factor alpha-induced viral transcription was a consequence of lower basal expression. In agreement, TRIM22 equally inhibited an LTR construct lacking the tandem NF-κB binding sites. In addition, TRIM22 did not affect Tat-mediated LTR transactivation. Finally, these effects were independent of TRIM22 E3 ubiquitin-ligase activity. In the context of replication-competent virus, significantly higher levels of HIV-1 production were observed in KD-nonpermissive versus control nonpermissive U937 cells after infection. In contrast, lower peak levels of HIV-1 replication characterized U937 and A3.01 cells expressing TRIM22 versus their control transduced counterpart. Thus, nuclear TRIM22 significantly impairs HIV-1 replication, likely by interfering with Tat- and NF-κB-independent LTR-driven transcription.

AB toxins: a paradigm switch from deadly to desirable

To ensure their survival, a number of bacterial and plant species have evolved a common strategy to capture energy from other biological systems. Being imperfect pathogens, organisms synthesizing multi-subunit AB toxins are responsible for the mortality of millions of people and animals annually. Vaccination against these organisms and their toxins has proved rather ineffective in providing long-term protection from disease. In response to the debilitating effects of AB toxins on epithelial cells of the digestive mucosa, mechanisms underlying toxin immunomodulation of immune responses have become the focus of increasing experimentation. The results of these studies reveal that AB toxins may have a beneficial application as adjuvants for the enhancement of immune protection against infection and autoimmunity. Here, we examine similarities and differences in the structure and function of bacterial and plant AB toxins that underlie their toxicity and their exceptional properties as immunomodulators for stimulating immune responses against infectious disease and for immune suppression of organ-specific autoimmunity.

Pertussis toxin and adenylate cyclase toxin: key virulence factors of Bordetella pertussis and cell biology tools

Pertussis toxin and adenylate cyclase toxin are two important virulence factors of Bordetella pertussis, the bacterial cause of the respiratory disease pertussis or whooping cough. In addition to studies on the structure, function and role in pathogenesis of these two toxins, they are both used as cell biology tools for a variety of applications owing to their ability to enter mammalian cells, perform enzymatic activities and modify cell signaling events. In this article, recent data from the research literature that enhance our understanding of the nature of these two toxins, their role in the pathogenesis of B. pertussis infection and disease, particularly in modulating host immune responses, and their use as tools for other areas of research will be outlined.

M1 and M2a polarization of human monocyte-derived macrophages inhibits HIV-1 replication by distinct mechanisms

The capacity of macrophages to support productive HIV-1 infection is known to be modulated by cytokines and other extracellular stimuli. In this study, we demonstrate that cytokine-induced polarization of human monocyte-derived macrophage (MDM) into either classical (M1) or alternatively activated (M2a) MDM is associated with a reduced capacity to support productive CCR5-dependent (R5) HIV-1 infection. M1 polarization was associated with a significant down-regulation of CD4 receptors, increased secretion of CCR5-binding chemokines (CCL3, CCL4, and CCL5), and a >90% decrease in HIV-1 DNA levels 48-h postinfection, suggesting that the inhibition occurred at an early preintegration step in the viral life cycle. In contrast, M2a polarization had no effect on either HIV-1 DNA or protein expression levels, indicating that inhibition occurred at a late/postintegration level in the viral life cycle. M2a inhibition was sustained for up to 72-h postinfection, whereas M1-effects were more short-lived. Most phenotypic and functional changes were fully reversible 7 days after removal of the polarizing stimulus, and a reciprocal down-regulation of M1-related chemokines and cytokines was observed in M2a MDM and vice versa. Since reversion to a nonpolarized MDM state was associated with a renewed capacity to support HIV replication to control levels, M1/M2a polarization may represent a mechanism that allows macrophages to cycle between latent and productive HIV-1 infection.

Ligand-engaged urokinase-type plasminogen activator receptor and activation of the CD11b/CD18 integrin inhibit late events of HIV expression in monocytic cells

Urokinase-type plasminogen activator (uPA) signaling via its receptor uPAR inhibits late events in HIV-1 replication in acutely infected primary monocyte-derived macrophages (MDMs) and promonocytic U937 cells. Here we show that U937-derived, chronically infected U1 cells stimulated with phorbol 12-myristate 13-acetate (PMA) express integrins, uPA, and soluble uPAR at levels similar to those of MDMs. uPA inhibited HIV expression in U1 cells incubated with either PMA or tumor necrosis factor-alpha (TNF-alpha), but not with other HIV-inductive cytokines or lipopolysaccharide. Of interest, only PMA and TNF-alpha, but not other HIV-inductive stimuli, induced surface expression of the alpha(M) chain CD11b in U1 cells constitutively expressing CD18, the beta(2) chain of the Mac-1 integrin. Like uPA, fibrinogen, a Mac-1 (CD11b/CD18) ligand, and M25, a peptide homologous to a portion of the beta-propeller region of CD11b preventing its association with uPAR, inhibited HIV virion release in PMA-stimulated U1 cells. Both uPAR small-interference RNA (siRNA) and soluble anti-beta(1)/-beta(2) monoclonal antibodies abolished the anti-HIV effects of uPA, whereas CD11b siRNA reversed the anti-HIV effect of M25, but not that induced by uPA. Thus, either uPA/uPAR interaction, Mac-1 activation, or prevention of its association with uPAR triggers a signaling pathway leading to the inefficient release of HIV from monocytic cells.

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.

Inhibition of HIV replication by the plasminogen activator is dependent on vitronectin-mediated cell adhesion

Urokinase-type plasminogen activator (uPA), an inducer of macrophage adhesion, inhibits HIV-1 expression in PMA-stimulated, chronically infected U1 cells. We investigated whether uPA-dependent cell adhesion played a role in uPA-dependent inhibition of HIV-1 replication in these cells. Monocyte-derived macrophages (MDM) were generated from monocytes of HIV-infected individuals or from cells of seronegative donors infected acutely in vitro. U1 cells were stimulated in the presence or absence of uPA in standard tissue culture (TC) plates, allowing firm cell adhesion or ultra-low adhesion (ULA) plates. Moreover, U1 cells were also maintained in the presence or absence of vitronectin (VN)-containing sera or serum from VN(-/-) mice. Virus production was evaluated by RT activity in culture supernatants, whereas cell adhesion was by crystal violet staining and optical microscopy. uPA inhibited HIV replication in MDM and PMA-stimulated U1 cells in TC plates but not in ULA plates. uPA failed to inhibit HIV expression in U1 cells stimulated with IL-6, which induces virus expression but not cell adhesion in TC plates. VN, known to bind to the uPA/uPA receptor complex, was crucial for these adhesion-dependent, inhibitory effects of uPA on HIV expression, in that they were not observed in TC plates in the presence of VN(-/-) mouse serum. HIV production in control cell cultures was increased significantly in ULA versus TC plates, indicating that macrophage cell adhesion per se curtails HIV replication. In conclusion, uPA inhibits HIV-1 replication in macrophages via up-regulation of cell adhesion to the substrate mediated by VN.

CCR5 signaling through phospholipase D involves p44/42 MAP-kinases and promotes HIV-1 LTR-directed gene expression

The chemokine receptor CCR5 plays an important role as an entry gate for the human immunodeficiency virus-1 (HIV-1) and for viral postentry events. Among signal transducers used by chemoattractant receptors, the phosphatidylcholine-specific phospholipase D (PLD) produces large amounts of second messengers in most cell types. However, the relevance of PLD isoforms to CCR5 signaling and HIV-1 infection process remains unexplored. We show here that CCR5 activation by MIP-1beta in HeLa-MAGI cells triggered a rapid and substantial PLD activity, as assessed by mass choline production. This activity required the activation of ERK1/2-MAP kinases and involved both PLD1 and PLD2. MIP-1beta also promoted the activation of an HIV-1 long terminal repeat (LTR) by the transactivator Tat in HeLa P4.2 cells through a process involving ERK1/2. Expression of wild-type and catalytically inactive PLDs dramatically boosted and inhibited the LTR activation, respectively, without altering Tat expression. Wild-type and inactive PLDs also respectively potentiated and inhibited HIV-1(BAL) replication in MAGI cells. Finally, in monocytic THP-1 cells, antisense oligonucleotides to both PLDs dramatically inhibited the HIV-1 replication. Thus, PLD is activated downstream of ERK1/2 upon CCR5 activation and plays a major role in promoting HIV-1 LTR transactivation and virus replication, which may open novel perspectives to anti-HIV-1 strategies.

Naturally occurring C-terminally truncated STAT5 is a negative regulator of HIV-1 expression

CD4(+) cells of most individuals infected with HIV-1 harbor a C-terminally truncated and constitutively activated form of signal transducer and activator of transcription-5 (STAT5 Delta). We report that the chronically HIV-infected U1 cell line expresses STAT5 Delta but not full-length STAT5. Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation of U1 cells promoted early activation of STAT5 Delta and of extracellular signal regulated kinases (ERKs), followed by later activation of activator protein 1 (AP-1) and HIV expression. Inhibition of ERK/AP-1 by PD98,059 abolished, whereas either tyrphostin AG490 or a STAT5 small interfering RNA (siRNA) enhanced, virion production in GM-CSF-stimulated U1 cells. Chromatin immunoprecipitation demonstrated the induction of STAT5 Delta binding to STAT consensus sequences in the HIV-1 promoter together with a decreased recruitment of RNA polymerase II after 1 hour of GM-CSF stimulation of U1 cells. Down-regulation of STAT5 Delta by siRNA resulted in the up-regulation of both HIV-1 gag-pol RNA and p24 Gag antigen expression in CD8-depleted leukocytes of several HIV-positive individuals cultivated ex vivo in the presence of interleukin-2 but not of interleukin-7. Thus, the constitutively activated STAT5 Delta present in the leukocytes of most HIV-positive individuals acts as a negative regulator of HIV expression.

Monocyte-derived macrophages and myeloid cell lines as targets of HIV-1 replication and persistence

HIV infection of mononuclear phagocytes (MP), mostly as tissue macrophages, is a dominant feature in the pathogenesis of HIV disease and its progression to AIDS. Although the general mechanism of infection is not dissimilar to that of CD4+ T lymphocytes occurring via interaction of the viral envelope with CD4 and a chemokine receptor (usually CCR5), other features are peculiar to MP infection. Among others, the long-term persistence of productive infection, sustained by the absence of substantial cell death, and the capacity of the virions to bud and accumulate in intracellular multivesicular bodies (MVB), has conferred to MP the role of "Trojan horses" perpetuating the chronic state of infection. Because the investigation of tissue macrophages is often very difficult for both ethical and practical reasons of accessibility, most studies of in vitro infection rely upon monocyte-derived macrophages (MDM), a methodology hampered by inter-patient variability and lack of uniformity of experimental protocols. A number of cell lines, mostly Mono Mac, THP-1, U937, HL-60, and their derivative chronically infected counterparts (such as U1 and OM-10.1 cell lines) have complemented the MDM system of infection providing useful information on the features of HIV replication in MP. This article describes and compares the most salient features of these different cellular models of MP infection by HIV.