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SARS-CoV-2 can cause acute respiratory distress and death in some patients(1). Although severe COVID-19 is linked to substantial inflammation, how SARS-CoV-2 triggers inflammation is not clear(2). Monocytes and macrophages are sentinel cells that sense invasive infection to form inflammasomes that activate caspase-1 and gasdermin D, leading to inflammatory death (pyroptosis) and the release of potent inflammatory mediators(3). Here we show that about 6% of blood monocytes of patients with COVID-19 are infected with SARS-CoV-2. Monocyte infection depends on the uptake of antibody-opsonized virus by Fcγ receptors. The plasma of vaccine recipients does not promote antibody-dependent monocyte infection. SARS-CoV-2 begins to replicate in monocytes, but infection is aborted, and infectious virus is not detected in the supernatants of cultures of infected monocytes. Instead, infected cells undergo pyroptosis mediated by activation of NLRP3 and AIM2 inflammasomes, caspase-1 and gasdermin D. Moreover, tissue-resident macrophages, but not infected epithelial and endothelial cells, from lung autopsies from patients with COVID-19 have activated inflammasomes. Taken together, these findings suggest that antibody-mediated SARS-CoV-2 uptake by monocytes and macrophages triggers inflammatory cell death that aborts the production of infectious virus but causes systemic inflammation that contributes to COVID-19 pathogenesis.

A well-tolerated and cost-effective oral drug that blocks SARS-CoV-2 growth and dissemination would be a major advance in the global effort to reduce COVID-19 morbidity and mortality. Here, we show that the oral FDA-approved drug nitazoxanide (NTZ) significantly inhibits SARS-CoV-2 viral replication and infection in different primate and human cell models including stem cell-derived human alveolar epithelial type 2 cells. Furthermore, NTZ synergizes with remdesivir, and it broadly inhibits growth of SARS-CoV-2 variants B.1.351 (beta), P.1 (gamma), and B.1617.2 (delta) and viral syncytia formation driven by their spike proteins. Strikingly, oral NTZ treatment of Syrian hamsters significantly inhibits SARS-CoV-2-driven weight loss, inflammation, and viral dissemination and syncytia formation in the lungs. These studies show that NTZ is a novel host-directed therapeutic that broadly inhibits SARS-CoV-2 dissemination and pathogenesis in human and hamster physiological models, which supports further testing and optimization of NTZ-based therapy for SARS-CoV-2 infection alone and in combination with antiviral drugs. ispartof: bioRxiv ispartof: location:United States status: Published online

Summary To establish stable infection, Mycobacterium tuberculosis (MTb) must overcome host innate immune mechanisms, including those that sense pathogen-derived nucleic acids. Here, we show that the host cytosolic RNA sensing molecules RIG-I-like receptor (RLR) signaling proteins RIG-I and MDA5, their common adaptor protein MAVS, and the RNA-dependent kinase PKR each independently inhibit MTb growth in human cells. Furthermore, we show that MTb broadly stimulates RIG-I, MDA5, MAVS, and PKR gene expression and their biological activities. We also show that the oral FDA-approved drug nitazoxanide (NTZ) significantly inhibits intracellular MTb growth and amplifies MTb-stimulated RNA sensor gene expression and activity. This study establishes prototypic cytoplasmic RNA sensors as innate restriction factors for MTb growth in human cells and it shows that targeting this pathway is a potential host-directed approach to treat tuberculosis disease., Graphical Abstract, Highlights • MTb infection induces RNA sensor (RIG-I, MDA5, PKR) mRNA levels and activities • RIG-I, MDA5, MAVS, and PKR restrict intracellular MTb growth in human cells • NTZ enhances MTb-driven RNA sensor mRNA levels and RLR activities • NTZ and NTZ derivatives inhibit intracellular MTb growth in primary human cells, Biological Sciences; Immunology; Immune Response; Microbiology; Molecular Microbiology

SARS-CoV-2 causes acute respiratory distress that can progress to multiorgan failure and death in a minority of patients. Although severe COVID-19 disease is linked to exuberant inflammation, how SARS-CoV-2 triggers inflammation is not understood. Monocytes and macrophages are sentinel immune cells in the blood and tissue, respectively, that sense invasive infection to form inflammasomes that activate caspase-1 and gasdermin D (GSDMD) pores, leading to inflammatory death (pyroptosis) and processing and release of IL-1 family cytokines, potent inflammatory mediators. Here we show that expression quantitative trait loci (eQTLs) linked to higher GSDMD expression increase the risk of severe COVID-19 disease (odds ratio, 1.3, p, One sentence summary: Antibody-mediated SARS-CoV-2 infection of monocytes activates inflammation and cytokine release.

Summary Here, we show that the US Food and Drug Administration-approved oral drug nitazoxanide (NTZ) broadly amplifies the host innate immune response to viruses and inhibits Ebola virus (EBOV) replication. We find that NTZ enhances retinoic-acid-inducible protein I (RIG-I)-like-receptor, mitochondrial antiviral signaling protein, interferon regulatory factor 3, and interferon activities and induces transcription of the antiviral phosphatase GADD34. NTZ significantly inhibits EBOV replication in human cells through its effects on RIG-I and protein kinase R (PKR), suggesting that it counteracts EBOV VP35 protein's ability to block RIG-I and PKR sensing of EBOV. NTZ also inhibits a second negative-strand RNA virus, vesicular stomatitis virus (VSV), through RIG-I and GADD34, but not PKR, consistent with VSV's distinct host innate immune evasion mechanisms. Thus, NTZ counteracts varied virus-specific immune evasion strategies by generally enhancing the RNA sensing and interferon axis that is triggered by foreign cytoplasmic RNA exposure, and holds promise as an oral therapy against EBOV., Graphical Abstract, Highlights • NTZ amplifies RNA sensor and type I interferon activities and induces GADD34 expression • NTZ inhibits infectious Ebola virus (EBOV) via RIG-I and PKR, but not GADD34 • NTZ inhibits a second negative-strand RNA virus, VSV, via RIG-I and GADD34, but not PKR • NTZ holds promise as an oral therapy against EBOV, Mechanism of Action; Pathogenic Organism; Immune Response; Viral Microbiology

This review aims to describe the key principles in treatment of drug-resistant tuberculosis (TB) in people living with HIV, including early access to timely diagnostics, linkage into care, TB treatment strategies including the use of new and repurposed drugs, co-management of HIV disease, and treatment complications and programmatic support to optimize treatment outcomes. These are necessary strategies to decrease the likelihood of poor treatment outcomes including lower treatment completion rates and higher mortality.Diagnosis of drug-resistant TB is the gateway into care; yet understanding the utility and the limitations of genotypic methods in this population is necessary. The principles of TB treatment in HIV-infected individuals are similar to those without HIV co-infection, with few exceptions. However, adverse effects with potential significant morbidity may emerge during treatment, and timely antiretroviral therapy is essential to improve mortality in this patient population. Emerging data on the use of new and repurposed drugs and short course multidrug-resistant TB regimens and adherence strategies benefiting this population are reviewed.The clinical complexity of co-managing drug-resistant TB and HIV, and the higher rate of poor treatment outcomes in this population demand careful clinical management strategies, and multidisciplinary and comprehensive programmatic interventions to optimize treatment success in this vulnerable group.

SARS-CoV-2 causes acute respiratory distress that can progress to multiorgan failure and death in some patients. Although severe COVID-19 disease is linked to exuberant inflammation, how SARS-CoV-2 triggers inflammation is not understood. Monocytes are sentinel blood cells that sense invasive infection to form inflammasomes that activate caspase-1 and gasdermin D (GSDMD) pores, leading to inflammatory death (pyroptosis) and processing and release of IL-1 family cytokines, potent inflammatory mediators. Here we show that ~10% of blood monocytes in COVID-19 patients are dying and infected with SARS-CoV-2. Monocyte infection, which depends on antiviral antibodies, activates NLRP3 and AIM2 inflammasomes, caspase-1 and GSDMD cleavage and relocalization. Signs of pyroptosis (IL-1 family cytokines, LDH) in the plasma correlate with development of severe disease. Moreover, expression quantitative trait loci (eQTLs) linked to higherGSDMDexpression increase the risk of severe COVID-19 disease (odds ratio, 1.3, pOne sentence summaryAntibody-mediated SARS-CoV-2 infection of monocytes activates inflammation and cytokine release.

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The human TNF/LT locus genes TNF, LTA, and LTB are expressed in a cell type–specific manner. In this study, we show that a highly conserved NFAT binding site within the distal noncoding element hHS-8 coordinately controls TNF and LTA gene expression in human T cells. Upon activation of primary human CD4(+) T cells, hHS-8 and the TNF and LTA promoters display increased H3K27 acetylation and nuclease sensitivity and coordinate induction of TNF, LTA, and hHS-8 enhancer RNA transcription occurs. Functional analyses using CRISPR/dead(d)Cas9 targeting of the hHS-8-NFAT site in the human T cell line CEM demonstrate significant reduction of TNF and LTA mRNA synthesis and of RNA polymerase II recruitment to their promoters. These studies elucidate how a distal element regulates the inducible cell type–specific gene expression program of the human TNF/LT locus and provide an approach for modulation of TNF and LTA transcription in human disease using CRISPR/dCas9.

SUMMARY The interferon (IFN)-induced transmembrane (IFITM) proteins are critical mediators of the host antiviral response. Here, we expand the role of IFITM proteins to host defense against intracellular bacterial infection by demonstrating that they restrict Mycobacterium tuberculosis (MTb) intracellular growth. Simultaneous knockdown of IFITM1, IFITM2, and IFITM3 by RNAi significantly enhances MTb growth in human monocytic and alveolar/epithelial cells, whereas individual overexpression of each IFITM impairs MTb growth in these cell types. Furthermore, MTb infection, Toll-like receptor 2 and 4 ligands, and several proinflammatory cytokines induce IFITM1–3 gene expression in human myeloid cells. We find that IFITM3 co-localizes with early and, in particular, late MTb phagosomes, and overexpression of IFITM3 enhances endosomal acidification in MTb-infected monocytic cells. These findings provide evidence that the antiviral IFITMs participate in the restriction of mycobacterial growth, and they implicate IFITM-mediated endosomal maturation in its antimycobacterial activity., Graphical abstract

IntroductionProlonged inpatient multidrug-resistant tuberculosis (MDR-TB) treatment for all patients is not sustainable for high-burden settings, but there is limited information on community-based treatment programme outcomes for MDR-TB.MethodsThe Cambodian Health Committee, a non-governmental organisation (NGO), launched the Cambodian MDR-TB programme in 2006 in cooperation with the National Tuberculosis Program (NTP) including a community-based treatment option as a key programme component. The programme was transferred to NTP oversight in 2011 with NGO clinical management continuing. Patients electing to receive home-based treatment were followed by a dedicated adherence supporter and a multidisciplinary outpatient team of nurses, physicians and community health workers. Patients hospitalised for >1 month of treatment (hospital based) received similar management after discharge. All patients received a standardised second-line MDR-TB regimen and were provided nutritional and adherence support. Outcomes were reviewed for patients completing 24 months of treatment and predictors of treatment success were evaluated using logistic regression.ResultsOf 582 patients with MDR-TB who initiated treatment between September 2006 and June 2016, 20% were HIV coinfected, 288 (49%) initiated community-based treatment and 294 (51%) received hospital-based treatment. Of 486 patients with outcomes available, 364 (75%) were cured, 10 (2%) completed, 28 (6%) were lost to follow-up, 3 (0.6%) failed and 77 (16%) died. There was no difference between treatment success in community versus hospital-based groups (adjusted OR (aOR) 1.0, p=0.99). HIV infection, older age and body mass index ConclusionsCambodia’s NGO–NTP partnership successfully developed and scaled up a model MDR-TB treatment programme. The first large-scale MDR-TB programme in Asia with a significant community-based component, the programme achieved equally high treatment success in patients with community-based compared with hospital-based initiation of MDR treatment.

Background In Africa, fewer than half of patients receiving therapy for multidrug-resistant TB (MDR TB) are successfully treated, with poor outcomes reported for HIV-coinfected patients. Methods A standardised second-line drug (SLD) regimen was used in a non-governmental organisation–Ministry of Health (NGO-MOH) collaborative community and hospital-based programme in Ethiopia that included intensive side effect monitoring, adherence strategies and nutritional supplementation. Clinical outcomes for patients with at least 24 months of follow-up were reviewed and predictors of treatment failure or death were evaluated by Cox proportional hazards models. Results From February 2009 to December 2014, 1044 patients were initiated on SLD. 612 patients with confirmed or presumed MDR TB had ≥24 months of follow-up, 551 (90.0%) were confirmed and 61 (10.0%) were suspected MDR TB cases. 603 (98.5%) had prior TB treatment, 133 (21.7%) were HIV coinfected and median body mass index (BMI) was 16.6. Composite treatment success was 78.6% with 396 (64.7%) cured, 85 (13.9%) who completed treatment, 10 (1.6%) who failed, 85 (13.9%) who died and 36 (5.9%) who were lost to follow-up. HIV coinfection (adjusted HR (AHR): 2.60, p

Summary: Interferon γ (IFN-γ) priming sensitizes monocytes and macrophages to lipopolysaccharide (LPS) stimulation, resulting in augmented expression of a set of genes including TNF. Here, we demonstrate that IFN-γ priming of LPS-stimulated TNF transcription requires a distal TNF/LT locus element 8 kb upstream of the TNF transcription start site (hHS-8). IFN-γ stimulation leads to increased DNase I accessibility of hHS-8 and its recruitment of interferon regulatory factor 1 (IRF1), and subsequent LPS stimulation enhances H3K27 acetylation and induces enhancer RNA synthesis at hHS-8. Ablation of IRF1 or targeting the hHS-8 IRF1 binding site in vivo with Cas9 linked to the KRAB repressive domain abolishes IFN-γ priming, but does not affect LPS induction of the gene. Thus, IFN-γ poises a distal enhancer in the TNF/LT locus by chromatin remodeling and IRF1 recruitment, which then drives enhanced TNF gene expression in response to a secondary toll-like receptor (TLR) stimulus. : Interferon γ (IFN-γ) priming is a critical immune event that enhances the monocyte and macrophage response, particularly expression of the TNF gene, to toll-like receptor (TLR) signaling. Chow et al. demonstrate that IFN-γ priming requires a distal enhancer element within the TNF/LT locus, thereby expanding the role of distal regulatory elements in the innate immune response.

Imaging flow cytometry (IFC) captures multichannel images of hundreds of thousands of single cells within minutes. IFC is seeing a paradigm shift from low- to high-information-content analysis, driven partly by deep learning algorithms. We predict a wealth of applications with potential translation into clinical practice.

Despite advances in tuberculosis diagnosis and access to treatment for human immunodeficiency virus (HIV) infection, tuberculosis remains a major cause of death in HIV-infected patients [1, 2]. In 2012, it was estimated that 1.0–1.2 million new tuberculosis cases and 0.32 million tuberculosis-related deaths occurred in HIV-infected persons, accounting for 13% of the global tuberculosis burden and 25% of tuberculosis mortality [1]. Several randomized clinical trials showed the positive impact upon mortality of shortening the delay between tuberculosis treatment onset and initiation of antiretroviral therapy (ART) [3–7]. The level of immunosuppression [3, 4] and the location or severity of tuberculosis disease [6] have been reported to impact the survival benefit gained from earlier ART initiation [3–7]. Notably, in general, data are scarce on tuberculosis-related factors associated with mortality in HIV-infected adults treated for tuberculosis. Observational and autopsy studies showed that tuberculosis itself constitutes the principal cause of death [8–10], but other HIV-related opportunistic infections are frequently reported as the etiology of death. Thus, a deeper understanding of the causes and factors associated with death is needed to develop strategies aiming to further reduce mortality in HIV-infected patients treated for tuberculosis. Here, we assessed mortality rates, causes, and risk factors of death in HIV-infected patients enrolled in the CAMELIA (Cambodian Early vs Late Introduction of Antiretroviral Therapy) randomized clinical trial. We specifically analyzed (1) early deaths before 26 weeks of follow-up (W26), where mortality is thought to be mainly linked to the severity of initial presentation and expected to be related to HIV and tuberculosis; and (2) late deaths after 50 weeks of follow-up (W50), at a time when most patients would be expected to have been cured from their tuberculosis and to have recovered a level of protective immunity in general [11, 12].

Imaging flow cytometry has been applied to address questions in infection biology, in particular, infections induced by intracellular pathogens. This methodology, which utilizes specialized analytic software makes it possible to analyze hundreds of quantified features for hundreds of thousands of individual cellular or subcellular events in a single experiment. Imaging flow cytometry analysis of host cell-pathogen interaction can thus quantitatively addresses a variety of biological questions related to intracellular infection, including cell counting, internalization score, and subcellular patterns of co-localization. Here, we provide an overview of recent achievements in the use of fluorescently labeled prokaryotic or eukaryotic pathogens in human cellular infections in analysis of host-pathogen interactions. Specifically, we give examples of Imagestream-based analysis of cell lines infected with Toxoplasma gondii or Mycobacterium tuberculosis. Furthermore, we illustrate the capabilities of imaging flow cytometry using a combination of standard IDEAS™ software and the more recently developed Feature Finder algorithm, which is capable of identifying statistically significant differences between researcher-defined image galleries. We argue that the combination of imaging flow cytometry with these software platforms provides a powerful new approach to understanding host control of intracellular pathogens.

In this review, we examine how a subset of signal transduction cascades initiated by Mycobacterium tuberculosis (Mtb) infection modulates transcription mediated by the human immunodeficiency virus type 1 long terminal repeat (HIV-1 LTR). We describe two distinct phases of signaling that target transcription factors known to bind the HIV-1 LTR, and thus drive viral transcription and replication, in cells of the Mtb-infected host. First, Mtb-derived molecules, including cell wall components and DNA, interact with a number of host pattern recognition receptors. Second, cytokines and chemokines secreted in response to Mtb infection initiate signal transduction cascades through their cognate receptors. Given the variation in cell wall components among distinct clinical Mtb strains, the initial pattern recognition receptor interaction leading to direct LTR activation and differential cytokine and chemokine production is likely to be an important aspect of Mtb strain-specific regulation of HIV-1 transcription and replication. Improved understanding of these molecular mechanisms in the context of bacterial and host genetics should provide key insights into the accelerated viral replication and disease progression characteristic of HIV/TB coinfection.

Here we provide a mechanism for specific, efficient transcription of the TNF gene and, potentially, other genes residing within multigene loci. We identify and characterize highly conserved noncoding elements flanking the TNF gene, which undergo activation-dependent intrachromosomal interactions. These elements, hypersensitive site (HSS)−9 and HSS+3 (9 kb upstream and 3 kb downstream of the TNF gene, respectively), contain DNase I hypersensitive sites in naive, T helper 1, and T helper 2 primary T cells. Both HSS-9 and HSS+3 inducibly associate with acetylated histones, indicative of chromatin remodeling, bind the transcription factor nuclear factor of activated T cells (NFAT)p in vitro and in vivo , and function as enhancers of NFAT-dependent transactivation mediated by the TNF promoter. Using the chromosome conformation capture assay, we demonstrate that upon T cell activation intrachromosomal looping occurs in the TNF locus. HSS-9 and HSS+3 each associate with the TNF promoter and with each other, circularizing the TNF gene and bringing NFAT-containing nucleoprotein complexes into close proximity. TNF gene regulation thus reveals a mode of intrachromosomal interaction that combines a looped gene topology with interactions between enhancers and a gene promoter.

The adaptive immune response mediated by T cells is critical for control of Mycobacterium tuberculosis (M. tuberculosis) infection in humans. However, the M. tuberculosis antigens and host T-cell responses that are required for an effective adaptive immune response to M. tuberculosis infection are yet to be defined. Here, we review recent findings on CD4(+) and CD8(+) T-cell responses to M. tuberculosis infection and examine the roles of distinct M. tuberculosis-specific T-cell subsets in control of de novo and latent M. tuberculosis infection, and in the evolution of T-cell immunity to M. tuberculosis in response to tuberculosis treatment. In addition, we discuss recent studies that elucidate aspects of M. tuberculosis-specific adaptive immunity during human immunodeficiency virus co-infection and summarize recent findings from vaccine trials that provide insight into effective adaptive immune responses to M. tuberculosis infection.

The authors are indebted to Wallis Annenberg whose generosity made this study possible, and to John Moores for his generous gift. We are grateful to Francoise Barré-Sinoussi for her help, advice, and support over the years. We thank Eric Nerrienet, Claire Rekacewicz, Daniel Scott, Gianfranco Pancino, Jean-Louis Sarthou, and Charles Mayaud for helpful discussions and advice as we began the study, and Jean-Louis Sarthou for his long time support of the Harvard team’s collaboration with the Institut Pasteur du Cambodge. We thank the CAMELIA study team, including the site nurses, doctors, and health workers, and Vincent Deubel and the staff at the Institut Pasteur du Cambodge. We thank Larry Fox, Rod Hoff, Jane Bupp, and Brigitte Bazin for their support and helpful discussions from the beginning of CAMELIA onward and the staff of the Cambodian Health Committee, especially Sam Sophan, for his contributions to and support of the work. We thank Leslie Kalish of Children’s Hospital Boston and the Harvard Catalyst Biostatistical Consulting program (NIH UL1 TR001102) for expert statistical advice and help as we started the analysis. We also thank Jerry Sadoff for his early support and Judy Lieberman for helpful comments on the manuscript. Finally, we are deeply indebted to the patients who took part in this study, who generously offered their participation to help the scientific community find solutions to AIDS and TB; International audience; OBJECTIVE: To investigate the impact of tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) upon immunological recovery and the T-cell compartment after initiation of TB and antiretroviral therapy (ART).DESIGN AND METHODS: We prospectively evaluated T-cell immunophenotypes by flow cytometry and cytokines by Luminex assays in a subset (n = 154) of highly immunosuppressed HIV-infected patients with TB from the Cambodian Early versus Late Introduction of Antiretrovirals randomized clinical trial. We compared findings from patients who developed TB-IRIS with findings from patients who did not develop TB-IRIS. Data were evaluated with mixed-effect linear regression, Kaplan-Meier estimates, and Wilcoxon rank-sum tests, and q-values were calculated to control for multiple comparisons.RESULTS: Development of TB-IRIS was associated with significantly greater pre-ART frequencies of HLA-DRCD45ROCD4, CCR5CD4, OX40CD4, and Fas effector memory CD8 T cells, and significantly elevated levels of plasma interleukin (IL)-6, IL-1β, IL-8, and IL-10, and viral load. Post-ART initiation, effector memory CD4 and Fas effector memory CD4 T-cell frequencies significantly expanded, and central memory CD4 T-cell frequencies significantly contracted in patients who experienced TB-IRIS. By week 34 post-TB treatment initiation, effector memory/central memory CD4 T-cell ratios were markedly higher in TB-IRIS versus non-TB-IRIS patients.CONCLUSIONS: A distinct pattern of pre-ART T-cell and cytokine markers appear to poise the immune response of certain patients to develop TB-IRIS. Experience of TB-IRIS is then associated with long-term remodeling of the CD4 T-cell memory compartment towards an effector memory-dominated phenotype. We speculate that these pre and post-ART TB-IRIS-associated immune parameters may contribute to superior immune control of TB/HIV co-infection and better clinical outcome.

The transactivator of transcription (Tat) protein is essential for efficient HIV type 1 (HIV-1) replication and is involved in the transcriptional regulation of the host immune response gene, TNF. In this study, we demonstrate that Tat proteins from representative HIV-1 subtype E isolates, but not from subtypes B or C, selectively inhibit TNF gene transcription and protein production in CD4+ Jurkat T cells. Strikingly, we show that this repression is due to a tryptophan at residue 32 of Tat E and is secondary to interference with recruitment of the histone acetyltransferase P/CAF to the TNF promoter and with chromatin remodeling of the TNF locus. This study presents a novel mechanism by which HIV-1 manipulates a host immune response gene that is important in its own replication. Moreover, these results demonstrate a new mechanism by which the TNF gene is regulated via chromatin remodeling secondary to viral infection.

Viral heterogeneity is a major hurdle for potential therapeutic use of RNA interference (RNAi) against HIV-1. To determine the extent of RNAi tolerance to mutations, we tested 3 viral target sites with differing propensity for mutations: a highly variable rev sequence, a gag sequence conserved only among clade B isolates, and a vif sequence highly conserved across clades. Lentiviral expression of all 3 shRNAs inhibited replication of the homologous HIVIIIB strain. However, they differed in their ability to protect primary CD4 T cells against multiple isolates within and across HIV clades. The least conserved rev sequence inhibited only 2 of 5 clade B isolates. The gag sequence (conserved within clade B) protected 5 of 5 clade B isolates but not other clade viruses with 2 or 3 mutations in the central region. In contrast, the vif sequence, which was conserved across clades except for single mutations at positions 14 and 17, inhibited viruses from 5 different clades. Moreover, siRNAs with introduced mutations at sites of gag sequence polymorphisms showed reduced antiviral activity, whereas mutations in vif siRNA only modestly decreased silencing. Thus, although 1 or 2 mutations at peripheral sites are tolerated, mutations in the central target cleavage region abolish RNAi activity.

The molecular mechanisms that regulate expression of the immunosuppressive cytokine IL-10 remain poorly understood. In this study, by measuring sensitivity to DNase I digestion, we show that production of IL-10 by primary mouse bone marrow-derived macrophages stimulated through pattern recognition receptors was associated with chromatin remodeling of the IL-10 locus. We also demonstrate that the IL-10 locus is remodeled in primary Th2 cells and IL-10-producing regulatory T cells that have been differentiated in vitro. Strikingly, a novel DNase I-hypersensitive site (HSS-4.5) was identified in stimulated macrophages, but not in T cells. We show that hyperacetylated histones were recruited to this site in stimulated macrophages. Furthermore, HSS-4.5 is highly conserved and contains a putative NF-κB binding site. In support of a function for this site, NF-κB p65/RelA was recruited to HSS-4.5 in vivo and its activation was required for optimal IL-10 gene expression in LPS-stimulated macrophages.

Tumor necrosis factor (TNF) is a pro-inflammatory cytokine that plays an important role in a variety of infectious and autoimmune disorders. Its transcription is regulated in a stimulus- and cell-type-specific manner via the recruitment of distinct DNA/activator complexes forming secondary structures or enhanceosomes. NFATp, a member of the nuclear factor of activated T cells (NFAT) family of transcription factors, plays a critical role in TNF gene regulation under a variety of conditions. In this study, we show that NFAT5, the most recently described NFAT family member, binds to the TNF promoter in a manner distinct from other NFAT proteins and is a key mediator in the activation of TNF gene transcription during hypertonic stress alone.

Mycobacterium tuberculosis (MTb) is the leading cause of death in the setting of AIDS. MTb enhances the pathogenicity and accelerates the course of HIV disease and, furthermore, infection with HIV-1 increases the risk of reactivation or reinfection with MTb. In this study, we show that host-specific recall responses to one pathogen, MTb, has a direct effect upon the regulation of a second pathogen, HIV-1. Using cells from immunocompetent former tuberculosis (TB) patients who displayed either a persistently positive (responsive) or negative (anergic), delayed-type hypersensitivity (DTH) reaction to intradermal injection of purified protein derivative (PPD), we investigated the effect of recall Ags to MTb upon the replication of HIV-1 primary isolates in vitro. We show that HIV-1 replication of a T cell-tropic isolate was significantly impaired in MTb-stimulated PBMC from PPD-anergic donors. Furthermore, these donors displayed a significant increase in CD8+ T cells and IL-10 levels and lower levels of IL-2 and TNF-α relative to PPD-responsive donors in response to PPD stimulation. Strikingly, CD8+ T cell depletion and blocking of IL-10 significantly increased HIV-1 replication in these PPD-anergic donors, indicating that an immunosuppressive response to MTb recall Ags inhibits HIV-1 replication in PPD-anergic individuals. Therefore, immunotherapeutic approaches aimed at recapitulating Ag-specific MTb anergy in vivo could result in novel and effective approaches to inhibit HIV-1 disease progression in MTb/HIV-1 coinfection.

Using a phylogenetic approach, we identified highly conserved sequences within intron 3 of the human TNF-α gene. These sequences form cell type-specific DNase I hypersensitivity sites and display cell type-specific DNA-protein contacts in in vivo genomic footprints. Consistent with these results, intron 3 confers specific activity upon a TNF-α reporter gene in Jurkat T cells, but not THP-1 monocytic cells. Thus, using a combinatorial approach of phylogenetic analysis, DNase I hypersensitivity analysis, in vivo footprinting, and transfection analysis, we demonstrate that intronic regulatory elements are involved in the cell type-specific regulation of TNF-α gene expression.

Control of HIV-1 viremia and progression to AIDS has been associated with specific HLA genes. The tumor necrosis factor ( TNF) and the non-classical major histocompatibility (MHC) class I chain-related A ( MICA) genes are located in the genomic segment between the HLA class I and II genes and variants of both genes have been identified. We thus analyzed TNF promoter and MICA variants in a well-characterized group of HIV-1 infected individuals with different abilities to control HIV-1 viremia. In our cohort, the -1030/-862-linked TNF promoter single-nucleotide polymorphisms (SNPs), but not MICA variants, are significantly associated with lack of control of HIV-1 viremia ( P=0.03). This association is independent of those HLA-B35 alleles associated with HIV-1 disease progression with which the -862 TNF SNP has previously been independently associated. Thus, non-randomly associated genes near the TNF locus are likely involved in control of HIV-1 viremia.

Tumor necrosis factor alpha (TNF-alpha) plays an important role in host containment of infection by Mycobacterium tuberculosis, one of the leading causes of death by an infectious agent globally. Using the pathogenic M. tuberculosis strain H37Rv, we present evidence that upon stimulation of monocytic cells by M. tuberculosis a unique TNF-alpha enhanceosome is formed, and it is distinct from the TNF-alpha enhanceosome that forms in T cells stimulated by antigen engagement or virus infection. A distinct set of activators including ATF-2, c-jun, Ets, Sp1, Egr-1 and the coactivator proteins CBP/p300 are recruited to the TNF-alpha promoter after stimulation with M. tuberculosis. Furthermore, the formation of this enhanceosome is dependent on inducer-specific helical phasing relationships between transcription factor binding sites. We also show that the transcriptional activity of CBP/p300 is potentiated by mycobacterial stimulation of monocytes. The identification of TNF-alpha regulatory elements and coactivators involved in M. tuberculosis-stimulated gene expression thus provides potential selective molecular targets in the modulation of TNF-alpha gene expression in the setting of mycobacterial infection.

�untranslated region, were associated with TB susceptibility and resistance, respectively. Other polymorphisms associated with differential susceptibility to TB were not associated with susceptibility or resistance to TB in Cambodians. The novel pattern of genetic associations with susceptibility and resistance to TB detected in Cambodia is consistent with the conclusion that unique environmental and natural selective factors have resulted in the development of ethnic-specific host genetic factors associated with TB susceptibility and resistance worldwide. Approximately one-third of the world’s population is infected with the bacteria that causes tuberculosis (TB), Mycobacterium tuberculosis. One in 10 of those infected are estimated to progress to active TB disease. Thus, TB is a significant cause of morbidity and mortality and causes ∼2 million deaths annually [1–3]. As early as 1949, Haldane [4] proposed that the maintenance of multiple genes that confer relative susceptibilities on the host to infectious diseases would be favored by evolution. In support of this hypothesis, certain populations appear to be at risk for both increased susceptibility to infection [5] and progressive clinical disease due to mycobacteria [6–9], and several case-control studies have identified associations between TB disease and candidate genes potentially involved in the immune response to TB [10, 11].

We present evidence that the inducer-specific regulation of the human tumor necrosis factor alpha (TNF-alpha) gene in T cells involves the assembly of distinct higher-order transcription enhancer complexes (enhanceosomes), which is dependent upon inducer-specific helical phasing relationships between transcription factor binding sites. While ATF-2, c-Jun, and the coactivator proteins CBP/p300 play a central role in TNF-alpha gene activation stimulated by virus infection or intracellular calcium flux, different sets of activators including NFATp, Sp1, and Ets/Elk are recruited to a shared set of transcription factor binding sites depending upon the particular stimulus. Thus, these studies demonstrate that the inducer-specific assembly of unique enhanceosomes is a general mechanism by which a single gene is controlled in response to different extracellular stimuli.

ObjectiveTo assess efavirenz plasma concentrations and their association with treatment efficacy and tolerance of efavirenz 600 mg daily in HIV-tuberculosis co-infected patients.MethodsHIV-infected adults with CD4+ T cell count ≤ 200/mm(3) received standard 6-month tuberculosis treatment and antiretroviral therapy including a daily-dose of 600 mg of efavirenz, irrespective of their body weight. Mid-dose blood samples were drawn both on tuberculosis treatment (week +2 and week +6 after antiretroviral therapy initiation, and week 22 of follow-up) and off tuberculosis treatment (week 50 of follow-up). Considered therapeutic range was 1,000 to 4,000 ng/mL. Multivariate analysis was performed to evaluate the association between efavirenz concentration below 1,000 ng/mL and virological failure. Linear regression was used to test the association between efavirenz exposure and CD4+ T cell gain. Severe side effects potentially related to efavirenz were described and their association with efavirenz exposure was tested by multivariate analysis.ResultsEfavirenz plasma concentrations were available in 540 patients. Median [interquartile range] efavirenz concentrations were 2,674 ng/mL [1,690-4,533], 2,667 ng/mL [1,753-4,494] and 2,799 ng/mL [1,804-4,744] at week +2, week +6, week 22, respectively, and 2,766 ng/mL [1,941-3,976] at week 50. Efavirenz concentrations were lower at week 50 (off rifampicin) compared to week 22 (on rifampicin) (pConclusionBody weight and tuberculosis treatment were not associated with low efavirenz concentrations or treatment failure, supporting the 600 mg daily-dose of efavirenz in HIV-tuberculosis co-infected patients. High efavirenz concentrations were related to a higher risk of central nervous system side effects and hepatotoxicity.Trial registrationClinicalTrials.gov NCT01300481.

Tumor necrosis factor alpha (TNF-alpha) is the key mediator of superantigen-induced T cell lethal shock. Here, we show that nuclear factor of activated T cells transcription factor, NFATp, controls susceptibility to superantigen-induced lethal shock in mice through its activation of TNF-alpha gene transcription. In NFATp-deficient mice, T cell stimulation leads to delayed induction and attenuation of TNF-alpha mRNA levels, decreased TNF-alpha serum levels, and resistance to superantigen-induced lethal shock. By contrast, after lipopolysaccharide (LPS) challenge, serum levels of TNF-alpha and susceptibility to shock are unaffected. These results demonstrate that NFATp is an essential activator of immediate early TNF-alpha gene expression in T cells and they present in vivo evidence of the inducer- and cell type-specific regulation of TNF-alpha gene expression. Furthermore, they suggest NFATp as a potential selective target in the treatment of superantigen-induced lethal shock.

The cAMP response element binding protein (CREB)-binding protein (CBP)/p300 family of coactivator proteins regulates gene transcription through the integration of multiple signal transduction pathways. Here, we show that induction of tumor necrosis factor alpha (TNF-alpha) gene expression in T cells stimulated by engagement of the T cell receptor (TCR) or by virus infection requires CBP/p300. Strikingly, in mice lacking one copy of the CBP gene, TNF-alpha gene induction by TCR activation is inhibited, whereas virus induction of the TNF-alpha gene is not affected. Consistent with these findings, the transcriptional activity of CBP is strongly potentiated by TCR activation but not by virus infection of T cells. Thus, CBP gene dosage and transcriptional activity are critical in TCR-dependent TNF-alpha gene expression, demonstrating a stimulus-specific requirement for CBP in the regulation of a specific gene.

The human tumor necrosis factor alpha (TNF-alpha) gene is rapidly activated in response to multiple signals of stress and inflammation. We have identified transcription factors present in the TNF-alpha enhancer complex in vivo following ionophore stimulation (ATF-2/Jun and NFAT) and virus infection (ATF-2/Jun, NFAT, and Sp1), demonstrating a novel role for NFAT and Sp1 in virus induction of gene expression. We show that virus infection results in calcium flux and calcineurin-dependent NFAT dephosphorylation; however, relatively lower levels of NFAT are present in the nucleus following virus infection as compared to ionophore stimulation. Strikingly, Sp1 functionally synergizes with NFAT and ATF-2/c-jun in the activation of TNF-alpha gene transcription and selectively associates with the TNF-alpha promoter upon virus infection but not upon ionophore stimulation in vivo. We conclude that the specificity of TNF-alpha transcriptional activation is achieved through the assembly of stimulus-specific enhancer complexes and through synergistic interactions among the distinct activators within these enhancer complexes.

Engagement of the tumor necrosis factor-alpha (TNF-alpha) receptors by the TNF-alpha ligand results in the rapid induction of TNF-alpha gene expression. The study presented here shows that autoregulation of TNF-alpha gene transcription by selective signaling through tumor necrosis factor receptor 1 (TNFR1) requires p38 mitogen-activated protein (MAP) kinase activity and the binding of the transcription factors ATF-2 and Jun to the TNF-alpha cAMP-response element (CRE) promoter element. Consistent with these findings, TNFR1 engagement results in increased p38 MAP kinase activity and p38-dependent phosphorylation of ATF-2. Furthermore, overexpression of MADD (MAP kinase-activating death domain protein), an adapter protein that binds to the death domain of TNFR1 and activates MAP kinase cascades, results in CRE-dependent induction of TNF-alpha gene expression. Thus, the TNF-alpha CRE site is the target of TNFR1 stimulation and mediates the autoregulation of TNF-alpha gene transcription.

The level of ongoing HIV-1 replication within an individual is critical to HIV-1 pathogenesis. Among host immune factors, the cytokine TNF-α has previously been shown to increase HIV-1 replication in various monocyte and T cell model systems. Here, we demonstrate that signaling through the TNF receptor family member, the lymphotoxin-β (LT-β) receptor (LT-βR), also regulates HIV-1 replication. Furthermore, HIV-1 replication is cooperatively stimulated when the distinct LT-βR and TNF receptor systems are simultaneously engaged by their specific ligands. Moreover, in a physiological coculture cellular assay system, we show that membrane-bound TNF-α and LT-α1β2 act virtually identically to their soluble forms in the regulation of HIV-1 replication. Thus, cosignaling via the LT-β and TNF-α receptors is probably involved in the modulation of HIV-1 replication and the subsequent determination of HIV-1 viral burden in monocytes. Intriguingly, surface expression of LT-α1β2 is up-regulated on a T cell line acutely infected with HIV-1, suggesting a positive feedback loop between HIV-1 infection, LT-α1β2 expression, and HIV-1 replication. Given the critical role that LT-α1β2 plays in lymphoid architecture, we speculate that LT-α1β2 may be involved in HIV-associated abnormalities of the lymphoid organs.

We investigated the role of Bruton's tyrosine kinase (Btk) in FcepsilonRI-dependent activation of mouse mast cells, using xid and btk null mutant mice. Unlike B cell development, mast cell development is apparently normal in these btk mutant mice. However, mast cells derived from these mice exhibited significant abnormalities in FcepsilonRI-dependent function. xid mice primed with anti-dinitrophenyl monoclonal IgE antibody exhibited mildly diminished early-phase and severely blunted late-phase anaphylactic reactions in response to antigen challenge in vivo. Consistent with this finding, cultured mast cells derived from the bone marrow cells of xid or btk null mice exhibited mild impairments in degranulation, and more profound defects in the production of several cytokines, upon FcepsilonRI cross-linking. Moreover, the transcriptional activities of these cytokine genes were severely reduced in FcepsilonRI-stimulated btk mutant mast cells. The specificity of these effects of btk mutations was confirmed by the improvement in the ability of btk mutant mast cells to degranulate and to secrete cytokines after the retroviral transfer of wild-type btk cDNA, but not of vector or kinase-dead btk cDNA. Retroviral transfer of Emt (= Itk/Tsk), Btk's closest relative, also partially improved the ability of btk mutant mast cells to secrete mediators. Taken together, these results demonstrate an important role for Btk in the full expression of FcepsilonRI signal transduction in mast cells.

We investigated the population pharmacokinetics and pharmacogenetics of efavirenz in 307 patients coinfected with human immunodeficiency virus and tuberculosis and included in the Cambodian Early vs Late Initiation of Antiretrovirals trial (CAMELIA) in Cambodia. Efavirenz (600 mg/d) and stavudine plus lamivudine were administered in addition to standard antituberculosis treatment, including rifampicin and isoniazid. Blood samples were obtained a mean of 14 hours after efavirenz intake at weeks 2 and 6 after initiation of efavirenz and weeks 22 (efavirenz plus antituberculosis drugs) and 50 (efavirenz alone) after initiation of antituberculosis treatment. Ten patients participated in an extensive pharmacokinetic study after week 50. CYP2B6 G516T and C485-18T polymorphisms were the most significant covariates, with weight showing a significant minor effect. Change in efavirenz apparent clearance in patients taking both efavirenz and antituberculosis treatment was highly dependent on NAT2 polymorphism, as a possible surrogate of isoniazid exposure. Patients carrying the CYP2B6 516 TT genotype and slow-acetylation NAT2 phenotype had the lowest efavirenz apparent clearance. These data suggest that the inducing effect of rifampicin is counterbalanced by a concentration-dependant inhibitory effect of isoniazid on efavirenz clearance. Efavirenz is a nonnucleoside reverse-transcriptase inhibitor of human immunodeficiency virus (HIV) type 1

Epigenetics encompasses transient and heritable modifications to DNA and nucleosomes in the native chromatin context. For example, enzymatic addition of chemical moieties to the N-terminal “tails” of histones, particularly acetylation and methylation of lysine residues in the histone tails of H3 and H4, plays a key role in regulation of gene transcription. The modified histones, which are physically associated with gene regulatory regions that typically occur within conserved noncoding sequences, play a functional role in active, poised, or repressed gene transcription. The “histone code” defined by these modifications, along with the chromatin-binding acetylases, deacetylases, methylases, demethylases, and other enzymes that direct modifications resulting in specific patterns of histone modification, shows considerable evolutionary conservation from yeast to humans. Direct modifications at the DNA level, such as cytosine methylation at CpG motifs that represses promoter activity, are another highly conserved epigenetic mechanism of gene regulation. Furthermore, epigenetic modifications at the nucleosome or DNA level can also be coupled with higher-order intra- or interchromosomal interactions that influence the location of regulatory elements and that can place them in an environment of specific nucleoprotein complexes associated with transcription. In the mammalian immune system, epigenetic gene regulation is a crucial mechanism for a range of physiological processes, including the innate host immune response to pathogens and T cell differentiation driven by specific patterns of cytokine gene expression. Here, we will review current findings regarding epigenetic regulation of cytokine genes important in innate and/or adaptive immune responses, with a special focus upon the tumor necrosis factor/lymphotoxin locus and cytokine-driven CD4+ T cell differentiation into the Th1, Th2, and Th17 lineages.

Objective To analyze cases of paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) in the CAMbodian Early versus Late Introduction of Antiretrovirals (CAMELIA) randomized trial designed to compare early (2 weeks) versus late (8 weeks) antiretroviral therapy (ART) initiation after tuberculosis treatment onset in Cambodia (NCT00226434). Methods ART-naive adults with CD4 cell count of 200 cells/μl or less, newly diagnosed tuberculosis, and at least one follow-up visit after ART initiation were included in this analysis. Each case of suspected TB-IRIS was systematically validated by two physicians not involved in patients' management. Factors associated with occurrence of TB-IRIS were identified using the Cox proportional hazard model. Results Among 597 patients, 26% experienced TB-IRIS with an incidence rate of 37.9 cases per 100 person-years [95% confidence interval (CI) 32.4-44.4]. Main clinical manifestations included new or worsening lymphadenopathy (77.4%) and fever (68.4%). Chest radiograph revealed new or worsening abnormalities in 53.4%. Symptoms resolved in 95.5% of patients. Six deaths were directly related to TB-IRIS. Initiating ART early increased the risk of TB-IRIS by 2.61 (95% CI 1.84-3.70). Extrapulmonary or disseminated tuberculosis, CD4 cell count of 100 cells/μl or less, and HIV RNA concentration more than 6 log10 copies/ml were also significantly associated with higher risk of TB-IRIS. Conclusion Shortening the delay between tuberculosis treatment onset and ART initiation to 2 weeks was associated with an increased risk of developing TB-IRIS. However, TB-IRIS was generally easily manageable. Given the marked reported survival advantage of early ART initiation after tuberculosis treatment onset, these data indicate that fear of TB-IRIS should not be an impediment to early ART in adults with advanced immunodeficiency in resource-limited, high burden settings.

Epigenetics encompasses transient and heritable modifications to DNA and nucleosomes in the native chromatin context. For example, enzymatic addition of chemical moieties to the N-terminal “tails” of histones, particularly acetylation and methylation of lysine residues in the histone tails of H3 and H4, plays a key role in regulation of gene transcription. The modified histones, which are physically associated with gene regulatory regions that typically occur within conserved noncoding sequences, play a functional role in active, poised, or repressed gene transcription. The “histone code” defined by these modifications, along with the chromatin-binding acetylases, deacetylases, methylases, demethylases, and other enzymes that direct modifications resulting in specific patterns of histone modification, shows considerable evolutionary conservation from yeast to humans. Direct modifications at the DNA level, such as cytosine methylation at CpG motifs that represses promoter activity, are another highly conserved epigenetic mechanism of gene regulation. Furthermore, epigenetic modifications at the nucleosome or DNA level can also be coupled with higher-order intra- or interchromosomal interactions that influence the location of regulatory elements and that can place them in an environment of specific nucleoprotein complexes associated with transcription. In the mammalian immune system, epigenetic gene regulation is a crucial mechanism for a range of physiological processes, including the innate host immune response to pathogens and T cell differentiation driven by specific patterns of cytokine gene expression. Here, we will review current findings regarding epigenetic regulation of cytokine genes important in innate and/or adaptive immune responses, with a special focus upon the tumor necrosis factor/lymphotoxin locus and cytokine-driven CD4+ T cell differentiation into the Th1, Th2, and Th17 lineages.

Background The optimal dose of efavirenz for HIV-infected patients receiving a tuberculosis regimen including rifampicin remains debated, especially for subjects weighing over 50 kg. To address this issue, we measured plasma efavirenz concentrations from Cambodian adults with tuberculosis enrolled in the CAMELIA randomized trial (ClinicalTrials.gov number, NCT01300481) 6 weeks after the onset of antiretroviral therapy. Methods Efavirenz concentrations and proportions of patients with concentrations below 1,000 ng/ml were compared across patient body weight below or above 50 kg using a Student's t-test and a c2 test, respectively. Factors associated with efavirenz concentrations below 1,000 ng/ml were identified by logistic regression analysis. Logistic regression analysis was also performed to check if efavirenz concentrations below 1,000 ng/ml were associated with virological failure. Results Plasma efavirenz concentrations were higher in the 332 patients who weighed Conclusions The current WHO guidelines recommending 600 mg efavirenz daily irrespective of patient's body weight remains a safe and effective approach to treating coinfected adults needing simultaneous tuberculosis and HIV therapy.

The tumor necrosis factor-alpha (TNF alpha) gene is an immediate early gene in activated T cells, in that it is rapidly induced without a requirement for protein synthesis. Maximal induction of TNF alpha mRNA can be induced by treatment of T cells with calcium ionophores alone, via a calcineurin-dependent process that is blocked by cyclosporin A. We have previously identified a promoter element, kappa 3, that is required for calcium-stimulated, cyclosporin A-sensitive induction of the TNF alpha gene in activated T cells. Here, we demonstrate that the kappa 3 binding factor contains NFATp, a cyclosporin-sensitive DNA-binding protein required for interleukin-2 gene transcription. NFATp binds to two sites within the kappa 3 element, and occupancy of both sites is required for TNF alpha gene induction. Thus, although the kappa 3 element has little sequence similarity to other NFATp-binding sites, it appears to function as a cyclosporin-sensitive promoter element in T cells by virtue of its ability to bind NFATp. The involvement of NFATp in transcriptional activation of both the interleukin-2 and TNF alpha genes suggests that this factor plays an important role in the coordinate induction of multiple cytokine genes, starting at the earliest stages of T cell activation.

Transcription of the human tumor necrosis factor alpha (TNF-alpha) gene is one of the earliest events that occurs after stimulation of B or T cells via their antigen receptors. Antibody directed at surface immunoglobulin (anti-Ig) on B cells has previously been shown to induce a rapid burst of TNF-alpha gene transcription, which can be blocked by the immunosuppressants cyclosporin A (CsA) and FK506. Here, TNF-alpha gene transcription is shown also to be highly and rapidly induced in human B cells after stimulation via the CD40 and interleukin 4 pathways, which similarly is inhibited by CsA and a panel of CsA or FK506 analogues that block calcineurin phosphatase activity. Endogenous TNF-alpha produced after stimulation was involved in B-cell proliferation since anti-TNF-alpha monoclonal antibody inhibited both anti-Ig- and anti-CD40-induced B-cell proliferative responses. Moreover, addition of TNF-alpha during stimulation resulted in augmentation of B-cell proliferation, which was also inhibited by anti-TNF-alpha monoclonal antibody. Although lymphotoxin alpha (LT-alpha) mRNA is induced by both pathways, it is not blocked by CsA, whereas LT-beta mRNA is constitutively expressed in B cells. Thus, TNF-alpha is a necessary autocrine growth factor for human B cells stimulated via two independent CsA-sensitive pathways and plays a role similar to that of interleukin 2 in T-cell proliferation. The autocrine nature of TNF-alpha in activated B cells implies a potential role for this cytokine in infection-related polyclonal B-cell expansion and in B-cell malignancies.