Intranasal pediatric parainfluenza virus-vectored SARS-CoV-2 vaccine is protective in monkeys.

Pediatric SARS-CoV-2 vaccines are needed that elicit immunity directly in the airways as well as systemically. Building on pediatric parainfluenza virus vaccines in clinical development, we generated a live-attenuated parainfluenza-virus-vectored vaccine candidate expressing SARS-CoV-2 prefusion-stabilized spike (S) protein (B/HPIV3/S-6P) and evaluated its immunogenicity and protective efficacy in rhesus macaques. A single intranasal/intratracheal dose of B/HPIV3/S-6P induced strong S-specific airway mucosal immunoglobulin A (IgA) and IgG responses. High levels of S-specific antibodies were also induced in serum, which efficiently neutralized SARS-CoV-2 variants of concern of alpha, beta, and delta lineages, while their ability to neutralize Omicron sub-lineages was lower. Furthermore, B/HPIV3/S-6P induced robust systemic and pulmonary S-specific CD4+ and CD8+ T cell responses, including tissue-resident memory cells in the lungs. Following challenge, SARS-CoV-2 replication was undetectable in airways and lung tissues of immunized macaques. B/HPIV3/S-6P will be evaluated clinically as pediatric intranasal SARS-CoV-2/parainfluenza virus type 3 vaccine.

Migration-induced cell shattering due to DOCK8 deficiency causes a type 2-biased helper T cell response.

Mutations that impact immune cell migration and result in immune deficiency illustrate the importance of cell movement in host defense. In humans, loss-of-function mutations in DOCK8, a guanine exchange factor involved in hematopoietic cell migration, lead to immunodeficiency and, paradoxically, allergic disease. Here, we demonstrate that, like humans, Dock8-/- mice have a profound type 2 CD4+ helper T (TH2) cell bias upon pulmonary infection with Cryptococcus neoformans and other non-TH2 stimuli. We found that recruited Dock8-/-CX3CR1+ mononuclear phagocytes are exquisitely sensitive to migration-induced cell shattering, releasing interleukin (IL)-1ß that drives granulocyte-macrophage colony-stimulating factor (GM-CSF) production by CD4+ T cells. Blocking IL-1ß, GM-CSF or caspase activation eliminated the type-2 skew in mice lacking Dock8. Notably, treatment of infected wild-type mice with apoptotic cells significantly increased GM-CSF production and TH2 cell differentiation. This reveals an important role for cell death in driving type 2 signals during infection, which may have implications for understanding the etiology of type 2 CD4+ T cell responses in allergic disease.

Label-free detection and profiling of individual solution-phase molecules.

Most chemistry and biology occurs in solution, in which conformational dynamics and complexation underlie behaviour and function. Single-molecule techniques1 are uniquely suited to resolving molecular diversity and new label-free approaches are reshaping the power of single-molecule measurements. A label-free single-molecule method2-16 capable of revealing details of molecular conformation in solution17,18 would allow a new microscopic perspective of unprecedented detail. Here we use the enhanced light-molecule interactions in high-finesse fibre-based Fabry-Pérot microcavities19-21 to detect individual biomolecules as small as 1.2 kDa, a ten-amino-acid peptide, with signal-to-noise ratios (SNRs) >100, even as the molecules are unlabelled and freely diffusing in solution. Our method delivers 2D intensity and temporal profiles, enabling the distinction of subpopulations in mixed samples. Notably, we observe a linear relationship between passage time and molecular radius, unlocking the potential to gather crucial information about diffusion and solution-phase conformation. Furthermore, mixtures of biomolecule isomers of the same molecular weight and composition but different conformation can also be resolved. Detection is based on the creation of a new molecular velocity filter window and a dynamic thermal priming mechanism that make use of the interplay between optical and thermal dynamics22,23 and Pound-Drever-Hall (PDH) cavity locking24 to reveal molecular motion even while suppressing environmental noise. New in vitro ways of revealing molecular conformation, diversity and dynamics can find broad potential for applications in the life and chemical sciences.

IL-10 suppresses T cell expansion while promoting tissue-resident memory cell formation during SARS-CoV-2 infection in rhesus macaques.

The regulation of inflammatory responses and pulmonary disease during SARS-CoV-2 infection is incompletely understood. Here we examine the roles of the prototypic pro- and anti-inflammatory cytokines IFNγ and IL-10 using the rhesus macaque model of mild COVID-19. We find that IFNγ drives the development of 18fluorodeoxyglucose (FDG)-avid lesions in the lungs as measured by PET/CT imaging but is not required for suppression of viral replication. In contrast, IL-10 limits the duration of acute pulmonary lesions, serum markers of inflammation and the magnitude of virus-specific T cell expansion but does not impair viral clearance. We also show that IL-10 induces the subsequent differentiation of virus-specific effector T cells into CD69+CD103+ tissue resident memory cells (Trm) in the airways and maintains Trm cells in nasal mucosal surfaces, highlighting an unexpected role for IL-10 in promoting airway memory T cells during SARS-CoV-2 infection of macaques.

Deductive automated pollen classification in environmental samples via exploratory deep learning and imaging flow cytometry.

Pollen and tracheophyte spores are ubiquitous environmental indicators at local and global scales. Palynology is typically performed manually by microscopic analysis; a specialised and time-consuming task limited in taxonomical precision and sampling frequency, therefore restricting data quality used to inform climate change and pollen forecasting models. We build on the growing work using AI (artificial intelligence) for automated pollen classification to design a flexible network that can deal with the uncertainty of broad-scale environmental applications. We combined imaging flow cytometry with Guided Deep Learning to identify and accurately categorise pollen in environmental samples; here, pollen grains captured within c. 5500 Cal yr BP old lake sediments. Our network discriminates not only pollen included in training libraries to the species level but, depending on the sample, can classify previously unseen pollen to the likely phylogenetic order, family and even genus. Our approach offers valuable insights into the development of a widely transferable, rapid and accurate exploratory tool for pollen classification in 'real-world' environmental samples with improved accuracy over pure deep learning techniques. This work has the potential to revolutionise many aspects of palynology, allowing a more detailed spatial and temporal understanding of pollen in the environment with improved taxonomical resolution.

Innate and adaptive interferons suppress IL-1α and IL-1ß production by distinct pulmonary myeloid subsets during Mycobacterium tuberculosis infection.

Interleukin-1 (IL-1) receptor signaling is necessary for control of Mycobacterium tuberculosis (Mtb) infection, yet the role of its two ligands, IL-1α and IL-1ß, and their regulation in vivo are poorly understood. Here, we showed that both IL-1α and IL-1ß are critically required for host resistance and identified two multifunctional inflammatory monocyte-macrophage and DC populations that coexpressed both IL-1 species at the single-cell level in lungs of Mtb-infected mice. Moreover, we demonstrated that interferons (IFNs) played important roles in regulating IL-1 production by these cells in vivo. Type I interferons inhibited IL-1 production by both subsets whereas CD4(+) T cell-derived IFN-γ selectively suppressed monocyte-macrophages. These data provide a cellular basis for both the anti-inflammatory effects of IFNs and probacterial functions of type I IFNs during Mtb infection and reveal differential regulation of IL-1 production by distinct cell populations as an additional layer of complexity in the activity of IL-1 in vivo.

Host-directed therapy of tuberculosis based on interleukin-1 and type I interferon crosstalk.

Tuberculosis remains second only to HIV/AIDS as the leading cause of mortality worldwide due to a single infectious agent. Despite chemotherapy, the global tuberculosis epidemic has intensified because of HIV co-infection, the lack of an effective vaccine and the emergence of multi-drug-resistant bacteria. Alternative host-directed strategies could be exploited to improve treatment efficacy and outcome, contain drug-resistant strains and reduce disease severity and mortality. The innate inflammatory response elicited by Mycobacterium tuberculosis (Mtb) represents a logical host target. Here we demonstrate that interleukin-1 (IL-1) confers host resistance through the induction of eicosanoids that limit excessive type I interferon (IFN) production and foster bacterial containment. We further show that, in infected mice and patients, reduced IL-1 responses and/or excessive type I IFN induction are linked to an eicosanoid imbalance associated with disease exacerbation. Host-directed immunotherapy with clinically approved drugs that augment prostaglandin E2 levels in these settings prevented acute mortality of Mtb-infected mice. Thus, IL-1 and type I IFNs represent two major counter-regulatory classes of inflammatory cytokines that control the outcome of Mtb infection and are functionally linked via eicosanoids. Our findings establish proof of concept for host-directed treatment strategies that manipulate the host eicosanoid network and represent feasible alternatives to conventional chemotherapy.

The Rate of CD4 T Cell Entry into the Lungs during Mycobacterium tuberculosis Infection Is Determined by Partial and Opposing Effects of Multiple Chemokine Receptors.

The specific chemokine receptors utilized by Th1 cells to migrate into the lung during Mycobacterium tuberculosis infection are unknown. We previously showed in mice that CXCR3+ Th1 cells enter the lung parenchyma and suppress M. tuberculosis growth, while CX3CR1+ KLRG1+ Th1 cells accumulate in the lung vasculature and are nonprotective. Here we quantify the contributions of these chemokine receptors to the migration and entry rate of Th1 cells into M. tuberculosis-infected lungs using competitive adoptive transfer migration assays and mathematical modeling. We found that in 8.6 h half of M. tuberculosis-specific CD4 T cells migrate from the blood to the lung parenchyma. CXCR3 deficiency decreases the average rate of Th1 cell entry into the lung parenchyma by half, while CX3CR1 deficiency doubles it. KLRG1 blockade has no effect on Th1 cell lung migration. CCR2, CXCR5, and, to a lesser degree, CCR5 and CXCR6 also promote the entry of Th1 cells into the lungs of infected mice. Moreover, blockade of G-protein-coupled receptors with pertussis toxin treatment prior to transfer only partially inhibits T cell migration into the lungs. Thus, the fraction of Th1 cell input into the lungs during M. tuberculosis infection that is regulated by chemokine receptors likely reflects the cumulative effects of multiple chemokine receptors that mostly promote but that can also inhibit entry into the parenchyma.

Limited Pulmonary Mucosal-Associated Invariant T Cell Accumulation and Activation during Mycobacterium tuberculosis Infection in Rhesus Macaques.

Mucosal-associated invariant T cells (MAITs) are positioned in airways and may be important in the pulmonary cellular immune response against Mycobacterium tuberculosis infection, particularly prior to priming of peptide-specific T cells. Accordingly, there is interest in the possibility that boosting MAITs through tuberculosis (TB) vaccination may enhance protection, but MAIT responses in the lungs during tuberculosis are poorly understood. In this study, we compared pulmonary MAIT and peptide-specific CD4 T cell responses in M. tuberculosis-infected rhesus macaques using 5-OP-RU-loaded MR-1 tetramers and intracellular cytokine staining of CD4 T cells following restimulation with an M. tuberculosis-derived epitope megapool (MTB300), respectively. Two of four animals showed a detectable increase in the number of MAIT cells in airways at later time points following infection, but by ∼3 weeks postexposure, MTB300-specific CD4 T cells arrived in the airways and greatly outnumbered MAITs thereafter. In granulomas, MTB300-specific CD4 T cells were ∼20-fold more abundant than MAITs. CD69 expression on MAITs correlated with tissue residency rather than bacterial loads, and the few MAITs found in granulomas poorly expressed granzyme B and Ki67. Thus, MAIT accumulation in the airways is variable and late, and MAITs display little evidence of activation in granulomas during tuberculosis in rhesus macaques.

Emergence of Polyfunctional Cytotoxic CD4+ T Cells in Mycobacterium avium Immune Reconstitution Inflammatory Syndrome in Human Immunodeficiency Virus-Infected Patients.

Background: Immune reconstitution inflammatory syndrome (IRIS) is an aberrant inflammatory response in individuals with advanced human immunodeficiency virus (HIV) infection, after antiretroviral therapy (ART) initiation. The pathogenesis of Mycobacterium avium complex (MAC)-associated IRIS has not been fully elucidated. Methods: We investigated monocyte and CD4+ T-cell responses in vitro, tumor necrosis factor (TNF) expression in tissues, and plasma cytokines and inflammatory markers, in 13 HIV-infected patients with MAC-IRIS and 14 HIV-uninfected patients with pulmonary MAC infection. Results: Prior to ART, HIV-infected compared with HIV-uninfected patients, had reduced TNF+ monocytes (P = .013), although similar cytokine (interferon gamma [IFN-γ], TNF, interleukin 2 [IL-2], and interleukin 17 [IL-17])-expressing CD4+ T cells. During IRIS, monocyte cytokine production was restored. IFN-γ+ (P = .027), TNF+ (P = .004), and polyfunctional CD4+ T cells (P = 0.03) also increased. These effectors were T-betlow, and some expressed markers of degranulation and cytotoxic potential. Blockade of cytotoxic T-lymphocyte associated protein 4 and lymphocyte activation gene-3 further increased CD4+ T-cell cytokine production. Tissue immunofluorescence showed higher proportions of CD4+ and CD68+ (monocyte/macrophage) cells expressed TNF during IRIS compared with HIV-uninfected patients. Plasma IFN-γ (P = .048), C-reactive protein (P = .008), and myeloperoxidase (P < .001) levels also increased, whereas interleukin 10 decreased (P = .008) during IRIS. Conclusions: Advanced HIV infection was associated with impaired MAC responses. Restoration of monocyte responses and expansion of polyfunctional MAC-specific T-betlow CD4+ T cells with cytotoxic potential after ART initiation may overwhelm existing regulatory and inhibitory mechanisms, leading to MAC-IRIS.

CD4 T Cell-Derived IFN-γ Plays a Minimal Role in Control of Pulmonary Mycobacterium tuberculosis Infection and Must Be Actively Repressed by PD-1 to Prevent Lethal Disease.

IFN-γ-producing CD4 T cells are required for protection against Mycobacterium tuberculosis (Mtb) infection, but the extent to which IFN-γ contributes to overall CD4 T cell-mediated protection remains unclear. Furthermore, it is not known if increasing IFN-γ production by CD4 T cells is desirable in Mtb infection. Here we show that IFN-γ accounts for only ~30% of CD4 T cell-dependent cumulative bacterial control in the lungs over the first six weeks of infection, but >80% of control in the spleen. Moreover, increasing the IFN-γ-producing capacity of CD4 T cells by ~2 fold exacerbates lung infection and leads to the early death of the host, despite enhancing control in the spleen. In addition, we show that the inhibitory receptor PD-1 facilitates host resistance to Mtb by preventing the detrimental over-production of IFN-γ by CD4 T cells. Specifically, PD-1 suppressed the parenchymal accumulation of and pathogenic IFN-γ production by the CXCR3+KLRG1-CX3CR1- subset of lung-homing CD4 T cells that otherwise mediates control of Mtb infection. Therefore, the primary role for T cell-derived IFN-γ in Mtb infection is at extra-pulmonary sites, and the host-protective subset of CD4 T cells requires negative regulation of IFN-γ production by PD-1 to prevent lethal immune-mediated pathology.

Orchestration of pulmonary T cell immunity during Mycobacterium tuberculosis infection: immunity interruptus.

Despite the introduction almost a century ago of Mycobacterium bovis BCG (BCG), an attenuated form of M. bovis that is used as a vaccine against Mycobacterium tuberculosis, tuberculosis remains a global health threat and kills more than 1.5 million people each year. This is mostly because BCG fails to prevent pulmonary disease--the contagious form of tuberculosis. Although there have been significant advances in understanding how the immune system responds to infection, the qualities that define protective immunity against M. tuberculosis remain poorly characterized. The ability to predict who will maintain control over the infection and who will succumb to clinical disease would revolutionize our approach to surveillance, control, and treatment. Here we review the current understanding of pulmonary T cell responses following M. tuberculosis infection. While infection elicits a strong immune response that contains infection, M. tuberculosis evades eradication. Traditionally, its intracellular lifestyle and alteration of macrophage function are viewed as the dominant mechanisms of evasion. Now we appreciate that chronic inflammation leads to T cell dysfunction. While this may arise as the host balances the goals of bacterial sterilization and avoidance of tissue damage, it is becoming clear that T cell dysfunction impairs host resistance. Defining the mechanisms that lead to T cell dysfunction is crucial as memory T cell responses are likely to be subject to the same subject to the same pressures. Thus, success of T cell based vaccines is predicated on memory T cells avoiding exhaustion while at the same time not promoting overt tissue damage.

Lethal CD4 T Cell Responses Induced by Vaccination Against Staphylococcus aureus Bacteremia.

Multiple candidate vaccines against Staphylococcus aureus infections have failed in clinical trials. Analysis of a recent prematurely halted vaccine trial revealed increased mortality rates among vaccine recipients in whom postsurgical S. aureus infection developed, emphasizing the potential for induction of detrimental immune responses and the need to better understand the requirements for protective immunity against S. aureus. These failures of single-antigen vaccines have prompted ongoing development of multicomponent vaccines to target the multitude of S. aureus virulence factors. In the current study, we used lethally irradiated S. aureus as a model multicomponent vaccine and showed that vaccination of mice decreased survival in a bacteremia challenge model. These deleterious effects were due to a CD4 T-cell-dependent interferon γ response and could be prevented by inhibiting development of this response during vaccination. Our results identify the potential for vaccination to induce pathological immune responses, and they have implications for recent vaccine failures and the design of future staphylococcal vaccines.

Type I IFN Induction via Poly-ICLC Protects Mice against Cryptococcosis.

Cryptococcus neoformans is the most common cause of fungal meningoencephalitis in AIDS patients. Depletion of CD4 cells, such as occurs during advanced AIDS, is known to be a critical risk factor for developing cryptococcosis. However, the role of HIV-induced innate inflammation in susceptibility to cryptococcosis has not been evaluated. Thus, we sought to determine the role of Type I IFN induction in host defense against cryptococci by treatment of C. neoformans (H99) infected mice with poly-ICLC (pICLC), a dsRNA virus mimic. Unexpectedly, pICLC treatment greatly extended survival of infected mice and reduced fungal burdens in the brain. Protection from cryptococcosis by pICLC-induced Type I IFN was mediated by MDA5 rather than TLR3. PICLC treatment induced a large, rapid and sustained influx of neutrophils and Ly6Chigh monocytes into the lung while suppressing the development of eosinophilia. The pICLC-mediated protection against H99 was CD4 T cell dependent and analysis of CD4 T cell polyfunctionality showed a reduction in IL-5 producing CD4 T cells, marginal increases in Th1 cells and dramatic increases in RORγt+ Th17 cells in pICLC treated mice. Moreover, the protective effect of pICLC against H99 was diminished in IFNγ KO mice and by IL-17A neutralization with blocking mAbs. Furthermore, pICLC treatment also significantly extended survival of C. gattii infected mice with reduced fungal loads in the lungs. These data demonstrate that induction of type I IFN dramatically improves host resistance against the etiologic agents of cryptococcosis by beneficial alterations in both innate and adaptive immune responses.

Prevalence and correlates of antibiotic sharing in the Philippines: antibiotic misconceptions and community-level access to non-medical sources of antibiotics.

OBJECTIVE: To identify sociodemographic, knowledge and attitudinal correlates to antibiotic sharing among a community-based sample of adults (age 18 and older) in a low-income setting of the Philippines and to explore community-level data on informal antibiotic distribution in roadside stands (i.e., sari-sari stands). METHODS: Participants (n = 307) completed self-administered surveys. Correlates to antibiotic sharing were assessed using logistic regression with Firth's bias-adjusted estimates. Study staff also visited 106 roadside stands and collected data on availability and characteristics of antibiotics in the stands. RESULTS: 78% had shared antibiotics in their lifetime, most often with family members. In multivariable analysis, agreement with the belief that it is safe to prematurely stop an antibiotic course (OR: 2.8, CI: 1.3-5.8) and concerns about antibiotic side effects (OR: 2.1, CI: 1.1-4.4) were significantly associated with increased odds of reported antibiotic sharing. Antibiotic sharing was not associated with sociodemographic characteristics or antibiotic knowledge. Antibiotics were widely available in 60% of sampled sari-sari stands, in which 59% of antibiotics were missing expiration dates. Amoxicillin and cephalexin were the most commonly available antibiotics for sale at the stands (60% and 21%, respectively). CONCLUSIONS: Antibiotic sharing was common and was associated with misconceptions about proper antibiotic use. Antibiotics were widely available in sari-sari stands, and usually without expiration information. This study suggests that multipronged and locally tailored approaches to curbing informal antibiotic access are needed in the Philippines and similar Southeast-Asian countries.

Heme Oxygenase-1 Regulation of Matrix Metalloproteinase-1 Expression Underlies Distinct Disease Profiles in Tuberculosis.

Pulmonary tuberculosis (TB) is characterized by oxidative stress and lung tissue destruction by matrix metalloproteinases (MMPs). The interplay between these distinct pathological processes and the implications for TB diagnosis and disease staging are poorly understood. Heme oxygenase-1 (HO-1) levels were previously shown to distinguish active from latent TB, as well as successfully treated Mycobacterium tuberculosis infection. MMP-1 expression is also associated with active TB. In this study, we measured plasma levels of these two important biomarkers in distinct TB cohorts from India and Brazil. Patients with active TB expressed either very high levels of HO-1 and low levels of MMP-1 or the converse. Moreover, TB patients with either high HO-1 or MMP-1 levels displayed distinct clinical presentations, as well as plasma inflammatory marker profiles. In contrast, in an exploratory North American study, inversely correlated expression of HO-1 and MMP-1 was not observed in patients with other nontuberculous lung diseases. To assess possible regulatory interactions in the biosynthesis of these two enzymes at the cellular level, we studied the expression of HO-1 and MMP-1 in M. tuberculosis-infected human and murine macrophages. We found that infection of macrophages with live virulent M. tuberculosis is required for robust induction of high levels of HO-1 but not MMP-1. In addition, we observed that CO, a product of M. tuberculosis-induced HO-1 activity, inhibits MMP-1 expression by suppressing c-Jun/AP-1 activation. These findings reveal a mechanistic link between oxidative stress and tissue remodeling that may find applicability in the clinical staging of TB patients.

Severe Paradoxical Reaction During Treatment of Disseminated Tuberculosis in a Patient With Neutralizing Anti-IFNγ Autoantibodies.

Interferon-gamma (IFNγ) neutralizing autoantibodies are associated with disseminated nontuberculous mycobacterial infections. We report a previously healthy Thai woman with disseminated tuberculosis and high-titer IFNγ-neutralizing autoantibodies, who developed a severe inflammatory reaction during anti-tuberculosis treatment. IFNγ contributes to host control of tuberculosis but appears inessential for tuberculosis paradoxical reactions.

DprA is required for natural transformation and affects pilin variation in Neisseria gonorrhoeae.

Natural transformation is the main means of horizontal genetic exchange in the obligate human pathogen Neisseria gonorrhoeae and drives the spread of antibiotic resistance and virulence determinants. Transformation can be divided into four steps: (1) DNA binding, (2) DNA uptake, (3) DNA processing and (4) DNA recombination into the chromosome. The DNA processing enzyme DprA has been shown to shuttle incoming ssDNA to the recombination enzyme RecA during transformation in Bacillus subtilis and Streptococcus pneumoniae. Here, we investigate the role of DprA during transformation in N. gonorrhoeae. Inactivation of dprA completely abrogated transformation of gyrB1-encoding DNA, which confers nalidixic acid resistance. The presence of the DNA uptake sequence enhances DNA uptake and transformation by binding to the minor pilus protein ComP. Loss of transformation in the dprA null mutants was independent of the DNA uptake sequence. DprA mutants exhibited increased RecA-dependent pilin variation suggesting that DprA affects pilin variation. Unlike the exquisite UV sensitivity of a recA mutant, inactivation of dprA did not affect survival following UV irradiation. These results demonstrate that DprA has a conserved function during transformation, and reveal additional effects of DprA in N. gonorrhoeae during pilin variation.

Mycobacterial antigen driven activation of CD14++CD16- monocytes is a predictor of tuberculosis-associated immune reconstitution inflammatory syndrome.

Paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is an aberrant inflammatory response occurring in a subset of TB-HIV co-infected patients initiating anti-retroviral therapy (ART). Here, we examined monocyte activation by prospectively quantitating pro-inflammatory plasma markers and monocyte subsets in TB-HIV co-infected patients from a South Indian cohort at baseline and following ART initiation at the time of IRIS, or at equivalent time points in non-IRIS controls. Pro-inflammatory biomarkers of innate and myeloid cell activation were increased in plasma of IRIS patients pre-ART and at the time of IRIS; this association was confirmed in a second cohort in South Africa. Increased expression of these markers correlated with elevated antigen load as measured by higher sputum culture grade and shorter duration of anti-TB therapy. Phenotypic analysis revealed the frequency of CD14(++)CD16(-) monocytes was an independent predictor of TB-IRIS, and was closely associated with plasma levels of CRP, TNF, IL-6 and tissue factor during IRIS. In addition, production of inflammatory cytokines by monocytes was higher in IRIS patients compared to controls pre-ART. These data point to a major role of mycobacterial antigen load and myeloid cell hyperactivation in the pathogenesis of TB-IRIS, and implicate monocytes and monocyte-derived cytokines as potential targets for TB-IRIS prevention or treatment.

Role of IL-6 in Mycobacterium avium--associated immune reconstitution inflammatory syndrome.

Immune reconstitution inflammatory syndrome (IRIS) is a major adverse event of antiretroviral therapy in HIV infection, and paradoxically occurs as HIV viremia is suppressed and CD4 T cell numbers recover. IRIS reflects pathogenic immune responses against opportunistic infections acquired during the period of immunodeficiency, but little is understood about the mechanisms of inflammatory pathology. In this study, we show that IL-6 and C-reactive protein levels transiently rise at the time of the IRIS event in HIV-infected patients, unmasking Mycobacterium avium complex infection after starting antiretroviral therapy. To directly test the role of IL-6 in IRIS pathology, we used a model of experimentally inducible IRIS in which M. avium-infected T cell-deficient mice undergo a fatal inflammatory disease after reconstitution with CD4 T cells. We find that IL-6 neutralization reduces C-reactive protein levels, alleviates wasting disease, and extends host survival during experimental IRIS. Moreover, we show that combined blockade of IL-6 and IFN-γ further reduces IRIS pathology, even after the onset of wasting disease. The combination of these clinical and experimental-model data show that the IL-6 pathway is not only a biomarker of mycobacterial IRIS but also a major mediator of pathology distinct from IFN-γ and may be a useful target for therapeutic intervention.