Screening for tuberculosis infection and effectiveness of preventive treatment among people with HIV in low-incidence settings.

OBJECTIVE: To determine the yield of screening for latent tuberculosis infection (LTBI) among people with HIV (PWH) in low tuberculosis (TB) incidence countries (<10 TB cases per 100 000 persons). DESIGN: A systematic review and meta-analysis were performed to assess prevalence and predictive factors of LTBI, rate of TB progression, effect of TB preventive treatment (TPT), and numbers needed to screen (NNS). METHODS: PubMed and Cochrane Library were searched for studies reporting primary data, excluding studies on active or paediatric TB. We extracted LTBI cases, odds ratios, and TB incidences; pooled estimates using a random-effects model; and used the Newcastle-Ottawa scale for bias. RESULTS: In 51 studies with 65 930 PWH, 12% [95% confidence interval (CI) 10-14] had a positive LTBI test, which was strongly associated with origin from a TB-endemic country [odds ratio (OR) 4.7] and exposure to TB (OR 2.9). Without TPT (10 629 PWH), TB incidence was 28/1000 person-years (PY; 95% CI 12-45) for LTBI-test positive versus 4/1000 PY (95% CI 0-7) for LTBI-test-negative individuals. Among 625 PWH (1644 PY) receiving TPT, 15 developed TB (6/1000 PY). An estimated 20 LTBI-positive individuals would need TPT to prevent one case of TB, and numbers NNS to detect LTBI or prevent active TB varied according to a-priori risk of LTBI. CONCLUSION: The relatively high prevalence of LTBI among PWH and the strong correlation with origin from a TB-endemic country support risk-stratified LTBI screening strategies for PWH in low-incidence countries and treating those who test positive.

A difficult to treat Leishmania infantum relapse after allogeneic stem cell transplantation.

Here we describe a complicated case of a relapsed Leishmania infantum infection after an allogeneic stem cell transplantation (allo-SCT) for primary myelofibrosis. Three years earlier the patient had been diagnosed with a hemophagocytic lymphohistiocytosis secondary to a visceral Leishmania infantum infection, for which he was effectively treated with a cumulative dose of 40 mg/kg liposomal amphotericin B. During the first disease episode he was also diagnosed with primary myelofibrosis for which he received medical follow-up. One year later ruxolitinib was started due to progressive disease. No Leishmania relapse occurred. Nevertheless, the marrow fibrosis progressed, and an allo-SCT was performed. Two months after allo-SCT prolonged fever and a persistent pancytopenia occurred, which was due to a relapse of visceral Leishmaniasis. The infection was refractory to a prolonged treatment with liposomal amphotericin B with a cumulative dose up to 100 mg/kg. Salvage treatment with miltefosine led to reduction of fever within a few days and was followed by a slow recovery of pancytopenia over the following months. The Leishmania parasite load by PCR started to decline and after 3.5 months no Leishmania DNA could be detected anymore and follow-up until ten months afterwards did not show a relapse.

Opposing Effects of Interleukin-36γ and Interleukin-38 on Trained Immunity.

Trained immunity is the process of long-term functional reprogramming (a de facto innate immune memory) of innate immune cells such as monocytes and macrophages after an exposure to pathogens, vaccines, or their ligands. The induction of trained immunity is mediated through epigenetic and metabolic mechanisms. Apart from exogenous stimuli, trained immunity can be induced by endogenous compounds such as oxidized LDL, urate, fumarate, but also cytokines including IL-1α and IL-1ß. Here, we show that also recombinant IL-36γ, a pro-inflammatory cytokine of the IL-1-family, is able to induce trained immunity in primary human monocytes, demonstrated by higher cytokine responses and an increase in cellular metabolic pathways both regulated by epigenetic histone modifications. These effects could be inhibited by the IL-36 receptor antagonist as well as by IL-38, an anti-inflammatory cytokine of the IL-1 family which shares its main receptor with IL-36 (IL-1R6). Further, we demonstrated that trained immunity induced by IL-36γ is mediated by NF-κB and mTOR signaling. The inhibitory effect of IL-38 on IL-36γ-induced trained immunity was confirmed in experiments using bone marrow of IL-38KO and WT mice. These results indicate that exposure to IL-36γ results in long-term pro-inflammatory changes in monocytes which can be inhibited by IL-38. Recombinant IL-38 could therefore potentially be used as a therapeutic intervention for diseases characterized by exacerbated trained immunity.

Oncogene-induced maladaptive activation of trained immunity in the pathogenesis and treatment of Erdheim-Chester disease.

Trained immunity (TI) is a proinflammatory program induced in monocyte/macrophages upon sensing of specific pathogens and is characterized by immunometabolic and epigenetic changes that enhance cytokine production. Maladaptive activation of TI (ie, in the absence of infection) may result in detrimental inflammation and development of disease; however, the exact role and extent of inappropriate activation of TI in the pathogenesis of human diseases is undetermined. In this study, we uncovered the oncogene-induced, maladaptive induction of TI in the pathogenesis of a human inflammatory myeloid neoplasm (Erdheim-Chester disease, [ECD]), characterized by the BRAFV600E oncogenic mutation in monocyte/macrophages and excess cytokine production. Mechanistically, myeloid cells expressing BRAFV600E exhibit all molecular features of TI: activation of the AKT/mammalian target of rapamycin signaling axis; increased glycolysis, glutaminolysis, and cholesterol synthesis; epigenetic changes on promoters of genes encoding cytokines; and enhanced cytokine production leading to hyperinflammatory responses. In patients with ECD, effective therapeutic strategies combat this maladaptive TI phenotype; in addition, pharmacologic inhibition of immunometabolic changes underlying TI (ie, glycolysis) effectively dampens cytokine production by myeloid cells. This study revealed the deleterious potential of inappropriate activation of TI in the pathogenesis of human inflammatory myeloid neoplasms and the opportunity for inhibition of TI in conditions characterized by maladaptive myeloid-driven inflammation.

Metformin Alters Human Host Responses to Mycobacterium tuberculosis in Healthy Subjects.

BACKGROUND: Metformin, the most widely administered diabetes drug, has been proposed as a candidate adjunctive host-directed therapy for tuberculosis, but little is known about its effects on human host responses to Mycobacterium tuberculosis. METHODS: We investigated in vitro and in vivo effects of metformin in humans. RESULTS: Metformin added to peripheral blood mononuclear cells from healthy volunteers enhanced in vitro cellular metabolism while inhibiting the mammalian target of rapamycin targets p70S6K and 4EBP1, with decreased cytokine production and cellular proliferation and increased phagocytosis activity. Metformin administered to healthy human volunteers led to significant downregulation of genes involved in oxidative phosphorylation, mammalian target of rapamycin signaling, and type I interferon response pathways, particularly following stimulation with M. tuberculosis, and upregulation of genes involved in phagocytosis and reactive oxygen species production was increased. These in vivo effects were accompanied by a metformin-induced shift in myeloid cells from classical to nonclassical monocytes. At a functional level, metformin lowered ex vivo production of tumor necrosis factor α, interferon γ, and interleukin 1ß but increased phagocytosis activity and reactive oxygen species production. CONCLUSION: Metformin has a range of potentially beneficial effects on cellular metabolism, immune function, and gene transcription involved in innate host responses to M. tuberculosis.

Inhibiting Inflammation with Myeloid Cell-Specific Nanobiologics Promotes Organ Transplant Acceptance.

Inducing graft acceptance without chronic immunosuppression remains an elusive goal in organ transplantation. Using an experimental transplantation mouse model, we demonstrate that local macrophage activation through dectin-1 and toll-like receptor 4 (TLR4) drives trained immunity-associated cytokine production during allograft rejection. We conducted nanoimmunotherapeutic studies and found that a short-term mTOR-specific high-density lipoprotein (HDL) nanobiologic treatment (mTORi-HDL) averted macrophage aerobic glycolysis and the epigenetic modifications underlying inflammatory cytokine production. The resulting regulatory macrophages prevented alloreactive CD8+ T cell-mediated immunity and promoted tolerogenic CD4+ regulatory T (Treg) cell expansion. To enhance therapeutic efficacy, we complemented the mTORi-HDL treatment with a CD40-TRAF6-specific nanobiologic (TRAF6i-HDL) that inhibits co-stimulation. This synergistic nanoimmunotherapy resulted in indefinite allograft survival. Together, we show that HDL-based nanoimmunotherapy can be employed to control macrophage function in vivo. Our strategy, focused on preventing inflammatory innate immune responses, provides a framework for developing targeted therapies that promote immunological tolerance.

The Potential Role of Trained Immunity in Autoimmune and Autoinflammatory Disorders.

During induction of trained immunity, monocytes and macrophages undergo a functional and transcriptional reprogramming toward increased activation. Important rewiring of cellular metabolism of the myeloid cells takes place during induction of trained immunity, including a shift toward glycolysis induced through the mTOR pathway, as well as glutaminolysis and cholesterol synthesis. Subsequently, this leads to modulation of the function of epigenetic enzymes, resulting in important changes in chromatin architecture that enables increased gene transcription. However, in addition to the beneficial effects of trained immunity as a host defense mechanism, we hypothesize that trained immunity also plays a deleterious role in the induction and/or maintenance of autoimmune and autoinflammatory diseases if inappropriately activated.

Glutaminolysis and Fumarate Accumulation Integrate Immunometabolic and Epigenetic Programs in Trained Immunity.

Induction of trained immunity (innate immune memory) is mediated by activation of immune and metabolic pathways that result in epigenetic rewiring of cellular functional programs. Through network-level integration of transcriptomics and metabolomics data, we identify glycolysis, glutaminolysis, and the cholesterol synthesis pathway as indispensable for the induction of trained immunity by ß-glucan in monocytes. Accumulation of fumarate, due to glutamine replenishment of the TCA cycle, integrates immune and metabolic circuits to induce monocyte epigenetic reprogramming by inhibiting KDM5 histone demethylases. Furthermore, fumarate itself induced an epigenetic program similar to ß-glucan-induced trained immunity. In line with this, inhibition of glutaminolysis and cholesterol synthesis in mice reduced the induction of trained immunity by ß-glucan. Identification of the metabolic pathways leading to induction of trained immunity contributes to our understanding of innate immune memory and opens new therapeutic avenues.

ß-Glucan Reverses the Epigenetic State of LPS-Induced Immunological Tolerance.

Innate immune memory is the phenomenon whereby innate immune cells such as monocytes or macrophages undergo functional reprogramming after exposure to microbial components such as lipopolysaccharide (LPS). We apply an integrated epigenomic approach to characterize the molecular events involved in LPS-induced tolerance in a time-dependent manner. Mechanistically, LPS-treated monocytes fail to accumulate active histone marks at promoter and enhancers of genes in the lipid metabolism and phagocytic pathways. Transcriptional inactivity in response to a second LPS exposure in tolerized macrophages is accompanied by failure to deposit active histone marks at promoters of tolerized genes. In contrast, ß-glucan partially reverses the LPS-induced tolerance in vitro. Importantly, ex vivo ß-glucan treatment of monocytes from volunteers with experimental endotoxemia re-instates their capacity for cytokine production. Tolerance is reversed at the level of distal element histone modification and transcriptional reactivation of otherwise unresponsive genes. VIDEO ABSTRACT.

Adaptive Characteristics of Innate Immune Responses in Macrophages.

The innate immune system is considered to have no immune memory. However, lately there has been as shift in paradigm. Cells of the innate immune system, and especially monocytes and macrophages, are capable of building a nonspecific memory, resulting in either better or worse responses to secondary stimulations/infections, as a result of epigenetic changes. This review gives a general overview of the at-the-moment available data.

Immunometabolic circuits in trained immunity.

The classical view that only adaptive immunity can build immunological memory has recently been challenged. Both in organisms lacking adaptive immunity as well as in mammals, the innate immune system can adapt to mount an increased resistance to reinfection, a de facto innate immune memory termed trained immunity. Recent studies have revealed that rewiring of cellular metabolism induced by different immunological signals is a crucial step for determining the epigenetic changes underlying trained immunity. Processes such as a shift of glucose metabolism from oxidative phosphorylation to aerobic glycolysis, increased glutamine metabolism and cholesterol synthesis, play a crucial role in these processes. The discovery of trained immunity opens the door for the design of novel generations of vaccines, for new therapeutic strategies for the treatment of immune deficiency states, and for modulation of exaggerated inflammation in autoinflammatory diseases.

Broad defects in the energy metabolism of leukocytes underlie immunoparalysis in sepsis.

The acute phase of sepsis is characterized by a strong inflammatory reaction. At later stages in some patients, immunoparalysis may be encountered, which is associated with a poor outcome. By transcriptional and metabolic profiling of human patients with sepsis, we found that a shift from oxidative phosphorylation to aerobic glycolysis was an important component of initial activation of host defense. Blocking metabolic pathways with metformin diminished cytokine production and increased mortality in systemic fungal infection in mice. In contrast, in leukocytes rendered tolerant by exposure to lipopolysaccharide or after isolation from patients with sepsis and immunoparalysis, a generalized metabolic defect at the level of both glycolysis and oxidative metabolism was apparent, which was restored after recovery of the patients. Finally, the immunometabolic defects in humans were partially restored by therapy with recombinant interferon-γ, which suggested that metabolic processes might represent a therapeutic target in sepsis.

Transcriptional and metabolic reprogramming induce an inflammatory phenotype in non-medullary thyroid carcinoma-induced macrophages.

Tumor-associated macrophages (TAMs) are key components of the tumor microenvironment in non-medullary thyroid cancer (TC), the most common endocrine malignancy. However, little is known regarding the regulation of their function in TC. Transcriptome analysis in a model of TC-induced macrophages identified increased inflammatory characteristics and rewiring of cell metabolism as key functional changes. This functional reprogramming was partly mediated by TC-derived lactate that induced upregulation of cytokine production through an AKT1/mTOR-dependent increase in aerobic glycolysis. This led to epigenetic modifications at the level of histone methylation, and subsequently long-term functional changes. Immunohistochemistry assessment validated the increase in glycolysis enzymes and lactate receptor in TAMs in tissue samples from patients with TC. In conclusion, Akt/mTOR-dependent glycolysis mediates TC-induced reprogramming of TAMs and inflammation, and this may represent a novel therapeutic target in TC.

mTOR- and HIF-1α-mediated aerobic glycolysis as metabolic basis for trained immunity.

Epigenetic reprogramming of myeloid cells, also known as trained immunity, confers nonspecific protection from secondary infections. Using histone modification profiles of human monocytes trained with the Candida albicans cell wall constituent ß-glucan, together with a genome-wide transcriptome, we identified the induced expression of genes involved in glucose metabolism. Trained monocytes display high glucose consumption, high lactate production, and a high ratio of nicotinamide adenine dinucleotide (NAD(+)) to its reduced form (NADH), reflecting a shift in metabolism with an increase in glycolysis dependent on the activation of mammalian target of rapamycin (mTOR) through a dectin-1-Akt-HIF-1α (hypoxia-inducible factor-1α) pathway. Inhibition of Akt, mTOR, or HIF-1α blocked monocyte induction of trained immunity, whereas the adenosine monophosphate-activated protein kinase activator metformin inhibited the innate immune response to fungal infection. Mice with a myeloid cell-specific defect in HIF-1α were unable to mount trained immunity against bacterial sepsis. Our results indicate that induction of aerobic glycolysis through an Akt-mTOR-HIF-1α pathway represents the metabolic basis of trained immunity.