Human host genetic factors in nontuberculous mycobacterial infection: lessons from single gene disorders affecting innate and adaptive immunity and lessons from molecular defects in interferon-gamma-dependent signaling

The detectable anti-interferon-γ autoantibodies in COVID-19 patients may be associated with disease severity

BACKGROUND

Neutralizing anti-interferon (IFN)-γ autoantibodies are linked to adult-onset immunodeficiency and opportunistic infections.

METHODS

To explore whether anti-IFN-γ autoantibodies are associated with disease severity of coronavirus disease 2019 (COVID-19), we examined the titers and functional neutralization of anti-IFN-γ autoantibodies in COVID-19 patients. In 127 COVID-19 patients and 22 healthy controls, serum titers of anti-IFN-γ autoantibodies were quantified using enzyme-linked immunosorbent assay, and the presence of autoantibodies was verified with immunoblotting assay. The neutralizing capacity against IFN-γ was evaluated with flow cytometry analysis and immunoblotting, and serum cytokines levels were determined using the MULTIPLEX platform.

RESULTS

A higher proportion of severe/critical COVID-19 patients had positivity for anti-IFN-γ autoantibodies (18.0%) compared with non-severe patients (3.4%, p < 0.01) or healthy control (HC) (0.0%, p < 0.05). Severe/critical COVID-19 patients also had higher median titers of anti-IFN-γ autoantibodies (5.01) compared with non-severe patients (1.33) or HC (0.44). The immunoblotting assay could verify the detectable anti-IFN-γ autoantibodies and revealed more effective inhibition of signal transducer and activator of transcription (STAT1) phosphorylation on THP-1 cells treated with serum samples from anti-IFN-γ autoantibodies-positive patients compared with those from HC (2.21 ± 0.33 versus 4.47 ± 1.64, p < 0.05). In flow-cytometry analysis, sera from autoantibodies-positive patients could also significantly more effectively suppress the STAT1 phosphorylation (median,67.28%, interquartile range [IQR] 55.2-78.0%) compared with serum from HC (median,106.7%, IQR 100.0-117.8%, p < 0.05) or autoantibodies-negative patients (median,105.9%, IQR 85.5-116.3%, p < 0.05). Multivariate analysis revealed that the positivity and titers of anti-IFN-γ autoantibodies were significant predictors of severe/critical COVID-19. Compared with non-severe COVID-19 patients, we reveal that a significantly higher proportion of severe/critical COVID-19 patients are positive for anti-IFN-γ autoantibodies with neutralizing capacity.

CONCLUSION

Our results would add COVID-19 to the list of diseases with the presence of neutralizing anti-IFN-γ autoAbs. Anti-IFN-γ autoantibodies positivity is a potential predictor of severe/critical COVID-19.

High-titer anti-interferon-γ neutralizing autoantibodies linked to opportunistic infections in patients with adult-onset still's disease

Objective

Neutralizing anti-interferon (IFN)-γ autoantibodies are linked to opportunistic infections (OIs). To explore the association between anti-IFN-γ autoantibodies and OIs in patients with adult-onset Still's disease (AOSD), we aimed to examine the ability of these autoantibodies to blockade signal transducer and activator of transcription (STAT1)-phosphorylation and chemokines production.

Methods

Serum titers of anti-IFN-γ autoantibodies were quantified using ELISA in 29 AOSD and 22 healthy controls (HC). The detectable autoantibodies were verified with immunoblotting assay, and their neutralizing capacity against IFN-γ-signaling was evaluated with flow-cytometry analysis and immunoblotting. IFN-γ-mediated production of supernatant chemokines, including monocyte chemoattractant protein-1 (MCP-1) and IFN-γ inducible protein-10 (IP-10), were measured by ELISA.

Results

Among 29 AOSD patients, high titers of anti-IFN-γ neutralizing autoantibodies were detectable in two patients with OIs. Immunoblotting assay revealed more effective inhibition of STAT1-phosphorylation in THP-1 cells treated with sera from autoantibody-positive AOSD patients (56.7 ± 34.79%) compared with those from HC (104.3 ±29.51%), which was also demonstrated in flow-cytometry analysis (47.13 ± 40.99 vs. 97.92 ± 9.48%, p < 0.05). Depleted serum IgG from anti-IFN-γ autoAbs-positive AOSD patients with OIs restored phosphorylated STAT-1 upon IFN-γ treatment. Sera from autoantibody-positive AOSD patients more effectively inhibited IFN-γ-mediated production of MCP-1 (45.65 pg/ml) and IP-10 (22.44 pg/ml) than sera from HC (263.1 pg/ml and 104.0 pg/ml, both p < 0.05). Serum samples showing the strongest inhibition of IFN-γ-signaling were from two patients with high-titer autoantibodies and OIs.

Conclusion

AOSD patients have a high positive rate and titers of anti-IFN-γ autoantibodies. The remarkable blockade effect of high-titer autoantibodies on IFN-γ-mediated STAT1-phosphorylation and chemokines could make these patients susceptible to OIs.

Mycobacterium avium Modulates the Protective Immune Response in Canine Peripheral Blood Mononuclear Cells

Mycobacterium avium, an opportunistic intracellular pathogen, is a member of the non-tuberculous mycobacteria species. M. avium causes respiratory disease in immunosuppressed individuals and a wide range of animals, including companion dogs and cats. In particular, the number of infected companion dogs has increased, although the underlying mechanism of M. avium pathogenesis in dogs has not been studied. Therefore, in the present study, the host immune response against M. avium in dogs was investigated by transcriptome analysis of canine peripheral blood mononuclear cells. M. avium was shown to induce different immune responses in canine peripheral blood mononuclear cells at different time points after infection. The expression of Th1-associated genes occurred early during M. avium infection, while that of Th17-associated genes increased after 12 h. In addition, the expression of apoptosis-related genes decreased and the abundance of intracellular M. avium increased in monocyte-derived macrophages after infection for 24 h. These results reveal the M. avium induces Th17 immune response and avoids apoptosis in infected canine cells. As the number of M. avium infection cases increases, the results of the present study will contribute to a better understanding of host immune responses to M. avium infection in companion dogs.

Immunological Evaluation for Personalized Interventions in Children with Tuberculosis: Should It Be Routinely Performed?

Childhood tuberculosis (TB) is a significant public health problem and the ninth leading cause of death worldwide. Progression of Mycobacterium tuberculosis infection to active disease depends on mycobacterial virulence, environmental diversity, and host susceptibility and immune response. In children, malnutrition and immaturity of the immune system contribute to an inadequate immune response. Coinfections, though rarely described in TB, might be associated with host immune deficiencies. Here, we describe the immunological evaluation of eight pediatric patients infected with a member of the M. tuberculosis complex, most of them with concomitant pulmonary infections (bacteria, viruses, or fungi). We assessed the functionality of several innate immunity receptors, IL-12 receptor, and IFN-γ receptor, as well as the antioxidant levels (glutathione), which are essential mechanisms for fighting intracellular pathogens such as M. tuberculosis. This study is aimed at developing a thorough immunological evaluation of patients with TB and a coinfection.

The Rise of Non-Tuberculosis Mycobacterial Lung Disease

The incidence and number of deaths from non-tuberculous mycobacterial (NTM) disease have been steadily increasing globally. These lesser known “cousins” of Mycobacterium tuberculosis (TB) were once thought to be harmless environmental saprophytics and only dangerous to individuals with defective lung structure or the immunosuppressed. However, NTM are now commonly infecting seemingly immune competent children and adults at increasing rates through pulmonary infection. This is of concern as the pathology of NTM is difficult to treat. Indeed, NTM have become extremely antibiotic resistant, and now have been found to be internationally dispersed through person-to-person contact. The reasons behind this NTM increase are only beginning to be elucidated. Solutions to the problem are needed given NTM disease is more common in the tropics. Importantly, 40% of the world's population live in the tropics and due to climate change, the Tropics are expanding which will increase NTM infection regions. This review catalogs the global and economic disease burden, at risk populations, treatment options, host-bacterial interaction, immune dynamics, recent developments and research priorities for NTM disease.

Microscopic polyangiitis secondary to Mycobacterium abscessus in a patient with bronchiectasis: a case report

Background

Non-Tuberculous Mycobacterial–pulmonary disease (NTM-PD) is increasing in incidence and prevalence. Mycobacterium abscessus (M.abscessus) is a rapid growing multi-resistant NTM associated with severe NTM-PD requiring prolonged antibiotic therapy. Complications of therapy are common but reports on direct complications of active NTM-PD are rare. Vasculitis has been described as a rare complication of NTM-PD, most often in individuals with inherited immune defects. This case is the first to describe an ANCA positive vasculitide (Microscopic Polyangiitis) secondary to M.abscessus pulmonary disease.

Case presentation

A 70 year old female with bronchiectasis underwent a clinical decline associated with the growth of M.abscessus and was diagnosed with NTM-PD. Before treatment could be initiated she developed small joint arthralgia and a glove and stocking axonal loss sensorimotor neuropathy. Positive Perinuclear Anti-Neutrophil Cytoplasmic Antibodies (P-ANCA) and Myeloperoxidase-ANCA (MPO-ANCA) titres led to a diagnosis of microscopic polyangiitis. Further investigation revealed reduced interferon-gamma production but no other significant immune dysfunction.

Dual treatment with immunosuppressive therapy (Corticosteroids/Cyclophosphamide) for vasculitis and antimicrobial therapy for M.abscessus NTM-PD was initiated. Clinical stability was difficult to achieve with reductions in immunosuppression triggering vasculitic flares. One flare led to retinal vein occlusion with impending visual loss requiring escalation in immunosuppression to Rituximab infusions. An increase in immunosuppression led to a deterioration in NTM-PD necessitating alterations to antibiotic regimes. Adverse effects including alopecia and Achilles tendonitis have further limited antibiotic choices resulting in a strategy of pulsed intra-venous therapy to stabilise NTM-PD.

Conclusions

This is the first reported case of an ANCA positive vasculitis secondary to M.abscessus pulmonary disease. This rare but important complication had a significant impact on the patient adding to the complexity of an already significant disease and treatment burden. The potential role of reduced interferon-gamma production in this case highlights the importance of investigating immune function in those with mycobacterial infection and the intricate relationship between mycobacterial infection and immune dysfunction. Immune dysfunction caused by genetic defects or immunosuppressive therapy is a known risk factor for NTM-PD. Balancing immunosuppressive therapy with prolonged antimicrobial treatment is challenging and likely to become more common as the number of individuals being treated with biologics and immunosuppressive agents increases.

[Nontuberculous mycobacterial infections]

Nontuberculous mycobacterial (NTM) are found ubiquitously in the environment and are usually of low pathogenicity. Infection occurs via inhalation of aerosols, and some species may cause severe infections. The incidence of NTM infections is rising worldwide. The risk of developing NTM disease depends on the susceptibility of the host as well as the frequency and duration of exposure. In addition to congenital immune deficiencies and immunosuppressive therapy, structural lung and systemic diseases, including rheumatoid arthritis (RA), are associated with an increased risk for NTM infections. The immune response to NTM is complex and relies on the interplay between professional phagocytes and lymphoid cells. This interplay is concerted by three key cytokines: interleukin-12 (IL-12), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ). Targeted immunotherapies, e. g., treatment with TNF inhibitors, interfere with these essential pathways and increase the risk of NTM infection significantly. This review focuses on the relationship between the immune response to NTM and intrinsic and iatrogenic dispositions for NTM infection, with an emphasis on RA.

The Distribution Frequency of Interferon-Gamma Receptor 1 Gene Polymorphisms in Interferon-γ Release Assay-Positive Patients

Tuberculosis is caused by mycobacterium, a potentially fatal infectious bacterium. In recent years, TB cases increased in the whole world. WHO statistics data shows that the world's annual tuberculosis incidence was 8~10 million with about 3 million deaths. Several studies have shown that susceptibility to tuberculosis may be associated with IFNGR1 gene polymorphisms. Here, we report the distribution frequency of IFNGR1 gene polymorphisms in 103 cases of IGA-negative patients and 100 cases of IGA-positive patients from China by sequencing the IFNGR1 proximal ~750 bp promoter region. We found a total of 5 types of site mutations: -611 (G/A), -56 (T/C), -255 (C/T), -359 (T/C), and -72 (C/T). The two main types of gene polymorphisms among the IGA-negative and IGA-positive groups were -611 (G/A), with mutation rates of 88.3% and 78.4%, respectively, and -56 (T/C), with mutation rates of 84.5% and 83.8%, respectively, which had no statistical significance, and there was no correlation with the incidence of tuberculosis.

Post-translational modification of the interferon-gamma receptor alters its stability and signaling

The IFN gamma receptor 1 (IFNGR1) binds IFN-γ and activates gene transcription pathways crucial for controlling bacterial and viral infections. Although decreases in IFNGR1 surface levels have been demonstrated to inhibit IFN-γ signaling, little is known regarding the molecular mechanisms controlling receptor stability. Here, we show in epithelial and monocytic cell lines that IFNGR1 displays K48 polyubiquitination, is proteasomally degraded, and harbors three ubiquitin acceptor sites at K277, K279, and K285. Inhibition of glycogen synthase kinase 3 beta (GSK3β) destabilized IFNGR1 while overexpression of GSK3β increased receptor stability. We identified critical serine and threonine residues juxtaposed to ubiquitin acceptor sites that impacted IFNGR1 stability. In CRISPR-Cas9 IFNGR1 generated knockout cell lines, cellular expression of IFNGR1 plasmids encoding ubiquitin acceptor site mutations demonstrated significantly impaired STAT1 phosphorylation and decreased STAT1-dependent gene induction. Thus, IFNGR1 undergoes rapid site-specific polyubiquitination, a process modulated by GSK3β. Ubiquitination appears to be necessary for efficient IFNGR1-dependent gamma gene induction and represents a relatively uncharacterized regulatory mechanism for this receptor.

Polyfunctional CD4+ T Cells As Targets for Tuberculosis Vaccination

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a leading cause of morbidity and mortality worldwide, despite the widespread use of the only licensed vaccine, Bacille Calmette Guerin (BCG). Eradication of TB will require a more effective vaccine, yet evaluation of new vaccine candidates is hampered by lack of defined correlates of protection. Animal and human studies of intracellular pathogens have extensively evaluated polyfunctional CD4⁺ T cells producing multiple pro-inflammatory cytokines (IFN-γ, TNF-α, and IL-2) as a possible correlate of protection from infection and disease. In this study, we review the published literature that evaluates whether or not BCG and/or novel TB vaccine candidates induce polyfunctional CD4⁺ T cells and if these T cell responses correlate with vaccine-mediated protection. Ample evidence suggests that BCG and several novel vaccine candidates evaluated in animal models and humans induce polyfunctional CD4⁺ T cells. However, while a number of studies utilizing the mouse TB model support that polyfunctional CD4⁺ T cells are associated with vaccine-induced protection, other studies in mouse and human infants demonstrate no correlation between these T cell responses and protection. We conclude that induction of polyfunctional CD4⁺ T cells is certainly not sufficient and may not even be necessary to mediate protection and suggest that other functional attributes, such as additional effector functions, T cell differentiation state, tissue homing potential, or long-term survival capacity of the T cell may be equally or more important to promote protection. Thus, a correlate of protection for TB vaccine development remains elusive. Future studies should address polyfunctional CD4⁺ T cells within the context of more comprehensive immunological signatures of protection that include other functions and phenotypes of T cells as well as the full spectrum of immune cells and mediators that participate in the immune response against Mtb.

Mycobacterium abscessus D-alanyl-D-alanine dipeptidase induces the maturation of dendritic cells and promotes Th1-biased immunity

Mycobacterium abscessus, a member of the group of non-tuberculous mycobacteria, has been identified as an emerging pulmonary pathogen in humans. However, little is known about the protective immune response of antigen-presenting cells, such as dendritic cells (DCs), which guard against M. abscessus infection. The M. abscessus gene MAB1843 encodes ᴅ-alanyl-ᴅ-alanine dipeptidase, which catalyzes the hydrolysis of ᴅ-alanyl-ᴅ-alanine dipeptide. We investigated whether MAB1843 is able to interact with DCs to enhance the effectiveness of the host’s immune response. MAB1843 was found to induce DC maturation via toll-like receptor 4 and its downstream signaling pathways, such as the mitogen-activated protein kinase and nuclear factor kappa B pathways. In addition, MAB1843-treated DCs stimulated the proliferation of T cells and promoted Th1 polarization. Our results indicate that MAB1843 could potentially regulate the immune response to M. abscessus, making it important in the development of an effective vaccine against this mycobacterium. [BMB Reports 2016; 49(10): 554-559]

Airway delivery of interferon-γ overexpressing macrophages confers resistance to Mycobacterium avium infection in SCID mice

Mycobacterium avium (M. avium) causes significant pulmonary infection, especially in immunocompromised hosts. Alveolar macrophages (AMs) represent the first line of host defense against infection in the lung. Interferon gamma (IFN‐γ) activation of AMs enhances in vitro killing of pathogens such as M. avium. We hypothesized that airway delivery of AMs into the lungs of immunodeficient mice infected with M. avium will inhibit M. avium growth in the lung and that this macrophage function is in part IFN‐γ dependent. In this study, normal BALB/c and BALB/c SCID mice received M. avium intratracheally while on mechanical ventilation. After 30 days, M. avium numbers increased in a concentration‐dependent manner in SCID mice compared with normal BALB/c mice. Airway delivery of IFN‐γ‐activated BALB/c AMs or J774A.1 macrophages overexpressing IFN‐γ into the lungs of SCID mice resulted in a significant decrease in M. avium growth (P < 0.01, both comparisons) and limited dissemination to other organs. In addition, airway delivery of IFN‐γ activated AMs and macrophages overexpressing IFN‐γ increased the levels of IFN‐γ and TNF‐α in SCID mice. A similar protective effect against M. avium infection using J774A.1 macrophages overexpressing IFN‐γ was observed in IFN‐γ knockout mice. These data suggest that administration of IFN‐γ activated AMs or macrophages overexpressing IFN‐γ may partially restore local alveolar host defense against infections like M. avium, even in the presence of ongoing systemic immunosuppression.

A Rhesus Macaque Model of Pulmonary Nontuberculous Mycobacterial Disease

In this study, we sought to develop a nonhuman primate model of pulmonary Mycobacterium avium complex (MAC) disease. Blood and bronchoalveolar lavage fluid were collected from three female rhesus macaques infected intrabronchially with escalating doses of M. avium subsp. hominissuis. Immunity was determined by measuring cytokine levels, lymphocyte proliferation, and antigen-specific responses. Disease progression was monitored clinically and microbiologically with serial thoracic radiographs, computed tomography scans, and quantitative mycobacterial cultures. The animal subjected to the highest inoculum showed evidence of chronic pulmonary MAC disease. Therefore, rhesus macaques could provide a robust model in which to investigate host-pathogen interactions during MAC infection.

Non-tuberculous mycobacterial infections in solid organ transplant recipients: An update

Non-tuberculous mycobacteria are ubiquitous environmental organisms that are now increasingly recognized as important causes of clinical disease in solid organ transplant recipients. Risk factors of non-tuberculous mycobacteria infection are severe immunologic defects and structural abnormalities. Lung transplant recipients are at higher risk for non-tuberculous mycobacterial disease compared to recipients of other solid organs. The clinical presentation could be skin and soft tissue infection, osteoarticular disease, pleuropulmonary infection, bloodstream (including catheter-associated) infection, lymphadenitis, and disseminated or multi-organ disease. Management of non-tuberculous mycobacteria infection is complex due to the prolonged treatment course with multi-drug regimens that are anticipated to interact with immunosuppressive medications. This review article provides an update on infections due to non-tuberculous mycobacteria after solid organ transplantation, and discusses the epidemiology, risk factors, clinical presentation, and management.

US Cystic Fibrosis Foundation and European Cystic Fibrosis Society consensus recommendations for the management of non-tuberculous mycobacteria in individuals with cystic fibrosis

Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms that can cause chronic pulmonary infection, particularly in individuals with pre-existing inflammatory lung disease such as cystic fibrosis (CF). Pulmonary disease caused by NTM has emerged as a major threat to the health of individuals with CF but remains difficult to diagnose and problematic to treat. In response to this challenge, the US Cystic Fibrosis Foundation (CFF) and the European Cystic Fibrosis Society (ECFS) convened an expert panel of specialists to develop consensus recommendations for the screening, investigation, diagnosis and management of NTM pulmonary disease in individuals with CF. Nineteen experts were invited to participate in the recommendation development process. Population, Intervention, Comparison, Outcome (PICO) methodology and systematic literature reviews were employed to inform draft recommendations. An anonymous voting process was used by the committee to reach consensus. All committee members were asked to rate each statement on a scale of: 0, completely disagree, to 9, completely agree; with 80% or more of scores between 7 and 9 being considered ‘good’ agreement. Additionally, the committee solicited feedback from the CF communities in the USA and Europe and considered the feedback in the development of the final recommendation statements. Three rounds of voting were conducted to achieve 80% consensus for each recommendation statement. Through this process, we have generated a series of pragmatic, evidence-based recommendations for the screening, investigation, diagnosis and treatment of NTM infection in individuals with CF as an initial step in optimising management for this challenging condition.

Mycobacterium abscessus Complex - a Particular Challenge in the Setting of Lung Transplantation

Mycobacterium abscessus complex is an emerging pathogen in lung transplant candidates and recipients. M. abscessus complex is widespread in the environment and can cause pulmonary, skin and soft tissue, and disseminated infection, particularly in lung transplant recipients. It is innately resistant to many antibiotics making it difficult to treat. Herein we describe the epidemiology, clinical manifestations, diagnosis and treatment of M. abscessus with an emphasis on lung transplant candidates and recipients. We also outline the areas where data are lacking and the areas where further research is urgently needed.

Immune Alterations in Patients with Anti-Interferon-γ Autoantibodies

Autoantibodies against interferon-gamma (IFN-γ) can cause immunodeficiency and are associated with various opportunistic infections. In the present study, we investigated other cellular immune parameters for a better understanding of the immunodeficiency condition in the patients. The numbers of WBC, monocytes and NK cells were increased in patients with anti-IFN-γ autoantibodies (AAbs). Upon TCR activation, T cell proliferation and IL-2 receptor of the patients remained intact. Nonetheless, the Th1 cytokine (IFN-γ and TNF-α) production was up-regulated. The production of Th2 (IL-4) and Th17 (IL-17) cytokines was unchanged. We suggest that, in addition to the presence of anti-IFN-γ autoantibodies, alterations in the cellular immune functions may also contribute to this immunodeficiency.

Host susceptibility to non-tuberculous mycobacterial infections

Non-tuberculous mycobacteria cause a broad range of clinical disorders, from cutaneous infections, such as cervical or intrathoracic lymphadenitis in children, to disseminated infections at all ages. Recognition of the underlying immune defect is crucial for rational treatment, preventive care, family screening, and, in some cases, transplantation. So far, at least seven autosomal mutations (in IL12B, IL12RB1, ISG15, IFNGR1, IFNGR2, STAT1, and IRF8) and two X-linked mutations (in IKBKG and CYBB), mostly presenting in childhood, have been reported to confer susceptibility to disseminated non-tuberculous mycobacterial infection. GATA2 deficiency and anti-interferon γ autoantibodies also give rise to disseminated infection, typically in late childhood or adulthood. Furthermore, isolated pulmonary non-tuberculous mycobacterial infection has been increasing in prevalence in people without recognised immune dysfunction. In this Review, we discuss how to detect and differentiate host susceptibility factors underlying localised and systemic non-tuberculous mycobacterial infections.

Nontuberculous Mycobacteria in Noncystic Fibrosis Bronchiectasis

During the past decades, a growing interest has been raised in evaluating nontuberculous mycobacteria (NTM) in patients with noncystic fibrosis bronchiectasis (NCFBE). This paper reviews several aspects of the correlations between NTM and NCFBE, including pathogenesis, radiological features, diagnosis, and management. Bronchiectasis and NTM lung disease are connected, but which one comes first is still an unresolved question. The rate of NTM lung disease in NCFBE varies through the studies, from 5% to 30%. The most frequent species isolated is MAC. NCFBE patients affected by NTM infection frequently present coinfections, including both other different NTM species and microorganisms, such as P. aeruginosa. Once a diagnosis of NTM disease has been reached, the initiation of therapy is not always mandatory. NTM species isolated, patients' conditions, and disease severity and its evolution should be considered. Risk factors for disease progression in NCFBE patients with NTM are low body mass index, cavitary disease, consolidations, and macrolide resistance at presentation.

Cellular immune responses in HIV-negative immunodeficiency with anti-interferon-γ antibodies and opportunistic intracellular microorganisms

Background

Cell-mediated immunity plays a crucial role in resistance to intracellular infection. We previously reported antibodies against interferon-gamma (IFN-γ) in HIV− negative (HIV−) patients with acquired immunodeficiency presenting with repeated episodes of disseminated infection caused by uncommon opportunistic intracellular fungal, bacterial, and viral pathogens. This follow-up study aimed to investigate cellular immune responses in these unusual patients.

Methods

Twenty HIV− patients presenting with ≥2 episodes of culture- or histopathologic-proven opportunistic infections were enrolled along with age- and sex-matched controls comprised of 20 HIV+ patients plus 20 healthy adults. Monocyte phenotyping and intracellular cytokine production were determined by staining with specific antibodies followed by flow cytometry. Anti-interferon-γ antibodies were measured by enzyme-linked immunosorbent assay, and inducible nitric oxide synthase by reverse-transcription polymerase chain reaction.

Results

There were no differences among cases, HIV+, and healthy controls in the percentage of monocytes, or CD68 and HLA-DR expression on their surfaces. FcR1 (CD119) expression on monocytes was significantly higher in cases than in HIV+ (p<0.05) and healthy controls (p<0.01), suggesting the presence of activated monocytes in the circulation. Interleukin (IL)-2 and tumor necrosis factor (TNF)-α production in CD4 cells were significantly lower in cases than in healthy controls (p<0.01 and p<0.001, respectively). CD8 production of TNF-α among cases was significantly lower than that of healthy controls (p<0.05).

Conclusion

Immunodeficiency in HIV− individuals with repeated infections with intracellular pathogens may be associated with one or more of the abnormal immune responses reflected by the reduced production of both IL-2 by CD4 T cells and TNF-α by CD4 T cells and CD8 T cells, as well as presence of anti-IFN-γ antibody, as previously reported.

Impaired cytokine responses in patients with cryopyrin-associated periodic syndrome (CAPS)

Cryopyrin-associated periodic syndrome (CAPS) is characterized by dysregulated inflammation with excessive interleukin (IL)-1β activation and secretion. Neonatal-onset multi-system inflammatory disease (NOMID) is the most severe form. We explored cytokine responses in 32 CAPS patients before and after IL-1β blocking therapy. We measured cytokines produced by activated peripheral blood monuclear cells (PBMCs) from treated and untreated CAPS patients after stimulation for 48 h with phytohaemagglutinin (PHA), PHA plus IL-12, lipopolysaccharide (LPS) or LPS plus interferon (IFN)-γ. We measured IL-1β, IL-6, IL-10, tumour necrosis factor (TNF), IL-12p70 and IFN-γ in the supernatants. PBMCs from three untreated CAPS patients were cultured in the presence of the IL-1β blocker Anakinra. Fifty healthy individuals served as controls. CAPS patients had high spontaneous production of IL-1β, IL-6, TNF and IFN-γ by unstimulated cells. However, stimulation indexes (SIs, ratio of stimulated to unstimulated production) of these cytokines to PHA and LPS were low in NOMID patients compared to controls. Unstimulated IL-10 and IL-12p70 production was normal, but up-regulation after PHA and LPS was also low. LPS plus IFN-γ inadequately up-regulated the production of IL-1β, IL-6, TNF and IL-10 in CAPS patients. In-vitro but not in-vivo treatment with Anakinra improved SIs by lowering spontaneous cytokine production. However, in-vitro treatment did not improve the low stimulated cytokine levels. Activating mutations in NLRP3 in CAPS are correlated with poor SIs to PHA, LPS and IFN-γ. The impairment in stimulated cytokine responses in spite of IL-1β blocking therapy suggests a broader intrinsic defect in CAPS patients, which is not corrected by targeting IL-1β.

Cytokine production assays reveal discriminatory immune defects in adults with recurrent infections and noninfectious inflammation

Cytokine production assays have been primarily used in research settings studying novel immunodeficiencies. We sought to determine the diagnostic value of cytokine production assays in patients with recurrent and/or severe infectious diseases (IDs) without known immunodeficiencies and unclassified noninfectious inflammatory disorders (NIIDs). We retrospectively examined cytokine production in whole-blood and peripheral blood mononuclear cell samples from 157 adult patients. A cytokine production rate of <5% of that of healthy controls was considered defective. While monocyte-derived cytokine (tumor necrosis factor alpha [TNF-α], interleukin-1β [IL-1β], and IL-6) production was rarely affected, 30% of all included patients had deficient production of interferon gamma (IFN-γ), IL-17A, or IL-22. Twenty-five percent of the NIID patients displayed defective IFN-γ production, whereas IL-17A production was generally unaffected. In the group of ID patients, defective IFN-γ production was found in 19% and 14% of the patients with viral and bacterial infections, respectively, and in 38%, 24%, and 50% of patients with mycobacterial, mucocutaneous, and invasive fungal infections, respectively. Defective IL-17A and IL-22 production was mainly confined to ID patients with mucocutaneous fungal infections. In conclusion, cytokine production assays frequently detect defective Th1 responses in patients with mycobacterial or fungal infections, in contrast to patients with respiratory tract infections or isolated bacterial infections. Defective IL-17A and IL-22 production was primarily found in patients with fungal infections, while monocyte-derived cytokine production was unaffected. Thus, lymphocyte-derived cytokine production assays are helpful in the diagnostic workup of patients with recurrent infections and suspected immunodeficiencies and have the potential to reveal immune defects that might guide adjunctive immunomodulatory therapy.

STAT3 and the Hyper-IgE syndrome: Clinical presentation, genetic origin, pathogenesis, novel findings and remaining uncertainties

During recent years a number of primary immunodeficiencies resulting from impaired function of JAK-STAT molecules have been described. One of these is the Hyper-IgE syndrome (HIES) characterized by elevated IgE levels, eczema, recurrent staphylococcal skin and pulmonary infections and pleiotropic somatic manifestations. In 2007 the genetic basis of HIES was revealed by identification of dominant negative STAT3 mutations in HIES patients. Subsequently impaired function of Tyk2 and DOCK8 have been implicated in milder forms of HIES. Since STAT3 acts as a central transcription factor downstream of multiple cytokine and growth factor receptors and thus regulates antimicrobial responses and cell survival, impaired STAT3 function results in immunodeficiency and in some cases tumorigenesis. However, as the immunological and molecular basis of HIES is being unraveled, important biological and immunological insight into JAK-STAT signaling is emerging that may have implications for our understanding of the pathogenesis and clinical management of patients with HIES.

Complement C4 deficiency--a plausible risk factor for non-tuberculous mycobacteria (NTM) infection in apparently immunocompetent patients

Background

Non-tuberculous mycobacteria (NTM) are ubiquitous in the environment and they infect mainly persons with underlying pulmonary diseases but also previously healthy elderly women. Defects in host resistance that lead to pulmonary infections by NTM are relatively unknown. A few genetic defects have been associated with both pulmonary and disseminated mycobacterial infections. Rare disseminated NTM infections have been associated with genetic defects in T-cell mediated immunity and in cytokine signaling in families. We investigated whether there was an association between NTM infections and deficiencies of complement components C4A or C4B that are encoded by major histocompatibility complex (MHC).

Methods

50 adult patients with a positive NTM culture with symptoms and findings of a NTM disease were recruited. Patients' clinical history was collected and symptoms and clinical findings were categorized according to 2007 diagnostic criteria of The American Thoracic Society (ATS). To investigate the deficiencies of complement, C4A and C4B gene copy numbers and phenotype frequencies of the C4 allotypes were analyzed. Unselected, healthy, 149 Finnish adults were used as controls.

Results

NTM patients had more often C4 deficiencies (C4A or C4B) than controls (36/50 [72%] vs 83/149 [56%], OR = 2.05, 95%CI = 1.019–4.105, p = 0.042). C4 deficiencies for female NTM patients were more common than for controls (29/36 [81%] vs 55/100 [55%], OR = 3.39, 95% CI = 1.358–8.460, p = 0.007). C4 deficiences seemed not to be related to any specific underlying disease or C4 phenotype.

Conclusions

C4 deficiency may be a risk factor for NTM infection in especially elderly female patients.

Risk factors for nontuberculous mycobacterial infections in solid organ transplant recipients: a case-control study

BACKGROUND

The epidemiology of nontuberculous mycobacteria (NTM) disease in solid organ transplant recipients is poorly defined.

METHODS

We identified all solid organ transplant recipients with NTM disease at a single center over a 7.5-year period, and collected data on patient demographics, co-morbidities, immunosuppressive medications, and rejection. We conducted a case-control study to identify risk factors for disease, matching 3 control patients to each case patient by date of transplantation.

RESULTS

A total of 34 cases of NTM disease occurred during the study period, involving 6 single lung, 13 bilateral lung, 8 heart, 4 liver, 2 kidney, and 1 pancreas-kidney recipients. Cases were predominantly male (24/34), with a median age of 55 years (interquartile range [IQR]: 46-61 years), and developed after a median of 8 months post transplantation (IQR: 2-87 months). Mycobacterium abscessus and Mycobacterium avium complex were the most common pathogens, and the lung (including pleura) was the most common site of disease. In the adjusted case-control analysis, lung transplant recipients had the highest risk of NTM disease.

CONCLUSIONS

Additional studies are needed to evaluate the role of targeted surveillance measures for NTM disease in high-risk patients, particularly lung transplant recipients, and to characterize the mechanisms of disease acquisition.

Nontuberculous mycobacterial infections in children with inborn errors of the immune system

Severe mycobacterial disease is mostly confined to patients who are immunocompromized either by acquired or inherited causes. One such genetic disorder is Mendelian Susceptibility to Mycobacterial Disease (MSMD), a hot topic within the field of primary immunodeficiency. This single gene disorder is characterized by isolated infection with mycobacteria or Salmonella due to a defect in the type-1 cytokine response. In the last two decades, ten genes have been labeled as causing MSMD when they harbor germline mutations, namely IL12B, IL12RB1, IFNGR1, IFNGR2, STAT1, IKBKG, CYBB, TYK2, IRF8 and ISG15. The mutations lead to either insufficient production of IFN-γ, or to an insufficient response to the cytokine. Current treatment options include recombinant IFN-γ and hematologic stem cell transplantation (HSCT). In the future, gene therapy, antisense-mediated exon skipping and chemical intervention in glycosylation problems may become successful alternatives. Furthermore, it is likely that many new candidate genes and pathways crucial for mycobacterial immunity will be identified.

Disseminated nontuberculous mycobacterial infection in two children with different immune responses

A diffuse, infiltrating abdominal mass accompanied with fever and anemia in a child raises the possibility of a benign or malignant tumor, pseudotumor, or infection. Herein, we describe a 9-year-old girl and a 14-year-old boy with multiple large abdominal masses, fever, weight loss, and anemia. During the evaluation of the children, the girl was found to be immunocompetent, while the boy was found to be immunocompromised. Computerized tomography of the abdomen in both cases demonstrated multiple large intra-abdominal masses. Tumors in the girl were composed of wide-spread necrotizing granulomas and necrosis with dystrophic calcifications. In the boy, non-necrotic, homogenous histiocytic infiltrates with rare multinucleated giant cells and lymphocytes were observed histologically. Review of histologic sections identified gram-positive, nonbranching acid-fast bacillary organisms in both cases. Diagnoses of Mycobacterium fortuitum (MF) and Mycobacterium avium-intracellulare complex (MAC) were confirmed by tissue microbiologic cultures in the girl and boy, respectively. The girl with MF infection was appropriately treated and is currently doing well. The boy with MAC was found to have human immunodeficiency virus infection/acquired immune deficiency syndrome (AIDS) and is currently undergoing AIDS treatment. These cases highlight the striking contrast between responses to nontuberculous mycobacteria infection based on immune status.

Signal transducer and activator of transcription 1 (STAT1) gain-of-function mutations and disseminated coccidioidomycosis and histoplasmosis

BACKGROUND

Impaired signaling in the IFN-γ/IL-12 pathway causes susceptibility to severe disseminated infections with mycobacteria and dimorphic yeasts. Dominant gain-of-function mutations in signal transducer and activator of transcription 1 (STAT1) have been associated with chronic mucocutaneous candidiasis.

OBJECTIVE

We sought to identify the molecular defect in patients with disseminated dimorphic yeast infections.

METHODS

PBMCs, EBV-transformed B cells, and transfected U3A cell lines were studied for IFN-γ/IL-12 pathway function. STAT1 was sequenced in probands and available relatives. Interferon-induced STAT1 phosphorylation, transcriptional responses, protein-protein interactions, target gene activation, and function were investigated.

RESULTS

We identified 5 patients with disseminated Coccidioides immitis or Histoplasma capsulatum with heterozygous missense mutations in the STAT1 coiled-coil or DNA-binding domains. These are dominant gain-of-function mutations causing enhanced STAT1 phosphorylation, delayed dephosphorylation, enhanced DNA binding and transactivation, and enhanced interaction with protein inhibitor of activated STAT1. The mutations caused enhanced IFN-γ-induced gene expression, but we found impaired responses to IFN-γ restimulation.

CONCLUSION

Gain-of-function mutations in STAT1 predispose to invasive, severe, disseminated dimorphic yeast infections, likely through aberrant regulation of IFN-γ-mediated inflammation.

Effects of IFN-γ on intracellular trafficking and activity of macrophage NADPH oxidase flavocytochrome b558

Flavocytochrome b(558), the catalytic core of the phagocyte NADPH oxidase (NOX2), mediates electron transfer from NADPH to molecular oxygen to generate superoxide, the precursor of highly ROS for host defense. Flavocytochrome b(558) is an integral membrane heterodimer consisting of a large glycosylated subunit, gp91(phox), and a smaller subunit, p22(phox). We recently showed in murine macrophages that flavocytochrome b(558) localizes to the PM and Rab11-positive recycling endosomes, whereas in primary hMDMs, gp91(phox) and p22(phox) reside in the PM and the ER. The antimicrobial activity of macrophages, including ROS production, is greatly enhanced by IFN-γ, but how this is achieved is incompletely understood. To further define the mechanisms by which IFN-γ enhances macrophage NADPH oxidase activity, we evaluated changes in flavocytochrome b(558) expression and localization, along with NADPH oxidase activity, in IFN-γ stimulated RAW 264.7 cells and primary murine BMDMs and hMDMs. We found that enhanced capacity for ROS production is, in part, a result of increased protein expression of gp91(phox) and p22(phox) but also demonstrate that IFN-γ induced a shift in the predominant localization of gp91(phox) and p22(phox) from intracellular membrane compartments to the PM. Our results are the first to show that a cytokine can change the distribution of macrophage flavocytochrome b(558) and provide a potential, new mechanism by which IFN-γ modulates macrophage antimicrobial activity. Altogether, our data suggest that the mechanisms by which IFN-γ regulates antimicrobial activity of macrophages are more complex than previously appreciated.

Translational research in infectious disease: current paradigms and challenges ahead

In recent years, the biomedical community has witnessed a rapid scientific and technologic evolution after the development and refinement of high-throughput methodologies. Concurrently and consequentially, the scientific perspective has changed from the reductionist approach of meticulously analyzing the fine details of a single component of biology to the "holistic" approach of broadmindedly examining the globally interacting elements of biological systems. The emergence of this new way of thinking has brought about a scientific revolution in which genomics, proteomics, metabolomics, and other "omics" have become the predominant tools by which large amounts of data are amassed, analyzed, and applied to complex questions of biology that were previously unsolvable. This enormous transformation of basic science research and the ensuing plethora of promising data, especially in the realm of human health and disease, have unfortunately not been followed by a parallel increase in the clinical application of this information. On the contrary, the number of new potential drugs in development has been decreasing steadily, suggesting the existence of roadblocks that prevent the translation of promising research into medically relevant therapeutic or diagnostic application. In this article, we will review, in a noninclusive fashion, several recent scientific advancements in the field of translational research, with a specific focus on how they relate to infectious disease. We will also present a current picture of the limitations and challenges that exist for translational research, as well as ways that have been proposed by the National Institutes of Health to improve the state of this field.

Mycobacterium avium subsp. avium and subsp. hominissuis give different cytokine responses after in vitro stimulation of human blood mononuclear cells

Background

Mycobacterium avium is the principal etiologic agent of non-tuberculous lymphadenitis in children. It is also a known pathogen for birds and other animals. Genetic typing of M. avium isolates has led to a proposal to expand the set of subspecies to include M. avium subsp. hominissuis. Isolates associated with disease in humans belong to this subspecies.

Methodology/Principal Findings

Peripheral blood mononuclear cells from six healthy blood donors were stimulated in vitro with ten isolates of M. avium avium and 11 isolates of M. avium hominissuis followed by multiplex bead array quantification of cytokines in supernatants. M. avium hominissuis isolates induced significantly more IL-10 and significantly less IL-12p70, TNF, IFN-γ and IL-17 when compared to M. avium avium isolates. All strains induced high levels of IL-17, but had very low levels of IL-12p70.

Conclusion/Significance

The strong association between M. avium subsp. hominissuis and disease in humans and the clear differences in the human immune response to M. avium subsp. hominissuis compared to M. avium subsp. avium isolates, as demonstrated in this study, suggest that genetic differences between M. avium isolates play an important role in the pathogenicity in humans.

Lung manifestations in an autopsy-based series of pulmonary or disseminated nontuberculous mycobacterial disease

BACKGROUND

Comparisons of lung manifestations in primary pulmonary vs disseminated nontuberculous mycobacterial disease have not been well described. The clinical, histopathologic, and radiologic disease manifestations of primary pulmonary or disseminated nontuberculous mycobacterial disease were compared in an autopsy series.

METHODS

Medical and microbiologic records, autopsy reports, histopathologic slides of the lungs, and chest CT scans were reviewed on patients at the National Institutes of Health with nontuberculous mycobacterial disease who died between 1996 and 2010.

RESULTS

The 11 patients with primary pulmonary nontuberculous mycobacterial disease were predominantly female (n = 9), with symptom onset at median 50 (range 35, 71) years and time from onset until death of 12 (3, 34) years. Bronchiectasis with cavity formation and necrotizing bronchocentric granulomatous inflammation predominated but extrapulmonary infection was absent. The five patients with disseminated disease and systemic immune defects were all men with age at onset of 2 (0.33, 33) years and time from onset of disease until death of 9 (1, 31) years. Miliary nodules and/or consolidation with poorly formed granulomatous inflammation were noted in the three disseminated patients with mycobacterial lung involvement. Significant extrapulmonary infection was noted in all five with a relative paucity of lung findings.

CONCLUSIONS

Nontuberculous mycobacteria can cause progressive, fatal disease. Primary pulmonary disease is bronchocentric and lacks extrathoracic infection consistent with impaired airway surface defenses. In contrast, fatal disseminated infections involving the lung have hematogenous spread, extensive extrathoracic disease, and a distinct pulmonary histopathology consistent with systemic immune dysfunction.

Novel STAT1 alleles in a patient with impaired resistance to mycobacteria

Partial defects in interferon (IFN)-γ signaling lead to susceptibility to infections with nontuberculous mycobacteria. The receptors for IFN-α and IFN-γ activate components of the Janus kinase-signal transducer and activator of transcription (STAT) signaling pathway. Some defects in STAT1 mainly affect IFN-γ signaling, thus resulting in mendelian susceptibility to mycobacterial disease (MSMD). MSMD is a severe disease but patients show a favorable response to anti-mycobacterial chemotherapy. Other defects in STAT1 affect both IFN-α and IFN-γ signaling resulting in mycobacterial and lethal viral disease. We report here a patient with two novel STAT1 alleles, which in combination results in a recessive trait with partial STAT1 deficiency and mycobacterial disease. Cells from the patient did respond to mycobacterial antigen, but both the expression of STAT1 and phosphorylation of STAT1 in response to IFN-γ treatment were reduced. This is the first report of a mutation in the N-terminal part of STAT1 involved in causing mycobacterial disease.

Mendelian susceptibility to mycobacterial disease

The host response to mycobacterial infection is mediated by the type I cytokine pathway (cell-mediated immunity). Deficiencies in this response result in susceptibility to poorly pathogenic mycobacterial species such as bacille Calmette-Guérin and environmental mycobacteria. In recent years a number of mutations in the genes encoding major components in the type I cytokine axis have been described which predispose to disseminated infection with these weakly virulent mycobacterial species. Affected individuals are also prone to extra-intestinal disease caused by non-typhoidal Salmonella. The genes involved display a high level of allelic heterogeneity, accounting for a number of distinct genetic disorders which vary in their mode of inheritance and clinical presentation. These disorders have been termed Mendelian susceptibility to mycobacterial disease and are discussed in this review article.

Mycobacterium avium complex cervical lymphadenitis in an immunocompetent adult

Nontuberculosis mycobacterial cervical lymphadenitis is a relatively common disease in immunocompetent children but a rare disease in immunocompetent adults. We report the diagnosis and treatment of Mycobacterium avium complex cervical lymphadenitis in an adult female. Our evaluation of immune competence, including gamma interferon (IFN-gamma) and interleukin-12 (IL-12) signaling, found no evidence of deficiency.

Nontuberculous mycobacterial cervicofacial lymphadenitis in children from the multicenter, randomized, controlled trial in The Netherlands: relevance of polymorphisms in candidate host immunity genes

OBJECTIVE

The annual incidence of nontuberculous mycobacterial (NTM) cervicofacial lymphadenitis in otherwise healthy children is unexpectedly high (8 per million). It mostly arises as localized cervicofacial lymphadenitis. Previous research has suggested environmental risk factors for oral exposure to NTM and a temporal association with eruption of teeth. We studied 22 polymorphisms in relevant candidate genes, some related to periodontitis, in children with NTM lymphadenitis. We also tested for the most common mutation in IFNGR1.

METHODS

We analyzed DNA from 81 Dutch children with NTM from a nationwide surveillance study and 215 community controls for 22 polymorphisms in CD209, IL1B, IL8, IL10, IL12B, IL12RB1, IL18, PTX3, TLR4, TNF, VDR and SLC11A1 by MassArray platform (Sequenom) and CONTING. We screened for 818del4 in IFNGR1 by PCR and VspI restriction enzyme cleavage.

RESULTS

We found a positive association between NTM lymphadenitis and +3953TT in IL1B (OR 2.9; 95%-CI: 1.2-7.2). Furthermore, our results showed that -592C/A heterozygosity in IL10 is linked to protection from disease (OR 0.54; 95%-CI: 0.3-0.95), but that other polymorphisms were unrelated to localized NTM disease. However, these associations were not robust to Bonferroni's correction for multiple testing. None of the children carried the IFNGR1 818del4 mutation.

CONCLUSIONS

Dominance of environmental factors over genetic ones and insufficient sample size might explain the fragility of this study's results. Nevertheless, the association between NTM lymphadenitis and 3953C>T, a polymorphism previously linked to periodontitis, supports our hypothesis that oral exposure to mycobacteria during eruption of teeth plays a role in the etiology of cervical NTM lymphadenitis.

Genetic susceptibility in tuberculosis

The importance of host genetic factors in determining susceptibility to tuberculosis (TB) has been studied extensively using various methods, such as case-control, candidate gene and genome-wide linkage studies. Several important candidate genes like human leucocyte antigen/alleles and non-human leucocyte antigen genes, such as cytokines and their receptors, chemokines and their receptors, pattern recognition receptors (including toll-like receptors, mannose binding lectin and the dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin), solute carrier family 11A member 1 (formerly known as natural resistance-associated macrophage protein 1) and purinergic P2X7 receptor gene polymorphisms, have been associated with differential susceptibility to TB in various ethnic populations. This heterogeneity has been explained by host-pathogen and gene-environment interactions and evolutionary selection pressures. Although the achievements of genetics studies might not yet have advanced the prevention and treatment of TB, researchers have begun to widen their scope of investigation to encompass these practical considerations.

Antimicrobial prophylaxis for primary immunodeficiencies

PURPOSE OF REVIEW

Antibiotic prophylaxis is one of the mainstays of therapy of primary immunodeficiencies. We aim to summarize what is known about antibiotic prophylaxis for select primary immunodeficiencies.

RECENT FINDINGS

In recent years, there has been a push towards more evidence-based practices for antimicrobial prophylaxis for many conditions such as antifungal prophylaxis for extremely premature neonates and antibiotic prophylaxis for neutropenia associated with chemotherapy. However, there are remarkably few data regarding antibiotic prophylaxis in primary immunodeficiencies and regimens vary greatly between practices.

SUMMARY

Currently, antibiotic prophylaxis is guided by the common microbial pathogens seen in specific immunodeficiencies, and experience with other chronic illnesses such as cystic fibrosis, HIV, and immunosuppression from transplantation. Controlled studies are necessary to address the preferred antimicrobial and immunomodulator regimens for most of the primary immunodeficiencies.

Mycobacterium abscessus and M. avium trigger Toll-like receptor 2 and distinct cytokine response in human cells

Mycobacterium avium (MAV) and M. abscessus (MAB) are ubiquitous environmental organisms increasingly recognized to cause chronic lung disease in patients with apparently normal immune function. Little is yet known about their human pathophysiology. Our objective was to examine cytokine and chemokine responses (protein and gene expression) and signaling pathways triggered by reference and clinical isolates of MAB and MAV in human peripheral blood mononuclear cells, monocytes, and murine bone marrow-derived macrophages in vitro. MAB-induced TNF-alpha production was higher than that induced by MAV. IFN-gamma, IL-1beta, and the chemokines macrophage inflammatory protein-1alpha and regulated on activation, normal T cell expressed and secreted were equally up-regulated. Differences between MAB and MAV do not require replication and are heat stable. We found no differential effect due to rough or smooth colonies within the same species. Similar to MAV, MAB triggered mitogen-activated protein kinase (MAPK) signaling and nuclear factor-kappaB translocation. Induction of TNF-alpha was dependent on MAPK pathways, since pre-incubation of cells with signaling inhibitors led to more than 85% reduction in cytokine secretion. MAB also triggered a Toll-like receptor 2 (TLR2)-mediated response that led to TNF-alpha production by human monocytes. Accordingly, stimulation of murine TLR2- or myeloid differentiation factor 88-deficient bone marrow-derived macrophages did not elicit TNF-alpha, reinforcing a critical role for TLR2 in MAB-induced cell activation. We concluded that MAB signals human cells through MAPK and TLR2 pathways and triggers more pronounced pro-inflammatory cytokines and chemokines than MAV.

Clinical and immunologic features of an atypical intracranial mycobacterium avium complex (MAC) infection compared with those of pulmonary MAC infections

Members of the Mycobacterium avium complex (MAC) may cause chronic pulmonary infections in otherwise healthy elderly persons but rarely invade parts of the body outside of the lungs in immunocompetent hosts. We present a case of an isolated intracranial MAC infection in an apparently immunocompetent individual and review previous reports. We studied the T-cell and monocyte responses in healthy volunteers, individuals with a pulmonary MAC infection, and one individual with an isolated intracranial MAC infection. Genomic DNA from the individual with the brain MAC infection was studied for gamma interferon (IFN-gamma) receptor mutations. Individuals with localized pulmonary MAC infections showed increased activation of monocytes and enhanced monocyte and T-cell tumor necrosis factor alpha (TNF-alpha) production in response to lipopolysaccharide and MAC antigens but defects in T-cell IFN-gamma secretion. The individual with an intracranial MAC infection showed a lack of monocyte activation and deficiencies in both monocyte and T-cell TNF-alpha production and monocyte interleukin-12 (IL-12) production but had preserved T-cell IFN-gamma production. Mutations or deletions in the IFN-gamma receptor were not detected in the individual with the intracranial MAC infection. Our data suggest that distinct immune defects characterize two different manifestations of MAC infection. A relative defect in IFN-gamma production in response to MAC may predispose an individual to localized but partially controlled lung disease, whereas defects leading to reduced IL-12 and TNF-alpha production may allow the dissemination of MAC. Further studies delineating the potential role of TNF-alpha in limiting the spread of MAC outside the lung are warranted.

Hepatoportal venopathy due to disseminated Mycobacterium avium complex infection in a child with IFN-gamma receptor 2 deficiency

The control of intracellular microorganisms such as mycobacteria is largely dependent on the adaptive immune response, specifically the interaction of T helper cells and antigen presenting cells such as macrophages. The interferon gamma (IFN-gamma) pathway activation is crucial for containment and killing of mycobacteria, as evidenced by the fact that defects in this pathway often result in profound infections with both tuberculous and non-tuberculous mycobacteria. We herein report a case of a child with autosomal recessive IFN-gamma receptor 2 (IFN-gammaR2) deficiency who developed hepatic venopathy secondary to disseminated Mycobacterium avium complex (MAC) infection.