Genetic heterogeneity of Mendelian susceptibility to mycobacterial infection

In vitro stimulation with nontuberculous mycobacteria induced a stronger cytokine response in leukocytes isolated from individuals with latent tuberculosis compared to those isolated from active tuberculosis or cystic fibrosis patients

Mycobacterium tuberculosis and opportunistic environmental non-tuberculous mycobacteria (NTM) can cause severe infection. Why latent tuberculosis infection advances to active disease, and why some individuals with cystic fibrosis (CF) develop pulmonary infections with NTM is still poorly understood. The aim of this study was to investigate the effector function of peripheral blood mononuclear cells (PBMC) from individuals with active or latent tuberculosis, individuals with CF with or without pulmonary NTM-infection and healthy controls, by measuring cytokine response to in vitro stimulation with different species of NTMs. The cytokine concentrations of IL-17A, IL-22, IL-23, IL-10, IL12p70 and IFN-γ were measured in PBMC-culture supernatants after stimulation with NTMs. PBMCs from individuals with latent tuberculosis infection showed strong IL-17A, IL-22, and IFN-γ responses compared to individuals with active tuberculosis or CF. IL-10 production was low in both tuberculosis groups compared to the CF groups and controls. This study suggests that IL-17A and IL-22 might be important to keep tuberculosis in a latent phase and that individuals with CF with an ongoing NTM infection seem to have a low cytokine response.

Primary Immunodeficiencies in India: Molecular Diagnosis and the Role of Next-Generation Sequencing

Primary immunodeficiency diseases (PIDs) are a group of clinically and genetically heterogeneous disorders showing ethnic and geographic diversities. Next-generation sequencing (NGS) is a comprehensive tool to diagnose PID. Although PID is common in India, data on the genetic spectrum of PIDs are limited due to financial restrictions. The study aims to characterize the clinical and genetic spectrum of PID patients in India and highlight the importance of a cost-effective targeted gene panel sequencing approach for PID in a resource-limited setting. The study includes 229 patients with clinical and laboratory features suggestive of PIDs. Mutation analysis was done by Sanger sequencing and NGS targeting a customized panel of genes. Pathogenic variants were identified in 97 patients involving 42 different genes with BTK and IL12RB1 being the most common mutated genes. Autosomal recessive and X-linked recessive inheritance were seen in 51.6% and 23.7% of patients. Mendelian susceptibility to mycobacterial diseases (MSMD) and IL12RB1 mutations was more common in our population compared to the Western world and the Middle East. Two patients with hypomorphic RAG1 mutations and one female with skewed CYBB mutation were also identified. Another 40 patients had variants classified as variants of uncertain significance (VUS). The study shows that targeted NGS is an effective diagnostic strategy for PIDs in countries with limited diagnostic resources. Molecular diagnosis of PID helps in genetic counseling and to make therapeutic decisions including the need for a stem cell transplantation.

Severe Disseminated Mycobacterium avium Infection in a Patient with a Positive Serum Autoantibody to Interferon-γ

We herein report a case of disseminated Mycobacterium avium infection that involved both optic nerves, the conjunctiva, the right lower lung, and multiple skin lesions, including a thoracic nodule. The patient was a 65-year-old man without any significant medical history. The pathogen was detected in the patient's eye discharge, sputum, bronchial lavage fluid, and thoracic nodule. Anti-mycobacterial chemotherapy, including clarithromycin, rifampicin, and ethambutol, was administered, and the thoracic nodule was resected. An autoantibody to interferon-γ was detected in the patient's serum. Bilateral swelling of his optic nerves and facial dermatitis improved after initiating anti-mycobacterial chemotherapy.

The transcription factor NFATp plays a key role in susceptibility to TB in mice

In T cells, the transcription factor nuclear factor of activated T cells p (NFATp) is a key regulator of the cytokine genes tumor necrosis factor (TNF) and interferon-γ (IFN-γ). Here, we show that NFATp-deficient (NFATp(-/-)) mice have a dramatic and highly significant increase in mortality after Mycobacterium tuberculosis (MTb) infection as compared to mortality of control animals after MTb infection. Animals deficient in NFATp have significantly impaired levels of TNF and IFN-γ transcription and protein expression in naïve or total CD4(+) T cells, but display wild-type levels of TNF mRNA or protein from MTb-stimulated dendritic cells (DC). The rapid mortality and disease severity observed in MTb-infected NFATp(-/-) mice is associated with dysregulated production of TNF and IFN-γ in the lungs, as well as with increased levels of TNF, in their serum. Furthermore, global blocking of TNF production by injection of a TNF neutralizaing agent at 6 weeks, but not 12 weeks, post-MTb-infection further decreased the survival rate of both wild-type and NFATp(-/-) mice, indicating an early role for TNF derived from cells from the monocyte lineage in containment of infection. These results thus demonstrate that NFATp plays a critical role in immune containment of TB disease in vivo, through the NFATp-dependent expression of TNF and IFN-γ in T cells.

Bacillus Calmette-Guérin (BCG) complications associated with primary immunodeficiency diseases

Primary immunodeficiency diseases (PIDs) are a group of inherited disorders, characterized by defects of the immune system predisposing individuals to variety of manifestations, including recurrent infections and unusual vaccine complications. There are a number of PIDs prone to Bacillus Calmette-Guérin (BCG) complications. This review presents an update on our understanding about the BCGosis-susceptible PIDs, including severe combined immunodeficiency, chronic granulomatous disease, and Mendelian susceptibility to mycobacterial diseases.

Candidate gene and genome-wide association studies of Mycobacterium avium subsp. paratuberculosis infection in cattle and sheep: a review

Paratuberculosis (Johne's disease), caused by Mycobacterium avium subspecies paratuberculosis, is responsible for significant economic losses in livestock industries worldwide. This organism is also of public health concern due to an unconfirmed link to Crohn's disease. Susceptibility to paratuberculosis has been suggested to have a genetic component. In livestock, a number of candidate genes have been studied, selected on their association to susceptibility in other mycobacterial diseases, their known role in disease pathogenesis or links to susceptibility of humans to Crohn's disease. These genes include solute carrier family 11 member 1 (SLC11A1, formerly NRAMP1), toll-like receptors, caspase associated recruitment domain 15 (CARD15, formerly NOD2), major histocompatibility complex (MHC) and cytokines (interleukin-10 and interferon-gamma) and their receptors. Genome wide association studies have attempted to confirm associations found and identify new genes involved in pathogenesis and susceptibility. There are a number of limitations and difficulties in these approaches, some peculiar to paratuberculosis but others generally applicable to identification of genetic associations for complex traits. The technical approaches and available information for paratuberculosis have expanded rapidly, particularly relating to sheep and cattle. Here we review the current published evidence for a genetic association with paratuberculosis susceptibility, technological advances that have progressed the field and potential avenues for future research.

Mycobacterium avium lymphadenopathy among children, Sweden

We studied Mycobacterium avium lymphadenopathy in 183 Swedish children (<7 years of age) from 1998 through 2003. Seasonal variation in the frequency of the disease, with a peak in October and a low point in April, suggests cyclic environmental factors. We also found a higher incidence of the disease in children who live close to water.

Primary Immunodeficiencies

Primary immunodeficiencies (PIDs), once considered to be very rare, are now increasingly recognized because of growing knowledge in the immunological field and the availability of more sophisticated diagnostic techniques and therapeutic modalities [161]. However in a database of >120,000 inpatients of a general hospital for conditions suggestive of ID 59 patients were tested, and an undiagnosed PID was found in 17 (29%) of the subjects tested [107]. The publication of the first case of agammaglobulinemia by Bruton in 1952 [60] demonstrated that the PID diagnosis is first done in the laboratory. However, PIDs require specialized immunological centers for diagnosis and management [33]. A large body of epidemiological evidence supports the hypothesis of the existence of a close etiopathogenetic relation between PID and atopy [73]. In particular, an elevated frequency of asthma, food allergy (FA), atopic dermatitis and enteric pathologies can be found in various PIDs. In addition we will discuss another subject that is certainly of interest: the pseudo-immunodepressed child with recurrent respiratory infections (RRIs), an event that often requires medical intervention and that very often leads to the suspicion that it involves antibody deficiencies [149].

Polarized helper T cells in tubercular pleural effusion: phenotypic identity and selective recruitment

Containment of Mycobacterium tuberculosis critically depends on orchestrated generation of Th1 cells and their selective recruitment at the pathologic sites. Understanding the mechanism involved in this process is important for defining better intervention strategies. We investigated the surface phenotype of Th1 cells and the role of chemotactic factors in their selective recruitment in tuberculosis pleural effusion and tuberculin site. Memory T cells obtained from the pleural fluid expressed a battery of homing receptors such as CD11a, CCR5 and CXCR3. Similar expression profile was noted on T cells infiltrating the tuberculin site. Expression of their respective ligands such as ICAM-1, RANTES, MIP1-alpha, Mig and IP-10 were detected at pathologic sites. In vitro assay of T cell adherence to activated human umbilical vein endothelial cells (HUVEC) expressing chemotactic ligands suggests an important role of these homing molecules in their selective trafficking. Here, we demonstrate a hierarchy of CXCR3 in effector cell adhesion to HUVEC in vitro, although CD11a and CCR5 were also observed to mediate cell adhesion in an additive fashion. Findings of the present study provide mechanistic insights into the critical events of T cell trafficking in tuberculosis and may help designing better therapeutic modalities.

A preliminary study of possible genetic influences on the susceptibility of sheep to Johne's disease

OBJECTIVE

To investigate possible genetic influences on susceptibility or resistance of sheep to Johne's disease.

DESIGN

A field and laboratory study of two fine-wool Merino flocks with a high prevalence of disease due to Mycobacterium avium subsp paratuberculosis infection.

PROCEDURE

Adult sheep were phenotypically classified as having severe, mild or no disease on the basis of clinical, pathological and cultural tests for paratuberculosis, and as positive or negative in tests for humoral immunity (agar gel immunodiffusion test) or cell mediated immunity (skin test for delayed type hypersensitivity). Correlations with phenotype were sought for polymorphisms at loci within selected immune function genes (NRAMP, MHC complex, IFN-gamma, lysozyme, leukaemia inhibiting factor).

RESULTS

Possible associations of particular NRAMP and MHC alleles with susceptibility or resistance to Johne's disease were detected.

CONCLUSION

If the results of this preliminary study are confirmed in further work, then the use of rams with "resistant" genotypes may assist in the control of Johne's disease in infected flocks.

Lack of an Association between Interleukin-12 Receptor β1 Polymorphisms and Tuberculosis in Koreans

BACKGROUND

The fact that only 10% of people infected with Mycobacterium tuberculosis develop clinical tuberculosis (TB) suggests the presence of genetic factors in the pathogenesis of TB. To date, a number of single nucleotide polymorphisms (SNPs) in several candidate genes have been proposed as genetic risk factors of TB; however, reports are conflicting.

OBJECTIVES

We investigated whether SNPs in the interleukin (IL)-12 receptor beta1 gene are associated with TB in Koreans.

METHODS

One hundred and fifteen patients with bacteriologically or pathologically confirmed TB and 151 healthy anonymous blood donors were enrolled. The genotypes of 5 SNPs on IL-12 receptor beta1 gene, +705A/G (Q214R), +1158T/C (M365T), +1196G/C (G378R), +1637G/A (A525T) and +1664 C/T (P534S), were determined by PCR-RFLP.

RESULTS

No difference was observed between TB patients and controls in terms of the genotype frequencies of the 5 SNPs of the IL-12 receptor beta1 gene or of their haplotypes.

CONCLUSIONS

In view of the finding that these SNPs have been reported to be associated with TB in the Japanese and Moroccan populations, our results may reflect racial differences in genetic susceptibility to TB.

Mycobacteria in drinking water distribution systems: ecology and significance for human health

In contrast to the notorious pathogens Mycobacterium tuberculosis and M. leprae, the majority of the mycobacterial species described to date are generally not considered as obligate human pathogens. The natural reservoirs of these non-primary pathogenic mycobacteria include aquatic and terrestrial environments. Under certain circumstances, e.g., skin lesions, pulmonary or immune dysfunctions and chronic diseases, these environmental mycobacteria (EM) may cause disease. EM such as M. avium, M. kansasii, and M. xenopi have frequently been isolated from drinking water and hospital water distribution systems. Biofilm formation, amoeba-associated lifestyle, and resistance to chlorine have been recognized as important factors that contribute to the survival, colonization and persistence of EM in water distribution systems. Although the presence of EM in tap water has been linked to nosocomial infections and pseudo-infections, it remains unclear if these EM provide a health risk for immunocompromised people, in particular AIDS patients. In this regard, control strategies based on maintenance of an effective disinfectant residual and low concentration of nutrients have been proposed to keep EM numbers to a minimum in water distribution systems.

Otolaryngologic manifestations of immunodeficiency

Otolaryngologists are frequently consulted to manage infectious and noninfectious complications of immune deficiency. Although defects of host defense and recurrent or severe infections are the most obvious manifestations of immune deficiency, patients are often at increased risk for autoimmune and malignant disease as well. Knowledge of primary and acquired immune deficiencies will facilitate appropriate identification, treatment, and referral of patients with these defects. When immunodeficiency is known or suspected, it is particularly important to have a high index of suspicion for unusual or severe manifestations of infection, to have a low threshold for obtaining imaging to aid in diagnosis, and to treat infections for longer periods of time with higher doses of antibiotic. Surgery may be required for definitive treatment of infections that do not respond to medical therapy and for management of complications of infectious disease

The genetics of nontuberculous mycobacterial infection

The molecular aetiology of familial susceptibility to disseminated mycobacterial disease, usually involving weakly pathogenic strains of mycobacteria, has now been elucidated in more than 30 families. Mutations have been identified in five genes in the interleukin-12-dependent interferon-gamma pathway, highlighting the importance of this pathway in human mycobacterial immunity. Knowledge derived from the study of these rare patients contributes to our understanding of the immune response to common mycobacterial pathogens such as Mycobacterium tuberculosis and Mycobacterium leprae, which remain major public health problems globally. This knowledge can be applied to the rational development of novel therapies and vaccines for these important mycobacterial diseases.

Correction of complete interferon-gamma receptor 1 deficiency by bone marrow transplantation

Complete interferon-gamma receptor 1 (IFNgammaR1) deficiency is a primary immunodeficiency disease characterized by high susceptibility to recurrent, severe mycobacterial and other intracellular infections. We here report the first successful treatment of the disorder by bone marrow transplantation (BMT). The 8-year-old girl had suffered from recurrent mycobacterial infections in the past and had developed liver cirrhosis with portal hypertension. For conditioning, fractionated total body irradiation (TBI) was used in combination with cyclophosphamide and antithymocyte globulin (ATG). The patient received red cell-depleted bone marrow from her HLA-identical sister. The transplantation course was uneventful and 4 years later, the child remains in excellent clinical condition and free of mycobacterial infections. She has stable mixed lymphohematopoietic chimerism after repeat T-cell transfusions. Liver disease has not further deteriorated. This experience shows that correction of IFNgammaR1 deficiency is possible by BMT and complications of the disease can be controlled.

Characterization of immune responses during infection with Mycobacterium avium strains 100, 101 and the recently sequenced 104

Mycobacterium avium strain 104 was chosen as the M. avium isolate to sequence, as it is virulent to humans, stable and readily transfectable. As this strain has not been widely studied we sought to investigate the pattern of 104 infection in mice. Bacterial growth and the immune response generated were compared with infection with the low virulence M. avium strain 100, and the high virulence common laboratory strain, 101. Mycobacterium avium strains 104 and 101 grew progressively within mice, while strain 100 was gradually cleared. Strains 104 and 101 induced strong T cell activation and spleen cell cultures produced similar levels of IFN-gamma. In mice infected with strain 100 no significant T cell activation or IFN-gamma production was measured. Further, mice infected with strain 104 or 101 also displayed comparable inflammatory responses and similar granuloma formation, while only minimal inflammation was seen in mice infected with strain 100. Strains 101 and 104 also grew in a similar fashion in bone-marrow-derived macrophages and induced significant levels of TNF and nitric oxide. Thus infection with M. avium strain 104 induced an immunological response comparable to M. avium strain 101 and, with the availability of its sequence, should be a useful tool for designing new vaccines or drugs therapies to treat the increasing incidence of M. avium infection in humans.

Mycobacterial lipoarabinomannans: modulators of dendritic cell function and the apoptotic response

The molecular bases of Mycobacterium tuberculosis pathogenicity remain unclear. We report here how M. tuberculosis mannosylated lipoarabinomannans contribute to the survival of bacilli in the human reservoir by (i) inhibiting IL-12 production by macrophages and dendritic cells and (ii) modulating M. tuberculosis-induced macrophage apoptosis.