Susan E. Dorman

A human IFNGR1 small deletion hotspot associated with dominant susceptibility to mycobacterial infection

The immunogenetic basis of severe infections caused by bacille Calmette-Guérin vaccine and environmental mycobacteria in humans remains largely unknown. We describe 18 patients from several generations of 12 unrelated families who were heterozygous for 1 to 5 overlapping IFNGR1 frameshift small deletions and a wild-type IFNGR1 allele. There were 12 independent mutation events at a single mutation site, defining a small deletion hotspot. Neighbouring sequence analysis favours a small deletion model of slipped mispairing events during replication. The mutant alleles encode cell-surface IFNγ receptors that lack the intra-cytoplasmic domain, which, through a combination of impaired recycling, abrogated signalling and normal binding to IFNγ exert a dominant-negative effect. We thus report a hotspot for human IFNGR1 small deletions that confer dominant susceptibility to infections caused by poorly virulent mycobacteria.

Mutation in the signal-transducing chain of the interferon-gamma receptor and susceptibility to mycobacterial infection.

IFN-gamma is critical in the immune response to mycobacterial infections, and deficits in IFN-gamma production and response have been associated with disseminated nontuberculous mycobacterial infections. Mutations in the IFN-gamma receptor ligand-binding chain (IFNgammaR1) have been shown to confer susceptibility to severe infection with nontuberculous mycobacteria. However, mutations in the IFN-gamma receptor signal-transducing chain (IFNgammaR2) have not been described. We describe a child with disseminated Mycobacterium fortuitum and M. avium complex infections and absent IFN-gamma signaling due to a mutation in the extracellular domain of IFNgammaR2. In vitro cytokine production by patient PBMCs showed 75% less PHA-induced IFN-gamma production than in normal cells, while patient PHA-induced TNF-alpha production was normal. The normal augmentation of TNF-alpha production when IFN-gamma was added to endotoxin was absent from patient cells. Expression of IFNgammaR1 was normal, but there was no phosphorylation of Stat1 in response to IFN-gamma stimulation. DNA sequence analysis of the gene for IFNgammaR2 showed a homozygous dinucleotide deletion at nucleotides 278 and 279, resulting in a premature stop codon in the protein extracellular domain. This novel gene defect associated with disseminated nontuberculous mycobacterial infection emphasizes the critical role that IFN-gamma plays in host defense against mycobacteria.

Clinical features of dominant and recessive interferon γ receptor 1 deficiencies

BACKGROUND Interferon gamma receptor 1 (IFNgammaR1) deficiency is a primary immunodeficiency with allelic dominant and recessive mutations characterised clinically by severe infections with mycobacteria. We aimed to compare the clinical features of recessive and dominant IFNgammaR1 deficiencies. METHODS We obtained data from a large cohort of patients worldwide. We assessed these people by medical histories, records, and genetic and immunological studies. Data were abstracted onto a standard form. FINDINGS We identified 22 patients with recessive complete IFNgammaR1 deficiency and 38 with dominant partial deficiency. BCG and environmental mycobacteria were the most frequent pathogens. In recessive patients, 17 (77%) had environmental mycobacterial disease and all nine BCG-vaccinated patients had BCG disease. In dominant patients, 30 (79%) had environmental mycobacterial disease and 11 (73%) of 15 BCG-vaccinated patients had BCG disease. Compared with dominant patients, those with recessive deficiency were younger at onset of first environmental mycobacterial disease (mean 3.1 years [SD 2.5] vs 13.4 years [14.3], p=0.001), had more mycobacterial disease episodes (19 vs 8 per 100 person-years of observation, p=0.0001), had more severe mycobacterial disease (mean number of organs infected by Mycobacterium avium complex 4.1 [SD 0.8] vs 2.0 [1.1], p=0.004), had shorter mean disease-free intervals (1.6 years [SD 1.4] vs 7.2 years [7.6], p<0.0001), and lower Kaplan-Meier survival probability (p<0.0001). M avium complex osteomyelitis was more frequent in dominant than in recessive patients (22/28 [79%] vs 1/8 [13%], p=0.002), and this disorder without other organ involvement arose only in dominant patients (9/28 [32%]). Disease caused by rapidly growing mycobacteria was present in more recessive than dominant patients (7/22 [32%] vs 1/38 [3%], p=0.002). INTERPRETATION Recessive complete and dominant partial IFNgammaR1 deficiencies have related clinical phenotypes, but are distinguishable by age at onset, dissemination, and clinical course of mycobacterial diseases. A strong correlation exists between IFNGR1 genotype, cellular responsiveness to interferon gamma, and clinical disease features.

Executive Summary: Official American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America Clinical Practice Guidelines: Treatment of Drug-Susceptible Tuberculosis

The American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America jointly sponsored the development of this guideline for the treatment of drug-susceptible tuberculosis, which is also endorsed by the European Respiratory Society and the US National Tuberculosis Controllers Association. Representatives from the American Academy of Pediatrics, the Canadian Thoracic Society, the International Union Against Tuberculosis and Lung Disease, and the World Health Organization also participated in the development of the guideline. This guideline provides recommendations on the clinical and public health management of tuberculosis in children and adults in settings in which mycobacterial cultures, molecular and phenotypic drug susceptibility tests, and radiographic studies, among other diagnostic tools, are available on a routine basis. For all recommendations, literature reviews were performed, followed by discussion by an expert committee according to the Grading of Recommendations, Assessment, Development and Evaluation methodology. Given the public health implications of prompt diagnosis and effective management of tuberculosis, empiric multidrug treatment is initiated in almost all situations in which active tuberculosis is suspected. Additional characteristics such as presence of comorbidities, severity of disease, and response to treatment influence management decisions. Specific recommendations on the use of case management strategies (including directly observed therapy), regimen and dosing selection in adults and children (daily vs intermittent), treatment of tuberculosis in the presence of HIV infection (duration of tuberculosis treatment and timing of initiation of antiretroviral therapy), as well as treatment of extrapulmonary disease (central nervous system, pericardial among other sites) are provided. The development of more potent and better-tolerated drug regimens, optimization of drug exposure for the component drugs, optimal management of tuberculosis in special populations, identification of accurate biomarkers of treatment effect, and the assessment of new strategies for implementing regimens in the field remain key priority areas for research. See the full-text online version of the document for detailed discussion of the management of tuberculosis and recommendations for practice.

From magic bullets back to the Magic Mountain: the rise of extensively drug-resistant tuberculosis

From magic bullets back to the Magic Mountain: the rise of extensively drug-resistant tuberculosis

Interleukin (IL)-12 and IL-23 Are Key Cytokines for Immunity against Salmonella in Humans

Patients with inherited deficiency of the interleukin (IL)-12/IL-23-interferon (IFN)- gamma axis show increased susceptibility to invasive disease caused by the intramacrophage pathogens salmonellae and mycobacteria. We analyzed data on 154 patients with such deficiency. Significantly more patients with IL-12/IL-23-component deficiency had a history of salmonella disease than did those with IFN- gamma -component deficiency. Salmonella disease was typically severe, extraintestinal, and caused by nontyphoidal serovars. These findings strongly suggest that IL-12/IL-23 is a key cytokine for immunity against salmonella in humans and that IL-12/IL-23 mediates this protective effect partly through IFN- gamma -independent pathways. Investigation of the IL-12/IL-23-IFN- gamma axis should be considered in patients with invasive salmonella disease.

Viral infections in interferon-γ receptor deficiency

Abstract Interferon-γ receptor deficiency is a recently described immunodeficiency that is associated with onset of severe mycobacterial infections in childhood. We describe the occurrence of symptomatic and often severe viral infections in 4 patients with interferon-γ receptor deficiency and mycobacterial disease. The viral pathogens included herpes viruses, parainfluenza virus type 3, and respiratory syncytial virus. We conclude that patients with interferon-γ receptor deficiency and mycobacterial disease have increased susceptibility to some viral pathogens. (J Pediatr 1999;135:640-3)

Interferon-γ Release Assays and Tuberculin Skin Testing for Diagnosis of Latent Tuberculosis Infection in Healthcare Workers in the United States

RATIONALE IFN-γ release assays (IGRAs) are alternatives to tuberculin skin testing (TST) for diagnosis of latent tuberculosis infection. Limited data suggest IGRAs may not perform well for serial testing of healthcare workers (HCWs). OBJECTIVES Determine the performance characteristics of IGRAs versus TST for serial testing of HCWs. METHODS A longitudinal study involving 2,563 HCWs undergoing occupational tuberculosis screening at four healthcare institutions in the United States, where the average tuberculosis case rate ranged from 4 to 9 per 100,000 persons. QuantiFERON-TB Gold In-Tube (QFT-GIT), T-SPOT.TB (T-SPOT), and TST were performed at baseline and every 6 months for 18 months between February 2008 and March 2011. MEASUREMENTS AND MAIN RESULTS A total of 2,418 HCWs completed baseline testing, which was positive for 125 (5.2%) by TST, 118 (4.9%) by QFT-GIT, and 144 (6.0%) by T-SPOT. A baseline positive TST with negative IGRAs was associated with bacillus Calmette-Guérin (BCG) vaccination (odds ratio: 25.1 [95% confidence interval: 15.5, 40.5] vs. no BCG). Proportions of participants with test conversion during the study period were 138 of 2,263 (6.1%) for QFT-GIT, 177 of 2,137 (8.3%) for T-SPOT, and 21 of 2,293 (0.9%) for TST (P < 0.001 for QFT-GIT vs. TST and for T-SPOT vs. TST; P = 0.005 for QFT-GIT vs. T-SPOT). Of the QFT-GIT and T-SPOT converters, 81 of 106 (76.4%) and 91 of 118 (77.1%), respectively, were negative when retested 6 months later. There was negative/positive discordance for 15 of 170 (8.8%) participants by QFT-GIT and for 19 of 151 (12.6%) by T-SPOT when blood was drawn 2 weeks later. CONCLUSIONS Most conversions among HCWs in low TB incidence settings appear to be false positives, and these occurred six to nine times more frequently with IGRAs than TST; repeat testing of apparent converters is warranted.

Mycobacterium tuberculosis cell envelope lipids and the host immune response

., 1999). The organism is a slow-growing bacillusthat is transmitted by the respiratory route. Although it iscapable of causing disease in most organs, pulmonaryinvolvement is most common. Soon after infection, thebacilli are phagocytosed by alveolar macrophages andsurvive within early phagosomes. Innate immuneresponses directed by macrophages predominate early ininfection. Subsequent recruitment of dendritic cells leadsto cell-mediated responses involving CD4

Diagnostic accuracy of a urine lipoarabinomannan test for tuberculosis in hospitalized patients in a high HIV prevalence setting

Background:Effective tuberculosis (TB) control in HIV-prevalent settings is hindered by absence of accurate, rapid TB diagnostic tests. We evaluated the accuracy of a urine lipoarabinomannan (LAM) test for TB diagnosis in South Africa. Methods:Hospitalized adults with signs and/or symptoms of active TB were enrolled. Sputum smear microscopy and mycobacterial culture, mycobacterial blood culture, and HIV testing were performed. A spot urine specimen was tested for LAM. Results:Four hundred ninety nine participants were enrolled; 422 (84.6%) were HIV infected. In microbiologically confirmed TB patients, the LAM test was positive in 114 of 193 [sensitivity 59%, (95% confidence interval: 52 to 66)], including 112 of 167 [67% (59 to 74)] who were HIV infected. Among individuals classified as “not TB”, the LAM test was negative in 117 of 122 [specificity 96% (91 to 99)], including 83 of 88 [94% (87 to 98)] who were HIV infected. In confirmed TB patients, the LAM test was more sensitive than sputum smear microscopy (42%, 82 of 193, P < 0.001) and detected 56% (62 of 111) of those who were sputum smear negative. HIV infection [adjusted odds ratio (AOR 13.4)], mycobacteremia (AOR 3.21), and positive sputum smear (AOR 2.42) were risk factors for a positive LAM test. Conclusions:The urine LAM test detected a subset of HIV-infected patients with severe TB in whom sputum smear microscopy had suboptimal sensitivity. The combination of urine LAM testing and sputum smear microscopy is attractive for use in settings with high HIV burden.