Pulmonary Mycobacterium Tuberculosis Infection Research Articles

The inflammatory microenvironment of the lung at the time of infection governs innate control of SARS-CoV-2 replication.

Severity of COVID-19 is affected by multiple factors; however, it is not understood how the inflammatory milieu of the lung at the time of SARS-CoV-2 exposure affects the control of viral replication. Here, we demonstrate that immune events in the mouse lung closely preceding SARS-CoV-2 infection affect viral control and identify innate immune pathways that limit viral replication. Pulmonary inflammatory stimuli including resolved, antecedent respiratory infections with Staphylococcus aureus or influenza, ongoing pulmonary Mycobacterium tuberculosis infection, ovalbumin/alum-induced asthma, or airway administration of TLR ligands and recombinant cytokines all establish an antiviral state in the lung that restricts SARS-CoV-2 replication. In addition to antiviral type I interferons, TNFα and IL-1 potently precondition the lung for enhanced viral control. Our work shows that SARS-CoV-2 may benefit from an immunologically quiescent lung microenvironment and suggests that heterogeneity in pulmonary inflammation preceding SARS-CoV-2 exposure may contribute to variability in disease outcomes.

Immunopathology of Pulmonary Mycobacterium tuberculosis Infection in a Humanized Mouse Model.

Despite the availability of antibiotic therapy, tuberculosis (TB) is prevailing as a leading killer among human infectious diseases, which highlights the need for better intervention strategies to control TB. Several animal model systems, including mice, guinea pigs, rabbits, and non-human primates have been developed and explored to understand TB pathogenesis. Although each of these models contributes to our current understanding of host-Mycobacterium tuberculosis (Mtb) interactions, none of these models fully recapitulate the pathological spectrum of clinical TB seen in human patients. Recently, humanized mouse models are being developed to improvise the limitations associated with the standard mouse model of TB, including lack of necrotic caseation of granulomas, a pathological hallmark of TB in humans. However, the spatial immunopathology of pulmonary TB in humanized mice is not fully understood. In this study, using a novel humanized mouse model, we evaluated the spatial immunopathology of pulmonary Mtb infection with a low-dose inoculum. Humanized NOD/LtSscidIL2Rγ null mice containing human fetal liver, thymus, and hematopoietic CD34+ cells and treated with human cytokines were aerosol challenged to implant <50 pathogenic Mtb (low dose) in the lungs. At 2 and 4 weeks post infection, the tissue bacterial load, disease pathology, and spatial immunohistology were determined in the lungs, liver, spleen, and adipose tissue using bacteriological, histopathological, and immunohistochemical techniques. The results indicate that implantation of <50 bacteria can establish a progressive disease in the lungs that transmits to other tissues over time. The disease pathology in organs correspondingly increased with the bacterial load. A distinct spatial distribution of T cells, macrophages, and natural killer cells were noted in the lung granulomas. The kinetics of spatial immune cell distribution were consistent with the disease pathology in the lungs. Thus, the novel humanized model recapitulates several key features of human pulmonary TB granulomatous response and can be a useful preclinical tool to evaluate potential anti-TB drugs and vaccines.

L-selectin-dependent and -independent homing of naïve lymphocytes through the lung draining lymph node support T cell response to pulmonary Mycobacterium tuberculosis infection.

Recruiting large numbers of naïve lymphocytes to lymph nodes is critical for mounting an effective adaptive immune response. While most naïve lymphocytes utilize homing molecule L-selectin to enter lymph nodes, some circulating cells can traffic to the lung-draining mediastinal lymph node (mLN) through lymphatics via the intermediate organ, lung. However, whether this alternative trafficking mechanism operates in infection and contributes to T cell priming are unknown. We report that in pulmonary Mycobacterium tuberculosis-infected mice, homing of circulating lymphocytes to the mLN is significantly less efficient than to non-draining lymph node. CD62L blockade only partially reduced the homing of naïve T lymphocytes, consistent with L-selectin-independent routing of naïve lymphocytes to the site. We further demonstrated that lymphatic vessels in infected mLN expanded significantly and inhibiting lymphangiogenesis with a vascular endothelial growth factor receptor 3 kinase inhibitor reduced the recruitment of intravenously injected naïve lymphocytes to the mLN. Finally, mycobacterium-specific T cells entering via the L-selectin-independent route were readily activated in the mLN. Our study suggests that both L-selectin-dependent and -independent pathways contribute to naïve lymphocyte entry into mLN during M. tuberculosis infection and the latter pathway may represent an important mechanism for orchestrating host defence in the lungs.

High Lethality of Mycobacterium tuberculosis Infection in Mice Lacking the Phagocyte Oxidase and Caspase1/11.

Immune networks that control antimicrobial and inflammatory mechanisms have overlapping regulation and functions to ensure effective host responses. Genetic interaction studies of immune pathways that compare host responses in single and combined knockout backgrounds are a useful tool to identify new mechanisms of immune control during infection. For disease caused by pulmonary Mycobacterium tuberculosis (Mtb) infections, which currently lacks an effective vaccine, understanding the genetic interactions between protective immune pathways may identify new therapeutic targets or disease-associated genes. Previous studies have suggested a direct link between the activation of NLRP3-Caspase1 inflammasome and the NADPH-dependent phagocyte oxidase complex during Mtb infection. Loss of the phagocyte oxidase complex alone resulted in increased activation of Caspase1 and IL-1β production during Mtb infection, resulting in failed disease tolerance during the chronic stages of disease. To better understand this interaction, we generated mice lacking both Cybb, a key subunit of the phagocyte oxidase, and Caspase1/11. We found that ex vivo Mtb infection of Cybb-/-Caspase1/11-/- macrophages resulted in the expected loss of IL-1β secretion but an unexpected change in other inflammatory cytokines and bacterial control. Mtb infected Cybb-/-Caspase1/11-/- mice rapidly progressed to severe TB, succumbing within 4 weeks to disease characterized by high bacterial burden, increased inflammatory cytokines, and the recruitment of granulocytes that associated with Mtb in the lungs. These results uncover a key genetic interaction between the phagocyte oxidase complex and Caspase1/11 that controls protection against TB and highlight the need for a better understanding of the regulation of fundamental immune networks during Mtb infection.

ADENOCARCINOMA OF THE LUNG MIMICKING MILIARY TB AND POTT DISEASE

ADENOCARCINOMA OF THE LUNG MIMICKING MILIARY TB AND POTT DISEASE

PULMONARY TB WITH HUMAN PARAINFLUENZA 3 VIRUS PRESENTING AS SEPTIC SHOCK WITH MULTIORGAN SYSTEM FAILURE

SESSION TITLE: Critical Care Presentations of TBSESSION TYPE: Rapid Fire Case ReportsPRESENTED ON: 10/18/2022 12:25 pm - 01:25 pmINTRODUCTION: Septic shock with Multiple Organ System Failure (MOSF) from Mycobacterium tuberculosis (MTB) is an uncommon, yet well-known clinical syndrome with high rate of in-hospital mortality (79.2%). Most Human Parainfluenza Virus (HPIV) in immunocompetent adults are mild or asymptomatic. However, not much is known about MTB co-infection with HPIV causing septic shock with MOSF. To the best of our knowledge, this is the first case of pulmonary MTB with HPIV infection presenting as septic shock with multiorgan failure reported in literature.CASE PRESENTATION: Patient is a 72 yo Spanish speaking male without significant past medical history, visiting from Mexico, who presented to the ED with cough. He was at baseline health until the day prior to the presentation when he noted cough with streaked hemoptysis, nausea, vomiting with fever. While in the ED, patient developed respiratory distress with hypotension, needing intubation, mechanical ventilation and vasopressors. CT of the chest demonstrated extensive right middle and lower lung consolidation, concerning for pneumonia. Respiratory pathogen panel was positive for HPIV, type 3. Pt developed multiorgan failure including renal failure needing CVVH, biventricular heart failure with EF of 15% and shock liver. Sputum culture was positive for MTB. Pt was started on anti-TB treatment with ethambutol, isoniazid, pyrazinamide, and rifampin. He clinically improved and after 2-week course of hospitalization was discharged home with outpatient follow up with Health Department and Infectious disease.DISCUSSION: Septic shock with multiorgan failure from MTB is rare yet known phenomenon with high rate of in-hospital mortality, however, co-infection of MTB with parainfluenza virus is not well described. The role of HPIV infection in causing respiratory tract illness is likely contributing factor making pulmonary MTB infection more complicated that can lead to septic shock with multiorgan failure.CONCLUSIONS: Pulmonary MTB co-infection with HPIV can present with septic shock with multiorgan failure. Further studies are needed to investigate and support significance of HPIV to pulmonary MTB.Reference #1: https://pubmed.ncbi.nlm.nih.gov/23429859/Reference #2: https://pubmed.ncbi.nlm.nih.gov/28283855/DISCLOSURES: No relevant relationships by Dovile BaniulisNo relevant relationships by Dovile CerkauskaiteNo relevant relationships by Momcilo Durdevic SESSION TITLE: Critical Care Presentations of TB SESSION TYPE: Rapid Fire Case Reports PRESENTED ON: 10/18/2022 12:25 pm - 01:25 pm INTRODUCTION: Septic shock with Multiple Organ System Failure (MOSF) from Mycobacterium tuberculosis (MTB) is an uncommon, yet well-known clinical syndrome with high rate of in-hospital mortality (79.2%). Most Human Parainfluenza Virus (HPIV) in immunocompetent adults are mild or asymptomatic. However, not much is known about MTB co-infection with HPIV causing septic shock with MOSF. To the best of our knowledge, this is the first case of pulmonary MTB with HPIV infection presenting as septic shock with multiorgan failure reported in literature. CASE PRESENTATION: Patient is a 72 yo Spanish speaking male without significant past medical history, visiting from Mexico, who presented to the ED with cough. He was at baseline health until the day prior to the presentation when he noted cough with streaked hemoptysis, nausea, vomiting with fever. While in the ED, patient developed respiratory distress with hypotension, needing intubation, mechanical ventilation and vasopressors. CT of the chest demonstrated extensive right middle and lower lung consolidation, concerning for pneumonia. Respiratory pathogen panel was positive for HPIV, type 3. Pt developed multiorgan failure including renal failure needing CVVH, biventricular heart failure with EF of 15% and shock liver. Sputum culture was positive for MTB. Pt was started on anti-TB treatment with ethambutol, isoniazid, pyrazinamide, and rifampin. He clinically improved and after 2-week course of hospitalization was discharged home with outpatient follow up with Health Department and Infectious disease. DISCUSSION: Septic shock with multiorgan failure from MTB is rare yet known phenomenon with high rate of in-hospital mortality, however, co-infection of MTB with parainfluenza virus is not well described. The role of HPIV infection in causing respiratory tract illness is likely contributing factor making pulmonary MTB infection more complicated that can lead to septic shock with multiorgan failure. CONCLUSIONS: Pulmonary MTB co-infection with HPIV can present with septic shock with multiorgan failure. Further studies are needed to investigate and support significance of HPIV to pulmonary MTB. Reference #1: https://pubmed.ncbi.nlm.nih.gov/23429859/ Reference #2: https://pubmed.ncbi.nlm.nih.gov/28283855/ DISCLOSURES: No relevant relationships by Dovile Baniulis No relevant relationships by Dovile Cerkauskaite No relevant relationships by Momcilo Durdevic

A novel two-codon deletion at codon 508 and 509 of the rpoB gene in pulmonary tuberculosis and HIV co-infection: A case report

We report a case of pulmonary Mycobacterium tuberculosis infection with a resistance to rifampicin (RIF) in a 39-year-old man who was co-infected with Human Immunodeficiency Virus (HIV) and hepatitis C. Phenotypic and genotypic test were performed to diagnose the patient. Sequencing analysis revealed novel two-codon deletion at codon 508 and 509 of the rpoB gene in M. tuberculosis. Keywords: Co-infection, Mycobacterium tuberculosis, rpoB gene, rifampicin-resistant.

Male reproductive hormones in patients treated with pretomanid.

SUMMARYBACKGROUND:Pretomanid (Pa) is a nitroimidazole-class drug recently approved by the US Food and Drug Administration and other regulatory authorities as part of a regimen for treating highly drug-resistant pulmonary Mycobacterium tuberculosis infections. Studies in rodents identified the testis as a target organ of concern, which led to monitoring of reproductive hormones in >800 male patients enrolled in four clinical trials of Pa-containing regimens and the HRZE (isoniazid+rifampin+pyrazinamide+ethambutol) control regimen.METHODS:Serum hormone levels relevant to male reproductive health – follicle stimulating hormone (FSH), luteinizing hormone (LH), inhibin B (InhB) and total testosterone (T) – from the four clinical trials were summarized numerically and analyzed by repeated-measures modeling.RESULTS:Hormone levels generally behaved similarly in Pa-containing and HRZE arms. Relative to baseline, serum T and InhB levels generally increased at the end of treatment and follow-up. FSH and LH levels were variable, but were generally at or below baseline levels by follow-up. Before treatment, many patients were borderline hypogonadal, with T levels near the lower limits of the normal range.CONCLUSION:Changes in male hormones in four clinical trials studying patients with TB indicate that Pa-containing treatment was not associated with testicular toxicity but rather led to improvement in the underlying hypogonadism.

Characterizing the molecular composition and diagnostic potential of Mycobacterium tuberculosis urinary cell-free DNA using next-generation sequencing

BackgroundUrine cell-free DNA (cfDNA) is an attractive target for diagnosing pulmonary Mycobacterium tuberculosis (MTB) infection, but has not been thoroughly characterized as a biomarker. MethodsThis study was performed to investigate the size and composition of urine cfDNA from tuberculosis (TB) patients with minimal bias using next-generation sequencing (NGS). A combination of DNA extraction and single-stranded sequence library preparation methods demonstrated to recover short, highly degraded cfDNA fragments was employed. Urine cfDNA from 10 HIV-positive patients with pulmonary TB and two MTB-negative controls was examined. ResultsMTB-derived cfDNA was identifiable by NGS from all MTB-positive patients and was absent from negative controls. MTB cfDNA was significantly shorter than human cfDNA, with median fragment lengths of ≤19–52 bp and 42–92 bp, respectively. MTB cfDNA abundance increased exponentially with decreased fragment length, having a peak fragment length of ≤19 bp in most samples. In addition, we identified a larger fraction of short human genomic cfDNA, ranging from 29 to 53 bp, than previously reported. Urine cfDNA fragments spanned the MTB genome with relative uniformity, but nucleic acids derived from multicopy elements were proportionately over-represented. ConclusionsTB urine cfDNA is a potentially powerful biomarker but is highly fragmented, necessitating special procedures to maximize its recovery and detection.

Mycobacterium tuberculosis (MTB) antigen-induced upregulation of interleukin-35 expression in patients with MTB infection: In vitro blockade of the effects of interleukin-35 on T lymphocyte subsets.

Immunosuppressive interleukin-35 (IL-35) serum concentrations were analyzed in patients with active pulmonary Mycobacterium tuberculosis (MTB) infections (PTB), PTB patients after two months treatment (stable PTB) and healthy controls. IL-35 concentrations were highest in active PTB followed by stable PTB cases and lowest in healthy control participants (all P <0.01). The same trents were found for supernatants of isolated blood mononuclear cells (PBMCs), with additional enhancements after MTB antigen stimulation only for PBMCs of active and stable PTB patients (P <0.001), for EBI3 and IL-12a transcriptions in PBMCs (P <0.001) and percentages of EBI3 expressing (CD4+CD25+Foxp3+) regulatory T cells (Treg) (P <0.001). IL-35 antibody applications significantly reversed MTB antigen stimulated IL-35 and IL-10 expression in PBMCs of active and stable PTB patients, and reduced Foxp3 expression in CD4+CD25+cells and EBI3 expression in Treg cells, but had no effects on healthy control cells. The percentages of Th1 and Th17 cells in CD4+cells were enhanced after MTB antigen stimulation of cells taken from active and stable PTB patients, which were partly increased only for Th1 cells after IL-35 antibody exposure. MTB antigen-driven upregulation of IL-35 may lead to reduced immune surveillance in PTB patients.

Gene Xpert/MTB RIF assay for spinal tuberculosis- sensitivity, specificity and clinical utility

BackgroundXpert MTB/RIF assay is a rapid automated molecular test with excellent reported sensitivity, specificity for diagnosis of pulmonary and extrapulmonary Mycobacterium tuberculosis (MTB) infections. However, the clinical utility and accuracy in STB is not well established. A study was conducted to report on the sensitivity, specificity and clinical utility of the Xpert MTB/RIF assay in spinal tuberculosis (STB). MethodsA retrospective review of medical records was performed for 136 patients that underwent spinal biopsy for suspected spondylodiscitis. Reports for acid fast bacilli (AFB) smear, gram stain, pyogenic culture, MTB culture, histopathology, Xpert MTB/RIF assay, and drug sensitivity testing were reviewed. ‘Reference standard for diagnosis of STB’ was based on positive histopathology and/or MTB culture evidence and was considered as MTB positive. Any samples returning a positive pyogenic or fungal culture were considered as MTB negative. The sensitivity, specificity for Xpert MTB/RIF was assessed against the reference standard. ResultsA total of 125 patients were considered for final analysis, 86 patients met the criteria for ‘Reference standard for diagnosis of TB spine’ (MTB positive). This includes nine patients that were MGIT culture only positive; 45 that were histopathology only positive and 32 were both culture and histopathology positive. There were 39 culture proven (pyogenic-37 and fungal-2) patients included in MTB negative group. The 86 MTB positive patients, included 53 (61.6%) tissue samples and 33 (38.4%) pus samples. The overall analysis showed a 65.1% sensitivity, 100% specificity, 100% PPV and 56.5% NPV for the Xpert MTB/RIF. ConclusionsGene Xpert MTB/RIF showed excellent specificity and was accurate in the identification of drug resistance. The sensitivity was 65% and sampling techniques using pus samples rather than tissue samples could be a possible reason for lower sensitivity.

Cytotoxic response of phagocytes in patients newly infected with pulmonary Mycobacterium tuberculosis determined using plasma tumor necrosis factor-alpha, malondialdehyde, and superoxide dismutase: an observational study

Abstract Objective: Pulmonary Mycobacterium tuberculosis infection can trigger cellular and humoral innate immune responses, which may cause death of the pathogen and or host cells/tissue. We aimed to determine the cytotoxic response of phagocytes in patients with pulmonary Mycobacterium tuberculosis infection based on plasma tumor necrosis factor-alpha (TNF-α), malondialdehyde (MDA), and superoxide dismutase (SOD) levels. Methods: In this observational study, patients newly infected with pulmonary Mycobacterium tuberculosis (n = 31; age 37–62 years) and age-matched uninfected volunteers (n = 50) were recruited as test and control volunteers, respectively in Owo, Nigeria. The study protocol was reviewed and approved by the Research and Ethics Committee of the Department of Medical Laboratory Science, Achievers University, Owo, Nigeria (AUO/MLS/VII/2009/212). Anti-hepatitis C virus, human immunodeficiency virus antigen/antibody, hepatitis B virus surface antigen, and plasma TNF-α were determined by enzyme-linked immunosorbent assay, SOD, and MDA were determined by colorimetry, Plasmodium by Giemsa thick blood film staining, and acid-fast bacilli in sputum were detected by Ziehl–Neelsen staining. Results: All participants had normal blood glucose levels and tested negative for human immunodeficiency virus antigen/antibody, anti-hepatitis C virus, hepatitis B virus surface antigen, and Plasmodium spp., and had no medical history of cancer. Infected patients had significantly higher plasma MDA and TNF-α levels and significantly lower SOD levels compared with control subjects (all P &lt; 0.05). Conclusion: Mycobacterium tuberculosis infection elicited a cytotoxic response by phagocytes, evidenced by significant increases in MDA and TNF-α and a significant decrease in SOD levels.

Caloric Restriction Promotes Immunometabolic Reprogramming Leading to Protection from Tuberculosis

There is a strong relationship between metabolic state and susceptibility to Mycobacterium tuberculosis (MTB) infection, with energy metabolism setting the basis for an exaggerated immuno-inflammatory response, which concurs with MTB pathogenesis. Herein, we show that controlled caloric restriction (CR), not leading to malnutrition, protects susceptible DBA/2 mice against pulmonary MTB infection by reducing bacterial load, lung immunopathology, and generation of foam cells, an MTB reservoir in lung granulomas. Mechanistically, CR induced a metabolic shift toward glycolysis, and decreased both fatty acid oxidation and mTOR activity associated with induction of autophagy in immune cells. An integrated multi-omics approach revealed a specific CR-induced metabolomic, transcriptomic, and proteomic signature leading to reduced lung damage and protective remodeling of lung interstitial tightness able to limit MTB spreading. Our data propose CR as a feasible immunometabolic manipulation to control MTB infection, and this approach offers an unexpected strategy to boost immunity against MTB.

Circulating MicroRNA 29a: An Evolving Biomarker for Diagnosis of Pulmonary Tuberculosis

Introduction: Tuberculosis (TB) is global health problem threatening millions every year. There is urgent need of effective biomarkers for its diagnostics and circulating microRNAs (miRNAs) have recently emerged as novel and non-invasive molecular markers in blood. Aim: This study was done to evaluate serum miRNAs as a potential biomarker for the diagnosis of pulmonary mycobacterium tuberculosis infection. Materials and Methods: In this prospective cross-sectional study, acute pulmonary TB patients were recruited based on positive Mycobacterium tuberculosis Polymerase Chain Reaction (PCR) in sputum samples and Microarray expression profiling was performed on blood of these patients to study differentially expressed miRNAs. The results were validated by Real-Time Polymerase Chain Reaction (RT-PCR) on pulmonary TB cases and healthy controls. Student’s t-tests and analysis variance tests were used for statistical analysis. The p-value &lt;0.05 was considered statistically significant. Results: Results of microarray expression profiling showed 75 differentially expressed miRNAs in cases of pulmonary TB; among these 5 upregulated and 2 downregulated miRNAs were evaluated by RT-PCR. miRNA 29a exhibited good distinguishing efficiency; followed by miRNA 384. ROC plot of expression data for miRNA in cases and control groups showed that AUC of miRNA-29a was 0.8268 (sensitivity=80%, specificity=82%) . Conclusion: This study suggests that altered levels of serum miRNAs have great potential to serve as non-invasive biomarkers for detection of Mycobacterium tuberculosisinfection. miRNA-29a can be used as an effective biomarker for diagnosis of pulmonary TB.

CapitalBio Mycobacterium real-time polymerase chain reaction detection test: Rapid diagnosis of Mycobacterium tuberculosis and nontuberculous mycobacterial infection

ObjectivesTo evaluate the accuracy of the CapitalBio Mycobacterium real-time polymerase chain reaction (RT-PCR) detection test for pulmonary Mycobacterium tuberculosis (MTB) and nontuberculous mycobacterial (NTM) infection. MethodsThis study analyzed 2,460 samples from patients with suspected pulmonary mycobacterial infection collected between 01 June 2018 and 31 July 2019. It aimed to determine the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) of the CapitalBio Mycobacterium detection test for MTB and NTM infections, and to evaluate its diagnostic accuracy compared with mycobacterial culture. ResultsThe sensitivity, specificity, PPV, NPV, and AUC of the CapitalBio Mycobacterium detection test for MTB was 83.0%, 79.9%, 80.8%, 82.2%, and 0.81, respectively. This was similar to the diagnostic accuracy of Xpert MTB/RIF for MTB and was significantly higher than that of smear. For pulmonary NTM infection, the sensitivity, specificity, PPV, NPV, and AUC of the test was 82.0%, 99.6%, 94.1%, 98.5%, and 0.91, respectively. The diagnostic accuracy of the CapitalBio Mycobacterium detection test was also significantly higher than that of smear for NTM. ConclusionsThe CapitalBio Mycobacterium detection test had good diagnostic accuracy for MTB and NTM infections. This is of great significance for the differential diagnosis of early pulmonary mycobacterial infection.

Pulmonary mucosal immunity mediated through CpG provides adequate protection against pulmonary Mycobacterium tuberculosis infection in the mouse model. A role for type I interferon

Toll-Like Receptor (TLR) 9 stimulation is required for induction of potent immune responses against pathogen invasion. The use of unmethylated CpG as adjuvants in vaccines provides an excellent means of stimulating adaptive immunity. Our data demonstrate that CpG-C provided prolonged immune responses in the mouse model of tuberculosis when formulated with liposomes and the Mycobacterium tuberculosis antigen ESAT-6. A reduction in the mycobacterial burden was best achieved when administered as an intranasal vaccine and was dependent on type I interferon (IFN). There was a significant difference between CpG-C inoculated wild type and IFN-αR1−/− mice, indicating that type I IFN plays a role in the immune response following CpG-C inoculation. Further analysis showed that early NK cell presence was not an absolute requirement, although elevated IFN-γ levels were detected in the lungs of mice within 48 h. The reduction in mycobacterial burden was MyD88-independent as CpG-C inoculated MyD88−/− mice showed comparable mycobacterial burdens to wild type mice with no detriment due to the lack of MyD88. Together our data show that pulmonary stimulation of TLR9 bearing antigen presenting cells resulted in the induction of protective immunity against M. tuberculosis infection that was dependent on type I IFN signaling.

β-Glucan Induces Protective Trained Immunity against Mycobacterium tuberculosis Infection: A Key Role for IL-1

Summaryβ-glucan is a potent inducer of epigenetic and functional reprogramming of innate immune cells, a process called “trained immunity,” resulting in an enhanced host response against secondary infections. We investigate whether β-glucan exposure confers protection against pulmonary Mycobacterium tuberculosis (Mtb) infection. β-glucan induces trained immunity via histone modifications at gene promoters in human monocytes, which is accompanied by the enhanced production of proinflammatory cytokines upon secondary Mtb challenge and inhibition of Mtb growth. Mice treated with β-glucan are significantly protected against pulmonary Mtb infection, which is associated with the expansion of hematopoietic stem and progenitor cells in the bone marrow and increased myelopoiesis. The protective signature of β-glucan is mediated via IL-1 signaling, as β-glucan shows no protection in mice lacking a functional IL-1 receptor (IL1R−/−). The administration of β-glucan may be used as a novel strategy in the treatment of mycobacterial infections and possibly as an adjuvant to improve anti-tuberculosis vaccines.

1346. Ruling out TB in New York City: Are Two NAATs (Nucleic Acid Amplification Testing) Enough?

BackgroundPrompt diagnosis of pulmonary Mycobacterium tuberculosis (TB) infection can prevent nosocomial exposure. However, sputum smears are insensitive, and turnaround time for cultures can take weeks. Rapid diagnostics, such as nucleic acid amplification testing (NAAT), on respiratory specimens of patients suspected to have TB can improve diagnostic accuracy. Current practice at our institution is to obtain ≥ 3 NAATs in high-risk patients prior to discontinuing airborne isolation, but some studies have suggested that 2 negative NAATs may be sufficient. We conducted a retrospective study of patients at our institution diagnosed with TB.MethodsThe study was conducted at an academic adult hospital, an academic pediatric hospital, and a community hospital in New York City. Line lists of positive cultures for TB and positive NAATs from 2014 to mid-2018 were obtained from microbiology. Chart review was performed. Patient demographics, comorbidities, and radiographic findings were collected. Concordance between culture results and NAATs was evaluated. Incidence of inpatient TB exposure was noted.Results82 cases of TB were found in the study period (see Figure 1). 45 cases were new inpatient diagnoses of pulmonary TB. The most common presenting symptoms were cough (69%), weight loss (49%), and fever (42%, see Table 1). 38/45 (84%) of patients were originally from a country other than the United States. 43/45 (96%) of patients had abnormal lung imaging. Cavitary disease was seen in 29%; other upper lobe disease was seen in 42%. Among smear-negative pulmonary TB cases, NAAT was positive in 11/16 (69%) of patients. Within this subgroup, the sensitivity of one NAAT was 41% when compared with culture. In smear-negative, NAAT-positive patients, NAATs were fully concordant with cultures in 4/11 patients (36%, see Table 2). The median number of positive NAATs was 1; the median number of positive cultures was 2. Five patients with pulmonary TB had negative NAATs altogether (median = 3); 2/5 resulted in TB exposure investigations after airborne precautions were discontinued following NAAT results. Overall, 13/45 (28%) of new diagnoses resulted in an exposure investigation.ConclusionObtaining ≥ 3 NAATs in patients suspected of pulmonary TB improved diagnostic accuracy compared with obtaining 2 or fewer. Disclosures All authors: No reported disclosures.

Effect of Iron Supplementation on the Outcome of Non-Progressive Pulmonary Mycobacterium tuberculosis Infection.

The human response to Mycobacterium tuberculosis (Mtb) infection is affected by the availability of iron (Fe), which is necessary for proper immune cell function and is essential for the growth and virulence of bacteria. Increase in host Fe levels promotes Mtb growth and tuberculosis (TB) pathogenesis, while Fe-supplementation to latently infected, asymptomatic individuals is a significant risk factor for disease reactivation. However, the effect of Fe-supplementation on the host immunity during latent Mtb infection remains unclear, due partly to the paucity in availability of animal models that recapitulate key pathophysiological features seen in humans. We have demonstrated that rabbits can develop non-progressive latency similar to infected humans. In this study, using this model we have evaluated the effect of Fe-supplementation on the bacterial growth, disease pathology, and immune response. Systemic and lung Fe parameters, gene expression profile, lung bacterial burden, and disease pathology were determined in the Mtb-infected/Fe- or placebo-supplemented rabbits. Results show that Fe-supplementation to Mtb-infected rabbits did not significantly change the hematocrit and Hb levels, although it elevated total Fe in the lungs. Expression of selected host iron- and immune-response genes in the blood and lungs was perturbed in Mtb-infected/Fe-supplemented rabbits. Iron-supplementation during acute or chronic stages of Mtb infection did not significantly affect the bacterial burden or disease pathology in the lungs. Data presented in this study is of significant relevance for current public health policies on Fe-supplementation therapy given to anemic patients with latent Mtb infection.

CXCR6-Deficiency Improves the Control of Pulmonary Mycobacterium tuberculosis and Influenza Infection Independent of T-Lymphocyte Recruitment to the Lungs.

T-lymphocytes are critical for protection against respiratory infections, such as Mycobacterium tuberculosis and influenza virus, with chemokine receptors playing an important role in directing these cells to the lungs. CXCR6 is expressed by activated T-lymphocytes and its ligand, CXCL16, is constitutively expressed by the bronchial epithelia, suggesting a role in T-lymphocyte recruitment and retention. However, it is unknown whether CXCR6 is required in responses to pulmonary infection, particularly on CD4+ T-lymphocytes. Analysis of CXCR6-reporter mice revealed that in naïve mice, lung leukocyte expression of CXCR6 was largely restricted to a small population of T-lymphocytes, but this population was highly upregulated after either infection. Nevertheless, pulmonary infection of CXCR6-deficient mice with M. tuberculosis or recombinant influenza A virus expressing P25 peptide (rIAV-P25), an I-Ab-restricted epitope from the immunodominant mycobacterial antigen, Ag85B, demonstrated that the receptor was redundant for recruitment of T-lymphocytes to the lungs. Interestingly, CXCR6-deficiency resulted in reduced bacterial burden in the lungs 6 weeks after M. tuberculosis infection, and reduced weight loss after rIAV-P25 infection compared to wild type controls. This was paradoxically associated with a decrease in Th1-cytokine responses in the lung parenchyma. Adoptive transfer of P25-specific CXCR6-deficient T-lymphocytes into WT mice revealed that this functional change in Th1-cytokine production was not due to a T-lymphocyte intrinsic mechanism. Moreover, there was no reduction in the number or function of CD4+ and CD8+ tissue resident memory cells in the lungs of CXCR6-deficient mice. Although CXCR6 was not required for T-lymphocyte recruitment or retention in the lungs, CXCR6 influenced the kinetics of the inflammatory response so that deficiency led to increased host control of M. tuberculosis and influenza virus.