Epidemiologic link between tuberculosis and cigarette/biomass smoke exposure: Limitations despite the vast literature

The clinical features and prognostic factors of miliary tuberculosis in a high tuberculosis burden area

BACKGROUND

Miliary Tuberculosis (TB) remains an important infectious disease that threatens human health. The clinical characteristics and prognostic factors of miliary TB are summarized in this study.

METHODS

The clinical information of miliary TB patients between 2010 and 2022 was retrospectively analyzed. Patients with miliary TB were characterized and compared to adverse outcomes cases. Factors independently associated with adverse outcomes were determined via multivariate logistic regression analysis.

RESULTS

A total of 288 patients were analyzed, including 181 with adverse outcomes. The clinical manifestations are atypical. 88.54% Of them experienced systemic symptoms, whilst 69.79% manifested respiratory symptoms. 40.97% Presented with neurologic symptoms, while 35.07% reported gastrointestinal symptoms. The major comorbidities were pharmacological immunosuppression (21.53%), pneumoconiosis (15.28%), diabetes (10.76%), and pregnancy or postpartum (7.29%). Regarding microbiology, most patients were diagnosed via sputum or Bronchoalveolar Lavage Fluid (BALF), pleural effusion, ascites, cerebrospinal fluid, urine TB-DNA, and tuberculosis culture. Meanwhile, 2.43% of patients were diagnosed via cerebrospinal fluid NGS. Independent risk factors predictive of adverse outcomes were current smoking, leukocytosis, elevated alanine aminotransferase (ALT) levels, and the combination of lymphopenia with bone marrow tuberculosis or tuberculous lymphadenitis. The accuracy of the model was validated by an area under the ROC curve of 0.753 (95% IC 0.697-0.810).

CONCLUSIONS

The clinical manifestations of miliary TB are atypical, and early diagnosis is challenging. The major comorbidities in miliary TB patients were pharmacological immunosuppression, pneumoconiosis, diabetes, pregnancy, and postpartum. Regarding etiological detection, multi-site and multi-type specimens should be collected for a timely diagnosis. Cerebrospinal fluid mNGS test may be a viable choice in some cases. Finally, current smoking, leukocytosis, elevated ALT levels, and the combination of lymphopenia with bone marrow tuberculosis or tuberculous lymphadenitis were identified as independent risk factors for adverse outcomes.

Cigarette Smoking as a Risk Factor for Tuberculosis in Adults: Epidemiology and Aspects of Disease Pathogenesis

It has been noted by the World Health Organisation that cases of tuberculosis in 2022 globally numbered 10.6 million, resulting in 1.3 million deaths, such that TB is one of the infectious diseases causing the greatest morbidity and mortality worldwide. Since as early as 1918, there has been an ongoing debate as to the relationship between cigarette smoking and TB. However, numerous epidemiological studies, as well as meta-analyses, have indicated that both active and passive smoking are independent risk factors for TB infection, development of reactivation TB, progression of primary TB, increased severity of cavitary disease, and death from TB, among several other considerations. With this considerable body of evidence confirming the association between smoking and TB, it is not surprising that TB control programmes represent a key potential preventative intervention. In addition to coverage of the epidemiology of TB and its compelling causative link with smoking, the current review is also focused on evidence derived from clinical- and laboratory-based studies of disease pathogenesis, most prominently the protective anti-mycobacterial mechanisms of the alveolar macrophage, the primary intracellular refuge of M. tuberculosis. This section of the review is followed by an overview of the major strategies utilised by the pathogen to subvert these antimicrobial mechanisms in the airway, which are intensified by the suppressive effects of smoke inhalation on alveolar macrophage function. Finally, consideration is given to a somewhat under-explored, pro-infective activity of cigarette smoking, namely augmentation of antibiotic resistance due to direct effects of smoke per se on the pathogen. These include biofilm formation, induction of cellular efflux pumps, which eliminate both smoke-derived toxicants and antibiotics, as well as gene modifications that underpin antibiotic resistance.

Ex vivo and in vivo evidence that cigarette smoke-exposed T regulatory cells impair host immunity against Mycobacterium tuberculosis

Introduction

A strong epidemiologic link exists between cigarette smoke (CS) exposure and susceptibility to tuberculosis (TB). Macrophage and murine studies showed that CS and nicotine impair host-protective immune cells against Mycobacterium tuberculosis (MTB) infection. While CS and nicotine may activate T regulatory cells (Tregs), little is known about how CS may affect these immunosuppressive cells with MTB infection.

Methods

We investigated whether CS-exposed Tregs could exacerbate MTB infection in co-culture with human macrophages and in recipient mice that underwent adoptive transfer of Tregs from donor CS-exposed mice.

Results

We found that exposure of primary human Tregs to CS extract impaired the ability of unexposed human macrophages to control an MTB infection by inhibiting phagosome-lysosome fusion and autophagosome formation. Neutralizing CTLA-4 on the CS extract-exposed Tregs abrogated the impaired control of MTB infection in the macrophage and Treg co-cultures. In Foxp3+GFP+DTR+ (Thy1.2) mice depleted of endogenous Tregs, adoptive transfer of Tregs from donor CS-exposed B6.PL(Thy1.1) mice with subsequent MTB infection of the Thy1.2 mice resulted in a greater burden of MTB in the lungs and spleens than those that received Tregs from air-exposed mice. Mice that received Tregs from donor CS-exposed mice and infected with MTB had modest but significantly reduced numbers of interleukin-12-positive dendritic cells and interferon-gamma-positive CD4+ T cells in the lungs, and an increased number of total programmed cell death protein-1 (PD-1) positive CD4+ T cells in both the lungs and spleens.

Discussion

Previous studies demonstrated that CS impairs macrophages and host-protective T effector cells in controlling MTB infection. We now show that CS-exposed Tregs can also impair control of MTB in co-culture with macrophages and in a murine model.

Assortative social mixing and sex disparities in tuberculosis burden

Globally, men have higher tuberculosis (TB) burden but the mechanisms underlying this sex disparity are not fully understood. Recent surveys of social mixing patterns have established moderate preferential within-sex mixing in many settings. This assortative mixing could amplify differences from other causes. We explored the impact of assortative mixing and factors differentially affecting disease progression and detection using a sex-stratified deterministic TB transmission model. We explored the influence of assortativity at disease-free and endemic equilibria, finding stronger effects during invasion and on increasing male:female prevalence (M:F) ratios than overall prevalence. Variance-based sensitivity analysis of endemic equilibria identified differential progression as the most important driver of M:F ratio uncertainty. We fitted our model to prevalence and notification data in exemplar settings within a fully Bayesian framework. For our high M:F setting, random mixing reduced equilibrium M:F ratios by 12% (95% CrI 0-30%). Equalizing male case detection there led to a 20% (95% CrI 11-31%) reduction in M:F ratio over 10 years-insufficient to eliminate sex disparities. However, this potentially achievable improvement was associated with a meaningful 8% (95% CrI 4-14%) reduction in total TB prevalence over this time frame.

Mystery Solved: Why Smoke Extract Worsens Disease in Smokers with Crohn's Disease and Not Ulcerative Colitis? Gut MAP!

Cigarette smoke (CS) exacerbates symptoms in Crohn’s disease (CD) patients while protecting those with ulcerative colitis (UC). CD has been associated with immuno-dysregulation, mucosal dysfunction, and infection. Among the CD-debated pathogens are Mycobacterium avium subsp. paratuberculosis (MAP), adherent invasive Escherichia coli (AIEC), and Klebsiella pneumoniae. The mechanism of how CS modulates nicotinic acetylcholine receptor-α7 (α7nAChR) and elicits inflammatory response in CD-like macrophages is unknown. Here, we investigated the effect of CS/nicotine on macrophages infected with CD-associated pathogens. We measured apoptosis, bacterial viability, macrophage polarization, and gene expression/cytokine levels involved in macrophage response to nicotine/CS extracts from Havana-Leave extract (HLE-nicotine rich) and germplasm line of Maryland tobacco (LAMD-nicotine less). Nicotine (4 µg/mL) and HLE extracts (0.18%) significantly favored anti-inflammatory response in macrophages (increased CD-206 (M2) and IL-10, and decreased M1/M2 ratio; p < 0.05). While macrophages infected with MAP or treated with LPS promoted pro-inflammatory response. Further treatment of these macrophages with nicotine or HLE extracts caused higher inflammatory response (increased iNOS (M1), TNF-α, IL-6, and M1/M2 ratio, p < 0.05), increased MAP burden, and decreased apoptosis. Pre-conditioning macrophages with nicotine ahead of infection resulted in lower pro-inflammatory response. Blocking α7nAChR with an antagonist voided the effect of nicotine on macrophages. Overall, the study provides an insight toward understanding the contradictory effect of nicotine on Inflammatory Bowel Disease patients and about the mechanistic role of α7nAChR in modulation of macrophages in tobacco smokers.

E-cigarettes: Effects in phagocytosis and cytokines response against Mycobacterium tuberculosis

Cigarette smoking and tuberculosis are a significant cause of death worldwide. Several epidemiological studies have demonstrated cigarette smoking is a risk factor for tuberculosis. Electronic cigarettes have recently appeared as a healthier alternative to conventional smoking, although their impact in tuberculosis is not well understood. The aim of this study was to explore the effect of electronic cigarettes in phagocytosis of Mycobacterium tuberculosis and cytokines production. In vitro infection was carried out by exposing THP-1 macrophages to four electronic vapor extracts and the intracellular burden of M. tuberculosis was determined. The percentage of infection was evaluated by confocal microscopy and the cytokine production by Luminex. A reduction of intracellular M. tuberculosis burden in THP-1 macrophages was found after its exposure to electronic vapor extract; the same trend was observed by confocal microscopy when Mycobacterium bovis BCG-GFP strain was used. Electronic cigarettes stimulate a pro-inflammatory cytokine response. We conclude that electronic cigarettes impair the phagocytic function and the cytokine response to M. tuberculosis.

Lack of an Association Between Household Air Pollution Exposure and Previous Pulmonary Tuberculosis

CONTEXT

Observational studies investigating household air pollution (HAP) exposure to biomass fuel smoke as a risk factor for pulmonary tuberculosis have reported inconsistent results.

OBJECTIVE

To evaluate the association between HAP exposure and the prevalence of self-reported previous pulmonary tuberculosis.

DESIGN

We analyzed pooled data including 12,592 individuals from five population-based studies conducted in Latin America, East Africa, and Southeast Asia from 2010 to 2015. We used multivariable logistic regression to model the association between HAP exposure and self-reported previous pulmonary tuberculosis adjusted for age, sex, tobacco smoking, body mass index, secondary education, site and country of residence.

RESULTS

Mean age was 54.6 years (range of mean age across settings 43.8-59.6 years) and 48.6% were women (range of % women 38.3-54.5%). The proportion of participants reporting HAP exposure was 38.8% (range in % HAP exposure 0.48-99.4%). Prevalence of previous pulmonary tuberculosis was 2.7% (range of prevalence 0.6-6.9%). While participants with previous pulmonary tuberculosis had a lower pre-bronchodilator FEV₁ (mean - 0.7 SDs, 95% CI - 0.92 to - 0.57), FVC (- 0.52 SDs, 95% CI - 0.69 to - 0.33) and FEV₁/FVC (- 0.59 SDs, 95% CI - 0.76 to - 0.43) as compared to those who did not, we did not find an association between HAP exposure and previous pulmonary tuberculosis (adjusted odds ratio = 0.86; 95% CI 0.56-1.32).

CONCLUSIONS

There was no association between HAP exposure and self-reported previous pulmonary tuberculosis in five population-based studies conducted worldwide.

Non-communicable diseases and tuberculosis: Anticipating the impending global storm

The epidemiological transitions that have occurred in low and middle income countries (LMIC) during the past decades have led to an increased prevalence on non-communicable diseases (NCDs) in these countries, where the burden of infectious diseases (IDs), especially tuberculosis (TB), remains high. Although the true dimensions of this comorbidity have not yet been fully understood, there is a growing amount of data, over the last 10 years, that suggest a clear association between NCDs and TB. In particular, there is a continuously increasing body of evidence that diabetes mellitus, chronic respiratory conditions, tobacco use, mental health illnesses and chronic kidney disease increase TB morbidity and mortality and vice versa. This bidirectional negative association between diseases may jeopardise the achievement of the Sustainable Development Goals (SDGs) specific TB targets, thus underlying the importance of integrated public health responses towards both epidemics. Population as well as individual based approaches are required, along with both strategic and operation integration on a global scale. This year's United Nations High Level Meetings (ΗLMs) presented a rare opportunity for the political foundations of the TB and NCD responses to be dug together, thus creating a potential breakthrough in the global response to both epidemics.

Smoking in Correctional Settings Worldwide: Prevalence, Bans, and Interventions

Smoking tobacco contributes to 11.5% of deaths worldwide and, in some countries, more hospitalizations than alcohol and drugs combined. Globally in 2015, 25% of men and 5% of women smoked. In the United States, a higher proportion of people in prison smoke than do community-dwelling individuals. To determine smoking prevalence in prisons worldwide, we systematically reviewed the literature using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines; we also examined whether prisons banned smoking or treated smokers. We searched databases for articles published between 2012 and 2016 and located 85 relevant articles with data representing 73.5% of all incarcerated persons from 50 countries. In 35 of 36 nations (97%) with published prevalence data, smoking for the incarcerated exceeded community rates 1.04- to 62.6-fold. Taking a conservative estimate of a 2-fold increase, we estimated that, globally, 14.5 million male and 26,000 female smokers pass through prisons annually. Prison authorities’ responses include permitting, prohibiting, or treating tobacco use. Bans may temporarily improve health and reduce in-prison health care costs but have negligible effect after prison release. Evidence-based interventions for smoking cessation effective outside prisons are effective inside; effects persist after release. Because smoking prevalence is heightened in prisons, offering evidence-based interventions to nearly 15 million smokers passing through yearly would improve global health.

Contribution of Smoking to Tuberculosis Incidence and Mortality in High-Tuberculosis-Burden Countries

Globally, 10 million incident cases of tuberculosis (TB) are reported annually, and 95% of TB cases and 80% of tobacco users reside in low- and middle-income countries. Smoking approximately doubles the risk of TB disease and TB mortality. We estimated the proportion of annual incident TB cases and TB mortality attributable to tobacco smoking in 32 high-TB-burden countries. We obtained country-specific estimates of TB incidence, TB mortality, and smoking prevalence from the World Health Organization Global TB Report (2017), tobacco surveillance reports (2015), and the Tobacco Atlas. Risk ratios for the effect of smoking on TB incidence and TB mortality were obtained from published meta-analyses. An estimated 17.6% (95% confidence interval (CI): 8.4, 21.4) of TB cases and 15.2% (95% CI: 1.8, 31.9) of TB mortality were attributable to smoking. Among high-TB-burden countries, Russia had the highest proportion of smoking-attributable TB disease (31.6%, 95% CI: 15.9, 37.6) and deaths (28.1%, 95% CI: 3.8, 51.4). Men had a greater proportion of TB cases attributable to smoking (30.3%, 95% CI: 14.7, 36.6) than did women (4.3, 95% CI: 1.7, 5.7). Our findings highlight the need for tobacco control in high-TB-burden countries to combat TB incidence and TB mortality.

Epidemiologic Evidence of and Potential Mechanisms by Which Second-Hand Smoke Causes Predisposition to Latent and Active Tuberculosis

Many studies have linked cigarette smoke (CS) exposure and tuberculosis (TB) infection and disease although much fewer have studied second-hand smoke (SHS) exposure. Our goal is to review the epidemiologic link between SHS and TB as well as to summarize the effects SHS and direct CS on various immune cells relevant for TB. PubMed searches were performed using the key words "tuberculosis" with "cigarette," "tobacco," or "second-hand smoke." The bibliography of relevant papers were examined for additional relevant publications. Relatively few studies associate SHS exposure with TB infection and active disease. Both SHS and direct CS can alter various components of host immunity resulting in increased vulnerability to TB. While the epidemiologic link of these 2 health maladies is robust, more definitive, mechanistic studies are required to prove that SHS and direct CS actually cause increased susceptibility to TB.

Nicotine Impairs Macrophage Control of Mycobacterium tuberculosis

Pure nicotine impairs macrophage killing of Mycobacterium tuberculosis (MTB), but it is not known whether the nicotine component in cigarette smoke (CS) plays a role. Moreover, the mechanisms by which nicotine impairs macrophage immunity against MTB have not been explored. To neutralize the effects of nicotine in CS extract, we used a competitive inhibitor to the nicotinic acetylcholine receptor (nAChR)-mecamylamine-as well as macrophages derived from mice with genetic disruption of specific subunits of nAChR. We also determined whether nicotine impaired macrophage autophagy and whether nicotine-exposed T regulatory cells (Tregs) could subvert macrophage anti-MTB immunity. Mecamylamine reduced the CS extract increase in MTB burden by 43%. CS extract increase in MTB was also significantly attenuated in macrophages from mice with genetic disruption of either the α7, β2, or β4 subunit of nAChR. Nicotine inhibited autophagosome formation in MTB-infected THP-1 cells and primary murine alveolar macrophages, as well as increased the intracellular MTB burden. Nicotine increased migration of THP-1 cells, consistent with the increased number of macrophages found in the lungs of smokers. Nicotine induced Tregs to produce transforming growth factor-β. Naive mouse macrophages co-cultured with nicotine-exposed Tregs had significantly greater numbers of viable MTB recovered with increased IL-10 production and urea production, but no difference in secreted nitric oxide as compared with macrophages cocultured with unexposed Tregs. We conclude that nicotine in CS plays an important role in subverting macrophage control of MTB infection.

Optimally capturing latency dynamics in models of tuberculosis transmission

Although different structures are used in modern tuberculosis (TB) models to simulate TB latency, it remains unclear whether they are all capable of reproducing the particular activation dynamics empirically observed. We aimed to determine which of these structures replicate the dynamics of progression accurately. We reviewed 88 TB-modelling articles and classified them according to the latency structure employed. We then fitted these different models to the activation dynamics observed from 1352 infected contacts diagnosed in Victoria (Australia) and Amsterdam (Netherlands) to obtain parameter estimates. Six different model structures were identified, of which only those incorporating two latency compartments were capable of reproducing the activation dynamics empirically observed. We found important differences in parameter estimates by age. We also observed marked differences between our estimates and the parameter values used in many previous models. In particular, when two successive latency phases are considered, the first period should have a duration that is much shorter than that used in previous studies. In conclusion, structures incorporating two latency compartments and age-stratification should be employed to accurately replicate the dynamics of TB latency. We provide a catalogue of parameter values and an approach to parameter estimation from empiric data for calibration of future TB-models.

A Systematic Review of the Prevalence and Pattern of Imaging Defined Post-TB Lung Disease

Background

Tuberculosis is an important risk factor for chronic respiratory disease in resource poor settings. The persistence of abnormal spirometry and symptoms after treatment are well described, but the structural abnormalities underlying these changes remain poorly defined, limiting our ability to phenotype post-TB lung disease in to meaningful categories for clinical management, prognostication, and ongoing research. The relationship between post-TB lung damage and patient-centred outcomes including functional impairment, respiratory symptoms, and health related quality of life also remains unclear.

Methods

We performed a systematic literature review to determine the prevalence and pattern of imaging-defined lung pathology in adults after medical treatment for pleural, miliary, or pulmonary TB disease. Data were collected on study characteristics, and the modality, timing, and findings of thoracic imaging. The proportion of studies relating imaging findings to spirometry results and patient morbidity was recorded. Study quality was assessed using a modified Newcastle-Ottowa score. (Prospero Registration number CRD42015027958)

Results

We identified 37 eligible studies. The principle features seen on CXR were cavitation (8.3–83.7%), bronchiectasis (4.3–11.2%), and fibrosis (25.0–70.4%), but prevalence was highly variable. CT imaging identified a wider range of residual abnormalities than CXR, including nodules (25.0–55.8%), consolidation (3.7–19.2%), and emphysema (15.0–45.0%). The prevalence of cavitation was generally lower (7.4–34.6%) and bronchiectasis higher (35.0–86.0%) on CT vs. CXR imaging. A paucity of prospective data, and data from HIV-infected adults and sub-Saharan Africa (sSA) was noted. Few studies related structural damage to physiological impairment, respiratory symptoms, or patient morbidity.

Conclusions

Post-TB structural lung pathology is common. Prospective data are required to determine the evolution of this lung damage and its associated morbidity over time. Further data are required from HIV-infected groups and those living in sSA.

Biomass smoke as a risk factor for chronic obstructive pulmonary disease: effects on innate immunity

Chronic obstructive pulmonary disease (COPD), a major cause of mortality and morbidity worldwide, is considered an archetypical disease of innate immunity, where inhaled particles and gases trigger an inflammatory response, favoring tissue proliferation in small airways and tissue destruction in lung parenchyma, in addition to the recruitment of immune cells to these compartments. Although cigarette smoking is still considered the main risk factor for developing COPD, the trend of proposing biomass smoke (BS) exposure as a principal risk factor is gaining importance, as around 3 billion people worldwide are exposed to this pollutant daily. A considerable amount of evidence has shown the potential of BS as an enhancer of lung inflammation. However, an impairment of some innate immune responses after BS exposure has also been described. Regarding the mechanisms by which biomass smoke alters the innate immune responses, three main classes of cell surface receptors-the TLRs, the scavenger receptors and the transient receptor potential channels-have shown the ability to transduce signals initiated after BS exposure. This article is an updated and comprehensive review of the immunomodulatory effects described after the interaction of BS components with these receptors.