Spatial Analysis of Drug-Susceptible and Multidrug-Resistant Cases of Tuberculosis, Ho Chi Minh City, Vietnam, 2020-2023

We characterized the spatial distribution of drug-susceptible (DS) and multidrug-resistant (MDR) tuberculosis (TB) cases in Ho Chi Minh City, Vietnam, a major metropolis in southeastern Asia, and explored demographic and socioeconomic factors associated with local TB burden. Hot spots of DS and MDR TB incidence were observed in the central parts of Ho Chi Minh City, and substantial heterogeneity was observed across wards. Positive spatial autocorrelation was observed for both DS TB and MDR TB. Ward-level TB incidence was associated with HIV prevalence and the male proportion of the population. No ward-level demographic and socioeconomic indicators were associated with MDR TB case count relative to total TB case count. Our findings might inform spatially targeted TB control strategies and provide insights for generating hypotheses about the nature of the relationship between DS and MDR TB in Ho Chi Minh City and the wider southeastern region of Asia.

Adjunctive Dexamethasone for Tuberculous Meningitis in HIV-Positive Adults

BACKGROUND

Adjunctive glucocorticoids are widely used to treat human immunodeficiency virus (HIV)-associated tuberculous meningitis despite limited data supporting their safety and efficacy.

METHODS

We conducted a double-blind, randomized, placebo-controlled trial involving HIV-positive adults (≥18 years of age) with tuberculous meningitis in Vietnam and Indonesia. Participants were randomly assigned to receive a 6-to-8-week tapering course of either dexamethasone or placebo in addition to 12 months of antituberculosis chemotherapy. The primary end point was death from any cause during the 12 months after randomization.

RESULTS

A total of 520 adults were randomly assigned to receive either dexamethasone (263 participants) or placebo (257 participants). The median age was 36 years; 255 of 520 participants (49.0%) had never received antiretroviral therapy, and 251 of 484 participants (51.9%) with available data had a baseline CD4 count of 50 cells per cubic millimeter or less. Six participants withdrew from the trial, and five were lost to follow-up. During the 12 months of follow-up, death occurred in 116 of 263 participants (44.1%) in the dexamethasone group and in 126 of 257 participants (49.0%) in the placebo group (hazard ratio, 0.85; 95% confidence interval, 0.66 to 1.10; P = 0.22). Prespecified analyses did not reveal a subgroup that clearly benefited from dexamethasone. The incidence of secondary end-point events, including cases of immune reconstitution inflammatory syndrome during the first 6 months, was similar in the two trial groups. The numbers of participants with at least one serious adverse event were similar in the dexamethasone group (192 of 263 participants [73.0%]) and the placebo group (194 of 257 participants [75.5%]) (P = 0.52).

CONCLUSIONS

Among HIV-positive adults with tuberculous meningitis, adjunctive dexamethasone, as compared with placebo, did not confer a benefit with respect to survival or any secondary end point. (Funded by the Wellcome Trust; ACT HIV ClinicalTrials.gov number, NCT03092817.).

Disruption of Aldehyde Dehydrogenase 2 protects against bacterial infection

The ALDH2*2 (rs671) allele is one of the most common genetic mutations in humans, yet the positive evolutionary selective pressure to maintain this mutation is unknown, despite its association with adverse health outcomes. ALDH2 is responsible for the detoxification of metabolically produced aldehydes, including lipid-peroxidation end products derived from inflammation. Here, we demonstrate that host-derived aldehydes 4-hydroxynonenal (4HNE), malondialdehyde (MDA), and formaldehyde (FA), all of which are metabolized by ALDH2, are directly toxic to the bacterial pathogens Mycobacterium tuberculosis and Francisella tularensis at physiological levels. We find that Aldh2 expression in macrophages is decreased upon immune stimulation, and that bone marrow-derived macrophages from Aldh2 -/- mice contain elevated aldehydes relative to wild-type mice. Macrophages deficient for Aldh2 exhibited enhanced control of Francisella infection. Finally , mice lacking Aldh2 demonstrated increased resistance to pulmonary infection by M. tuberculosis , including in a hypersusceptible model of tuberculosis, and were also resistant to Francisella infection. We hypothesize that the absence of ALDH2 contributes to the host's ability to control infection by pathogens such as M. tuberculosis and F. tularensis , and that host-derived aldehydes act as antimicrobial factors during intracellular bacterial infections.

One sentence summary

Aldehydes produced by host cells contribute to the control of bacterial infections.

MUC5AC Genetic Variation Is Associated With Tuberculous Meningitis Cerebral Spinal Fluid Cytokine Responses and Mortality

BACKGROUND

The purpose of this study was to assess if single nucleotide polymorphisms (SNPs) in lung mucins MUC5B and MUC5AC are associated with Mycobacterium tuberculosis outcomes.

METHODS

Independent SNPs in MUC5B and MUC5AC (genotyped by Illumina HumanOmniExpress array) were assessed for associations with tumor necrosis factor (TNF) concentrations (measured by immunoassay) in cerebral spinal fluid (CSF) from tuberculous meningitis (TBM) patients. SNPs associated with CSF TNF concentrations were carried forward for analyses of pulmonary and meningeal tuberculosis susceptibility and TBM mortality.

RESULTS

MUC5AC SNP rs28737416 T allele was associated with lower CSF concentrations of TNF (P = 1.8 × 10-8) and IFN-γ (P = 2.3 × 10-6). In an additive genetic model, rs28737416 T/T genotype was associated with higher susceptibility to TBM (odds ratio [OR], 1.24; 95% confidence interval [CI], 1.03-1.49; P = .02), but not pulmonary tuberculosis (OR, 1.11, 95% CI, .98-1.25; P = .10). TBM mortality was higher among participants with the rs28737416 T/T and T/C genotypes (35/119, 30.4%) versus the C/C genotype (11/89, 12.4%; log-rank P = .005) in a Vietnam discovery cohort (n = 210), an independent Vietnam validation cohort (n = 87; 9/87, 19.1% vs 1/20, 2.5%; log-rank P = .02), and an Indonesia validation cohort (n = 468, 127/287, 44.3% vs 65/181, 35.9%; log-rank P = .06).

CONCLUSIONS

MUC5AC variants may contribute to immune changes that influence TBM outcomes.

Distribution and origins of Mycobacterium tuberculosis L4 in Southeast Asia

Molecular and genomic studies have revealed that Mycobacterium tuberculosis Lineage 4 (L4, Euro-American lineage) emerged in Europe before becoming distributed around the globe by trade routes, colonial migration and other historical connections. Although L4 accounts for tens or hundreds of thousands of tuberculosis (TB) cases in multiple Southeast Asian countries, phylogeographical studies have either focused on a single country or just included Southeast Asia as part of a global analysis. Therefore, we interrogated public genomic data to investigate the historical patterns underlying the distribution of L4 in Southeast Asia and surrounding countries. We downloaded 6037 genomes associated with 29 published studies, focusing on global analyses of L4 and Asian studies of M. tuberculosis. We identified 2256 L4 genomes including 968 from Asia. We show that 81 % of L4 in Thailand, 51 % of L4 in Vietnam and 9 % of L4 in Indonesia belong to sub-lineages of L4 that are rarely seen outside East and Southeast Asia (L4.2.2, L4.4.2 and L4.5). These sub-lineages have spread between East and Southeast Asian countries, with no recent European ancestor. Although there is considerable uncertainty about the exact direction and order of intra-Asian M. tuberculosis dispersal, due to differing sampling frames between countries, our analysis suggests that China may be the intermediate location between Europe and Southeast Asia for two of the three predominantly East and Southeast Asian L4 sub-lineages (L4.2.2 and L4.5). This new perspective on L4 in Southeast Asia raises the possibility of investigating host population-specific evolution and highlights the need for more structured sampling from Southeast Asian countries to provide more certainty of the historical and current routes of dispersal.

REL and BHLHE40 Variants Are Associated with IL-12 and IL-10 Responses and Tuberculosis Risk

The major human genes regulating Mycobacterium tuberculosis-induced immune responses and tuberculosis (TB) susceptibility are poorly understood. Although IL-12 and IL-10 are critical for TB pathogenesis, the genetic factors that regulate their expression in humans are unknown. CNBP, REL, and BHLHE40 are master regulators of IL-12 and IL-10 signaling. We hypothesized that common variants in CNBP, REL, and BHLHE40 were associated with IL-12 and IL-10 production from dendritic cells, and that these variants also influence adaptive immune responses to bacillus Calmette-Guérin (BCG) vaccination and TB susceptibility. We characterized the association between common variants in CNBP, REL, and BHLHE40, innate immune responses in dendritic cells and monocyte-derived macrophages, BCG-specific T cell responses, and susceptibility to pediatric and adult TB in human populations. BHLHE40 single-nucleotide polymorphism (SNP) rs4496464 was associated with increased BHLHE40 expression in monocyte-derived macrophages and increased IL-10 from peripheral blood dendritic cells and monocyte-derived macrophages after LPS and TB whole-cell lysate stimulation. SNP BHLHE40 rs11130215, in linkage disequilibrium with rs4496464, was associated with increased BCG-specific IL-2+CD4+ T cell responses and decreased risk for pediatric TB in South Africa. SNPs REL rs842634 and rs842618 were associated with increased IL-12 production from dendritic cells, and SNP REL rs842618 was associated with increased risk for TB meningitis. In summary, we found that genetic variations in REL and BHLHE40 are associated with IL-12 and IL-10 cytokine responses and TB clinical outcomes. Common human genetic regulation of well-defined intermediate cellular traits provides insights into mechanisms of TB pathogenesis.

Sources of Multidrug Resistance in Patients With Previous Isoniazid-Resistant Tuberculosis Identified Using Whole Genome Sequencing: A Longitudinal Cohort Study

BACKGROUND

Meta-analysis of patients with isoniazid-resistant tuberculosis (TB) given standard first-line anti-TB treatment indicated an increased risk of multidrug-resistant TB (MDR-TB) emerging (8%), compared to drug-sensitive TB (0.3%). Here we use whole genome sequencing (WGS) to investigate whether treatment of patients with preexisting isoniazid-resistant disease with first-line anti-TB therapy risks selecting for rifampicin resistance, and hence MDR-TB.

METHODS

Patients with isoniazid-resistant pulmonary TB were recruited and followed up for 24 months. Drug susceptibility testing was performed by microscopic observation drug susceptibility assay, mycobacterial growth indicator tube, and by WGS on isolates at first presentation and in the case of re-presentation. Where MDR-TB was diagnosed, WGS was used to determine the genomic relatedness between initial and subsequent isolates. De novo emergence of MDR-TB was assumed where the genomic distance was 5 or fewer single-nucleotide polymorphisms (SNPs), whereas reinfection with a different MDR-TB strain was assumed where the distance was 10 or more SNPs.

RESULTS

Two hundred thirty-nine patients with isoniazid-resistant pulmonary TB were recruited. Fourteen (14/239 [5.9%]) patients were diagnosed with a second episode of TB that was multidrug resistant. Six (6/239 [2.5%]) were identified as having evolved MDR-TB de novo and 6 as having been reinfected with a different strain. In 2 cases, the genomic distance was between 5 and 10 SNPs and therefore indeterminate.

CONCLUSIONS

In isoniazid-resistant TB, de novo emergence and reinfection of MDR-TB strains equally contributed to MDR development. Early diagnosis and optimal treatment of isoniazid-resistant TB are urgently needed to avert the de novo emergence of MDR-TB during treatment.

Variations in Antimicrobial Activities of Human Monocyte-Derived Macrophage and Their Associations With Tuberculosis Clinical Manifestations

Macrophages play a significant role in preventing infection through antimicrobial activities, particularly acidification, and proteolysis. Mycobacterium tuberculosis (Mtb) infection can lead to diverse outcomes, from latent asymptomatic infection to active disease involving multiple organs. Monocyte-derived macrophage is one of the main cell types accumulating in lungs following Mtb infection. The variation of intracellular activities of monocyte-derived macrophages in humans and the influence of these activities on the tuberculosis (TB) spectrum are not well understood. By exploiting ligand-specific bead-based assays, we investigated macrophage antimicrobial activities real-time in healthy volunteers (n = 53) with 35 cases of latent TB (LTB), and those with active TB (ATB), and either pulmonary TB (PTB, n = 70) or TB meningitis (TBM, n = 77). We found wide person-to-person variations in acidification and proteolytic activities in response to both non-immunogenic IgG and pathogenic ligands comprising trehalose 6,6'−dimycolate (TDM) from Mtb or β-glucan from Saccharamyces cerevisiase. The variation in the macrophage activities remained similar regardless of stimuli; however, IgG induced stronger acidification activity than immunogenic ligands TDM (P = 10⁻⁵, 3 × 10⁻⁵ and 0.01 at 30, 60, and 90 min) and β-glucan (P = 10⁻⁴, 3 × 10⁻⁴ and 0.04 at 30, 60, and 90 min). Variation in proteolysis activity was slightly higher in LTB than in ATB (CV = 40% in LTB vs. 29% in ATB, P = 0.03). There was no difference in measured antimicrobial activities in response to TDM and bacterial killing in macrophages from LTB and ATB, or from PTB and TBM. Our results indicate that antimicrobial activities of monocyte-derived macrophages vary among individuals and show immunological dependence, but suggest these activities cannot be solely responsible for the control of bacterial replication or dissemination in TB.

Value of lipocalin 2 as a potential biomarker for bacterial meningitis

OBJECTIVES

Central nervous system (CNS) infections are common causes of morbidity and mortality worldwide. We aimed to discover protein biomarkers that could rapidly and accurately identify the likely cause of the infections, essential for clinical management and improving outcome.

METHODS

We applied liquid chromatography tandem mass spectrometry on 45 cerebrospinal fluid (CSF) samples from a cohort of adults with and without CNS infections to discover potential diagnostic biomarkers. We then validated the diagnostic performance of a selected biomarker candidate in an independent cohort of 364 consecutively treated adults with CNS infections admitted to a referral hospital in Vietnam.

RESULTS

In the discovery cohort, we identified lipocalin 2 (LCN2) as a potential biomarker of bacterial meningitis (BM) other than tuberculous meningitis. The analysis of the validation cohort showed that LCN2 could discriminate BM from other CNS infections (including tuberculous meningitis, cryptococcal meningitis and virus/antibody-mediated encephalitis), with sensitivity of 0.88 (95% confident interval (CI), 0.77-0.94), specificity of 0.91 (95% CI, 0.88-0.94) and diagnostic odds ratio of 73.8 (95% CI, 31.8-171.4). LCN2 outperformed other CSF markers (leukocytes, glucose, protein and lactate) commonly used in routine care worldwide. The combination of LCN2, CSF leukocytes, glucose, protein and lactate resulted in the highest diagnostic performance for BM (area under the receiver operating characteristics curve, 0.96; 95% CI, 0.93-0.99). Data are available via ProteomeXchange with identifier PXD020510.

CONCLUSIONS

LCN2 is a sensitive and specific biomarker for discriminating BM from a broad spectrum of other CNS infections. A prospective study is needed to assess the diagnostic utility of LCN2 in the diagnosis and management of CNS infections.

Pretreatment Cerebrospinal Fluid Bacterial Load Correlates With Inflammatory Response and Predicts Neurological Events During Tuberculous Meningitis Treatment

BACKGROUND

The Mycobacterium tuberculosis load in the brain of individuals with tuberculous meningitis (TBM) may reflect the host's ability to control the pathogen, determine disease severity, and determine treatment outcomes.

METHODS

We used the GeneXpert assay to measure the pretreatment M. tuberculosis load in cerebrospinal fluid (CSF) specimens from 692 adults with TBM. We sought to understand the relationship between CSF bacterial load and inflammation, and their respective impact on disease severity and treatment outcomes.

RESULTS

A 10-fold higher M. tuberculosis load was associated with increased disease severity (odds ratio, 1.59; P = .001 for the comparison between grade 1 and grade 3 severity), CSF neutrophil count (r = 0.364 and P < .0001), and cytokine concentrations (r = 0.438 and P < .0001). A high M. tuberculosis load predicted new neurological events after starting treatment (P = .005, by multinomial logistic regression) but not death. Patients who died had an attenuated inflammatory response at the start of treatment, with reduced cytokine concentrations as compared to survivors. In contrast, patients with high pretreatment CSF bacterial loads, cytokine concentrations, and neutrophil counts were more likely to subsequently experience neurological events.

CONCLUSIONS

The pretreatment GeneXpert-determined M. tuberculosis load may be a useful predictor of neurological complications occurring during TBM treatment. Given the evidence for the divergent pathogenesis of TBM-associated neurological complications and deaths, therapeutic strategies to reduce them may need reassessment.

Comparison of the Mycobacterium tuberculosis molecular bacterial load assay, microscopy and GeneXpert versus liquid culture for viable bacterial load quantification before and after starting pulmonary tuberculosis treatment

Molecular bacterial load assay (MBLA) rapidly quantifies viable Mycobacterium tuberculosis (Mtb) and may be useful for monitoring treatment response and treatment efficacy. We conducted a prospective study in 56 adults with pulmonary tuberculosis from whom 244 sputum samples were collected before and during the first month of treatment. We evaluated MBLA for early monitoring of bacterial burden and investigated bactericidal activities of first-line therapy in patients infected with drug susceptible and resistant isolates. Mtb loads measured by MBLA and culture were correlated after one-week (r = 0.56) and one-month (r = 0.73) of treatment. Correlations between culture and GeneXpert or microscopy were weaker during treatment. Mtb load by MBLA declined more rapidly than GeneXpert after one-week (2.73 Ct, P < 0.001; 0.95 Ct, P = 0.297, respectively) and one-month (8.94 Ct, P < 0.001; 6.78 Ct, P < 0.001). Mtb loads in multidrug resistant (MDR) infections were significantly greater than in both sensitive and poly/mono-resistance after one-week (P < 0.02) and one-month treatment (P = 0.001). MBLA performed better than GeneXpert and microscopy in comparison to culture for quantifying viable Mtb during treatment. It can be used for monitoring bacterial load during TB treatment, facilitating early detection of treatment failure thus improving outcomes.

Development of ligand-coated beads to measure macrophage antimicrobial activities

BACKGROUND INFORMATION

After macrophage recognises and phagocytoses the microorganism, their phagosome undergoes a maturation process, which creates a hostile environment for the bacterium. The lumen is acidified, and proteolysis occurs to kill and degrade pathogen for further antigen presentation. It is important to understand the association between the macrophage intracellular activities and the outcome of infection. Different methods have been developed to measure the phagosome dynamics of macrophages, but there are still limitations.

RESULTS

We used Mycobacterium tuberculosis (Mtb) antigens, the causative agent of tuberculosis (TB), as a model of infectious disease. Adopting a fluorescent bead-based assay, we developed beads coated with trehalose 6,6'dimycolate (TDM) from Mtb cell wall and β-glucan from yeast cell wall to measure the macrophage phagosomal activities using a microplate reader. We examined the consistency of the assay using J774 cells and validated it using human monocyte-derived macrophages (hMDM) from healthy volunteers and TB patients. There was a decreased pH and increased proteolysis in the lumen of J774 cells after phagocytosing the ligand-coated beads. J774 macrophage showed no difference in the acidification and proteolysis in response to control IgG beads, TDM and β-glucan beads. hMDM from healthy volunteers or TB patients showed heterogeneity in the intracellular activities when treated with ligand-coated beads.

CONCLUSIONS AND SIGNIFICANCE

The beads coated with specific ligands from Mtb worked well in both macrophage cell line and human primary macrophages, which can be exploited to further study the phagosomal function of macrophage in TB. Our bead model can be applied to different ligands from other pathogens, which could extend the understanding of the associations between macrophage antimicrobial functions and outcomes of infectious diseases and the possible cellular mechanisms involved.

Virulence of Mycobacterium tuberculosis Clinical Isolates Is Associated With Sputum Pre-treatment Bacterial Load, Lineage, Survival in Macrophages, and Cytokine Response

It is uncertain whether differences in Mycobacterium tuberculosis (Mtb) virulence defined in vitro influence clinical tuberculosis pathogenesis, transmission, and mortality. We primarily used a macrophage lysis model to characterize the virulence of Mtb isolates collected from 153 Vietnamese adults with pulmonary tuberculosis. The virulence phenotypes were then investigated for their relationship with sputum bacterial load, bacterial lineages, bacterial growth, and cytokine responses in macrophages. Over 6 days of infection, 34 isolates (22.2%) showed low virulence (< 5% macrophages lysed), 46 isolates (30.1%) showed high virulence (≥90% lysis of macrophages), and 73 isolates (47.7%) were of intermediate virulence (5–90% macrophages lysed). Highly virulent isolates were associated with an increased bacterial load in patients' sputum before anti-tuberculosis therapy (P = 0.02). Isolate-dependent virulence phenotype was consistent in both THP-1 and human monocyte-derived macrophages. High virulence isolates survived better and replicated in macrophages one hundred fold faster than those with low virulence. Macrophages infected with high virulence isolates produced lower concentrations of TNF-α and IL-6 (P = 0.002 and 0.0005, respectively), but higher concentration of IL-1β (P = 5.1 × 10⁻⁵) compared to those infected with low virulence isolates. High virulence was strongly associated with East Asian/Beijing lineage [P = 0.002, Odd ratio (OR) = 4.32, 95% confident intervals (CI) 1.68–11.13]. The association between virulence phenotypes, bacterial growth, and proinflammatory cytokines in macrophages suggest the suppression of certain proinflammatory cytokines (TNF-α and IL-6) but not IL-1β allows better intracellular survival of highly virulent Mtb. This could result in rapid macrophage lysis and higher bacterial load in sputum of patients infected with high virulence isolates, which may contribute to the pathogenesis and success of the Beijing lineage.

Ultrastructural Analysis of Cell Envelope and Accumulation of Lipid Inclusions in Clinical Mycobacterium tuberculosis Isolates from Sputum, Oxidative Stress, and Iron Deficiency

Introduction: Mycobacteria have several unique cellular characteristics, such as multiple cell envelope layers, elongation at cell poles, asymmetric cell division, and accumulation of intracytoplasmic lipid inclusions, which contributes to their survival under stress conditions. However, the understanding of these characteristics in clinical Mycobacterium tuberculosis (M. tuberculosis) isolates and under host stress is limited. We previously reported the influence of host stress on the cell length distribution in a large set of clinical M. tuberculosis isolates (n = 158). Here, we investigate the influence of host stress on the cellular ultrastructure of few clinical M. tuberculosis isolates (n = 8) from that study. The purpose of this study is to further understand the influence of host stress on the cellular adaptations of clinical M. tuberculosis isolates. Methods: We selected few M. tuberculosis isolates (n = 8) for analyzing the cellular ultrastructure ex vivo in sputum and under in vitro stress conditions by transmission electron microscopy. The cellular adaptations of M. tuberculosis in sputum were correlated with the ultrastructure of antibiotic sensitive and resistant isolates in liquid culture, under oxidative stress, iron deficiency, and exposure to isoniazid. Results: In sputum, M. tuberculosis accumulated intracytoplasmic lipid inclusions. In liquid culture, clinical M. tuberculosis revealed isolate to isolate variation in the extent of intracytoplasmic lipid inclusions, which were absent in the laboratory strain H37Rv. Oxidative stress, iron deficiency, and exposure to isoniazid increased the accumulation of lipid inclusions and decreased the thickness of the cell envelope electron transparent layer in M. tuberculosis cells. Furthermore, intracytoplasmic compartments were observed in iron deficient cells. Conclusion: Our ultrastructural analysis has revealed significant influence of host stress on the cellular adaptations in clinical M. tuberculosis isolates. These adaptations may contribute to the survival of M. tuberculosis under host and antibiotic stress conditions. Variation in the cellular adaptations among clinical M. tuberculosis isolates may correlate with their ability to persist in tuberculosis patients during antibiotic treatment. These observations indicate the need for further analyzing these cellular adaptations in a large set of clinical M. tuberculosis isolates. This will help to determine the significance of these cellular adaptations in the tuberculosis treatment.

Influence of Stress and Antibiotic Resistance on Cell-Length Distribution in Mycobacterium tuberculosis Clinical Isolates

Mycobacterial cellular variations in growth and division increase heterogeneity in cell length, possibly contributing to cell-to-cell variation in host and antibiotic stress tolerance. This may be one of the factors influencing Mycobacterium tuberculosis persistence to antibiotics. Tuberculosis (TB) is a major public health problem in developing countries, antibiotic persistence, and emergence of antibiotic resistance further complicates this problem. We wanted to investigate the factors influencing cell-length distribution in clinical M. tuberculosis strains. In parallel we examined M. tuberculosis cell-length distribution in a large set of clinical strains (n = 158) from ex vivo sputum samples, in vitro macrophage models, and in vitro cultures. Our aim was to understand the influence of clinically relevant factors such as host stresses, M. tuberculosis lineages, antibiotic resistance, antibiotic concentrations, and disease severity on the cell size distribution in clinical M. tuberculosis strains. Increased cell size and cell-to-cell variation in cell length were associated with bacteria in sputum and infected macrophages rather than liquid culture. Multidrug-resistant (MDR) strains displayed increased cell length heterogeneity compared to sensitive strains in infected macrophages and also during growth under rifampicin (RIF) treatment. Importantly, increased cell length was also associated with pulmonary TB disease severity. Supporting these findings, individual host stresses, such as oxidative stress and iron deficiency, increased cell-length heterogeneity of M. tuberculosis strains. In addition we also observed synergism between host stress and RIF treatment in increasing cell length in MDR-TB strains. This study has identified some clinical factors contributing to cell-length heterogeneity in clinical M. tuberculosis strains. The role of these cellular adaptations to host and antibiotic tolerance needs further investigation.

Leukotriene A4 Hydrolase Genotype and HIV Infection Influence Intracerebral Inflammation and Survival From Tuberculous Meningitis

Background

Tuberculous meningitis (TBM) is the most devastating form of tuberculosis, yet very little is known about the pathophysiology. We hypothesized that the genotype of leukotriene A4 hydrolase (encoded by LTA4H), which determines inflammatory eicosanoid expression, influences intracerebral inflammation, and predicts survival from TBM.

Methods

We characterized the pretreatment clinical and intracerebral inflammatory phenotype and 9-month survival of 764 adults with TBM. All were genotyped for single-nucleotide polymorphism rs17525495, and inflammatory phenotype was defined by cerebrospinal fluid (CSF) leukocyte and cytokine concentrations.

Results

LTA4H genotype predicted survival of human immunodeficiency virus (HIV)-uninfected patients, with TT-genotype patients significantly more likely to survive TBM than CC-genotype patients, according to Cox regression analysis (univariate P = .040 and multivariable P = .037). HIV-uninfected, TT-genotype patients had high CSF proinflammatory cytokine concentrations, with intermediate and lower concentrations in those with CT and CC genotypes. Increased CSF cytokine concentrations correlated with more-severe disease, but patients with low CSF leukocytes and cytokine concentrations were more likely to die from TBM. HIV infection independently predicted death due to TBM (hazard ratio, 3.94; 95% confidence interval, 2.79-5.56) and was associated with globally increased CSF cytokine concentrations, independent of LTA4H genotype.

Conclusions

LTA4H genotype and HIV infection influence pretreatment inflammatory phenotype and survival from TBM. LTA4H genotype may predict adjunctive corticosteroid responsiveness in HIV-uninfected individuals.

TLR9 gene region polymorphisms and susceptibility to tuberculosis in Vietnam

Humans exposed to Mycobacterium tuberculosis (Mtb) show variation in susceptibility to infection and differences in tuberculosis (TB) disease outcome. Toll-like receptor 9 (TLR9) is a pattern recognition receptor that mediates recognition of Mtb and modulates Mtb-specific T-cell responses. Using a case-population design, we evaluated whether single nucleotide polymorphisms (SNPs) in the TLR9 gene region are associated with susceptibility to pulmonary or meningeal TB as well as neurologic presentation and mortality in the meningeal TB group. In a discovery cohort (n = 352 cases, 382 controls), three SNPs were associated with TB (all forms, p < 0.05) while three additional SNPs neared significance (0.05 < p < 0.1). When these six SNPs were evaluated in a validation cohort (n = 339 cases, 367 controls), one was significant (rs352142) while another neared significance (rs352143). When the cohorts were combined, rs352142 was most strongly associated with meningeal tuberculosis (dominant model; p = 0.0002, OR 2.36, CI 1.43-3.87) while rs352143 was associated with pulmonary tuberculosis (recessive model; p = 0.006, OR 5.3, CI 1.26-31.13). None of the SNPs were associated with mortality. This is the first demonstration of an association between a TLR9 gene region SNP and tuberculous meningitis. In addition, this extends previous findings that support associations of TLR9 SNPs with pulmonary tuberculosis.

Epiregulin (EREG) variation is associated with susceptibility to tuberculosis

Although host genetics influences susceptibility to Mycobacterium tuberculosis, the human genes regulating pathogenesis remain largely unknown. We used M. tuberculosis-stimulated macrophage gene expression profiling in conjunction with a case-control genetic association study to discover epiregulin (EREG), as a novel candidate tuberculosis (TB) susceptibility gene. Using a genome-wide association study dataset, we found that among the 21 genes with greater than 50-fold induction, EREG had the most polymorphisms associated with TB. We genotyped haplotype-tagging polymorphisms in discovery (N = 337 cases, N = 380 controls) and validation (N = 332 cases) datasets and an EREG polymorphism (rs7675690) was associated with susceptibility to TB (genotypic comparison; corrected P = 0.00007). rs7675690 was also associated more strongly with infections caused by the Beijing lineage of M. tuberculosis when compared with non-Beijing strains (controls vs Beijing, OR 7.81, P = 8.7 × 10(-5); non-Beijing, OR 3.13, P = 0.074). Furthermore, EREG expression was induced in monocytes and peripheral blood mononuclear cells stimulated with M. tuberculosis as well as TLR4 and TLR2/1/6 ligands. In murine macrophages, EREG expression induced by M. tuberculosis was MYD88- and TLR2-dependent. Together, these data provide the first evidence for an important role for EREG as a susceptibility gene for human TB.

A polymorphism in human TLR2 is associated with increased susceptibility to tuberculous meningitis

Tuberculous meningitis (TBM) results from the haematogenous dissemination of Mycobacterium tuberculosis from the lung to the brain. Dissemination is believed to occur early during infection, before the development of adaptive immunity. Toll-like receptor 2 (TLR2) mediates recognition of M. tuberculosis and initiates the innate immune response to infection. We hypothesized that polymorphisms in the TLR2 gene influence bacterial dissemination and the development of TBM. A case-control study was designed to test the hypothesis. Cases of bacteriologically confirmed pulmonary tuberculosis (TB) (n=183) and TBM (n=175), and cord blood controls (n=389) were enrolled in Vietnam. TLR2 genotype 597CC was associated with susceptibility to TB (odds ratio (OR)=2.22, 95% confidence interval (CI): 1.23-3.99). The association was found with meningeal rather than pulmonary TB (TBM vs control, OR=3.26, 95% CI: 1.72-6.18), and was strongest when miliary TB was found on chest radiography (controls vs TBM with miliary TB, OR=5.28, 95% CI: 2.20-12.65). Furthermore, the association increased with the severity of neurologic symptoms (grade I TBM, OR=1.93, 95% CI: 0.54-6.92; grade II, OR=3.32, 95% CI: 0.84-13.2; and grade III, OR=5.70, 95% CI: 1.81-18.0). These results demonstrate a strong association of TLR2 SNP T597C with the development of TBM and miliary TB and indicate that TLR2 influences the dissemination of M. tuberculosis.

Polymorphisms of the gene coding for copper/zinc superoxide dismutase (SOD1) in patients with Japanese encephalitis

Japanese encephalitis is the commonest form of encephalitis globally. Most cases develop characteristic encephalitis but some also present with flaccid paralysis. The paralysis is secondary to damage at the alpha motor neurone, the site that is also damaged in amyotrophic lateral sclerosis (ALS). The gene coding for superoxide dismutase 1 (SOD1) is thought to be involved in ALS and may also be linked to susceptibility to Japanese encephalitis. To investigate this possibility, polymorphisms in the SOD1 gene were investigated, in 61 cases of Japanese encephalitis, 61 matched controls and 171 population controls, in Vietnam. Novel polymorphisms, found only in three of the cases and one of the population controls, may be involved with susceptibility to Japanese encephalitis and potentially to other flavivirus infections that lead to damage to the cells of the anterior horn. Further research on this possible association is required.