Tuberculosis

The polyphosphate kinase gene ppk2 is required for Mycobacterium tuberculosis inorganic polyphosphate regulation and virulence

The Mycobacterium tuberculosis gene Rv3232c/MT3329 (ppk2) encodes a class II polyphosphate kinase, which hydrolyzes inorganic polyphosphate (poly P) to synthesize GTP. We assessed the role of ppk2 in M. tuberculosis poly P regulation, antibiotic tolerance, and virulence. A ppk2-deficient mutant (ppk2::Tn) and its isogenic wild-type (WT) and complemented (Comp) strains were studied. For each strain, the intrabacillary poly P content, MIC of isoniazid, and growth kinetics during infection of J774 macrophages were determined. Multiplex immunobead assays were used to evaluate cytokines elaborated during macrophage infection. The requirement of ppk2 for M. tuberculosis virulence was assessed in the murine model. The ppk2::Tn mutant was found to have significantly increased poly P content and a 4-fold increase in the MIC of isoniazid relative to the WT and Comp strains. The ppk2::Tn mutant showed reduced survival at day 7 in activated and naive J774 macrophages relative to the WT. Naive ppk2::Tn mutant-infected macrophages showed increased expression of interleukin 2 (IL-2), IL-9, IL-10, IL-12p70, and gamma interferon (IFN-γ) relative to WT-infected macrophages. The ppk2::Tn mutant exhibited significantly lower lung CFU during acute murine infection compared to the control groups. ppk2 is required for control of intrabacillary poly P levels and optimal M. tuberculosis growth and survival in macrophages and mouse lungs.

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a highly successful human pathogen because it has developed mechanisms to multiply and survive in the lungs by circumventing the immune system. Identification of virulence factors responsible for M. tuberculosis growth and persistence in host tissues may assist in the development of novel strategies to treat TB. In this study, we found that the mycobacterial enzyme polyphosphate kinase 2 (PPK2) is required for controlling intracellular levels of important regulatory molecules and for maintaining susceptibility to the first-line anti-TB drug isoniazid. In addition, PPK2 was found to be required for M. tuberculosis growth in the lungs of mice, at least in part by suppressing the expression of certain key cytokines and chemokines by inactivated lung macrophages.

Diagnosis of latent tuberculosis infection among HIV-infected clients in Far North Queensland: use of an interferon-gamma release assay

Latent Mycobacterium tuberculosis infection is a significant risk for those infected with HIV. We examined the use of an interferon-gamma release assay for the diagnosis of latent tuberculosis among HIV-infected clients attending two sexual health services in Far North Queensland. Of 240 clients tested, 19 returned a positive result (7.9%, 95% confidence interval (CI): 4.5-11.3%) and three were indeterminate (1.3%, 95% CI: -0.2%-2.7%). Low CD4 count was found to be significantly associated with an indeterminate test result (P=0.004). However, we found no significant association between test results and client demographics, self-reported prior tuberculosis infection, Bacille Calmette-Guérin vaccine status or selected tuberculosis risk factors (P-values=0.2-0.9).

Association between tuberculosis infections and non-pulmonary malignancies: a nationwide population-based study

Background:

In addition to lung cancers, tuberculosis infections have been associated with increased risk of non-pulmonary malignancies in case reports. Our population-based study employed standardized incidence ratios (SIRs) to systemically survey non-pulmonary cancer risks after tuberculosis infections.

Methods:

Data of patients who had newly diagnosed tuberculosis, were aged 20 years or older, and had no prior cancer or tuberculosis were sampled from the Taiwan National Health Insurance database between 2000 and 2010. SIRs compared cancer incidence in patients with tuberculosis infections to the general population. SIRs of specific cancers were further analyzed with respect to gender and time after tuberculosis infections.

Results:

After a follow-up period of 28 866 person–years, 530 tuberculosis cases developed cancers compared with 256 cases in the general populations (2.07, 95% confidence interval (CI), 1.90–2.26). The SIR of non-pulmonary malignancies was also increased (1.71, 95% CI, 1.54–1.90). For males, SIRs were increased within 1 year after tuberculosis diagnosis for the following cancers: head and neck, esophageal, colorectal, liver, lung, melanomas, and Hodgkin's disease. SIRs were increased for liver, biliary, lung, and bladder cancers beyond the first year after tuberculosis diagnosis. For females, SIRs were increased for leukemia, esophageal, and lung cancers within the first year, and only for leukemia beyond 1 year post diagnosis.

Conclusion:

Having found increased risks of several cancers that differ with gender and time after tuberculosis diagnosis, physicians may consider these factors in patients following tuberculosis diagnosis.

Socio-demographic and clinical differences in subjects with tuberculosis with and without diabetes mellitus in Brazil--a multivariate analysis

BACKGROUND

Several studies have evaluated the relationship between diabetes mellitus (DM) and tuberculosis (TB), but the nature of this relationship is not fully understood. TB incidence may be influenced by immunosuppression from DM, but this association may be confounded by other clinical and socioeconomic factors. We aimed to assess socio-demographic and clinical differences in TB patients with and without DM.

METHODS

Using the Brazilian national surveillance system (SINAN), we compared 1,797 subjects with TB and DM with 29,275 subjects diagnosed with TB only in 2009. We performed multivariate analysis to identify factors associated with the presence of DM among TB patients.

RESULTS

Subjects with TB - DM were older; have initial positive sputum smear test (OR = 1.42, 95% CI 1.26-1.60), and were more likely to die from TB (OR = 1.44, 95% CI 1.03-2.01). They were less likely to have been institutionalized [in prison, shelter, orphanage, psychiatric hospital (OR = 0.74, 95% CI 0.60-0.93)]; developed extra pulmonary TB (OR = 0.62, 95% CI 0.51-0.75) and to return to TB treatment after abandonment (OR = 0.66, 95% CI 0.51-0.86).

CONCLUSIONS

Prevalence of NCD continues to rise in developing countries, especially with the rise of elderly population, the prevention and treatment of infectious diseases will be urgent. DM and TB represent a critical intersection between communicable and non-communicable diseases in these countries and the effect of DM on TB incidence and outcomes provide numerous opportunities for collaboration and management of these complex diseases in the national public health programs.

Examining the evidence on the causal effect of HAART on transmission of HIV using the Bradford Hill criteria

In recent years, evidence has accumulated regarding the ability of HAART to prevent HIV transmission. Early supportive evidence was derived from observational, ecological and population-based studies. More recently, a randomized clinical trial showed that immediate use of HAART led to a 96% decrease in HIV transmission events within HIV serodiscordant heterosexual couples. However, the generalizability of the effect of HAART, and the population-level impact on HIV transmission continues to generate substantial debate. We, therefore, conducted a review of the evidence regarding the preventive effect of HAART on HIV transmission within the context of the Bradford Hill criteria for causality. Taken together, we find the accumulated evidence supporting HIV treatment as prevention meets each of the Bradford Hill criteria for causality. We conclude that the opportunity cost of inaction while waiting for additional evidence on the generalizability of effect in other risk groups is too high. Efforts should be redoubled to mobilize the financial capital and political will to optimize implementation of HIV Treatment as Prevention strategies on a wide scale.

Evaluation of respiratory disease

The spectrum of HIV-associated pulmonary diseases is broad. Opportunistic infections, neoplasms, and noninfectious complications are all major considerations. Clinicians caring for persons infected with HIV must have a systematic approach. The approach begins with a thorough history and physical examination and often involves selected laboratory tests and a chest radiograph. Frequently, the clinical, laboratory, and chest radiographic presentation suggests a specific diagnosis or a few diagnoses, which then prompts specific diagnostic testing and treatment. This article presents an overview of the evaluation of respiratory disease in persons with HIV/AIDS.

Human immunodeficiency virus-associated tuberculosis: update on prevention and treatment

Tuberculosis (TB) is the leading cause of opportunistic infection and mortality among HIV-infected persons. Screening for symptoms of TB in people with HIV infection, use of isoniazid preventive therapy for those with latent TB infection, earlier diagnosis and treatment of active TB disease, and early initiation of antiretroviral therapy are essential for controlling the spread of TB. Treatment of HIV-related TB is complicated by overlapping drug toxicities and drug-drug interactions between antiretroviral therapy and anti-TB therapy and risk for development of immune reconstitution inflammatory disease. This review provides an overview of the prevention and treatment of TB in HIV-infected persons.

Updating the mild encephalitis hypothesis of schizophrenia

Schizophrenia seems to be a heterogeneous disorder. Emerging evidence indicates that low level neuroinflammation (LLNI) may not occur infrequently. Many infectious agents with low overall pathogenicity are risk factors for psychoses including schizophrenia and for autoimmune disorders. According to the mild encephalitis (ME) hypothesis, LLNI represents the core pathogenetic mechanism in a schizophrenia subgroup that has syndromal overlap with other psychiatric disorders. ME may be triggered by infections, autoimmunity, toxicity, or trauma. A 'late hit' and gene-environment interaction are required to explain major findings about schizophrenia, and both aspects would be consistent with the ME hypothesis. Schizophrenia risk genes stay rather constant within populations despite a resulting low number of progeny; this may result from advantages associated with risk genes, e.g., an improved immune response, which may act protectively within changing environments, although they are associated with the disadvantage of increased susceptibility to psychotic disorders. Specific schizophrenic symptoms may arise with instances of LLNI when certain brain functional systems are involved, in addition to being shaped by pre-existing liability factors. Prodrome phase and the transition to a diseased status may be related to LLNI processes emerging and varying over time. The variability in the course of schizophrenia resembles the varying courses of autoimmune disorders, which result from three required factors: genes, the environment, and the immune system. Preliminary criteria for subgrouping neurodevelopmental, genetic, ME, and other types of schizophrenias are provided. A rare example of ME schizophrenia may be observed in Borna disease virus infection. Neurodevelopmental schizophrenia due to early infections has been estimated by others to explain approximately 30% of cases, but the underlying pathomechanisms of transition to disease remain in question. LLNI (e.g. from reactivation related to persistent infection) may be involved and other pathomechanisms including dysfunction of the blood-brain barrier or the blood-CSF barrier, CNS-endogenous immunity and the volume transmission mode balancing wiring transmission (the latter represented mainly by synaptic transmission, which is often described as being disturbed in schizophrenia). Volume transmission is linked to CSF signaling; and together could represent a common pathogenetic link for the distributed brain dysfunction, dysconnectivity, and brain structural abnormalities observed in schizophrenia. In addition, CSF signaling may extend into peripheral tissues via the CSF outflow pathway along brain nerves and peripheral nerves, and it may explain the peripheral topology of neuronal dysfunctions found, like in olfactory dysfunction, dysautonomia, and even in peripheral tissues, i.e., the muscle lesions that were found in 50% of cases. Modulating factors in schizophrenia, such as stress, hormones, and diet, are also modulating factors in the immune response. Considering recent investigations of CSF, the ME schizophrenia subgroup may constitute approximately 40% of cases.

Associations between selected immune-mediated diseases and tuberculosis: record-linkage studies

BACKGROUND

Previous studies have suggested that there may be an association between some immune-mediated diseases and risk of tuberculosis (TB).

METHODS

We analyzed a database of linked statistical records of hospital admissions and death certificates for the whole of England (1999 to 2011), and a similar database (the Oxford Record Linkage Study (ORLS)) for a region of southern England in an earlier period. Rate ratios for TB were determined, comparing immune-mediated disease cohorts with comparison cohorts.

RESULTS

In the all-England dataset, there were significantly elevated risks of TB after hospital admission for the following individual immune-mediated diseases: Addison's disease, ankylosing spondylitis, autoimmune hemolytic anemia, chronic active hepatitis, coeliac disease, Crohn's disease, dermatomyositis, Goodpasture's syndrome, Hashimoto's thyroiditis, idiopathic thrombocytopenia purpura (ITP), myasthenia gravis, myxedema, pemphigoid, pernicious anemia, polyarteritis nodosa, polymyositis, primary biliary cirrhosis, psoriasis, rheumatoid arthritis, scleroderma, Sjögren's syndrome, systemic lupus erythematosus (SLE), thyrotoxicosis and ulcerative colitis. Particularly high levels of risk were found for Addison's disease (rate ratio (RR) = 11.9 (95% CI 9.5 to 14.7)), Goodpasture's syndrome (RR = 10.8 (95% CI 4.0 to 23.5)), SLE (RR = 9.4 (95% CI 7.9 to 11.1)), polymyositis (RR = 8.0 (95% CI 4.9 to 12.2)), polyarteritis nodosa (RR = 6.7 (95% CI 3.2 to 12.4)), dermatomyositis (RR = 6.6 (95% CI 3.0 to 12.5)), scleroderma (RR = 6.1 (95% CI 4.4 to 8.2)) and autoimmune hemolytic anemia (RR = 5.1 (95% CI 3.4 to 7.4)).

CONCLUSIONS

These two databases show that patients with some immune-mediated diseases have an increased risk of TB, although we cannot explicitly state the direction of risk or exclude confounding. Further study of these associations is warranted, and these findings may aid TB screening, control and treatment policies.

Removal of user fees no guarantee of universal health coverage: observations from Burkina Faso

In theory, the removal of user fees puts health services within reach of everyone, including the very poor. When Burkina Faso adopted the DOTS strategy for the control of tuberculosis, the intention was to provide free tuberculosis care. In 2007-2008, interviews were used to collect information from 242 smear-positive patients with pulmonary tuberculosis who were enrolled in the national tuberculosis control programme in six rural districts. The median direct costs associated with tuberculosis were estimated at 101 United States dollars (US$) per patient. These costs represented 23% of the mean annual income of a patient's household. During the course of their care, three quarters of the interviewed patients apparently faced "catastrophic" health expenditure. Inadequacies in the health system and policies appeared to be responsible for nearly half of the direct costs (US$ 45 per patient). Although the households of patients developed coping strategies, these had far-reaching, adverse effects on the quality of lives of the households' members and the socioeconomic stability of the households. Each tuberculosis patient lost a median of 45 days of work as a result of the illness. For a population living on or below the poverty line, every failure in health-care delivery increases the risk of "catastrophic" health expenditure, exacerbates socioeconomic inequalities, and reduces the probability of adequate treatment and cure. In Burkina Faso, a policy of "free" care for tuberculosis patients has not met with complete success. These observations should help define post-2015 global strategies for tuberculosis care, prevention and control.

HIV infection disrupts the sympatric host-pathogen relationship in human tuberculosis

The phylogeographic population structure of Mycobacterium tuberculosis suggests local adaptation to sympatric human populations. We hypothesized that HIV infection, which induces immunodeficiency, will alter the sympatric relationship between M. tuberculosis and its human host. To test this hypothesis, we performed a nine-year nation-wide molecular-epidemiological study of HIV–infected and HIV–negative patients with tuberculosis (TB) between 2000 and 2008 in Switzerland. We analyzed 518 TB patients of whom 112 (21.6%) were HIV–infected and 233 (45.0%) were born in Europe. We found that among European-born TB patients, recent transmission was more likely to occur in sympatric compared to allopatric host–pathogen combinations (adjusted odds ratio [OR] 7.5, 95% confidence interval [95% CI] 1.21–infinity, p = 0.03). HIV infection was significantly associated with TB caused by an allopatric (as opposed to sympatric) M. tuberculosis lineage (OR 7.0, 95% CI 2.5–19.1, p<0.0001). This association remained when adjusting for frequent travelling, contact with foreigners, age, sex, and country of birth (adjusted OR 5.6, 95% CI 1.5–20.8, p = 0.01). Moreover, it became stronger with greater immunosuppression as defined by CD4 T-cell depletion and was not the result of increased social mixing in HIV–infected patients. Our observation was replicated in a second independent panel of 440 M. tuberculosis strains collected during a population-based study in the Canton of Bern between 1991 and 2011. In summary, these findings support a model for TB in which the stable relationship between the human host and its locally adapted M. tuberculosis is disrupted by HIV infection.

Human tuberculosis (TB) caused by Mycobacterium tuberculosis kills 1.5 million people each year. M. tuberculosis has been affecting humans for millennia, suggesting that different strain lineages may be adapted to specific human populations. The combination of a particular strain lineage and its corresponding patient population can be classified as sympatric (e.g. Euro-American lineage in Europeans) or allopatric (e.g. East-Asian lineage in Europeans). We hypothesized that infection with the human immunodeficiency virus (HIV), which impairs the human immune system, will interfere with this host–pathogen relationship. We performed a nation-wide molecular-epidemiological study of HIV–infected and HIV–negative TB patients between 2000 and 2008 in Switzerland. We found that HIV infection was associated with the less adapted allopatric lineages among patients born in Europe, and this was not explained by social or other patient factors such as increased social mixing in HIV–infected individuals. Strikingly, the association between HIV infection and less adapted M. tuberculosis lineages was stronger in patients with more pronounced immunodeficiency. Our observation was replicated in a second independent panel of M. tuberculosis strains collected during a population-based study in the Canton of Bern. In summary, our study provides evidence that the sympatric host–pathogen relationship in TB is disrupted by HIV infection.

Tuberculosis incidence correlates with sunshine: an ecological 28-year time series study

Background

Birmingham is the largest UK city after London, and central Birmingham has an annual tuberculosis incidence of 80 per 100,000. We examined seasonality and sunlight as drivers of tuberculosis incidence. Hours of sunshine are seasonal, sunshine exposure is necessary for the production of vitamin D by the body and vitamin D plays a role in the host response to tuberculosis.

Methods

We performed an ecological study that examined tuberculosis incidence in Birmingham from Dec 1981 to Nov 2009, using publicly-available data from statutory tuberculosis notifications, and related this to the seasons and hours of sunshine (UK Meteorological Office data) using unmeasured component models.

Results

There were 9,739 tuberculosis cases over the study period. There was strong evidence for seasonality, with notifications being 24.1% higher in summer than winter (p<0.001). Winter dips in sunshine correlated with peaks in tuberculosis incidence six months later (4.7% increase in incidence for each 100 hours decrease in sunshine, p<0.001).

Discussion and Conclusion

A potential mechanism for these associations includes decreased vitamin D levels with consequent impaired host defence arising from reduced sunshine exposure in winter. This is the longest time series of any published study and our use of statutory notifications means this data is essentially complete. We cannot, however, exclude the possibility that another factor closely correlated with the seasons, other than sunshine, is responsible. Furthermore, exposure to sunlight depends not only on total hours of sunshine but also on multiple individual factors. Our results should therefore be considered hypothesis-generating. Confirmation of a potential causal relationship between winter vitamin D deficiency and summer peaks in tuberculosis incidence would require a randomized-controlled trial of the effect of vitamin D supplementation on future tuberculosis incidence.

Screening of patients with diabetes mellitus for tuberculosis in India

OBJECTIVE

To assess the feasibility, results and challenges of screening patients with diabetes mellitus (DM) for tuberculosis (TB) within the healthcare setting of six DM clinics in tertiary hospitals across India.

METHOD

Agreement on how to screen, monitor and record the screening was reached in October 2011 at a national stakeholders' meeting, and training was carried out for staff in the six tertiary care facilities in December 2011. Implementation started in the first quarter of 2012, and we report on activities up to 30th September 2012. Patients with DM were screened for TB on each clinic attendance using a symptom-based enquiry, and those with positive symptoms were referred for TB investigations.

RESULTS

In the three quarters, 26% of 7218, 52% of 12237 and 48% of 11691 patients with DM were screened for TB. A total of 254 patients were identified with TB, of whom 46% had smear-positive pulmonary disease. There were 18 patients newly diagnosed with TB as a result of screening and referral, with the remainder being patients already diagnosed from elsewhere. TB case rates per 100,000 patients attending the DM clinic each quarter were 859, 956 and 642. Almost 90% of patients with TB were recorded as starting or being on anti-TB treatment. Major implementation challenges related to human resources and recording systems.

CONCLUSION

In India, it is feasible to screen patients with DM for TB resulting in high rates of TB detection. More attention to detail, human resource requirements and electronic medical records are needed to improve performance.

Fluorescent probes reveal a minimal ligase recognition motif in the prokaryotic ubiquitin-like protein from Mycobacterium tuberculosis

The prokaryotic ubiquitin-like protein (Pup)-based proteasomal system in the pathogen Mycobacterium tuberculosis (Mtb) is essential for its survival in a mammalian host. The Pup ligase enzyme, PafA, conjugates Pup to a suite of proteins targeted for proteasomal degradation and is necessary for persistent infection by Mtb. We report the design and application of fluorescent probes for use in elucidating the mechanisms of Pup and substrate recognition by PafA. Our studies revealed that the C-terminal 26 amino acid sequence of Pup is the minimal ligase recognition motif in Mtb. Specific hydrophobic residues within this sequence that are known to be important for the interactions of Pup with proteasomes are also critical for the activation of Pup by PafA.

Mobile phone text messaging for promoting adherence to anti-tuberculosis treatment: a systematic review protocol

BACKGROUND

In 2010, there were approximately 8.8 million incident cases of tuberculosis (TB) worldwide. The treatment of TB is at least six months long and may be complicated by a high pill burden. In addition, TB patients often do not take their medication on schedule simply because they forget. Mobile phone text messaging has the potential to help promote TB treatment adherence. We, therefore, propose to conduct a review of current best evidence for the use of mobile phone text messaging to promote patient adherence to TB treatment.

METHODS

This is a systematic review of the literature. We will preferably include randomized controlled trials (RCTs). However, non-randomized studies (NRS) will be considered if there is an inadequate number of RCTs.We will search PubMed, EMBASE, CINAHL, CENTRAL, Science Citation Index, Africa-Wide Information, and WHOLIS electronic databases for eligible studies available by 30 November 2012 regardless of language or publication status. We will also check reference lists for additional studies, identify abstracts from conference proceedings and communicate with authors for any relevant material.At least two authors will independently screen search outputs, select studies, extract data and assess the risk of bias (using separate criteria for RCTs and NRS); resolving discrepancies by discussion and consensus. We will assess clinical heterogeneity by examining the types of participants, interventions and outcomes in each study and pool studies judged to be clinically homogenous. We will also assess statistical heterogeneity using the chi-square test of homogeneity and quantify it using the I-square statistic. If study results are found to be statistically homogeneous (that is heterogeneity P > 0.1), we will pool them using the fixed-effect meta-analysis. Otherwise, we will use random-effects meta-analysis. We will calculate risk ratios and their corresponding 95% confidence intervals for dichotomous outcomes, and mean differences for continuous outcomes. For other outcomes without quantitative data, a descriptive analysis will be used.

DISCUSSION

Our results can be used by researchers and policy-makers to help inform them of the efficacy of mobile phone text messaging interventions to promote patient adherence to TB treatment.

Development of a new generation of vectors for gene expression, gene replacement, and protein-protein interaction studies in mycobacteria

Escherichia coli-mycobacterium shuttle vectors are important tools for gene expression and gene replacement in mycobacteria. However, most of the currently available vectors are limited in their use because of the lack of extended multiple cloning sites (MCSs) and convenience of appending an epitope tag(s) to the cloned open reading frames (ORFs). Here we report a new series of vectors that allow for the constitutive and regulatable expression of proteins, appended with peptide tag sequences at their N and C termini, respectively. The applicability of these vectors is demonstrated by the constitutive and induced expression of the Mycobacterium tuberculosis pknK gene, coding for protein kinase K, a serine-threonine protein kinase. Furthermore, a suicide plasmid with expanded MCS for creating gene replacements, a plasmid for chromosomal integrations at the commonly used L5 attB site, and a hypoxia-responsive vector, for expression of a gene(s) under hypoxic conditions that mimic latency, have also been created. Additionally, we have created a vector for the coexpression of two proteins controlled by two independent promoters, with each protein being in fusion with a different tag. The shuttle vectors developed in the present study are excellent tools for the analysis of gene function in mycobacteria and are a valuable addition to the existing repertoire of vectors for mycobacterial research.

Interpretation and Relevance of Advanced Technique Results

Advanced techniques in the field of diagnostic microbiology have made amazing progress over the past two decades due largely to a technological revolution in the molecular aspects of microbiology [1, 2]. In particular, rapid molecular methods for nucleic acid amplification and characterization combined with automation and user-friendly software have significantly broadened the diagnostic capabilities of modern clinical microbiology laboratories. Molecular methods such as nucleic acid amplification tests (NAATs) rapidly are being developed and introduced in the clinical laboratory setting. Indeed, every section of the clinical microbiology laboratory, including bacteriology, mycology, mycobacteriology, parasitology, and virology, have benefited from these advanced techniques. Because of the rapid development and adaptation of these molecular techniques, the interpretation and relevance of the results produced by such molecular methods has lagged somewhat behind. The purpose of this chapter is to review and discuss the interpretation and relevance of results produced by these advanced molecular techniques. Moreover, this chapter will address the “myths” of NAATs, as these myths can markedly influence the interpretation and relevance of these results.

The -159C/T polymorphism in the CD14 gene and tuberculosis risk: a meta-analysis

BACKGROUND

The -159C/T polymorphism in the CD14 gene has been implicated in susceptibility to tuberculosis, but the results were inconclusive. The present meta-analysis aimed to perform a comprehensive assessment of the literature on the possible association between the -159C/T polymorphism and tuberculosis risk.

METHODS

We searched in Pubmed and Embase for studies evaluating the association between the -159C/T gene polymorphism and tuberculosis risk. Data were extracted and statistical analysis was performed using Revman 5.1 and STATA 12.0 software.

RESULTS

A total of seven case-control studies involving 3253 subjects (1,574 tuberculosis cases and 1,679 controls) were included. Combined analysis revealed an obvious association between this polymorphism and tuberculosis risk (odds ratio=1.66 and 95% confidence interval: 1.23-2.25, P<0.05 for TT vs. TC+ CC). Sub-group analysis by ethnicity suggested that the risk of tuberculosis associated with the -159C/T polymorphism was significantly elevated among Asians (odds ratio=1.87 and 95% confidence interval: 1.58-2.21, P<0.05 for TT vs. TC+ CC).

CONCLUSION

This meta-analysis suggests that the -159C/T polymorphism in the CD14 gene contributes to tuberculosis susceptibility. To further investigate gene-gene and gene-environment interactions between this polymorphism and tuberculosis risk, more studies are needed.

Primary gingival tuberculosis diagnosis: a difficult endeavor

AIM

To highlight the importance of considering tuberculosis in the differential diagnosis even in the absence of confirmation from several investigations and diagnostic aides.

BACKGROUND

Tuberculosis is a common infectious granulomatous disease caused by various strains of mycobacteria. An oral lesion when seen in association with tuberculosis is very rare and in most cases is noticed secondary to pulmonary forms.

CASE REPORT

We report a case of primary gingival tuberculosis in 20-year-old female patient who presented with treatment resistant gingivitis. Patient had no evidence of disease elsewhere in the body and several diagnostic tests also failed to reveal the presence of the causative organism. Resolution of gingivitis was noted following a therapeutic trial of antitubercular drugs.

CONCLUSION

Therefore the importance of including tuberculosis in the differential diagnosis of inflammatory disorder of the gingiva is very essential in order to avoid one of the most lethal forms of infections often overlooked.

CLINICAL SIGNIFICANCE

It is essential to consider tuberculosis as one of the differential diagnosis in India even when several diagnostic tests are negative for tuberculosis.

Diagnosis of intestinal tuberculosis using a monoclonal antibody to Mycobacterium tuberculosis

AIM: To investigate the utility of immunohistochemical (IHC) staining with an antibody to Mycobacterium tuberculosis (M. tuberculosis) for the diagnosis of intestinal tuberculosis (TB).

METHODS: We retrospectively identified 10 patients (4 males and 6 females; mean age = 65.1 ± 13.6 years) with intestinal TB. Clinical characteristics, including age, gender, underlying disease, and symptoms were obtained. Chest radiograph and laboratory tests, including sputum Ziehl-Neelsen (ZN) staining, M. tuberculosis culture, and sputum polymerase chain reaction (PCR) for tubercle bacilli DNA, as well as Tuberculin skin test (TST) and QuantiFERON-TB gold test (QFT), were examined. Colonoscopic records recorded on the basis of Sato’s classification were also reviewed, in addition to data from intestinal biopsies examined for histopathological findings, including hematoxylin and eosin staining, and ZN staining, as well as M. tuberculosis culture, and PCR for tubercle bacilli DNA. For the present study, archived formalin-fixed paraffin-embedded (FFPE) intestinal tissue samples were immunohistochemically stained using a commercially available species-specific monoclonal antibody to the 38-kDa antigen of the M. tuberculosis complex. These sections were also stained with the pan-macrophage marker CD68 antibody.

RESULTS: From the clinical data, we found that no patients were immunocompromised, and that the main symptoms were diarrhea and weight loss. Three patients displayed active pulmonary TB, six patients (60%) had a positive TST, and 4 patients (40%) had a positive QFT. Colonoscopic findings revealed that all patients had type 1 findings (linear ulcers in a circumferential arrangement or linear ulcers arranged circumferentially with mucosa showing multiple nodules), all of which were located in the right hemicolon and/or terminal ileum. Seven patients (70%) had concomitant healed lesions in the ileocecal area. No acid-fast bacilli were detected with ZN staining of the intestinal tissue samples, and both M. tuberculosis culture and PCR for tubercle bacilli DNA were negative in all samples. The histopathological data revealed that tuberculous granulomas were present in 4 cases (40%). IHC staining in archived FFPE samples with anti-M. tuberculosis monoclonal antibody revealed positive findings in 4 patients (40%); the same patients in which granulomas were detected by hematoxylin and eosin staining. M. tuberculosis antigens were found to be mostly intracellular, granular in pattern, and primarily located in the CD68⁺ macrophages of the granulomas.

CONCLUSION: IHC staining with a monoclonal antibody to M. tuberculosis may be an efficient and simple diagnostic tool in addition to classic examination methods for the diagnosis of intestinal TB.

Vaccination against tuberculosis: how can we better BCG?

Tuberculosis remains one of the most significant human diseases of the developing world, accounting for 3800 worldwide deaths per day. Although we currently have a vaccine for tuberculosis, BCG, this is insufficient at protecting from adult pulmonary tuberculosis in the parts of the world where a good vaccine is most needed. This has prompted the search for new vaccination strategies that can protect better than BCG, or can boost BCG-induced immunity. We discuss these subjects in line with what is known of the immune responses to BCG and Mycobacterium tuberculosis - the etiological agent of the disease, as well as the particular difficulties facing development of new vaccines against tuberculosis. A greater understanding of the factors constituting optimal protection against Mycobacterium tuberculosis infection, as well as which pathogenic factors facilitate active disease, will accelerate the delivery of safe vaccines able to restrict active tuberculosis and thus impede contagion.

Childhood tuberculosis and malnutrition

Despite the burden of both malnutrition and tuberculosis in children worldwide, there are few studies on the mechanisms that underlie this relationship. From available research, it appears that malnutrition is a predictor of tuberculosis disease and is associated with worse outcomes. This is supported through several lines of evidence, including the role of vitamin D receptor genotypes, malnutrition's effects on immune development, respiratory infections among malnourished children, and limited work specifically on pediatric tuberculosis and malnutrition. Nutritional supplementation has yet to suggest significant benefits on the course of tuberculosis in children. There is a critical need for research on childhood tuberculosis, specifically on how nutritional status affects the risk and progression of tuberculosis and whether nutritional supplementation improves clinical outcomes or prevents disease.

Association between gallium-67 uptake by lung foci and sputum smear status in patients with pulmonary tuberculosis

OBJECTIVES

Rapid determination of the inflammatory and sputum smear status in patients with pulmonary tuberculosis (PTB) is crucial for clinical decision making. The purpose of this study was to assess the relationship between gallium-67 (Ga-67) uptake by lung foci and sputum smear status in patients with PTB. We also attempted to predict the patients with acid-fast bacilli (AFB) smear-positive PTB by means of a semiquantitative measurement of Ga-67 uptake ratio using single-photon emission computed tomography images.

PATIENTS AND METHODS

Ninety-five patients with PTB were enrolled in this retrospective study. A volume-of-interest method was used to quantify Ga-67 uptake in single-photon emission computed tomography images. The Ga-67 uptake ratio was defined as the maximum voxel value of the pulmonary lesion divided by the maximum voxel value of normal lung tissue.

RESULTS

The Ga-67 uptake ratio was higher in patients with active PTB than in those with inactive PTB (3.11 ± 1.52 vs. 1.42 ± 0.14, P<0.01). In active PTB, the Ga-67 uptake ratio was higher in smear-positive patients than in smear-negative patients (3.41 ± 1.60 vs. 2.16 ± 0.61, P<0.01). In patients with AFB smear grades 1+, 2+, and 3+, the Ga-67 uptake ratios were 2.51 ± 0.81, 3.30 ± 1.57, and 4.23 ± 1.73, respectively. The correlation between Ga-67 uptake ratio and AFB smear grading was statistically significant (Spearman's ρ=0.60, P<0.01). In receiver operating characteristic curve analyses, the area under the curve for the Ga-67 uptake ratio was 0.95 ± 0.02 (P<0.01) for predicting active PTB and 0.87 ± 0.04 (P<0.01) for predicting smear-positive active PTB.

CONCLUSION

In patients with active PTB, more-intense Ga-67 uptake was associated with more AFB load in the sputum - that is a greater potential to transmit PTB. This finding might facilitate clinical decision making for immediate isolation and treatment to reduce transmission of PTB.

The role of sex differences in the prevalence and transmission of tuberculosis

Tuberculosis (TB) epidemiology is characterized by significant differences in prevalence between men and women worldwide, with cases among men exceeding those found in women by a ratio of 2:1 in some regions. In this paper, we review the literature concerning differences in TB prevalence by sex, as well as arguments that have been offered to explain these differences. We conclude that, while underreporting and latent variables undoubtedly bias the observed differences in prevalence between males and females to some degree, there is also strong evidence that sex-based differences in TB prevalence represent real epidemiological differences. Such differences have implications for models of TB dynamics in countries with skewed population sex ratios such as China and India, and should be incorporated into models for TB control and forecasting.

Recent epidemiological trends in tuberculous pleural effusion in Galicia, Spain

OBJECTIVE

Knowledge on the distribution and determinants of tuberculous pleural effusions (TBPE) is incomplete. We aimed to describe the epidemiological trends and individual characteristics of TBPE in Galicia, Spain, over a 10-year period (2000-2009).

DESIGN

A retrospective, observational study based on epidemiological data obtained from the Galician Tuberculosis Register.

RESULTS

There were 1835 cases of TBPE (16.3% of the total 11,241 TB cases reported). The number and incidence of TBPE decreased significantly during the study period, from (262 and 9.6/100,000 inhabitants in 2000, to 133 and 4.8 in 2009, respectively; P<.001 for both). The mean annual decrease in TBPE incidence was 6.9%, and 50% overall. TBPE mainly affected males (63.5%), precisely 61.2% young males between 15 and 44 years. Twenty-five percent had lung involvement (chest X-ray), and 41.7% had a positive sputum culture. A significant increase (P<.001) was observed during the study in the percentage of patients who had more TB risk factors.

CONCLUSIONS

The incidence of TBPE decreased significantly during the study period, with no changes in epidemiological characteristics, and with trends similar to the total number of TB cases. The introduction of the Galician Prevention and Control Plan (GPCP) for tuberculosis appears to be effective for better control of TB.

Home videophones improve direct observation in tuberculosis treatment: a mixed methods evaluation

BACKGROUND

THE USE OF DIRECT OBSERVATION TO MONITOR TUBERCULOSIS TREATMENT IS CONTROVERSIAL: cost, practical difficulties, and lack of patient acceptability limit effectiveness. Telehealth is a promising alternative delivery method for improving implementation. This study aimed to evaluate the clinical and cost-effectiveness of a telehealth service delivering direct observation, compared to an in-person drive-around service.

METHODOLOGY/PRINCIPAL FINDINGS

The study was conducted within a community nursing service in South Australia. Telehealth patients received daily video calls at home on a desktop videophone provided by the nursing call center. A retrospective cohort study assessed the effectiveness of the telehealth and traditional forms of observation, defined by the proportion of missed observations recorded in case notes. This data was inputted to a model, estimating the incremental cost-effectiveness ratio (ICER) of telehealth. Semi-structured interviews were conducted with current patients, community nursing and Chest Clinic staff, concerning service acceptability, usability and sustainability. The percentage of missed observations for the telehealth service was 12.1 (n = 58), compared to 31.1 for the in-person service (n = 70). Most of the difference of 18.9% (95% CI: 12.2 - 25.4) was due to fewer pre-arranged absences. The economic analysis calculated the ICER to be AUD$1.32 (95% CI: $0.51 - $2.26) per extra day of successful observation. The video service used less staff time, and became dominant if implemented on a larger scale and/or with decreased technology costs. Qualitative analysis found enabling factors of flexible timing, high patient acceptance, staff efficiency, and Chest Clinic support. Substantial technical problems were manageable, and improved liaison between the nursing service and Chest Clinic was an unexpected side-benefit.

CONCLUSIONS/SIGNIFICANCE

Home video observation is a patient-centered, resource efficient way of delivering direct observation for TB, and is cost-effective when compared with a drive-around service. Future research is recommended to determine applicability and effectiveness in other settings.

Systematic review of TST responses in people living with HIV in under-resourced settings: implications for isoniazid preventive therapy

BACKGROUND

People living with HIV (PLWH) who have positive tuberculin skin tests (TST) benefit from isoniazid preventive therapy (IPT) whereas those testing TST-negative do not. Revised World Health Organization guidelines explicitly state that assessment of TST is not a requirement for initiation of IPT. However, it is not known what proportions of patients will benefit from IPT if implemented without targeting according to TST status. We therefore determined the proportions of PLWH who test TST-positive.

METHODOLOGY/PRINCIPAL FINDINGS

We systematically reviewed the literature published between January 1990 and February 2012 to determine the proportions of patients without active tuberculosis attending HIV care services in low and middle-income countries who tested TST-positive (≥5 mm induration). Proportions were also determined for different CD4 count strata. Data from 19 studies with 9,478 PLWH from sub-Saharan Africa, Asia and Central and South America were summarized. The vast majority were not receiving antiretroviral therapy (ART). A sub-analysis was conducted of 5 studies (5,567 subjects) from high TB prevalence countries of PLWH with negative TB screens attending HIV care and treatment settings for whom CD4 stratified data were available. The median proportion of PLWH testing TST-positive overall was 22.8% (range, 19.5-32.6%). The median (range) proportions with CD4 cell counts of <200, 200-499 or ≥500 cells/µL who tested positive were 12.4% (8.2-15.3%), 28.4% (20.1-36.9%) and 37.4% (31.3-56.3%), respectively. Heterogeneity in the data precluded calculation of pooled summary estimates.

CONCLUSIONS/SIGNIFICANCE

In most settings, if IPT is administered to PLWH pre-ART without assessment of TST status, only a minority of those treated are likely to benefit, especially among those with the lowest CD4 cell counts. This may be inefficient use of resources and cost-effectiveness analyses should take this into account. Local knowledge of TST response rates may help inform policies. New simple means of identifying those who will benefit from IPT are needed to permit appropriate targeting of this intervention.

Meta-analysis: the association between HIV infection and extrapulmonary tuberculosis

BACKGROUND

Extrapulmonary tuberculosis has been an AIDS-defining condition. Individual studies that highlight the association between HIV and extrapulmonary TB are available. Our objectives were to synthesis evidence on the association between extrapulmonary tuberculosis and HIV and to explore the effective preventive measures of these two diseases.

METHODS

This is a meta-analysis of observational studies reporting effect estimates on how HIV is associated with extrapulmonary tuberculosis. We searched for the eligible studies in the electronic databases using search terms related to HIV and extrapulmonary tuberculosis. Where possible, we estimated the summary odds ratios using random effects meta-analysis. We stratified analysis by the type of study design. We assessed heterogeneity of effect estimates within each group of studies was assessed using I (2) test.

RESULTS

Nineteen studies (7 case control studies and 12 cohort studies) were identified for the present study. The pooled analysis shows a significant association between HIV and extrapulmonary tuberculosis (summary odds ratio: 1.3; 95 % confidence interval (CI) 1.05-1.6; I (2): 0 %). In a subgroup analysis with two studies, a significant association was found between CD4+ count less than 100 and the incidence of extrapulmonary tuberculosis (summary OR: 1.31; 95 % CI 1.02-1.68; I (2): 0 %).

CONCLUSIONS

Findings show evidence on the association between extrapulmonary tuberculosis and HIV, based on case control studies. Further studies to understand the mechanisms of interaction of the two pathogens are recommended.

Animal welfare in studies on murine tuberculosis: assessing progress over a 12-year period and the need for further improvement

There is growing concern over the welfare of animals used in research, in particular when these animals develop pathology. The present study aims to identify the main sources of animal distress and to assess the possible implementation of refinement measures in experimental infection research, using mouse models of tuberculosis (TB) as a case study. This choice is based on the historical relevance of mouse studies in understanding the disease and the present and long-standing impact of TB on a global scale. Literature published between 1997 and 2009 was analysed, focusing on the welfare impact on the animals used and the implementation of refinement measures to reduce this impact. In this 12-year period, we observed a rise in reports of ethical approval of experiments. The proportion of studies classified into the most severe category did however not change significantly over the studied period. Information on important research parameters, such as method for euthanasia or sex of the animals, were absent in a substantial number of papers. Overall, this study shows that progress has been made in the application of humane endpoints in TB research, but that a considerable potential for improvement remains.

Antiretroviral treatment uptake in patients with HIV-associated TB attending co-located TB and ART services

BACKGROUND

Delivery of integrated care for patients with HIV-associated TB is challenging. We assessed the uptake and timing of antiretroviral treatment (ART) among eligible patients attending a primary care service with co-located ART and TB clinics.

METHODS

In a retrospective cohort study, all HIV-associated TB patients (≥18 years old) who commenced TB treatment in 2010 were included. Data were analysed using basic descriptive statistics and log-binomial regression analysis.

RESULTS

Of a total of 497 patients diagnosed with HIV-associated TB, 274 were eligible to start ART for the first time (median CD4 count, 159 cells/µl). ART was started during TB treatment by 220 (80.3%) patients. Among the 54 (19.7%) who did not start ART, 23 (42.6%) were either lost to follow-up (LTFU) or died before enrolling for ART; 12 (22.2%) were either LTFU or died after enrolling but before starting ART; 5 (9.3%) were transferred out; and 14 (25.9%) only started ART after completion of TB treatment. The median delay between starting TB treatment and starting ART was 51 days (IQR 29 - 77). Overall, only 58.6% of patients started ART within 8 weeks of TB treatment, and 12.7% of those with CD4 counts <50 cells/µl started ART within 2 weeks.

CONCLUSIONS

In a setting with co-located TB and ART clinics, delays to starting ART were substantial, and one-fifth of eligible patients did not start ART during TB treatment. Co-location of services alone is insufficient to permit timely initiation of ART; further measures need to be implemented to facilitate integrated treatment.

Old antibiotics target TB with a new trick

Autophagy is now recognized as a cellular defense mechanism that can restrict the growth of Mycobacterium tuberculosis (Mtb). In this issue of Cell Host & Microbe, Kim et al. (2012) demonstrate that antibiotics routinely used to treat Mtb infection elicit a host autophagy response critical for bacterial clearance.

A diagnostic accuracy study of Xpert®MTB/RIF in HIV-positive patients with high clinical suspicion of pulmonary tuberculosis in Lima, Peru

Background

Diagnosis of pulmonary tuberculosis (TB) among human immunodeficiency virus (HIV) patients remains complex and demands easy to perform and accurate tests. Xpert®MTB/RIF (MTB/RIF) is a molecular TB diagnostic test which is rapid and convenient; the test requires minimal human resources and reports results within two hours. The majority of performance studies of MTB/RIF have been performed in high HIV burden settings, thus TB diagnostic studies among HIV patients in low HIV prevalence settings such as Peru are still needed.

Methodology/Principal Findings

From April 2010 to May 2011, HIV-positive patients with high clinical suspicion of TB were enrolled from two tertiary hospitals in Lima, Peru. Detection of TB by MTB/RIF was compared to a composite reference standard Löwenstein-Jensen (LJ) and liquid culture. Detection of rifampicin resistance was compared to the LJ proportion method. We included 131 patients, the median CD4 cell count was 154.5 cells/mm³ and 45 (34.4%) had TB. For TB detection among HIV patients, sensitivity of MTB/RIF was 97.8% (95% CI 88.4–99.6) (44/45); specificity was 97.7% (95% CI 91.9–99.4) (84/86); the positive predictive value was 95.7% (95% CI 85.5–98.8) (44/46); and the negative predictive value, 98.8% (95% CI 93.6–99.8) (84/85). MTB/RIF detected 13/14 smear-negative TB cases, outperforming smear microscopy [97.8% (44/45) vs. 68.9% (31/45); p = 0.0002]. For rifampicin resistance detection, sensitivity of MTB/RIF was 100% (95% CI 61.0–100.0) (6/6); specificity was 91.0% (95% CI 76.4–96.9) (30/33); the positive predictive value was 66.7% (95% CI 35.4–87.9) (6/9); and the negative predictive value was 100% (95% CI 88.7 –100.0) (30/30).

Conclusions/Significance

In HIV patients in our population with a high clinical suspicion of TB, MTB/RIF performed well for TB diagnosis and outperformed smear microscopy.

Variation of Mycobacterium tuberculosis antigen-specific IFN-γ and IL-17 responses in healthy tuberculin skin test (TST)-positive human subjects

Objective

To determine the variation of IFN-γ and IL-17 responses to M. tuberculosis antigens in healthy TST+ humans.

Methods

We isolated peripheral blood mononuclear cells from 21 TST+ healthy adults, stimulated them with phytohemagglutinin (PHA), PPD, Ag85B, ESAT-6, and live M. bovis BCG, and assayed IFN-γ and IL-17 secretion by ELISA in supernatants after 24 or 72 hours of incubation respectively.

Results

As in other studies, we found a wide range of IFN-γ responses to M. tuberculosis antigens; the variation significantly exceeded that observed in the same donors to the polyclonal T cell stimulus, phytohemagglutinin (PHA). In addition, we assayed IL-17 secretion in response to the same stimuli, and found less subject-to-subject variation. Analysis of the ratio of IFN-γ to IL-17 secretion on a subject-to-subject basis also revealed a wide range, with the majority of results distributed in a narrow range, and a minority with extreme results all of which were greater than that in the majority of subjects. The data suggest that study of exceptional responses to M. tuberculosis antigens may reveal immunologic correlates with specific outcomes of M. tuberculosis infection.

Conclusion

Variation of IFNγ and IFN-γ/IL-17 responses to mycobacterial antigens exceeds that of responses to the polyclonal stimulus, PHA, in TST positive healthy humans. This indicates a quantitative spectrum of human immune responses to infection with M. tuberculosis. Since the outcome of human infection with M. tuberculosis varies greatly, systematic study of multiple immune responses to multiple antigens is likely to reveal correlations between selected immune responses and the outcomes of infection.

Spatial and temporal distribution of tuberculosis in the State of Mexico, Mexico

Tuberculosis (TB) is one of the oldest human diseases that still affects large population groups. According to the World Health Organization (WHO), there were approximately 9.4 million new cases worldwide in the year 2010. In Mexico, there were 18,848 new cases of TB of all clinical variants in 2010. The identification of clusters in space-time is of great interest in epidemiological studies. The objective of this research was to identify the spatial and temporal distribution of TB during the period 2006–2010 in the State of Mexico, using geographic information system (GIS) and SCAN statistics program. Nine significant clusters (P < 0.05) were identified using spatial and space-time analysis. The conclusion is that TB in the State of Mexico is not randomly distributed but is concentrated in areas close to Mexico City.

The -2518A/G polymorphism in the MCP-1 gene and tuberculosis risk: a meta-analysis

Background

The -2518A/G polymorphism in the monocyte chemoattractant protein-1 (MCP-1) gene has been implicated in the susceptibility to tuberculosis (TB), but the results are not conclusive. The aim of this study is to investigate the association between the -2518A/G polymorphism in the MCP-1 gene and the risk of tuberculosis by meta-analysis.

Methods

We searched Pubmed, Embase, CNKI and Wanfang databases, covering all studies until April 29^th, 2011. Statistical analyses were performed using the Revman4.2 and STATA10.0 software.

Results

A total of 5341 cases and 6075 controls in 13 case-control studies were included in the meta-analysis. The results indicated that the GG homozygote carriers had a 67% increased risk of TB compared with the A allele carriers (GG vs. GA+AA: OR = 1.67, 95%CI = 1.25–2.23, P = 0.0006). In the subgroup analysis by ethnicity, significant elevated risks were found in Asians and Latinos, but not in Africans (GG vs. GA+AA: OR = 1.79, 95%CI = 1.19–2.70 and P = 0.005 for Asians; OR = 2.15, 95%CI = 1.32–3.51 and P = 0.002 for Latinos; OR = 1.28, 95%CI = 0.45–3.64 and P = 0.65 for Africans).

Conclusion

This meta-analysis suggested that the -2518A/G polymorphism of MCP-1 gene would be a risk factor for TB in Asians and Latinos, while not in Africans.

Effects of helminths and Mycobacterium tuberculosis infection on HIV-1: a cellular immunological perspective

PURPOSE OF REVIEW

In many regions of the world, a high prevalence of HIV-1, helminthic and Mycobacterium tuberculosis (Mtb) infections can be found. Here, we summarize the types of immune responses induced and/or modulated by these pathogens and the consequences for HIV-1 disease.

RECENT FINDINGS

Helminths predominantly induce strong T helper (Th) 2 cellular responses which are downregulated in chronic disease. The anatomical niche populated by helminths plays a key factor in the effect these parasites have on HIV-1 transmission and subsequent replication. Gut-associated helminths have been found to increase HIV-1 transmission via the lesions they provide. In spite of this, the many immune modulatory molecules secreted by the parasites may inhibit or slow HIV-1 infection. In contrast, Mtb is mainly restricted to the lung and the Mtb-specific Th cells induced are highly susceptible to HIV-1 infection and replication. Antigens from both pathogens have immunomodulatory activity that can skew cellular immune responses in specific directions.

SUMMARY

The effect of helminths and Mtb on modulating immune responses is varied and complex with both their location and phenotype potentially influencing HIV-1 disease. These pathogens have evolved a complex array of molecules which have the capacity to modulate immunity and preserve pathogen survival.

Regulation of TB vaccine-induced airway luminal T cells by respiratory exposure to endotoxin

Tuberculosis (TB) vaccine-induced airway luminal T cells (ALT) have recently been shown to be critical to host defense against pulmonary TB. However, the mechanisms that maintain memory ALT remain poorly understood. In particular, whether respiratory mucosal exposure to environmental agents such as endotoxin may regulate the size of vaccine-induced ALT population is still unclear. Using a murine model of respiratory genetic TB vaccination and respiratory LPS exposure, we have addressed this issue in the current study. We have found that single or repeated LPS exposure increases the number of antigen-specific ALT which are capable of robust secondary responses to pulmonary mycobacterial challenge. To investigate the potential mechanisms by which LPS exposure modulates the ALT population, we have examined the role of ALT proliferation and peripheral T cell recruitment. We have found that LPS exposure-increased ALT is not dependent on increased ALT proliferation as respiratory LPS exposure does not significantly increase the rate of proliferation of ALT. But rather, we find it to be dependent upon the recruitment of peripheral T cells into the airway lumen as blockade of peripheral T cell supplies markedly reduces the initially increased ALT. Thus, our data suggest that environmental exposure to airborne agents such as endotoxin has a profound modulatory effect on TB vaccine-elicited T cells within the respiratory tract. Our study provides a new, M.tb antigen-independent mechanism by which the respiratory mucosal anti-TB memory T cells may be maintained.

Biomarkers of inflammation, immunosuppression and stress with active disease are revealed by metabolomic profiling of tuberculosis patients

Although tuberculosis (TB) causes more deaths than any other pathogen, most infected individuals harbor the pathogen without signs of disease. We explored the metabolome of >400 small molecules in serum of uninfected individuals, latently infected healthy individuals and patients with active TB. We identified changes in amino acid, lipid and nucleotide metabolism pathways, providing evidence for anti-inflammatory metabolomic changes in TB. Metabolic profiles indicate increased activity of indoleamine 2,3 dioxygenase 1 (IDO1), decreased phospholipase activity, increased abundance of adenosine metabolism products, as well as indicators of fibrotic lesions in active disease as compared to latent infection. Consistent with our predictions, we experimentally demonstrate TB-induced IDO1 activity. Furthermore, we demonstrate a link between metabolic profiles and cytokine signaling. Finally, we show that 20 metabolites are sufficient for robust discrimination of TB patients from healthy individuals. Our results provide specific insights into the biology of TB and pave the way for the rational development of metabolic biomarkers for TB.

[Papilledema secondary to tuberculous meningitis in a patient with type 1 diabetes mellitus]

CASE REPORT

The case is presented of a 29-year-old woman who complained of headache over a period of several days, with loss of visual acuity and pain in her left eye. She had a 3-year history of type 1 diabetes mellitus, and was an immigrant from Ecuador. The funduscopic examination revealed a papilledema. The polymerase chain reaction (PCR) study of the cerebrospinal fluid was positive for Mycobacterium tuberculosis (MTB). She showed a marked improvement after treatment with anti-TB drugs.

DISCUSSION

About a third of the world's population has a latent infection of MTB, comorbidity between diabetes mellitus and tuberculosis has been reported, particularly in undeveloped countries.