Latent tuberculosis infection in children: diagnostic approaches

Overcome low levels of detection limit and choice of antibody affects detection of lipoarabinomannan in pediatric tuberculosis

The World Health Organization (WHO) emphasizes that tuberculosis (TB) in children and adolescents is often overlooked by healthcare providers and difficult to diagnose. As childhood TB cases rise, finding a diagnostic high in sensitivity and specificity is critical. In this study 91 urine samples from children aged 1–10 years were analyzed for tuberculostearic acid (TBSA) by gas chromatography/mass spectrometry (GC/MS) and capture ELISA (C-ELISA). In C-ELISA the CS35/A194-01 antibody performed very poorly with both curve-based and model-based cutoffs. The area under the ROC curve (AUC) of the CS35 OD₄₅₀ values was only 0.60. Replacing the capture antibody with BJ76 gave a better performance in both sensitivity and specificity (AUC = 0.95). When these samples were analyzed by GC/MS, 41 classified as ‘probable/possible’ for TB were distinctly TBSA positive with ten samples having <3 ng/mL LAM. However, from the 50 samples with ‘unlikely’ TB classification, 36 were negative but 7 had >3 ng/mL and were designated as LAM positive. This experimental assay assessment study signifies that i) the antibody pair CS35/A194-01 that has been successful for adult active TB diagnosis is not adequate when LAM level is low as in pediatric TB; ii) no one mAb appears to recognize all TB-specific LAM epitopes.

The Diagnostic Value of Blood and Urine IP-10 Test in Children Having Active Tuberculosis or Latent Tuberculosis Infection

Objective This study aimed to investigate interferon-gamma-inducible protein-10 (IP-10) values in serum and urine in pediatric patients in the diagnosis of active tuberculosis (TB) or latent TB infection (LTBI). It also aimed to investigate whether it can be used as a biomarker to distinguish between active TB and LTBI.

Methods Our study comprised active TB (25 patients), LTBI (25 patients), and the “infected” group (50 patients) formed by combining the two groups. As the control group, 37 healthy children were included in the study. TB skin test, plasma IP-10, and urine IP-10 measurements were performed in all patients included in the study. An additional QuantiFERON-TB Gold In-Tube (QFT-GIT) test was performed on patients evaluated as active TB or LTBI.

Results Plasma IP-10 levels of the patients in the active TB, LTBI, and the “infected” groups were significantly higher than the control group (p = 0.022, p = 0.028, and p = 0.007, respectively). Urine IP-10 was successful in distinguishing the active TB and “infected” groups from the control group (p = 0.007 and p = 0.047, respectively). Also, in the combined use of the tests, when QFT-GIT and urine IP-10 were positive together, active TB and LTBI could be distinguished (p = 0.044). Urine IP-10 levels were found to be significantly higher in those with pulmonary TB than those with extrapulmonary TB (p = 0.012).

Conclusion Our findings suggest that IP-10 can be used as a useful biomarker in the diagnosis of active TB in children.

Engineered Mycobacterium tuberculosis antigen assembly into core-shell nanobeads for diagnosis of tuberculosis

Despite recent advances in diagnosis, tuberculosis (TB) remains one of the ten leading causes of death worldwide. Here, we engineered Mycobacterium tuberculosis (Mtb) proteins (ESAT6, CFP10, and MTB7.7) to self-assemble into core-shell nanobeads for enhanced TB diagnosis. Respective purified Mtb antigen-coated polyester beads were characterized and their functionality in TB diagnosis was tested in whole blood cytokine release assays. Sensitivity and specificity were studied in 11 pulmonary TB patients (PTB) and 26 healthy individuals composed of 14 Tuberculin Skin Test negative (TSTn) and 12 TST positive (TSTp). The production of 6 cytokines was determined (IFNγ, IP10, IL2, TNFα, CCL3, and CCL11). To differentiate PTB from healthy individuals (TSTp + TSTn), the best individual cytokines were IL2 and CCL11 (>80% sensitivity and specificity) and the best combination was IP10 + IL2 (>90% sensitivity and specificity). We describe an innovative approach using full-length antigens attached to biopolyester nanobeads enabling sensitive and specific detection of human TB.

Evidence-based consensus on opportunistic infections in inflammatory bowel disease (republication)

Inflammatory bowel disease (IBD) patients are a high-risk population for opportunistic infections. The IBD group of the Chinese Society of Gastroenterology of the Chinese Medical Association organized an expert group to discuss and develop this consensus opinion. This consensus opinion referenced clinical study results from China and other countries to provide guidance for clinical practices. Eight major topics, including cytomegalovirus infection, Epstein-Barr virus infection, viral hepatitis, bacterial infection, Mycobacterium tuberculosis infection, fungal infection, parasitic infection, and vaccines were introduced in this article.

IFN-γ and IL-2 Responses to Recombinant AlaDH against ESAT-6/CFP-10 Fusion Antigens in the Diagnosis of Latent versus Active Tuberculosis Infection

BACKGROUND

Discriminating latent tuberculosis infection (LTBI) from active TBI may be challenging. The objective of this study was to produce the recombinant L-alanine dehydrogenase (AlaDH) antigen and evaluate individuals with LTBI, those with active TBI, and uninfected individuals by enzyme-linked immunospot assay (ELISPOT) in order to distinguish LTBI from active TBI.

METHODS

This exploratory study was performed in the Iranian city of Shiraz from 2014 to 2015. The study population (N=99) was divided into 3 groups: individuals with newly diagnosed active TBI (n=33), their household contacts (n=33), and controls (n=33). AlaDH was produced through PCR and cloning methods. The diagnostic characteristics of AlaDH vs. ESAT-6/CFP-10 were evaluated in responses to interferon-γ (IFN-γ) and interleukin-2 (IL-2) with ELISPOT. Differences between the groups were assessed with the Kruskal-Wallis and Mann-Whitney tests for nonparametric data analysis. The statistical analyses were performed with SPSS, version 16.

RESULTS

IFN-γ responses to both ESAT-6/CFP-10 (P=0.81) and AlaDH (P=0.18) revealed that there were no significant differences between the individuals with LTBI and those with active TBI. The same results were determined for IL-2 responses to ESAT-6/CFP-10 between the 2 groups, while significantly higher IL-2 responses to AlaDH were observed in LTBI than in active TBI. According to the ROC curve analysis, a cutoff value of 275 SFC showed sensitivity of 75.8% and specificity of 78.8% for distinguishing LTBI from active TBI by IL-2 responses to AlaDH.

CONCLUSION

The current study suggests that it may be possible to discriminate LTBI from active TBI by IL-2 responses to AlaDH.

Discordance Between Tuberculin Skin Test and Interferon-γ Release Assay in Children Younger Than 5 Years Who Have Been Vaccinated With Bacillus Calmette-Guérin

BACKGROUND

Interferon-γ release assays (IGRAs) offer the possibility of improved detection of latent tuberculosis infection (LTBI).

OBJECTIVE

To analyze discordant tuberculin skin testing (TST) and IGRA results in ethnic Croatian children as old as 5 years for whom there is documented exposure to an adult with active tuberculosis (TB) and who have been vaccinated with Bacillus Calmette-Guérin.

METHODS

In specimens from our cohort individuals, we tested the performances of the QuantiFERON-TB Gold In-Tube (QFT-GIT) test and TST and analyzed discordant results.

RESULTS

At the TST cutoff value of 10 mm or greater, the estimated prevalence of M. tuberculosis infection was 18.1% (31/171) using TST and 15.2% (26/171) using QFT-GIT. The results of these 2 tests showed an overall concordance of 87.7%. There was no evidence that subjects' age correlated with discordant results.

CONCLUSIONS

The reasons for discordant results in young children are still unclear, which highlights the importance of further longitudinal studies to better understand the interpretation and any possible clinical implications of the results of these tests.

PpiA antigen specific immune response is a potential biomarker for latent tuberculosis infection

One third of the world's population is estimated to harbour latent tuberculosis infection (LTBI). Around 10% of them have the life time risk of developing active tuberculosis (PTB). Currently there is no gold standard test for identifying LTBI. Therefore identification of specific markers for LTBI will help as to develop a test specific for LTBI. Earlier, in our immunoproteomic analysis, we found that peptidyl-prolyl cis-trans isomerase A (PpiA) protein-containing fractions induced significantly higher interferon-gamma (IFN-γ) response in LTBI than in PTB. Immunological characterisation of recombinant PpiA protein was carried out in the current study. We have studied 10 cytokines and 2 chemokine responses against PpiA and standard antigens such as early secretory antigenic target-6 (ESAT-6) and culture filtrate antigen-10 (CFP-10). In healthy household contacts (HHC), all the tested antigens induced significantly higher levels of IFN-γ and Interlukin-8 (IL-8) compared with those in PTB. PpiA-specific IL-12p40 response was significantly increased in HHC compared with that in PTB. PpiA antigen-specific IFN-γ and IL-12p40 both showed 86% positivity in HHC, whereas in PTB, they showed 20% and 38% positivity, respectively. In terms of IFN-γ/TNF-α ratio, PpiA displayed 86% (30/35) positivity in HHC and 18% (7/39) positivity in PTB. In summary we found that PpiA-specific IFN-γ and IFN-γ/TNF-α ratio response were specific biomarkers for LTBI identification.

Host RNA signatures for diagnostics: an example from paediatric tuberculosis in Africa

Host gene expression profiling is a widely used research tool for assessing the host response to infection in order to provide insight into the immunopathophysiology of disease, as well as the analysis of disease progression and treatment response. It has recently been applied for the diagnosis of tuberculosis in children in Africa, as a result of the implementation of novel statistical methodology that enabled the reduction of a large number of significantly differentially expressed genes into a minimal set, and the development of a 'disease risk score' that could be used to develop a diagnostic test. Whilst the experimental and statistical methodologies are now in place to generate minimal transcriptional signatures that can distinguish disease states, the challenge is how to take these forward into development of a diagnostic test for use in clinical resource-poor settings.

miRNA signatures in sera of patients with active pulmonary tuberculosis

Several studies showed that assessing levels of specific circulating microRNAs (miRNAs) is a non-invasive, rapid, and accurate method for diagnosing diseases or detecting alterations in physiological conditions. We aimed to identify a serum miRNA signature to be used for the diagnosis of tuberculosis (TB). To account for variations due to the genetic makeup, we enrolled adults from two study settings in Europe and Africa. The following categories of subjects were considered: healthy (H), active pulmonary TB (PTB), active pulmonary TB, HIV co-infected (PTB/HIV), latent TB infection (LTBI), other pulmonary infections (OPI), and active extra-pulmonary TB (EPTB). Sera from 10 subjects of the same category were pooled and, after total RNA extraction, screened for miRNA levels by TaqMan low-density arrays. After identification of “relevant miRNAs”, we refined the serum miRNA signature discriminating between H and PTB on individual subjects. Signatures were analyzed for their diagnostic performances using a multivariate logistic model and a Relevance Vector Machine (RVM) model. A leave-one-out-cross-validation (LOOCV) approach was adopted for assessing how both models could perform in practice. The analysis on pooled specimens identified selected miRNAs as discriminatory for the categories analyzed. On individual serum samples, we showed that 15 miRNAs serve as signature for H and PTB categories with a diagnostic accuracy of 82% (CI 70.2–90.0), and 77% (CI 64.2–85.9) in a RVM and a logistic classification model, respectively. Considering the different ethnicity, by selecting the specific signature for the European group (10 miRNAs) the diagnostic accuracy increased up to 83% (CI 68.1–92.1), and 81% (65.0–90.3), respectively. The African-specific signature (12 miRNAs) increased the diagnostic accuracy up to 95% (CI 76.4–99.1), and 100% (83.9–100.0), respectively. Serum miRNA signatures represent an interesting source of biomarkers for TB disease with the potential to discriminate between PTB and LTBI, but also among the other categories.

Mycobacterium tuberculosis-specific TNF-α is a potential biomarker for the rapid diagnosis of active tuberculosis disease in Chinese population

Interferon-gamma release assays (IGRAs) have proven to be useful to accurately detect Mycobacterium tuberculosis (Mtb) infection, but they cannot reliably discriminate between active tuberculosis (TB) and latent tuberculosis infection (LTBI). This study aims to test whether Mtb-specific tumor necrosis factor-alpha (TNF-α) could be used as a new tool for the rapid diagnosis of active TB disease. The secretion of TNF-α by Mtb-specific antigen-stimulated peripheral blood mononuclear cells (PBMCs) of sixty seven participants was investigated in the study. Our results showed that the total measurement of TNF-α secretion by Mtb-specific antigen-stimulated PBMCs is not a good biomarker for active TB diagnosis. However, we found that calculation of Mtb-specific TNF-α not only distinguish between active and latent TB infection, but also can differentiate active TB from non-TB patients. Using the cutoff value of 136.9 pg/ml for Mtb-specific TNF-α, we were able to differentiate active TB from LTBI. Sensitivity and specificity were 72% and 90.91%. These data suggest that Mtb-specific TNF-α could be a potential biomarker for the diagnosis of active TB disease.

Potential role of M. tuberculosis specific IFN-γ and IL-2 ELISPOT assays in discriminating children with active or latent tuberculosis

Background

Although currently available IGRA have been reported to be promising markers for TB infection, they cannot distinguish active tuberculosis (TB) from latent infection (LTBI).

Objective

Children with LTBI, active TB disease or uninfected were prospectively evaluated by an in-house ELISPOT assay in order to investigate possible immunological markers for a differential diagnosis between LTBI and active TB.

Methods

Children at risk for TB infection prospectively enrolled in our infectious disease unit were evaluated by in-house IFN-γ and IL-2 based ELISPOT assays using a panel of Mycobacterium tuberculosis antigens.

Results

Twenty-nine children were classified as uninfected, 21 as LTBI and 25 as active TB cases (including 5 definite and 20 probable cases). Significantly higher IFN-γ ELISPOT responses were observed in infected vs. uninfected children for ESAT-6 (p<0.0001), CFP-10 (p<0.0001), TB 10.3 (p = 0.003), and AlaDH (p = 0.001), while differences were not significant considering Ag85B (p = 0.063), PstS1 (p = 0.512), and HspX (16 kDa) (p = 0.139). IL-2 ELISPOT assay responses were different for ESAT-6 (p<0.0001), CFP-10 (p<0.0001), TB 10.3 (p<0.0001), HspX (16 kDa) (p<0.0001), PstS1 (p<0.0001) and AlaDH (p = 0.001); but not for Ag85B (p = 0.063). Comparing results between children with LTBI and those with TB disease differences were significant for IFN-γ ELISPOT only for AlaDH antigen (p = 0.021) and for IL-2 ELISPOT assay for AlaDH (p<0.0001) and TB 10.3 antigen (p = 0.043). ROC analyses demonstrated sensitivity of 100% and specificity of 81% of AlaDH-IL-2 ELISPOT assay in discriminating between latent and active TB using a cut off of 12.5 SCF per million PBMCs.

Conclusion

Our data suggest that IL-2 based ELISPOT with AlaDH antigen may be of help in discriminating children with active from those with latent TB.