Suitability of saliva for Tuberculosis diagnosis: comparing with serum

The Role of Salivary Diagnostic Techniques in Screening for Active Pulmonary Tuberculosis: A Systematic Review and Meta-Analysis

Since the World Health Organization (WHO) issued guidelines for developing a non-sputum test for active tuberculosis (TB) diagnosis that exhibits similar performance characteristics to sputum-based diagnosis, salivary diagnostic techniques have gained prominence as potential screening tools or adjuncts to existing diagnostics. We searched online databases for studies that looked at salivary diagnostic techniques. Afterwards, duplicates were removed, titles and abstracts were screened, and full-text studies were assessed for eligibility based on inclusion and exclusion criteria. The studies chosen for final analysis underwent a rigorous quality assessment following a QUADAS-2 template, and data were extracted. The primary outcome assessed the difference in mean levels of interleukins between TB+ patients and TB-controls (Hedges' g). We then conducted two subgroup analyses: the first segregated the control group into healthy patients, and those with other respiratory diseases (ORD), and the second addressed three different interleukins separately (IL-6, IL-5, IL-17). The secondary outcome involved comparing salivary molecular diagnostic assays to WHO guidelines. This study is registered with PROSPERO, CRD42024536884. A total of 17 studies, out of an initial 1010, were chosen for the final analysis, but one was then excluded for being of poor quality. Our meta-analyses for the primary outcome revealed minimal diagnostic potential for interleukins. Our first subgroup analysis showed that interleukins were incapable of differentiating active TB patients from both healthy controls and ORD patients. Our second subgroup analysis showed that IL-17 was reduced in active TB patients. Assessment of the secondary outcome revealed that most studies relied on a GeneXpert MTB/RIF assay on saliva, but none fulfilled WHO guidelines for a non-sputum test. Individual biomarkers currently lack sufficient discriminatory power to definitively distinguish active tuberculosis from healthy individuals or those with other respiratory diseases (ORD), reinforcing the need for multi-biomarker panels. Interleukins may be alternatively used as markers for prognosis, severity, or treatment response. Our findings also suggest that assays are unable to meet WHO guidelines.

Performance of 2 Finger-Stick Blood Tests to Triage Adults With Symptoms of Pulmonary Tuberculosis: A Prospective Multisite Diagnostic Accuracy Study

BACKGROUND

Non-sputum-based, point-of-care triage tests for pulmonary tuberculosis could enhance tuberculosis diagnostic programs. We assessed the diagnostic accuracy of 2 finger-stick blood tests: the Cepheid 3 gene host-response cartridge (Xpert-HR), which measures 3 host messenger RNA transcripts, and the 3-host protein multibiomarker test (MBT).

METHODS

We performed a prospective diagnostic accuracy study of consecutive participants with symptoms compatible with pulmonary tuberculosis in The Gambia, South Africa, Uganda, and Vietnam. A composite reference standard for active pulmonary tuberculosis incorporated chest radiography, symptom resolution, and sputum microbiological test results. A training-test set approach was used to evaluate test cutoff specificities at 90% sensitivity.

RESULTS

Between 1 November 2020 and 1 May 2023, we screened 1262 participants aged 12-70 years with cough lasting >2 weeks and another symptom suggestive of tuberculosis. Of those who were classifiable by reference tests, 1154 participants had evaluable Xpert-HR results and 961 had evaluable MBT results. Xpert-HR had an area under the receiver operating characteristic (AUROC) curve of 0.92 at a cutoff of -1.275 or below, with a sensitivity of 92.8%, specificity of 62.5%, positive predictive value of 47.9%, and negative predictive value of 95.9%. The MBT had an AUROC of 0.91 at a cutoff of ≥0.42, with a sensitivity of 91.4%, specificity of 73.2%, positive predictive value of 52.0%, and negative predictive value of 96.4%.

CONCLUSIONS

Our results show that both Xpert-HR and the MBT are promising non-sputum-based point-of-care tests. The MBT met the World Health Organization target product profile for a triage test, which suggests it should be further developed.

Rapid tuberculosis diagnosis from respiratory or blood samples by a low cost, portable lab-in-tube assay

Rapid portable assays are needed to improve diagnosis, treatment, and reduce transmission of tuberculosis (TB), but current tests are not suitable for patients in resource-limited settings with high TB burden. Here we report a low complexity, lab-in-tube system that is read by an integrated handheld device that detects Mycobacterium tuberculosis (Mtb) DNA in blood and respiratory samples from a variety of clinical settings. This microprocessor-controlled device uses an LCD user interface to control assay performance, automate assay analysis, and provide results in a simple readout. This point-of-care single-tube assay uses a DNA enrichment membrane and a low-cost cellulose disc containing lyophilized recombinase polymerase amplification and CRISPR-Cas12a reagents to attain single-nucleotide specificity and high sensitivity within 1 hour of sample application, without a conventional DNA isolation procedure. Assay results obtained with serum cell-free DNA isolated from a cohort of children aged 1 to 16 years detected pulmonary and extrapulmonary TB with high sensitivity versus culture and GeneXpert MTB/RIF results (81% versus 55% and 68%) and good specificity (94%), meeting the World Health Organization target product profile criteria for new nonsputum TB diagnostics. Changes in assay results for serum isolated during treatment were also highly predictive of clinical response. Results obtained with noninvasive sputum and saliva specimens from adults with bacteriologically confirmed pulmonary TB were also comparable to those reported for reference methods. This rapid and inexpensive lab-in-tube assay approach thus represents one means to address the need for point-of-care TB diagnostics useable in low-resource settings.

Overview of mucosal immunity and respiratory infections in children: a focus on Africa

PURPOSE OF REVIEW

Given the substantial burden of respiratory tract infections (RTIs) on global paediatric health, enhancing our understanding of mucosal immunity can help us advance mucosal biomarkers for diagnosis, prognosis and possible interventions in order to improve health outcomes. This review highlights the critical role of mucosal immunity in paediatric RTIs and recent advances in mucosal interventions, which offer promising strategies to improve outcomes.

RECENT FINDINGS

The significant burden of paediatric RTIs and growing interest in mucosal immunity advanced our understanding of the role of the respiratory mucosal immune system in protective immunity against RTIs. Studies show that sub-Saharan Africa is disproportionately affected by paediatric RTIs with poverty-associated factors such as human immunodeficiency virus (HIV) and malnutrition as risk factors. Emerging evidence highlights the important role of the respiratory microbiome and mucosal innate and adaptive immune responses in protective immunity against RTIs.

SUMMARY

The growing interest in mucosal immunity in RTIs has not only advanced our understanding of the overall immune responses in RTIs but also created opportunities to improve RTI care through translation of knowledge from these studies into diagnostics, therapeutics, and vaccines.

Simplified Co-extraction of total Nucleic Acids from Respiratory Samples for detection of Mycobacterium tuberculosis and SARS-CoV-2 optimized for compatibility across Diagnostic Platforms

Tuberculosis (TB) and COVID-19 are leading infectious diseases with high mortality, caused by Mycobacterium tuberculosis (Mtb) and SARS-CoV-2 (SC2), respectively. Co-infection is common but is often undiagnosed as it is challenging to process both pathogens from a single sample. In this study, we present a simple and efficient method for co-extracting nucleic acids (NA) from these two distinct respiratory pathogens for downstream diagnostic testing. We evaluated three different nucleic acid amplification (NAA)-based platforms, LightCycler480 (LC480) qPCR, Qiacuity digital PCR (dPCR), and Cytation3 for CRISPR-Cas13a-based SHINE-TB/SC2 detection assays. Chelex-100 chelating resin-based boiling preparation method was optimized for Mtb NA extraction from saliva and sputum. Saliva showed compatibility with all three platforms, with sensitivity as low as 100 CFU/ml (or 2 genomic copies/μl). This method worked well for sputum using dPCR at 100% (21/21) positivity, though the CRISPR-based SHINE-TB assay showed more variability and sensitivity to sputum inhibitor carry-over, resulting in an 81% positive rate (17/21). Diluting sputum with TE buffer (1:1) improved the detection (2/4). Extraction efficiency of our method was 48%, 62.2%, 86.4% and 99.3% for concentrations 105, 104, 103 and 10 CFU/ml, respectively. The dynamic range for Mtb spiked in pooled sputum showed 100% detection (N=8) at ≥103 CFU/ml with all three methods. Dual-pathogen co-extraction and detection of SC2 (105 PFU/ml) and Mtb (105 CFU/ml) in salivary sputum was successful using CRISPR-Cas13a assays. We have developed a rapid and efficient co-extraction method for multi-pathogen testing across diagnostic platforms and believe this is the first protocol optimized to co-extract Mtb and SARS-CoV-2 from a single sample.

Non-sputum-based samples and biomarkers for detection of Mycobacterium tuberculosis: the hope to improve childhood and HIV-associated tuberculosis diagnosis

In 2014, the World Health Organisation (WHO) published target product profiles (TPP) for development of novel tuberculosis (TB) diagnostics. One of the key highlights is the need for point-of-care non-sputum-based tests capable of detecting all forms of TB through identification of characteristic biomarkers or biosignatures. Compared to the limitations associated with sputum-based TB tests, non-sputum samples are easy to collect, non-invasive, with potential to improve TB diagnosis among children and among people living with HIV/AIDS (PLHIV). This review gives an overview of the existing evidence on TB diagnostic studies of non-sputum-based samples collected non-invasively from or through the oral-gastrointestinal tract (GI) and nasal pharynx regions of humans and the biomarkers detected. We further summarized evidence of these biomarkers and sample types from research done in paediatric and PLHIV. The review identified; saliva, cough aerosols, oral swabs, oral wash, dental plaque, tongue swabs, face mask sampling, exhaled breath, and stool, as the non-sputum samples investigated. These biomarkers can be categorized into Deoxyribose Nucleic Acid (DNA), Ribonucleic Acid (RNA), inflammatory, antigen-antibody, volatile and non-volatile compounds, microbiome and microbiota. The biomarkers identified were derived both from the host and pathogen. Similar biomarkers were identified in the general population, children and among PLHIV. These biomarkers have been detected by either already approved simple point of care or sophisticated devices. Differences in methodology and sample types investigated, small sample size of children and PLHIV populations, bias due to confounding factors, were some of the identified challenges in these studies. There is need to conduct larger and standardized multi centre studies to evaluate non-sputum-based biomarker-based tests in children and PLHIV.

Differential levels of anti-Mycobacterium tuberculosis-specific IgAs in saliva of household contacts with latent tuberculosis infection

Introduction

Mucosal immunity is strongly elicited in early stages of many respiratory and enteric infections; however, its role in tuberculosis pathogenesis has been scarcely explored. We aimed to investigate Mycobacterium tuberculosis (Mtb) specific IgA levels in saliva in different stages of latent Tuberculosis Infection (TBI).

Methodology

A multiplex bead-based Luminex immunoassay was developed to detect specific IgA against 12 highly immunogenic Mtb antigens. A prospective cohort of household contacts (>14 years) of pulmonary TB cases was established in Santiago, Chile. Contacts were classified as Mtb-infected or not depending on serial interferon-γ release assay results. Saliva samples were collected and tested at baseline and at a 12-week follow-up.

Results

Mtb-specific IgA was detectable at all visits in all participants (n = 168), including the "non-Mtb infected" (n = 64). Significantly higher median levels of IgA were found in the "Mtb infected" compared to the uninfected for anti-lipoarabinomannan (LAM) (110 vs. 84.8 arbitrary units (AU), p < 0.001), anti-PstS1 (117 vs. 83 AU, p < 0.001), anti-Cell Membrane Fraction (CMF) (140 vs. 103 AU, p < 0.001) and anti-Culture Filtrate Proteins (CFP) (median 125 vs. 96 AU, p < 0.001), respectively. Nonetheless, the discriminatory performance of these specific mucosal IgA for TBI diagnosis was low.

Conclusion

Saliva holds Mtb-specific IgA against several antigens with increased levels for anti-LAM, anti-PstS1, anti-CMF and anti-CFP found in household contacts with an established TBI. The role of these mucosal antibodies in TB pathogenesis, and their kinetics in different stages of Mtb infection merits further exploring.

Differential expression of host protein biomarkers among symptomatic clinic attendees finally diagnosed with tuberculosis and other respiratory diseases with or without latent Mycobacterium tuberculosis infection

BACKGROUND

There is a need for new tools for the diagnosis of tuberculosis (TB) amongst patients who present at primary health care centers with symptoms suggestive of TB.

OBJECTIVES

To assess the abilities of selected blood-based host biomarkers to discriminate between patients who self-presented with symptoms suggestive of TB and were subsequently diagnosed with pulmonary tuberculosis (PTB), other respiratory diseases (ORD) with latent Mycobacterium tuberculosis infection (ORD_LTBI) or ORD without latent infection (ORD_NoLTBI).

METHODS

Presumptive TB patients (n = 161) were enrolled at a TB Clinic in Kampala, Uganda, and blood was collected. Participants were later classified as having PTB or ORD using standard microbiological confirmatory tests. Patients with ORD were subsequently classified as having LTBI or no LTBI using the QuantiFERON Gold-plus test. The concentrations of 27 host biomarkers were evaluated in patient sera using the Luminex platform, followed by an evaluation of their abilities to discriminate between PTB, ORD_LTBI, and ORD_NoLTBI.

RESULTS

Multiple host biomarkers including IP10, IL6, IL2, IL1β, TNFα, IFNγ, and IL12p70, were significantly different between patients with PTB (n = 55), ORDs (n = 106), and between PTB and the two ORD sub-groups. A bio-signature comprising IP10, IL6, TNFα IL1β, IL1ra, and IL12p70 best diagnosed PTB disease, with an area under the ROC curve of 90.

CONCLUSION

We identified host biomarkers that discriminated between different M.tb infection states amongst patients who presented with symptoms requiring investigation for TB. The biomarkers that showed diagnostic potential in our study may be considered as additional candidate markers for future active PTB rapid screening tests.

Feasibility and Sensitivity of Saliva GeneXpert MTB/RIF Ultra for Tuberculosis Diagnosis in Adults in Uganda

The objective of this prospective observational study carried out at China-Uganda Friendship Hospital-Naguru in Kampala, Uganda, was to determine the performance of GeneXpert MTB/RIF Ultra (Xpert Ultra) molecular testing on saliva for active tuberculosis (TB) disease among consecutive adults undergoing TB diagnostic evaluation who were Xpert Ultra positive on sputum. We calculated sensitivity to determine TB diagnostic performance in comparison to a composite reference standard of Mycobacterium tuberculosis liquid and solid cultures on two spot sputum specimens. Xpert Ultra on a single saliva sample had a sensitivity of 90% (95% confidence interval [CI], 81 to 95%) relative to the composite sputum culture-based reference standard, similar to the composite sensitivity of 87% (95% CI, 77 to 94%) for fluorescence microscopy (FM) for acid-fast bacilli on two sputum smears. The sensitivity of salivary Xpert Ultra was 24% lower (95% CI for difference, 2 to 48%; P = 0.003) among persons living with HIV (71%; 95% CI, 44 to 90%) than among persons living without HIV (95%; 95% CI, 86 to 99%) and 46% higher (95% CI, 14 to 77%; P < 0.0001) among FM-positive (96%; 95% CI, 87 to 99%) than among FM-negative (50%; 95% CI, 19 to 81%) patients. The semiquantitative Xpert Ultra grade was systematically higher in sputum than in a paired saliva sample from the same patient. In conclusion, molecular testing of saliva for active TB diagnosis was feasible and almost as sensitive as molecular testing of sputum in a high TB burden setting. IMPORTANCE Tuberculosis is among the leading causes of morbidity and mortality worldwide, in large part because >3 million people go undiagnosed and untreated each year. Sputum has been the mainstay for TB diagnosis for over a century but can be difficult for patients to produce. In addition, the vigorous coughing required during sputum collection can lead to infection of nearby individuals and health workers. In this case-only study, applying the ultra-sensitive GeneXpert MTB/RIF Ultra molecular diagnostic assay to saliva detected 90% of culture-confirmed TB cases among 81 adults who were undergoing TB evaluation at the outpatient department of a general hospital in Uganda and tested sputum GeneXpert MTB/RIF Ultra positive. These results suggest that saliva may be a feasible and sensitive alternative to sputum for TB diagnosis, thereby meeting two key metrics proposed by the World Health Organization in its target performance profile for a nonsputum test for TB.

Diagnosing Tuberculosis: What Do New Technologies Allow Us to (Not) Do?

New tuberculosis (TB) diagnostics are at a crossroads: their development, evaluation, and implementation is severely damaged by resource diversion due to COVID-19. Yet several technologies, especially those with potential for non-invasive non-sputum-based testing, hold promise for efficiently triaging and rapidly confirming TB near point-of-care. Such tests are, however, progressing through the pipeline slowly and will take years to reach patients and health workers. Compellingly, such tests will create new opportunities for difficult-to-diagnose populations, including primary care attendees (all-comers in high burden settings irrespective of reason for presentation) and community members (with early stage disease or risk factors like HIV), many of whom cannot easily produce sputum. Critically, all upcoming technologies have limitations that implementers and health workers need to be cognizant of to ensure optimal deployment without undermining confidence in a technology that still offers improvements over the status quo. In this state-of-the-art review, we critically appraise such technologies for active pulmonary TB diagnosis. We highlight strengths, limitations, outstanding research questions, and how current and future tests could be used in the presence of these limitations and uncertainties. Among triage tests, CRP (for which commercial near point-of-care devices exist) and computer-aided detection software with digital chest X-ray hold promise, together with late-stage blood-based assays that detect host and/or microbial biomarkers; however, aside from a handful of prototypes, the latter category has a shortage of promising late-stage alternatives. Furthermore, positive results from new triage tests may have utility in people without TB; however, their utility for informing diagnostic pathways for other diseases is under-researched (most sick people tested for TB do not have TB). For confirmatory tests, few true point-of-care options will be available soon; however, combining novel approaches like tongue swabs with established tests like Ultra have short-term promise but first require optimizations to specimen collection and processing procedures. Concerningly, no technologies yet have compelling evidence of meeting the World Health Organization optimal target product profile performance criteria, especially for important operational criteria crucial for field deployment. This is alarming as the target product profile criteria are themselves almost a decade old and require urgent revision, especially to cater for technologies made prominent by the COVID-19 diagnostic response (e.g., at-home testing and connectivity solutions). Throughout the review, we underscore the importance of how target populations and settings affect test performance and how the criteria by which these tests should be judged vary by use case, including in active case finding. Lastly, we advocate for health workers and researchers to themselves be vocal proponents of the uptake of both new tests and those - already available tests that remain suboptimally utilized.

The intersecting pandemics of tuberculosis and COVID-19: population-level and patient-level impact, clinical presentation, and corrective interventions

The global tuberculosis burden remains substantial, with more than 10 million people newly ill per year. Nevertheless, tuberculosis incidence has slowly declined over the past decade, and mortality has decreased by almost a third in tandem. This positive trend was abruptly reversed by the COVID-19 pandemic, which in many parts of the world has resulted in a substantial reduction in tuberculosis testing and case notifications, with an associated increase in mortality, taking global tuberculosis control back by roughly 10 years. Here, we consider points of intersection between the tuberculosis and COVID-19 pandemics, identifying wide-ranging approaches that could be taken to reverse the devastating effects of COVID-19 on tuberculosis control. We review the impact of COVID-19 at the population level on tuberculosis case detection, morbidity and mortality, and the patient-level impact, including susceptibility to disease, clinical presentation, diagnosis, management, and prognosis. We propose strategies to reverse or mitigate the deleterious effects of COVID-19 and restore tuberculosis services. Finally, we highlight research priorities and major challenges and controversies that need to be addressed to restore and advance the global response to tuberculosis.

Past and Present Approaches to Diagnosis of Active Pulmonary Tuberculosis

Tuberculosis disease continues to contribute to the mortality burden globally. Due to the several shortcomings of the available diagnostic methods, tuberculosis disease continues to spread. The difficulty to obtain sputum among the very ill patients and the children also affects the quick diagnosis of tuberculosis disease. These challenges warrant investigating different sample types that can provide results in a short time. Highlighted in this review are the approved pulmonary tuberculosis diagnostic methods and ongoing research to improve its diagnosis. We used the PRISMA guidelines for systematic reviews to search for studies that met the selection criteria for this review. In this review we found out that enormous biosignature research is ongoing to identify host biomarkers that can be used as predictors of active PTB disease. On top of this, more research was also being done to improve already existing diagnostic tests. Host markers required more optimization for use in different settings given their varying sensitivity and specificity in PTB endemic and non-endemic settings.

A narrative review of exploring potential salivary biomarkers in respiratory diseases: still on its way

Saliva is abundant with proteins, metabolites, DNA, and a diverse range of bacterial species. During the past two decades, saliva has emerged as a novel diagnostic and evaluation medium for several diseases. Collection of saliva samples is simple, minimally invasive, and convenient even in infants, children, and patients with anxious. Furthermore, with the development of hypersensitive techniques [e.g., microsensor arrays, enzyme-labeled immunosensors, nanoparticle-labeled immunosensors, capacitive or impedimetric immunosensors, magneto immunosensors, field effect transistor immunosensors, and surface enhanced Raman spectroscopy (SERS)], the sensitivity and accuracy of saliva diagnostic procedures have been improved. Nowadays, saliva has been used as a potential medium for several disease diagnosis and assessment, such as periodontitis, caries, cancers, diabetes mellitus, and cardiovascular diseases. Saliva has been used widely for studying microbiomics, genomics, transcriptomics, proteomics, and metabolomics of respiratory diseases, however, the use of salivary biomarkers for the diagnosis, prognosis, and monitoring of respiratory disease is still in its infancy. Herein, we review the progress of research on salivary biomarkers related to several respiratory diseases, including bronchial asthma, chronic obstructive pulmonary disease (COPD), obstructive sleep apnea (OSA), pneumonia, tuberculosis (TB), Langerhans cell histiocytosis (LCH) and cystic fibrosis (CF). Furthermore, several limitations of saliva test such as the lack of standard protocol for saliva collection and reasonable reference values for saliva test are also mentioned in this review.

A Plasma 5-Marker Host Biosignature Identifies Tuberculosis in High and Low Endemic Countries

Background: Several host inflammatory markers have been proposed as biomarkers for diagnosis and treatment response in Tuberculosis (TB), but few studies compare their utility in different demographic, ethnic, and TB endemic settings.

Methods: Fifty-four host biomarkers were evaluated in plasma samples obtained from presumed TB cases recruited at the Oslo University Hospital in Norway, and a health center in Cape Town, South Africa. Based on clinical and laboratory assessments, participants were classified as having TB or other respiratory diseases (ORD). The concentrations of biomarkers were analyzed using the Luminex multiplex platform.

Results: Out of 185 study participants from both study sites, 107 (58%) had TB, and 78 (42%) ORD. Multiple host markers showed diagnostic potential in both the Norwegian and South African cohorts, with I-309 as the most accurate single marker irrespective of geographical setting. Although study site-specific biosignatures had high accuracy for TB, a site-independent 5-marker biosignature (G-CSF, C3b/iC3b, procalcitonin, IP-10, PDGF-BB) was identified diagnosing TB with a sensitivity of 72.7% (95% CI, 49.8–82.3) and specificity of 90.5% (95% CI, 69.6–98.8) irrespective of geographical site.

Conclusion: A 5-marker host plasma biosignature has diagnostic potential for TB disease irrespective of TB setting and should be further explored in larger cohorts.

Tuberculous Meningitis: Pathogenesis, Immune Responses, Diagnostic Challenges, and the Potential of Biomarker-Based Approaches

Tuberculous meningitis (TBM) is the most devastating form of tuberculosis (TB), causing high mortality or disability. Clinical management of the disease is challenging due to limitations of the existing diagnostic approaches. Our knowledge on the immunology and pathogenesis of the disease is currently limited. More research is urgently needed to enhance our understanding of the immunopathogenesis of the disease and guide us toward the identification of targets that may be useful for vaccines or host-directed therapeutics.

Tuberculous meningitis (TBM) is the most devastating form of tuberculosis (TB), causing high mortality or disability. Clinical management of the disease is challenging due to limitations of the existing diagnostic approaches. Our knowledge on the immunology and pathogenesis of the disease is currently limited. More research is urgently needed to enhance our understanding of the immunopathogenesis of the disease and guide us toward the identification of targets that may be useful for vaccines or host-directed therapeutics. In this review, we summarize the current knowledge about the immunology and pathogenesis of TBM and summarize the literature on existing and new, especially biomarker-based, approaches that may be useful in the management of TBM. We identify research gaps and provide directions for research which may lead to the development of new tools for the control of the disease in the near future.

Toll-like receptor 4 signaling-mediated responses are critically engaged in optimal host protection against highly virulent Mycobacterium tuberculosis K infection

Toll-like receptors (TLRs) play critical roles in the innate recognition of Mycobacterium tuberculosis (Mtb) by host immune cells. However, controversy has arisen regarding the role of TLR4 in determining the outcomes of Mtb infection. To address this controversy, the function of TLR4 in the induction of an optimal protective immune response against the highly virulent Mtb K-infection was comparatively investigated in C3 H/HeJ (TLR4-deficient mutant) and C3 H/HeN (TLR4-competent wild-type) mice. Interestingly, following Mtb infection, C3 H/HeJ mice showed a more severe disease phenotype than C3 H/HeN mice, exhibiting reduced weight and a marked increase in bacterial burden along with necrotic lung inflammation. Analysis of the immune cell composition revealed significantly increased neutrophils in the lung and significant production of IL-10 accompanied by the impairment of the protective Th1 response in C3 H/HeJ mice. Reducing the neutrophil numbers by treating C3 H/HeJ mice with an anti-Ly6 G monoclonal antibody (mAb) and blocking IL-10 signaling with an anti-IL-10 receptor mAb reduced the excessive lung inflammation and bacterial burden in C3 H/HeJ mice. Therefore, abundant IL-10 signaling and neutrophils have detrimental effects in TLR4-deficient mice during Mtb infection. However, the blockade of IL-10 signaling produced an increase in the CD11b^hiLy6 G^hi neutrophil population, but the phenotypes of these neutrophils were different from those of the CD11b^intLy6 G^int neutrophils from mice with controlled infections. Collectively, these results show that TLR4 positively contributes to the generation of an optimal protective immunity against Mtb infection. Furthermore, investigating the TLR4-mediated response will provide insight for the development of effective control measures against tuberculosis.

Host-Based Biomarkers in Saliva for the Diagnosis of Pulmonary Tuberculosis in Children: A Mini-Review

The diagnosis of pulmonary tuberculosis (TB) in children remains a significant challenge due to its paucibacillary nature, non-specificity of symptoms and suboptimal sensitivity of available diagnostic methods. In young children particularly, it is difficult to obtain high-quality sputum specimens for testing, with this group the least likely to be diagnosed, while most at risk of severe disease. The World Health Organization (WHO) has prioritized research into rapid biomarker-based tests for TB using easily obtainable non-sputum samples, such as saliva. However, the role of biomarkers in saliva for diagnosing TB in children has not been fully explored. In this mini-review, we discuss the value of saliva as a diagnostic specimen in children given its ready availability and non-invasive nature of collection, and review the literature on the use of host-based biomarkers in saliva for diagnosing active pulmonary TB in adults and children. Based on available data from adult studies, we highlight that combinations of cytokines and other proteins show promise in reaching WHO-endorsed target product profiles for new TB triage tests. Given the lack of pediatric research on host biomarkers in saliva and the differing immune response to TB infection between children and adults, we recommend that pediatric studies are now performed to discover and validate salivary host biosignatures for diagnosing pulmonary TB in children. Future directions for pediatric saliva studies are discussed, with suggestions for technologies that can be applied for salivary biomarker discovery and point-of-care test development.

Identification of candidate host serum and saliva biomarkers for a better diagnosis of active and latent tuberculosis infection

In our work, we aim to identify new candidate host biomarkers to discriminate between active TB patients (n = 28), latent infection (LTBI; n = 27) and uninfected (NoTBI; n = 42) individuals. For that, active TB patients and their contacts were recruited that donated serum and saliva samples. A multiplex assay was performed to study the concentration of different cytokines, chemokines and growth factors. Proteins with significant differences between groups were selected and logistic regression and the area under the ROC curve (AUC) was used to assess the diagnostic accuracy. The best marker combinations that discriminate active TB from NoTBI contacts were [IP-10 + IL-7] in serum and [Fractalkine + IP-10 + IL-1α + VEGF] in saliva. Best discrimination between active TB and LTBI was achieved using [IP-10 + BCA-1] in serum (AUC = 0.83) and IP-10 in saliva (p = 0.0007; AUC = 0.78). The levels of TNFα (p = 0.003; AUC = 0.73) in serum and the combination of [Fractalkine+IL-12p40] (AUC = 0.83) in saliva, were able to differentiate between NoTBI and LTBI contacts. In conclusion, different individual and combined protein markers could help to discriminate between active TB and both uninfected and latently-infected contacts. The most promising ones include [IP-10 + IL-7], [IP-10 + BCA-1] and TNFα in serum and [Fractalkine + IP-10 + IL-1α + VEGF], IP-10 and [Fractalkine+IL-12p40] in saliva.

Rapid diagnosis of periodontitis, a feasibility study using MALDI-TOF mass spectrometry

AIM

The aim of the present study was to assess the feasibility and diagnostic contribution of protein profiling using MALDI-TOF mass spectrometry applied to saliva, gingival crevicular fluid (GCF) and dental plaque from periodontitis and healthy subjects. We hypothesized that rapid routine and blinded MALDI-TOF analysis could accurately classify these three types of samples according to periodontal state.

MATERIALS AND METHODS

Unstimulated saliva, GCF and dental plaque, collected from periodontitis subjects and healthy controls, were analyzed by MALDI-TOF MS. Based on the differentially expressed peaks between the two groups, diagnostic decision trees were built for each sample.

RESULTS

Among 141 patients (67 periodontitis and 74 healthy controls), the decision trees diagnosed periodontitis with a sensitivity = 70.3% (± 0.211) and a specificity = 77.8% (± 0.165) for saliva, a sensitivity = 79.6% (± 0.188) and a specificity = 75.7% (± 0.195) for GCF, and a sensitivity = 72.1% (± 0.202) and a specificity = 72.2% (± 0.195) for dental plaque. The sensitivity and specificity of the tests were improved to 100% (CI 95% = [0.91;1]) and 100% (CI 95% = [0.92;1]), respectively, when two samples were tested.

CONCLUSION

We developed, for the first time, diagnostic tests based on protein profiles of saliva, GCF and dental plaque between periodontitis patients and healthy subjects. When at least 2 of these samples were tested, the best results were obtained.

Diagnostic performance of serum interferon gamma, matrix metalloproteinases, and periostin measurements for pulmonary tuberculosis in Japanese patients with pneumonia

Serum markers that differentiate between tuberculous and non-tuberculous pneumonia would be clinically useful. However, few serum markers have been investigated for their association with either disease. In this study, serum levels of interferon gamma (IFN-γ), matrix metalloproteinases 1 and 9 (MMP-1 and MMP-9, respectively), and periostin were compared between 40 pulmonary tuberculosis (PTB) and 28 non-tuberculous pneumonia (non-PTB) patients. Diagnostic performance was assessed by analysis of receiver-operating characteristic (ROC) curves and classification trees. Serum IFN-γ and MMP-1 levels were significantly higher and serum MMP-9 levels significantly lower in PTB than in non-PTB patients (p < 0.001, p = 0.002, p < 0.001, respectively). No significant difference was observed in serum periostin levels between groups. ROC curve analysis could not determine the appropriate cut-off value with high sensitivity and specificity; therefore, a classification tree method was applied. This method identified patients with limited infiltration into three groups with statistical significance (p = 0.01), and those with MMP-1 levels < 0.01 ng/mL and periostin levels ≥ 118.8 ng/mL included only non-PTB patients (95% confidence interval 0.0–41.0). Patients with extensive infiltration were also divided into three groups with statistical significance (p < 0.001), and those with MMP-9 levels < 3.009 ng/mL included only PTB patients (95% confidence interval 76.8–100.0). In conclusion, the novel classification tree developed using MMP-1, MMP-9, and periostin data distinguished PTB from non-PTB patients. Further studies are needed to validate our cut-off values and the overall clinical usefulness of these markers.

Chloride and sodium ion concentrations in saliva and sweat as a method to diagnose cystic fibrosis

OBJECTIVE

Cystic fibrosis diagnosis is dependent on the chloride ion concentration in the sweat test (≥60mEq/mL - recognized as the gold standard indicator for cystic fibrosis diagnosis). Moreover, the salivary glands express the CFTR protein in the same manner as sweat glands. Given this context, the objective was to verify the correlation of saliva chloride concentration and sweat chloride concentration, and between saliva sodium concentration and sweat sodium concentration, in patients with cystic fibrosis and healthy control subjects, as a tool for cystic fibrosis diagnosis.

METHODS

There were 160 subjects enrolled: 57/160 (35.70%) patients with cystic fibrosis and two known CFTR mutations and 103/160 (64.40%) healthy controls subjects. Saliva ion concentration was analyzed by ABL 835 Radiometer^® equipment and, sweat chloride concentration and sweat sodium concentration, respectively, by manual titration using the mercurimetric procedure of Schales & Schales and flame photometry. Statistical analysis was performed by the chi-squared test, the Mann-Whitney test, and Spearman's correlation. Alpha=0.05.

RESULTS

Patients with cystic fibrosis showed higher values of sweat chloride concentration, sweat sodium concentration, saliva chloride concentration, and saliva sodium concentration than healthy controls subjects (p-value<0.001). The correlation between saliva chloride concentration and sweat chloride concentration showed a positive Spearman's Rho (correlation coefficient)=0.475 (95% CI=0.346 to 0.587). Also, the correlation between saliva sodium concentration and sweat sodium concentration showed a positive Spearman's Rho=0.306 (95% CI=0.158 to 0.440).

CONCLUSIONS

Saliva chloride concentration and saliva sodium concentration are candidates to be used in cystic fibrosis diagnosis, mainly in cases where it is difficult to achieve the correct sweat amount, and/or CFTR mutation screening is difficult, and/or reference methods for sweat test are unavailable to implement or are not easily accessible by the general population.

A new DNA sensor system for specific and quantitative detection of mycobacteria

In the current study, we describe a novel DNA sensor system for specific and quantitative detection of mycobacteria, which is the causative agent of tuberculosis. Detection is achieved by using the enzymatic activity of the mycobacterial encoded enzyme topoisomerase IA (TOP1A) as a biomarker. The presented work is the first to describe how the catalytic activities of a member of the type IA family of topoisomerases can be exploited for specific detection of bacteria. The principle for detection relies on a solid support anchored DNA substrate with dual functions namely: (1) the ability to isolate mycobacterial TOP1A from crude samples and (2) the ability to be converted into a closed DNA circle upon reaction with the isolated enzyme. The DNA circle can act as a template for rolling circle amplification generating a tandem repeat product that can be visualized at the single molecule level by fluorescent labelling. This reaction scheme ensures specific, sensitive, and quantitative detection of the mycobacteria TOP1A biomarker as demonstrated by the use of purified mycobacterial TOP1A and extracts from an array of non-mycobacteria and mycobacteria species. When combined with mycobacteriophage induced lysis as a novel way of effective yet gentle extraction of the cellular content from the model Mycobacterium smegmatis, the DNA sensor system allowed detection of mycobacteria in small volumes of cell suspensions. Moreover, it was possible to detect M. smegmatis added to human saliva. Depending on the composition of the sample, we were able to detect 0.6 or 0.9 million colony forming units (CFU) per mL of mycobacteria, which is within the range of clinically relevant infection numbers. We, therefore, believe that the presented assay, which relies on techniques that can be adapted to limited resource settings, may be the first step towards the development of a new point-of-care diagnostic test for tuberculosis.