Commercial serological tests for the diagnosis of active pulmonary and extrapulmonary tuberculosis: an updated systematic review and meta-analysis

Antibodies as clinical tools for tuberculosis

Tuberculosis (TB) is a leading cause of morbidity and mortality worldwide. Global research efforts to improve TB control are hindered by insufficient understanding of the role that antibodies play in protective immunity and pathogenesis. This impacts knowledge of rational and optimal vaccine design, appropriate diagnostic biomarkers, and development of therapeutics. Traditional approaches for the prevention and diagnosis of TB may be less efficacious in high prevalence, remote, and resource-poor settings. An improved understanding of the immune response to the causative agent of TB, Mycobacterium tuberculosis (Mtb), will be crucial for developing better vaccines, therapeutics, and diagnostics. While memory CD4+ T cells and cells and cytokine interferon gamma (IFN-g) have been the main identified correlates of protection in TB, mounting evidence suggests that other types of immunity may also have important roles. TB serology has identified antibodies and functional characteristics that may help diagnose Mtb infection and distinguish between different TB disease states. To date, no serological tests meet the World Health Organization (WHO) requirements for TB diagnosis, but multiplex assays show promise for improving the sensitivity and specificity of TB serodiagnosis. Monoclonal antibody (mAb) therapies and serum passive infusion studies in murine models of TB have also demonstrated some protective outcomes. However, animal models that better reflect the human immune response to Mtb are necessary to fully assess the clinical utility of antibody-based TB prophylactics and therapeutics. Candidate TB vaccines are not designed to elicit an Mtb-specific antibody response, but evidence suggests BCG and novel TB vaccines may induce protective Mtb antibodies. The potential of the humoral immune response in TB monitoring and control is being investigated and these studies provide important insight into the functional role of antibody-mediated immunity against TB. In this review, we describe the current state of development of antibody-based clinical tools for TB, with a focus on diagnostic, therapeutic, and vaccine-based applications.

Phylactic role of anti-lipoarabinomannan IgM directed against mannan core during mycobacterial infection in macrophages

Mycobacteria enter host phagocytes, such as macrophages by binding to several receptors on phagocytes. Several mycobacterial species, including Mycobacterium tuberculosis have evolved systems to evade host bactericidal pathways. Lipoarabinomannan (LAM) is an essential mycobacterial molecule for both binding to phagocytes and escaping from bactericidal pathways. Integrin CD11b plays critical roles as a phagocytic receptor and contributes to host defense by mediating both nonopsonic and opsonic phagocytosis. However, the mechanisms by which CD11b-mediated phagocytosis associates with LAM and drives the phagocytic process of mycobacteria remain to be fully elucidated. We recently identified TMDU3 as anti-LAM IgM antibody against the mannan core of LAM. The present study investigated the roles of CD11b and TMDU3 in macrophage phagocytosis of mycobacteria and subsequent bactericidal lysosomal fusion to phagosomes. CD11b knockout cells generated by a CRISPR/Cas9 system showed significant attenuation of the ability to phagocytose non-opsonized mycobacteria and LAM-conjugated beads. Moreover, recombinant human CD11b protein was found to bind to LAM. TMDU3 markedly inhibited macrophage phagocytosis of non-opsonized mycobacteria. This antibody slightly increased the phagocytosis of mycobacteria under opsonized conditions, whereas it significantly enhanced CD11b-mediated bactericidal functions. Taken together, these results show a novel phylactic role of anti-LAM IgM during mycobacterial infection in macrophages.

Humoral immune response to SARS-CoV-2 and endemic coronaviruses in urban and indigenous children in Colombia

BACKGROUND

Although anti-SARS-CoV-2 humoral immune responses and epidemiology have been extensively studied, data gaps remain for certain populations such as indigenous people or children especially in low- and middle-income countries. To address this gap, we evaluated SARS-CoV-2 seroprevalence and humoral immunity towards the parental B.1 strain, local SARS-CoV-2 variants, and endemic coronaviruses in children from Colombia from March to April 2021.

METHODS

We performed a cross-sectional seroprevalence study with 80 children from Bogotá and expanded our analysis by comparing results with an independent observational study of 82 children from the Wiwa community living in the north-eastern Colombian territories. Antibody IgG titers towards SARS-CoV-2 and the endemic coronaviruses as well as ACE2 binding inhibition as a proxy for neutralization towards several SARS-CoV-2 variants were analyzed using two multiplex-based immunoassays.

RESULTS

While we find seroprevalence estimates of 21.3% in children from Bogotá, seroprevalence is higher with 34.1% in Wiwa children. We observe a robust induction of antibodies towards the surface-exposed spike protein, its S1-, S2- and receptor-binding-subdomains in all SARS-CoV-2 seropositive children. Only nucleocapsid-specific IgG is significantly lower in the indigenous participants. ACE2 binding inhibition is low for all SARS-CoV-2 variants examined. We observe a dominance of NL63 S1 IgG levels in urban and indigenous children which suggests an early exposure to this respiratory virus independent of living conditions and geographic location. SARS-CoV-2 seropositivity does not correlate with antibody levels towards any of the four endemic coronaviruses indicating the absence of cross-protective immunity.

CONCLUSIONS

Overall, antibody titers, but in particular ACE2 binding inhibition are low within Colombian samples, requiring further investigation to determine any potential clinical significance.

Serological analysis reveals differential antibody responses between TB patients and latently infected individuals from the TB endemic country of Mozambique

Serological antibody profiling of tuberculosis (TB) patients and household contacts with latent TB infection (LTBI) could identify risk indicators of disease progression, and potentially also serve as an easily accessible diagnostic tool to discriminate between these two stages of Mycobacterium tuberculosis (Mtb) infection. Yet, despite significant efforts over many decades, neither application has yet fully materialised, and this is at least in part due to inconsistent and varying antibody profiles from different TB endemic regions. In this study, we conducted a retrospective exploratory analysis of serum antibodies in a cohort of active TB patients (ATB) and their interferon-gamma release assay (IGRA) positive household contacts (LTBI), as well as healthy controls (HC) from Mozambique, a country with a high TB burden from the Sub-Saharan region. Using several Mtb antigens as well as crude preparations of culture filtrate proteins (CFP) from Mtb and Bacille Calmette Guérin (BCG), we report that the most discriminatory response for TB and LTBI was observed for serum IgA antibodies to the MPT64 antigen, followed by IgG antibodies to Ag85B and CFP, with ATB patients having significantly higher levels than LTBI or BCG-vaccinated healthy controls. Conversely, sera from LTBI individuals had higher levels of IgG antibodies to the HBHA antigen than ATB. While our sample size (n = 21 for ATB, 18 for LTBI and 17 for HC) was too small to fully evaluate the diagnostic potential of these differing serological profiles, our study however preliminarily indicated high level of sensitivity (95%) and specificity (97%) of an ELISA MPT64-IgA test for discriminating TB from LTBI and healthy controls, supporting the notion that it alone, or possibly in combination with other antigens such as Ag85B or CFP could lead to development of an easily accessible diagnostic tool for TB.

Spotlight on mycobacterial lipid exploitation using nanotechnology for diagnosis, vaccines, and treatments

Tuberculosis (TB), historically the most significant cause of human morbidity and mortality, has returned as the top infectious disease worldwide, under circumstances worsened by the COVID-19 pandemic's devastating effects on public health. Although Mycobacterium tuberculosis, the causal agent, has been known of for more than a century, the development of tools to control it has been largely neglected. With the advancement of nanotechnology, the possibility of engineering tools at the nanoscale creates unique opportunities to exploit any molecular type. However, little attention has been paid to one of the major attributes of the pathogen, represented by the atypical coat and its abundant lipids. In this review, an overview of the lipids encountered in M. tuberculosis and interest in exploiting them for the development of TB control tools are presented. Then, the amalgamation of nanotechnology with mycobacterial lipids from both reported and future works are discussed.

Development of an enzyme-linked immunosorbent assay for the diagnosis of feline tuberculosis

Cases of feline tuberculosis (TB) can be challenging to diagnose. Currently, this is achieved through a combination of mycobacterial culture, polymerase chain reaction (PCR), or interferon-gamma release assay (IGRA); however, these each have limitations. There is limited data regarding the use of humoral immunodiagnostics for TB in cats. Therefore, we sought to develop an enzyme-linked immunosorbent assay (ELISA) to further facilitate the diagnosis of feline TB. A comparative PPD (purified protein derivative) antibody ELISA was optimised for use on serum and plasma, and was tested against samples from 14 cats with culture-confirmed TB and 24 uninfected controls. Selection of an appropriate positive cut-off value based on receiver-operator characteristic curve analysis gave test sensitivity of 64.3 % and specificity of 100 %. When tested on further samples from cats with strongly suspected mycobacteriosis, 32.9 % (23/70) were antibody positive. Notably, positive results were recorded in cats that failed to respond to the IGRA, and in one PCR and IGRA negative cat. No positive responses were identified in cats with non-tuberculous mycobacterial infections, or with non-mycobacterial diseases (n = 12). Therefore, antibody-based diagnostics may be useful adjunctive tests for cases of TB missed by the IGRA, helping protect both feline and, in turn, human health.

Review and Updates on the Diagnosis of Tuberculosis

Diagnosis of tuberculosis, and especially the diagnosis of extrapulmonary tuberculosis, still faces challenges in clinical practice. There are several reasons for this. Methods based on the detection of Mycobacterium tuberculosis (Mtb) are insufficiently sensitive, methods based on the detection of Mtb-specific immune responses cannot always differentiate active disease from latent infection, and some of the serological markers of infection with Mtb are insufficiently specific to differentiate tuberculosis from other inflammatory diseases. New tools based on technologies such as flow cytometry, mass spectrometry, high-throughput sequencing, and artificial intelligence have the potential to solve this dilemma. The aim of this review was to provide an updated overview of current efforts to optimize classical diagnostic methods, as well as new molecular and other methodologies, for accurate diagnosis of patients with Mtb infection.

A scoring model for diagnosis of tuberculous pleural effusion

Background

Due to the low efficiency of a single clinical feature or laboratory variable in the diagnosis of tuberculous pleural effusion (TBPE), the diagnosis of TBPE is still challenging. This study aimed to build a scoring diagnostic model based on laboratory variables and clinical features to differentiate TBPE from non-tuberculous pleural effusion (non-TBPE).

Methods

A retrospective study of 125 patients (63 with TBPE; 62 with non-TBPE) was undertaken. Univariate analysis was used to select the laboratory and clinical variables relevant to the model composition. The statistically different variables were selected to undergo binary logistic regression. Variables B coefficients were used to define a numerical score to calculate a scoring model. A receiver operating characteristic (ROC) curve was used to calculate the best cut-off value and evaluate the performance of the model. Finally, we add a validation cohort to verify the model.

Results

Six variables were selected in the scoring model: Age ≤ 46 years old (4.96 points), Male (2.44 points), No cancer (3.19 points), Positive T-cell Spot (T-SPOT) results (4.69 points), Adenosine Deaminase (ADA) ≥ 24.5U/L (2.48 point), C-reactive Protein (CRP) ≥ 52.8 mg/L (1.84 points). With a cut-off value of a total score of 11.038 points, the scoring model’s sensitivity, specificity, and accuracy were 93.7%, 96.8%, and 99.2%, respectively. And the validation cohort confirms the model with the sensitivity, specificity, and accuracy of 92.9%, 93.3%, and 93.1%, respectively.

Conclusion

The scoring model can be used in differentiating TBPE from non-TBPE.

Tuberculosis Phenotypic and Genotypic Drug Susceptibility Testing and Immunodiagnostics: A Review

Tuberculosis (TB), considered an ancient disease, is still killing one person every 21 seconds. Diagnosis of Mycobacterium tuberculosis (M.tb) still has many challenges, especially in low and middle-income countries with high burden disease rates. Over the last two decades, the amount of drug-resistant (DR)-TB cases has been increasing, from mono-resistant (mainly for isoniazid or rifampicin resistance) to extremely drug resistant TB. DR-TB is problematic to diagnose and treat, and thus, needs more resources to manage it. Together with+ TB clinical symptoms, phenotypic and genotypic diagnosis of TB includes a series of tests that can be used on different specimens to determine if a person has TB, as well as if the M.tb strain+ causing the disease is drug susceptible or resistant. Here, we review and discuss advantages and disadvantages of phenotypic vs. genotypic drug susceptibility testing for DR-TB, advances in TB immunodiagnostics, and propose a call to improve deployable and low-cost TB diagnostic tests to control the DR-TB burden, especially in light of the increase of the global burden of bacterial antimicrobial resistance, and the potentially long term impact of the coronavirus disease 2019 (COVID-19) disruption on TB programs.

The role of antibodies in tuberculosis diagnosis, prophylaxis and therapy: a review from the ESGMYC study group

Tuberculosis (TB) is still responsible for the deaths of >1 million people yearly worldwide, and therefore its correct diagnosis is one of the key components of any TB eradication programme. However, current TB diagnostic tests have many limitations, and improved diagnostic accuracy is urgently needed. To improve the diagnostic performance of traditional serology, a combination of different Mycobacterium tuberculosis (MTB) antigens and different antibody isotypes has been suggested, with some showing promising performance for the diagnosis of active TB. Given the incomplete protection conferred by bacille Calmette-Guérin (BCG) vaccination against adult pulmonary TB, efforts to discover novel TB vaccines are ongoing. Efficacy studies from advanced TB vaccines designed to stimulate cell-mediated immunity failed to show protection, suggesting that they may not be sufficient and warranting the need for other types of immunity. The role of antibodies as tools for TB therapy, TB diagnosis and TB vaccine design is discussed. Finally, we propose that the inclusion of antibody-based TB vaccines in current clinical trials may be advisable to improve protection.

Mycobacterium tuberculosis Affects Protein and Lipid Content of Circulating Exosomes in Infected Patients Depending on Tuberculosis Disease State

Tuberculosis (TB), which is caused by the bacterium Mycobacterium tuberculosis (Mtb), is still one of the deadliest infectious diseases. Understanding how the host and pathogen interact in active TB will have a significant impact on global TB control efforts. Exosomes are increasingly recognized as a means of cell-to-cell contact and exchange of soluble mediators. In the case of TB, exosomes are released from the bacillus and infected cells. In the present study, a comprehensive lipidomics and proteomics analysis of size exclusion chromatography-isolated plasma-derived exosomes from patients with TB lymphadenitis (TBL) and treated as well as untreated pulmonary TB (PTB) was performed to elucidate the possibility to utilize exosomes in diagnostics and knowledge building. According to our findings, exosome-derived lipids and proteins originate from both the host and Mtb in the plasma of active TB patients. Exosomes from all patients are mostly composed of sphingomyelins (SM), phosphatidylcholines, phosphatidylinositols, free fatty acids, triacylglycerols (TAG), and cholesterylesters. Relative proportions of, e.g., SMs and TAGs, vary depending on the disease or treatment state and could be linked to Mtb pathogenesis and dormancy. We identified three proteins of Mtb origin: DNA-directed RNA polymerase subunit beta (RpoC), Diacyglycerol O-acyltransferase (Rv2285), and Formate hydrogenase (HycE), the latter of which was discovered to be differently expressed in TBL patients. Furthermore, we discovered that Mtb infection alters the host protein composition of circulating exosomes, significantly affecting a total of 37 proteins. All TB patients had low levels of apolipoproteins, as well as the antibacterial proteins cathelicidin, Scavenger Receptor Cysteine Rich Family Member (SSC5D), and Ficolin 3 (FCN3). When compared to healthy controls, the protein profiles of PTB and TBL were substantially linked, with 14 proteins being co-regulated. However, adhesion proteins (integrins, Intercellular adhesion molecule 2 (ICAM2), CD151, Proteoglycan 4 (PRG4)) were shown to be more prevalent in PTB patients, while immunoglobulins, Complement component 1r (C1R), and Glutamate receptor-interacting protein 1 (GRIP1) were found to be more abundant in TBL patients, respectively. This study could confirm findings from previous reports and uncover novel molecular profiles not previously in focus of TB research. However, we applied a minimally invasive sampling and analysis of circulating exosomes in TB patients. Based on the findings given here, future studies into host–pathogen interactions could pave the way for the development of new vaccines and therapies.

Towards Accurate Point-of-Care Tests for Tuberculosis in Children

In childhood tuberculosis (TB), with an estimated 69% of missed cases in children under 5 years of age, the case detection gap is larger than in other age groups, mainly due to its paucibacillary nature and children’s difficulties in delivering sputum specimens. Accurate and accessible point-of-care tests (POCTs) are needed to detect TB disease in children and, in turn, reduce TB-related morbidity and mortality in this vulnerable population. In recent years, several POCTs for TB have been developed. These include new tools to improve the detection of TB in respiratory and gastric samples, such as molecular detection of Mycobacterium tuberculosis using loop-mediated isothermal amplification (LAMP) and portable polymerase chain reaction (PCR)-based GeneXpert. In addition, the urine-based detection of lipoarabinomannan (LAM), as well as imaging modalities through point-of-care ultrasonography (POCUS), are currently the POCTs in use. Further to this, artificial intelligence-based interpretation of ultrasound imaging and radiography is now integrated into computer-aided detection products. In the future, portable radiography may become more widely available, and robotics-supported ultrasound imaging is currently being trialed. Finally, novel blood-based tests evaluating the immune response using “omic-“techniques are underway. This approach, including transcriptomics, metabolomic, proteomics, lipidomics and genomics, is still distant from being translated into POCT formats, but the digital development may rapidly enhance innovation in this field. Despite these significant advances, TB-POCT development and implementation remains challenged by the lack of standard ways to access non-sputum-based samples, the need to differentiate TB infection from disease and to gain acceptance for novel testing strategies specific to the conditions and settings of use.

Nontubercular mycobacterial cough

SummaryHabitual cough suppression leading to non-tuberculous mycobacteria infections and bronchiectasis has been reported. We present a case of a 55-year-old woman with a chronic history of cough with mild expectoration and frequent lower respiratory tract infections, remitting with antibiotic therapy and other supportive measures. She also reported habitual cough suppression for several years. She was eventually diagnosed with Mycobacterium avium complex (MAC) positive right middle lobe bronchiectasis-Lady Windermere syndrome and obstructive sleep apnoea (OSA), causing disabling symptoms limiting her daily activities. We aim to highlight two key issues-diagnosing MAC infections in a tuberculosis endemic country, and OSA and its long-term clinical implications.

Concurrent evaluation of cytokines improves the accuracy of antibodies against Mycobacterium tuberculosis antigens in the diagnosis of active tuberculosis

BACKGROUND

Antibodies against mycobacterial proteins are highly specific, but lack sensitivity, whereas cytokines have been shown to be sensitive but not very specific in the diagnosis of tuberculosis (TB). We assessed combinations between antibodies and cytokines for diagnosing TB.

METHODS

Immuoglubulin (Ig) A and IgM antibody titres against selected mycobacterial antigens including Apa, NarL, Rv3019c, PstS1, LAM, "Kit 1" (MTP64 and Tpx)", and "Kit 2" (MPT64, Tpx and 19 kDa) were evaluated by ELISA in plasma samples obtained from individuals under clinical suspicion for TB. Combinations between the antibody titres and previously published cytokine responses in the same participants were assessed for diagnosing active TB.

RESULTS

Antibody responses were more promising when used in combination (AUC of 0.80), when all seven antibodies were combined. When anti-"Kit 1"-IgA levels were combined with five host cytokine biomarkers, the AUC increased to 97% (92-100%) with a sensitivity of 95% (95% CI, 73-100%), and specificity of 88.5% (95% CI, 68.7-97%) achieved after leave-one-out cross validation.

CONCLUSION

When used in combination, IgA titres measured with ELISA against multiple Mycobacterium tuberculosis antigens may be useful in the diagnosis of TB. However, diagnostic accuracy may be improved if the antibodies are used in combination with cytokines.

Identification of anti-lipoarabinomannan antibodies against mannan core and their effects on phagocytosis of mycobacteria by human neutrophils

Mycobacterium tuberculosis (MTB) and M. avium-intracellulare complex (MAC) enter host phagocytes, such as neutrophils through lipoarabinomannan (LAM) binding to pattern-recognition receptors, inducing innate immune responses including phagocytosis. Phagocytosis of mycobacteria by human neutrophils depends on the binding of α(1 → 2)-monomannose branching α(1 → 6)-mannan core of LAM/lipomannan (LM), a common component among mycobacterial species, to lactosylceramide (LacCer)-enriched lipid microdomains. We investigated the binding specificities of several anti-LAM antibodies (Abs) to LAMs/LM and found anti-LAM monoclonal IgMs TMDU3 and LA066 were directed against mannan core. Each IgM showed different binding specificity to mannan core. Confocal and stimulated emission depletion microscopy revealed TMDU3 and LA066 strongly bind to MTB and MAC, respectively. Flow cytometric analysis revealed human neutrophils do not express Dectin-2, DC-SIGN or mannose receptor. Furthermore, neutrophil phagocytosis of mycobacteria was markedly inhibited by TMDU3 and LA066, respectively. Similarly, treatment of each mAb with neutrophils reduced the numbers of intracellular MAC. Together, our results suggest that the interaction of LacCer-enriched lipid microdomains with mannan core and its blocking are therapeutic or diagnostic targets for both TB and non-tuberculous mycobacteria infection.

Insight into diagnosis of female genital tuberculosis

INTRODUCTION

Female genital tuberculosis (TB) is a common manifestation of extrapulmonary TB (EPTB) with varied clinical presentations, i.e. infertility, pelvic pain and menstrual irregularities. Diagnosis of female genital TB is challenging predominantly due to paucibacillary nature of specimens and inconclusive results obtained by most of the routine laboratory tests.

AREAS COVERED

This review has briefly summarized the epidemiology, clinical features and transmission of female genital TB. Commonly used laboratory tests include bacteriological examination (smear/culture), tuberculin skin testing, interferon-γ release assays, imaging, laparoscopy/hysteroscopy and histopathological/cytological observations. Further, utility of nucleic acid amplification tests (NAATs), like loop-mediated isothermal amplification, PCR, multiplex-PCR, nested PCR, real-time PCR and GeneXpert® could significantly improve the detection of female genital TB.

EXPERT OPINION

Currently, there is no single test available for the efficient diagnosis of female genital TB, rather a combination of tests is being employed, which yields moderate diagnostic accuracy. The latest modalities developed for diagnosing pulmonary TB and other clinical EPTB forms, i.e. aptamer-linked immobilized sorbent assay, immuno-PCR (I-PCR), analysis of circulating cell-free DNA by NAATs, and identification of Mycobacterium tuberculosis biomarkers within extracellular vesicles of bodily fluids by I-PCR/nanoparticle-based I-PCR, may also be exploited to further improve the diagnosis of female genital TB.

A systematic review of potential screening biomarkers for active TB disease

INTRODUCTION

The standard TB Four Symptom Screen does not meet the World Health Organization (WHO) ideal screening criteria for having greater than 90% sensitivity to identify active TB disease, regardless of HIV status. To identify novel screening biomarkers for active TB, we performed a systematic review of any cohort or case-control study reporting associations between screening biomarkers and active TB disease.

METHODS

We searched PubMed and Embase for articles published before October 10, 2021. We included studies from high or medium tuberculosis burden countries. We excluded articles focusing on C-reactive protein and lipoarabinomannan. For all included biomarkers, we calculated sensitivity, specificity and 95% confidence intervals, and assessed study quality using a tool adapted from the QUADAS-2 risk of bias.

RESULTS

From 8,062 abstracts screened, we included 79 articles. The articles described 302 unique biomarkers, including host antibodies, host proteins, TB antigens, microRNAs, whole blood gene PCRs, and combinations of biomarkers. Of these, 23 biomarkers had sensitivity greater than 90% and specificity greater than 70%, meeting WHO criteria for an ideal screening test. Among the eleven biomarkers described in people living with HIV, only one had a sensitivity greater than 90% and specificity greater than 70% for active TB.

CONCLUSION

Further evaluation of biomarkers of active TB should be pursued to accelerate identification of TB disease.

Serological detection of Mycobacterium Tuberculosis complex infection in multiple hosts by One Universal ELISA

Tuberculosis (TB), a contagious disease mainly caused by Mycobacterium tuberculosis (M. tb), Mycobacterium bovis (M. bovis), and Mycobacterium caprae (M. caprae), poses a major global threat to the health of humans and many species of animals. Developing an ante-mortem detection technique for different species would be of significance in improving the surveillance employing a One Health strategy. To achieve this goal, a universal indirect ELISA was established for serologically detecting Mycobacterium tuberculosis complex infection for multiple live hosts by using a fusion protein of MPB70, MPB83, ESAT6, and CFP10 common in M. tb, M. bovis, and M. caprae as the coating antigen (MMEC) and HRP-labeled fusion protein A and G as a secondary antibody. After testing the known positive and negative sera, the receiver operating characteristic curves were constructed to decide the cut-off values. Then, the diagnostic sensitivity and specificity of MMEC/AG-iELISA were determined as 100.00% (95% CI: 96.90%, 100.00%) and 100.00% (95% CI: 98.44%, 100.00%) for M. bovis infection of cattle, 100.00% (95% CI: 95.00%, 100.00%) and 100.0% (95% CI: 96.80%, 100.00%) for M. bovis infection of sheep, 90.74% (95% CI: 80.09%, 95.98%) and 98.63% (95% CI: 95.14%, 99.76%) for M. bovis infection of cervids, 100.00% (95% CI: 15.81%, 100.00%) and 98.81% (95% CI: 93.54%, 99.97%) for M. bovis infection of monkeys, 100.00% (95% CI: 86.82%, 100.00%) and 94.85% (95% CI: 91.22%, 97.03%) for M. tb infection of humans. Furthermore, this MMEC/AG-iELISA likely detects M. caprae infection in roe deer. Thus this method has a promising application in serological TB surveillance for multiple animal species thereby providing evidence for taking further action in TB control.

Serological biomarkers for the diagnosis of Mycobacterium abscessus infections in cystic fibrosis patients

BACKGROUND

Culture conditions sometimes make it difficult to detect non-tuberculous mycobacteria (NTM), particularly Mycobacterium abscessus, an emerging cystic fibrosis (CF) pathogen. The diagnosis of NTM positive cases not detected by classical culture methods might benefit from the development of a serological assay.

METHODS

As part of a diagnostic accuracy study, a total of 173 sera CF-patients, including 33 patients with M. abscessus positive cultures, and 31 non-CF healthy controls (HC) were evaluated. Four M. abscessus antigens were used separately, comprising two surface extracts (Interphase (INP) and a TLR2 positive extract (TLR2eF)) and two recombinant proteins (rMAB_2545c and rMAB_0555 also known as the phospholipase C (rPLC)).

RESULTS

TLR2eF and rPLC were the most efficient antigens to discriminate NTM-culture positive CF-patients from NTM-culture negative CF-patients. The best clinical values were obtained for the detection of M. abscessus-culture positive CF-patients; with sensitivities for the TLR2eF and rPLC of 81.2% (95% CI:65.7-92.3%) and 87.9% (95% CI:71.9-95.6%) respectively, and specificities of 88.9% (95% CI:85.3-94.8%) and 84.8% (95% CI:80.6-91.5%) respectively. When considering as positive all sera, giving a positive response in at least one of the two tests, and, as negative, all sera negative for both tests, we obtained a sensitivity of 93.9% and a specificity of 80.7% for the detection of M. abscessus-culture positive CF-patients.

CONCLUSION

High antibody titers against TLR2eF and rPLC were obtained in M. abscessus-culture positive CF-patients, allowing us to consider these serological markers as potential tools in the detection of CF-patients infected with M. abscessus.

LIODetect®TB-ST: Evaluation of novel blood test for a rapid diagnosis of active pulmonary and extra-pulmonary tuberculosis in IGRA confirmed patients

Because of the current limits of immunological tests in the diagnosis of tuberculosis there is a need to identify new and rapid tests that can be carried out on a large scale in endemic countries and useful in the identification of infected subjects, but also able to discriminate those with latent infection from subjects with active. We have taken into consideration and analysed the LIODetect®TB-ST Tuberculosis Rapid Test, a membrane test for the qualitative detection of specific IgG, IgA, and IgM antibodies against Mycobacterium tuberculosis, performed on serum, plasma, or whole blood.85 samples positive to QuantiFERON TB-GOLD PLUS test were processed using this test and the results obtained were concordant with clinical diagnosis.To our knowledge, the LIODetect®TB-ST Tuberculosis Rapid Test is the only test; that identifies active tuberculosis disease with high sensitivity and specificity and its use might be of help in the diagnosis of tuberculosis, especially in endemic countries.

Aptamer-Based Diagnostic Systems for the Rapid Screening of TB at the Point-of-Care

The transmission of Tuberculosis (TB) is very rapid and the burden it places on health care systems is felt globally. The effective management and prevention of this disease requires that it is detected early. Current TB diagnostic approaches, such as the culture, sputum smear, skin tuberculin, and molecular tests are time-consuming, and some are unaffordable for low-income countries. Rapid tests for disease biomarker detection are mostly based on immunological assays that use antibodies which are costly to produce, have low sensitivity and stability. Aptamers can replace antibodies in these diagnostic tests for the development of new rapid tests that are more cost effective; more stable at high temperatures and therefore have a better shelf life; do not have batch-to-batch variations, and thus more consistently bind to a specific target with similar or higher specificity and selectivity and are therefore more reliable. Advancements in TB research, in particular the application of proteomics to identify TB specific biomarkers, led to the identification of a number of biomarker proteins, that can be used to develop aptamer-based diagnostic assays able to screen individuals at the point-of-care (POC) more efficiently in resource-limited settings.

Neoteric advancements in TB diagnostics and its future frame

Tuberculosis (TB) is one of the major infectious disease that causes threat to human health and leads to death in most of the cases. Mycobacterium tuberculosis is the causative agent that can affect both pulmonary and extra pulmonary regions of the body. This infection can be presented either as an active or latent form in the patients. Although this disease has been declared curable and preventable by WHO, it still holds its position as a global emergency. Over the past decade many hurdles such as low immunity, co-infections like HIV, autoimmune disorders, poverty, malnutrition and emerging trends in drug resistance patterns are hindering the eradication of this infection. However, many programmes have been launched by WHO with involvement of governments at various level to put a full stop over the disease. Under the Revised National Tuberculosis Control Programme (RNTCP) which was recently renamed as National Tuberculosis Elimination Programme (NTEP), the major focus is on eliminating tuberculosis by the year 2025. The main aim of the programme is to identify feasible quality testing, evaluate through NIKSHYA poshak yozana, restrict through BCG vaccination and assemble with public awareness to eradicate MTB. Numerous novel diagnostic techniques and molecular tools have been developed to elucidate and differentiate report of various suspected and active tuberculosis patients. However, improvements are still required to cut short the duration of the overall process ranging from screening of patients to their successful treatment.

Medical Thoracoscopy for the Management of Exudative Pleural Effusion: A Retrospective Study

Objective

The aim of this study was to evaluate the efficacy of medical thoracoscopy in the diagnosis and treatment of exudative pleural effusion.

Methods

A total of 82 patients with exudative pleural effusion underwent medical thoracoscopy under local anesthesia and mild sedation. The clinical characteristics, pleural fluid routine and biochemical tests, pleural biopsy, and outcomes were retrospectively evaluated.

Results

Among 82 patients, the color and transparency of pleural fluid and the levels of white blood cells (WBC), lactate dehydrogenase (LDH), neutrophil proportion, lymphocyte proportion, adenosine deaminase (ADA), and glucose were different among tuberculosis (TB), malignant (M), acute and chronic inflammation (ACI), and purulent (P) cases. Furthermore, 70% of M cases had a low positive rate of exfoliated cells in the sputum and pleural fluid, and more than 90% of TB cases had low positive rates of anti-tuberculosis antibodies and acid-fast bacilli in the sputum and pleural fluid. Pleural biopsy showed that 11% of cases were M, 74.4% were TB, 11% were ACI, and 3.6% were P. Medical thoracoscopy showed that 66.7% of ACI cases had pleural adhesions, 34.4% of TB cases had moderate and 34.4% of TB cases had severe pleural adhesions, 100% of M and TB cases had pleural surface nodules and 77.8% of ACI cases had pleural surface nodules, 49.2% of TB cases showed encapsulated pleural effusion, and 33.3% of M cases showed encapsulated pleural effusion.

Conclusion

Medical thoracoscopy has high feasibility and accuracy in the diagnosis and treatment of exudative pleural effusion.

IL-18 and related function proteins associated with tuberculosis severity and screening for active TB among patients with non-mycobacterial community-acquired pneumonia (CAP)

Background

Differentiation of active pulmonary tuberculosis (TB) from non-mycobacterial community-acquired pneumonia (CAP) still remains a diagnostic challenge.

Objective

The study aimed to quantify the IL-18, IFN-γ, IL-18BP, IL-37, and IP-10 levels in serum and Mycobacterium tuberculosis (M.tb) antigens-stimulated blood cultures from TB or CAP patients and explore if the proteins can be a useful basis for discriminating these diseases.

Methods

In total, 124 Polish adults, including mild/moderate (M/MTB) or advanced (ATB) TB patients, and CAP patients, were enrolled in the study. The concentrations of IL-18, IL-18BP, IFN-γ, IL-37, and IP-10 in sera and M.tb-stimulated cultures were measured by ELISA.

Results

The most specific and sensitive serum proteins discriminating TB from CAP were IP-10 and IL-18BP; however, IP-10 had the highest AUC in the ROC curve for the diagnosis. Serum IP-10 and IL-18BP levels increased significantly in M/MTB or ATB groups. The IL-18BP elevation in ATB group was accompanied by an increase in IL-18. No single protein measured in M.tb-stimulated cultures differed TB from CAP patients.

Conclusions

The combined analysis of serum IL-18BP and IP-10 might be considered as an auxiliary tool in the differentiation of TB from CAP.

A plasmonic fiberoptic absorbance biosensor for mannose-capped lipoarabinomannan based tuberculosis diagnosis

Tuberculosis (TB) is a resurgent infectious disease affecting a large number of people in the developing countries. An on-site, affordable diagnostic screening at an early-stage for an immediate anti-TB treatment is known to tremendously minimize the high mortality rates. Lipoarabinomannan (LAM), a surface glycolipid, has been identified as a potential TB biomarker present in urine at ultra-low concentrations of a few fg/mL. Here, we report a plasmonic fiber optic absorbance biosensor (P-FAB) strategy for mannosylated LAM (Man-LAM or Mtb LAM) detection down to attomolar concentrations. It involves a plasmonic sandwich immunoassay on a U-bent fiber optic probe with gold plasmonic (AuNP) labels functionalized with anti-Mtb LAM immunoglobulin M (IgM) and anti-Mtb LAM IgG respectively. The Mtb LAM is quantified in terms of absorption of light passing through the fiber probe using a green LED and a photodetector. The choice of fiber optic probes (fused silica versus polymer), the optimum size (20, 40, 60 and 80 nm) and concentration (2 × , 10 × , and 20 × ) of AuNP labels were investigated to obtain high sensitivity and lower limits of analyte detection (LoD). P-FAB with a simple LED-photodetector pair, 200 μm fused silica U-bent fiber probe and 60 nm (20 × ) AuNP labels gave LoDs down to 1 fg/mL and 10 fg/mL in the buffer and synthetic urine respectively. Moreover, the anti-Mtb LAM IgM bound sensor probes and the AuNP reagent stored at 4 °C were stable up to 45 days. P-FAB based Mtb LAM sensor demonstrates its potential for an on-site TB diagnosis.

Diagnostic Potential of IgG and IgA Responses to Mycobacterium tuberculosis Antigens for Discrimination among Active Tuberculosis, Latent Tuberculosis Infection, and Non-Infected Individuals

Tuberculosis remains a major public health problem. Conventional tests are inadequate to distinguish between active tuberculosis (ATB) and latent tuberculosis infection (LTBI). We measured antibody responses to Mycobacterium tuberculosis antigens (Mycobacterium tuberculosis chorismate mutase (TBCM), antigen 85B (Ag85B), early secreted antigen-6 (ESAT-6), and culture filtrate protein-10 (CFP-10) in ATB, LTBI, and non-infected (NI) individuals. Serum immunoglobulin G (IgG) and immunoglobulin A (IgA) levels were measured and the QuantiFERON-TB Gold In-Tube assay was used to diagnose LTBI. IgG levels against TBCM were significantly higher in LTBI than NI subjects. IgG and IgA levels against Ag85B and IgG levels against CFP-10 were significantly higher in ATB, followed by LTBI, and then NI. When the ATB group was subdivided, IgG levels against Ag85B and CFP-10 were significantly higher in each subgroup compared with those in LTBI and NI groups. Positive correlation trends between interferon-gamma and IgG levels against Ag85B, TBCM, and CFP-10 and IgA levels against Ag85B in LTBI and NI subjects were observed. Age- and sex-adjusted models showed that IgG against TBCM and CFP-10 was independently related to LTBI diagnosis, and IgG against Ag85B was independently related to the diagnosis of ATB and could distinguish between LTBI and ATB. Overall, IgG antibody responses to TBCM, Ag85B, and CFP-10 can discriminate among ATB, LTBI, and NI groups.

Serological biomarkers for monitoring response to treatment of pulmonary and extrapulmonary tuberculosis in children and adolescents

Key measures to halt the spread of tuberculosis (TB) include early diagnosis, effective treatment, and monitoring disease management. We sought to evaluate the use of serum immunoglobulin levels against antigens present in cell envelope of Mycobacterium tuberculosis to monitor TB treatment response in children and adolescents with pulmonary (PTB) or extrapulmonary TB (EPTB). Blood samples were collected prior to and one, two, and six months following treatment initiation. Serum immunoglobulin levels against cardiolipin, sulfatide, mycolic acid and Mce1A protein were measured by ELISA. Serum from 53 TB patients and 12 healthy participants were analyzed. After six months of successful treatment, there was a significant decrease (p < 0.0001) in IgM levels against cardiolipin, sulfatide, mycolic acid and Mce1A protein and IgG levels against Mce1A protein when compared to baseline immunoglobulin levels. There was no significant variation in antibody levels during follow-up between participants with PTB and EPTB, confirmed and unconfirmed TB diagnosis, and HIV infection status. Antibody levels in control participants without TB did not decrease during follow-up. These results suggest that immunoglobulin responses to mycobacterial cell wall products may be a useful tool to monitor treatment response in children and adolescents with PTB or EPTB.

Early treatment outcome of bedaquiline plus optimised background regimen in drug resistant tuberculosis patients

AIMS

Bedaquiline (BDQ) has been recently approved for drug resistant tuberculosis with active drug safety monitoring under programmatic condition. The present study was conducted to evaluate safety, tolerability and efficacy of bedaquiline plus optimised background regimen.

METHODS

A prospective study was conducted on cohort of pre-extensively drug resistant (XDR) and XDR pulmonary TB patients. Eligible patients were closely monitored for cardiac safety, adverse events (AEs), clinical and microbiological improvement during BDQ (6 months) and post BDQ phase for twelve months.

RESULTS

Of 127 patients enrolled, a significant increase in mean QTc interval was observed on 13th day and 3rd week as compared to baseline (p < 0.0001). Mean maximum increase of QTc was 37.92ms (95% CI, 14.1-61.74ms). Concomitant anti-TB medications, age, gender, low body mass index (BMI) had significant effect on QTc prolongation (p < 0.0001, p < 0.05). However, none of the patient required discontinuation of BDQ. Majority of AEs (86.3%) were non-serious and not preventable 108 (87.1%). The median time for sputum-culture conversion was 40.89 ± 3.5 days (95% CI, 34-48 days) and the treatment outcome was successful in 102 (80.3%) patients with negative sputum culture conversion.

CONCLUSIONS

Bedaquiline containing regimen achieved favourable outcome. Although, bedaquiline along with concomitant anti-TB medications has the potential to prolong QTc interval, the benefit certainly outweighs the risk. This calls for a through pre-treatment cardiovascular and biochemical evaluation as a preventive measure and appropriate selection of patients for safe use of BDQ and successful outcome.

Evaluation of multi-antigen serological screening for active tuberculosis among people living with HIV

Better triage tests for screening tuberculosis (TB) disease are needed for people living with HIV (PLHIV). We performed the first evaluation of a previously-validated 8-antigen serological panel to screen PLHIV for pulmonary TB in Kampala, Uganda. We selected a random 1:1 sample with and without TB (defined by sputum culture) from a cohort of PLHIV initiating antiretroviral therapy. We used a multiplex microbead immunoassay and an ensemble machine learning classifier to determine the area under the receiver operating characteristic curve (AUC) for Ag85A, Ag85B, Ag85C, Rv0934-P38, Rv3881, Rv3841-BfrB, Rv3873, and Rv2878c. We then assessed the performance with the addition of four TB-specific antigens ESAT-6, CFP-10, Rv1980-MPT64, and Rv2031-HSPX, and every antigen combination. Of 262 participants (median CD4 cell-count 152 cells/μL [IQR 65-279]), 138 (53%) had culture-confirmed TB. The 8-antigen panel had an AUC of 0.53 (95% CI 0.40-0.66), and the additional 4 antigens did not improve performance (AUC 0.51, 95% CI 0.39-0.64). When sensitivity was restricted to ≥90% for the 8- and 12-antigen panel, specificity was 2.2% (95% CI 0-17.7%) and 8.1% (95% CI 0-23.9%), respectively. A three-antigen combination (Rv0934-P38, Ag85A, and Rv2031-HSPX) outperformed both panels, with an AUC of 0.60 (95% CI 0.48-0.73), 90% sensitivity (95% CI 78.2-96.7%) and 29.7% specificity (95% CI 15.9-47%). The multi-antigen panels did not achieve the target accuracy for a TB triage test among PLHIV. We identified a new combination that improved performance for TB screening in an HIV-positive sample compared to an existing serological panel in Uganda, and suggests an approach to identify novel antigen combinations specifically for screening TB in PLHIV.

Integrative proteomic and glycoproteomic profiling of Mycobacterium tuberculosis culture filtrate

Despite being the subject of intensive research, tuberculosis, caused by Mycobacterium tuberculosis, remains at present the leading cause of death from an infectious agent. Secreted and cell wall proteins interact with the host and play important roles in pathogenicity. These proteins are explored as candidate diagnostic markers, potential drug targets or vaccine antigens, and more recently special attention is being given to the role of their post-translational modifications. With the purpose of contributing to the proteomic and glycoproteomic characterization of this important pathogen, we performed a shotgun analysis of culture filtrate proteins of M. tuberculosis based on a liquid nano-HPLC tandem mass spectrometry and a label-free spectral counting normalization approach for protein quantification. We identified 1314 M. tuberculosis proteins in culture filtrate and found that the most abundant proteins belong to the extracellular region or cell wall compartment, and that the functional categories with higher protein abundance factor were virulence, detoxification and adaptation, and cell wall and cell processes. We could identify a group of proteins consistently detected in previous studies, most of which were highly abundant proteins. In culture filtrate, 140 proteins were predicted to contain one of the three types of bacterial N-terminal signal peptides. Besides, various proteins belonging to the ESX secretion systems, and to the PE and PPE families, secreted by the type VII secretion system using nonclassical secretion signals, were also identified. O-glycosylation was identified in 46 proteins, many of them lipoproteins and cell wall associated proteins. Finally, we provide proteomic evidence for 33 novel O-glycosylated proteins, aiding to the glycoproteomic characterization of relevant antigenic membrane and exported proteins. These findings are expected to collaborate with the research on pathogen derived biomarkers, virulence factors and vaccine candidates, and to provide clues to the understanding of the pathogenesis and survival strategies adopted by M. tuberculosis.

GRADE guidelines: 21 part 1. Study design, risk of bias, and indirectness in rating the certainty across a body of evidence for test accuracy

OBJECTIVES

This article provides updated GRADE guidance about how authors of systematic reviews and health technology assessments and guideline developers can assess the results and the certainty of evidence (also known as quality of the evidence or confidence in the estimates) of a body of evidence addressing test accuracy (TA).

STUDY DESIGN AND SETTING

We present an overview of the GRADE approach and guidance for rating certainty in TA in clinical and public health and review the presentation of results of a body of evidence regarding tests. Part 1 of the two parts in this 21st guidance article about how to apply GRADE focuses on understanding study design issues in test accuracy, provide an overview of the domains, and describe risk of bias and indirectness specifically.

RESULTS

Supplemented by practical examples, we describe how raters of the evidence using GRADE can evaluate study designs focusing on tests and how they apply the GRADE domains risk of bias and indirectness to a body of evidence of TA studies.

CONCLUSION

Rating the certainty of a body of evidence using GRADE in Cochrane and other reviews and World Health Organization and other guidelines dealing with in TA studies helped refining our approach. The resulting guidance will help applying GRADE successfully for questions and recommendations focusing on tests.

GRADE guidelines: 21 part 2. Test accuracy: inconsistency, imprecision, publication bias, and other domains for rating the certainty of evidence and presenting it in evidence profiles and summary of findings tables

OBJECTIVES

This article provides updated GRADE guidance about how authors of systematic reviews and health technology assessments and guideline developers can rate the certainty of evidence (also known as quality of the evidence or confidence in the estimates) of a body of evidence addressing test accuracy (TA) on the domains imprecision, inconsistency, publication bias, and other domains. It also provides guidance for how to present synthesized information in evidence profiles and summary of findings tables.

STUDY DESIGN AND SETTING

We present guidance for rating certainty in TA in clinical and public health and review the presentation of results of a body of evidence regarding tests.

RESULTS

Supplemented by practical examples, we describe how raters of the evidence can apply the GRADE domains inconsistency, imprecision, and publication bias to a body of evidence of TA studies.

CONCLUSION

Using GRADE in Cochrane and other reviews as well as World Health Organization and other guidelines helped refining the GRADE approach for rating the certainty of a body of evidence from TA studies. Although several of the GRADE domains (e.g., imprecision and magnitude of the association) require further methodological research to help operationalize them, judgments need to be made on the basis of what is known so far.

Immune Biomarkers for Diagnosis and Treatment Monitoring of Tuberculosis: Current Developments and Future Prospects

Tuberculosis (TB) treatment monitoring is paramount to clinical decision-making and the host biomarkers appears to play a significant role. The currently available diagnostic technology for TB detection is inadequate. Although GeneXpert detects total DNA present in the sample regardless live or dead bacilli present in clinical samples, all the commercial tests available thus far have low sensitivity. Humoral responses against Mycobacterium tuberculosis (Mtb) antigens are generally low, which precludes the use of serological tests for TB diagnosis, prognosis, and treatment monitoring. Mtb-specific CD4⁺ T cells correlate with Mtb antigen/bacilli burden and hence might serve as good biomarkers for monitoring treatment progress. Omics-based techniques are capable of providing a more holistic picture for disease mechanisms and are more accurate in predicting TB disease outcomes. The current review aims to discuss some of the recent advances on TB biomarkers, particularly host biomarkers that have the potential to diagnose and differentiate active TB and LTBI as well as their use in disease prognosis and treatment monitoring.

Polymorphism of MPT64 and PstS1 in Mycobacterium tuberculosis is not likely to affect relative immune reaction in human

BACKGROUND

MPT64 and PstS1 are the earliest known immune-dominant antigens of Mycobacterium tuberculosis and have been commonly used as candidates in the diagnosis of tuberculosis.

METHODS

We constructed recombinant plasmids pET-32a-Rv0934 and pET-32a-Rv1980c to express both wild and mutant forms of MPT64 and PstS1 and purified them. From November 9 to December 9, 2016, and November 9 to December 10, 2017, 96 patients with tuberculosis, 53 patients without tuberculosis, and 96 healthy volunteers were enrolled in this study. We used the purified proteins as antigens to perform T-spot and enzyme-linked immunosorbent assay (ELISA) for samples obtained from healthy volunteers and tuberculosis patients.

RESULTS

Regarding T-spot, the area under the curve (AUC) values for MPT64-wild protein (MPT64-H37Rv) and MPT64-mutant protein (MPT64-FJ05395) were 0.723 and 0.750, respectively. The AUC values for PstS1-H37Rv, PstS1-FJ05132, and PstS1-JL06035 were 0.817, 0.796, and 0.745, respectively. With regard to ELISA, the AUC values for MPT64-H37Rv and MPT64-FJ05395 were 0.525 and 0.528, respectively, while those for PstS1-H37Rv, PstS1-FJ05132, PstS1-JL06035 were 0.588, 0.509, and 0.560, respectively. There was no difference between wild and mutant proteins when we used them as antigens to perform T-spot and ELISA assays.

CONCLUSION

MPT64 and PstS1 are likely candidate diagnostic antigens for M tuberculosis T-spot test, at least in combination with other proteins. Polymorphisms of MPT64 and PstS1 had little effect on cell-mediated and humoral immunity in the host.

Initiative for Promoting Affordable and Quality Tuberculosis Tests (IPAQT): a market-shaping intervention in India

A majority of patients with tuberculosis (TB) in India are diagnosed and treated in the private sector. Yet, most private providers do not use most recent WHO-endorsed microbiological tests such as liquid cultures, line probe assays and Xpert MTB/RIF due to a combination of factors such as lack of awareness, misaligned incentives and high prices that are unaffordable for patients. We designed a market-based approach to transform a high-price, low-volume market equilibrium into a low-price, high-volume equilibrium to improve the uptake of these tests. Toward this end, a non-profit consortium of private laboratories, called Initiative for Promoting Affordable and Quality Tuberculosis Tests (IPAQT) was formed in India in March 2013. It negotiated lower pricing on equipment and reagents with manufacturers, closer to that offered to the public sector. In return, IPAQT assured that this discount was passed on to patients, who typically paid for these tests out of their pockets, through an informally agreed on retail ceiling price. IPAQT also invested in demand generation activities that complemented the supply-side effort. IPAQT membership grew from 56 laboratories in 2013 to 211 in 2018. During this period, the initiative resulted in a 10-fold increase in the uptake of Xpert and a 30%-50% reduction in price. This initiative is planned to be expanded to other South Asian countries with similar TB epidemic and private market structure and dynamics. However, long-term sustainability of the initiative would require developing more cost-effective marketing activities and integration with broader private sector engagement agenda of the national TB programme.

Clinical characteristics and potential indicators for definite diagnosis of tuberculous pleural effusion

AIMS

The study aimed to investigate the clinical characteristics of patients with pleural effusion (PE), and explore the effective indicators for definite diagnosis of tuberculous pleural effusion (TBPE).

METHODS

The adult patients with the presence of PE were enrolled. All the patients received pleural fluid Mycobacterium tuberculosis DNA detection, ADA activity measure and blood T-SPOT.TB test. The clinical characteristics and examination results were recorded.

RESULTS

A total of 77 PE patients, including 30 (38.96%) TBPE, 19 (24.67%) malignant PE, 6 (7.79%) empyema, 10 (12.99%) parapneumonic effusion and 12 (15.58%) miscellaneous causes, were enrolled. The diagnostic sensitivity and specificity of pleural fluid M. tuberculosis DNA detection were 33.3% and 100%, respectively. The diagnostic parameters of pleural fluid ADA for TBPE were as follows: sensitivity 50% and specificity 78.7%. In PE cases with pleural fluid lactate dehydrogenase (LDH) more than 500 U/L, the diagnostic values of DNA detection and ADA activity were enhanced, and DNA detection was superior to ADA activity. In addition, the ratio of blood T-STOP.TB A + B to lymphocyte was a potential diagnostic biomarker for TBPE with the sensitivity of 83.3% and the specificity of 66.0%.

CONCLUSION

The clinical significance of pleural fluid M. tuberculosis DNA detection is superior to ADA activity in the diagnosis of TBPE, especially in PE cases with LDH value more than 500 U/L. The ratio of blood T-STOP.TB A + B to lymphocyte is a potential indicator for definite diagnosis of TBPE, with high sensitivity.

Tuberculosis: Current Status, Diagnosis, Treatment and Development of Novel Vaccines

Tuberculosis (TB) is an infectious disease that mainly affects the lungs and spreads to other organs of the body through the haematogenous route. It is one of the ten major causes of mortality worldwide. India has the highest incidence of new- and multidrug-resistant (MDR) - TB cases in the world. Bacille Calmette-Guerin (BCG) is the vaccine commonly available against TB. BCG does offer some protection against serious forms of TB in childhood but its protective effect wanes with age. Many new innovative strategies are being trailed for the development of effective and potent vaccines like mucosal- and epitope-based vaccines, which may replace BCG or boost BCG responses. The use of nanotechnology for diagnosis and treatment of TB is also in the pipeline along with many other vaccines, which are under clinical trials. Further, in-silico models were developed for finding new drug targets and designing drugs against Mycobacterium tuberculosis (Mtb). These models offer the benefit of computational experiments which are easy, inexpensive and give quick results. This review will focus on the available treatments and new approaches to develop potent vaccines for the treatment of TB.

Lipoarabinomannan in Active and Passive Protection Against Tuberculosis

Glycolipids of the cell wall of Mycobacterium tuberculosis (Mtb) are important immunomodulators in tuberculosis. In particular, lipoarabinomannan (LAM) has a profound effect on the innate immune response. LAM and its structural variants can be recognized by and activate human CD1b-restricted T cells, and emerging evidence indicates that B cells and antibodies against LAM can modulate the immune response to Mtb. Anti-LAM antibodies are induced during Mtb infection and after bacille Calmette-Guerin (BCG) vaccination, and monoclonal antibodies against LAM have been shown to confer protection by passive administration in mice and guinea pigs. In this review, we describe the immune response against LAM and the potential use of the mannose-capped arabinan moiety of LAM in the construction of vaccine candidates against tuberculosis.

Sandwich antibody-based biosensor system for identification of Mycobacterium tuberculosis complex and nontuberculous mycobacteria

Mycobacterial infection, leading to pulmonary disease, remains a world health problem. Clinical symptoms of pulmonary disease caused by Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM) are very similar. A rapid method for the differentiation of MTBC and NTM infection is essential for appropriate therapy. In this study, we aim to establish an antibody-based biosensor system for the identification of MTBC and NTM infection. Monoclonal antibodies (mAbs) specific for Ag85B proteins of mycobacteria were generated and characterized. The generated anti-Ag85B mAb clones AM85B-5 and AM85B-8 reacted to Ag85B of Mycobacterium spp.; in contrast, clone AM85B-9 specifically reacted to Ag85B of MTBC. By employing the produced mAbs, single and sandwich antibody-based biosensors using bio-layer interferometry were established for determination of Ag85B proteins. The sandwich antibody-based biosensor system was demonstrated to be suitable for detection of Ag85B protein and identification of MTBC and NTM. Using anti-Ag85B mAbs AM85B-8 and AM85B-9 as immobilized antibodies on sensor chips and using mAb AM85B-5 as secondary antibody, the established sandwich antibody-based biosensor could discriminate MTBC and NTM. The developed biosensor system can be used for culture confirmation of mycobacteria and speciation to MTBC and NTM.

The Mycobacterial HBHA Protein: A Promising Biomarker for Tuberculosis

A major goal in tuberculosis (TB) research is the identification, among the subjects infected with Mycobacterium tuberculosis (Mtb), of those with active TB, or at higher risk of developing active disease, from the latently infected subjects. The classical heterogeneity of Mtb infection and TB disease is a major obstacle toward the identification of reliable biomarkers that can stratify Mtb infected subjects based on disease risk. The heparin-binding haemagglutinin (HBHA) is a mycobacterial surface antigen that is implicated in tuberculosis (TB) pathogenesis. The host immune response against HBHA varies depending on the TB status and several studies are supporting the role of HBHA as a useful biomarker of TB.

Combining urine lipoarabinomannan with antibody detection as a simple non-sputum-based screening method for HIV-associated tuberculosis

Background

Simple methods for the accurate triaging and screening of HIV-associated tuberculosis (TB) are urgently needed. We hypothesized that combining serum antibody with urine lipoarabinomannan (U-LAM) detection can improve the detection of HIV-associated TB.

Methods

We performed a case-control study with sampling from a prospective study of South African HIV-infected subjects who were screened for TB prior to initiating antiretroviral therapy. Sera from all available TB cases (n = 74) and randomly selected non-TB controls (n = 30), all tested for U-LAM, sputum microscopy, GeneXpert, and cultures, were evaluated for antibodies to LAM and arabinomannan (AM). Diagnostic logistic regression models for TB were developed based on the primary test results and the additive effect of antibodies with leave-one-out cross-validation.

Results

Antibody responses to LAM and AM correlated strongly (p<0.0001), and IgG and IgM reactivities were significantly higher in TB than non-TB patients (p<0.0001). At 80% specificity, the target specificity for a non-sputum-based simple triage/screening test determined by major TB stakeholders, combining U-LAM with IgG detection significantly increased the sensitivity for HIV-associated TB to 92% compared to 30% for U-LAM alone (p<0.001). Sputum microscopy combined with IgG detection increased sensitivity to 88% compared to 31% for microscopy alone, and Xpert with IgG increased sensitivity to 96% and 99% compared to 57% for testing one, and 70% for testing two sputa with Xpert alone, respectively.

Conclusion

Combining U-LAM with serum antibody detection could provide a simple low-cost method that meets the requirements for a non-sputum-based test for the screening of HIV-associated TB.

Integrated bioinformatics analysis and validation revealed potential immune-regulatory miR-892b, miR-199b-5p and miR-582-5p as diagnostic biomarkers in active tuberculosis

Tuberculosis (TB) is one of the most prevalent pulmonary diseases caused by Mycobacterium tuberculosis (Mtb). MiRNAs (miRNAs) participate in TB progression by modulating the host-pathogen interaction. Bioinformatics advancements provide basis for exploring novel immunoregulatory miRNAs and their performance as diagnostic biomarkers. Gene and miRNA expression datasets, GSE29190 and GSE54992, were downloaded from Gene Expression Omnibus (GEO) database. Based on fold changes and statistical significance, a total of 7463 differentially expressed mRNAs (DE-mRNAs) and 38 differentially expressed miRNAs (DE-miRNAs) were screened. Function annotation and protein-protein interaction (PPI) network were constructed to reveal underlying mechanisms of TB pathogenesis. Functional annotation identified the MAPK signalling pathway and leukocyte migration as the top enriched processes. The PPI and MGIP networks indicated that chemokine ligands like CXCL1/CXCL2 and receptors, like CCR7 were important down-regulated genes, implying that a protective mechanism against overdue inflammation induced cell death. MiRNA-gene-immune processes (MGIP) network enriched 7 deregulated miRNAs, and their expression was further examined with quantitative real-time PCR (qRT-PCR), in PBMC samples of 20 active TB patients and 20 healthy donors. The diagnostic performance was evaluated with ROC curves. MiR-892b; miR-199b-5p and miR-582-5p were significantly deregulated in TB patients, compared with healthy participants. The best overall performance was from miR-892b, with an area under curve (AUC) of 0.77, 55% sensitivity and 90% specificity. AUC of miR-199b-5p and miR-582-5p were 0.71 and 0.70, respectively. MiR-892b, miR-199b-5p and miR-582-5p could be considered promising novel diagnostic biomarkers for active tuberculosis.

Sensitive electrochemiluminescence (ECL) immunoassays for detecting lipoarabinomannan (LAM) and ESAT-6 in urine and serum from tuberculosis patients

BACKGROUND

Tuberculosis (TB) infection was responsible for an estimated 1.3 million deaths in 2017. Better diagnostic tools are urgently needed. We sought to determine whether accurate TB antigen detection in blood or urine has the potential to meet the WHO target product profiles for detection of active TB.

MATERIALS AND METHODS

We developed Electrochemiluminescence (ECL) immunoassays for Lipoarabinomannan (LAM) and ESAT-6 detection with detection limits in the pg/ml range and used them to compare the concentrations of the two antigens in the urine and serum of 81 HIV-negative and -positive individuals with presumptive TB enrolled across diverse geographic sites.

RESULTS

LAM and ESAT-6 overall sensitivities in urine were 93% and 65% respectively. LAM and ESAT-6 overall sensitivities in serum were 55% and 46% respectively. Overall specificity was ≥97% in all assays. Sensitivities were higher in HIV-positive compared to HIV-negative patients for both antigens and both sample types, with signals roughly 10-fold higher on average in urine than in serum. The two antigens showed similar concentration ranges within the same sample type and correlated.

CONCLUSIONS

LAM and ESAT-6 can be detected in the urine and serum of TB patients, regardless of the HIV status and further gains in clinical sensitivity may be achievable through assay and reagent optimization. Accuracy in urine was higher with current methods and has the potential to meet the WHO accuracy target if the findings can be transferred to a point-of-care TB test.

Genetically-encoded fragment-based discovery (GE-FBD) of glycopeptide ligands with differential selectivity for antibodies related to mycobacterial infections

Accurate identification of tuberculosis (TB), caused by Mycobacterium tuberculosis, is important for global disease management. Point-of-care serological tests may improve TB diagnosis; however, specificities of available serodiagnostics are sub-optimal. We employed genetically encoded fragment-based discovery (GE-FBD) to select ligands for antibodies directed against the mycobacterial cell wall component lipoarabinomannan (LAM), a potent antigen. GE-FBD employed a phage displayed library of 10⁸ heptapeptides, chemically modified with an arabinofuranosyl hexasaccharide fragment of LAM (Ara₆), and the anti-LAM antibody CS-35 as a bait. The selection gave rise to glycopeptides with an enhanced affinity and selectivity for CS-35 but not for 906.4321 antibody, both of which bind to Ara₆ with a comparable affinity. Multivalent assays incorporating the discovered ligands Ara₆-ANSSFAP, Ara₆-DAHATLR and Ara₆-TTYVVNP exhibited up to 19-fold discrimination between CS-35 and 906.4321. The use of the Ara₆ antigen alone failed to distinguish these antibodies. Thus, GE-FBD gives rise to ligands that differentiate monoclonal antibodies with enhanced specificity. This technology could facilitate the development of effective point-of-care serological tests for mycobacterial and other infections.

Exploration of some new secretory proteins to be employed for companion diagnosis of Mycobacterium tuberculosis

Tuberculosis (TB) is a highly infectious disease and its early and precise diagnosis is essential to reduce morbidity and mortality of patients. Since the routine diagnostic tests (like Monteux, AFB smear microscopy, chest X-Ray) do not give infallible results, additional tests are always recommended. Therefore to address the concerns about non-specificity of the present battery of diagnostic tests, we have attempted to analyze some unique secretory antigens which could be able to identify the stage specific infection of MTB. In this study, we have used recombinant proteins CFP-10, ESAT-6, Ag85 A, Ag85B, Ag85C, PE3, PE4 and Mycp1 to eliminate heterogeneity and cross reactivity in clinical diagnosis. Amplified genes were cloned and over-expressed in Escherichia coli BL21 (DE3). The recombinantly purified proteins were used as antigens against 158 sera samples of TB patients. Secretory proteins showed better response than the PPD control. Among all the used antigens PE3 and PE4 proteins showed better reactivity levels among all the groups of TB patients. The secretions of CFP-10 and ESAT-6 were also higher as compared to other secretory proteins like Ag85 A, Ag85B, Ag85C and MycP1.The clinical use of these newly identified secretory antigens could be of significant value for the confirmatory, rapid, simple and low-cost diagnosis of TB patients.

A systematic review of biomarkers to detect active tuberculosis

Millions of cases of tuberculosis (TB) go undiagnosed each year. Better diagnostic tools are urgently needed. Biomarker-based or multiple marker biosignature-based tests, ideally performed on blood or urine, for the detection of active TB might help to meet target product profiles proposed by the World Health Organization for point-of-care testing. We conducted a systematic review to summarize evidence on proposed biomarkers and biosignatures and evaluate their quality and level of evidence. We screened the titles and abstracts of 7,631 citations and included 443 publications that fulfilled the inclusion criteria and were published in 2010-2017. The types of biomarkers identified included antibodies, cytokines, metabolic activity markers, mycobacterial antigens and volatile organic compounds. Only 47% of studies reported a culture-based reference standard and diagnostic sensitivity and specificity. Forty-four biomarkers (4%) were identified in high-quality studies and met the target product profile minimum criteria, of which two have been incorporated into commercial assays. Of the 44 highest-quality biomarkers, 24 (55%) were multiple marker biosignatures. No meta-analyses were performed owing to between-study heterogeneity. In conclusion, TB biomarker discovery studies are often poorly designed and findings are rarely confirmed in independent studies. Few markers progress to a further developmental stage. More validation studies that consider the intended diagnostic use cases and apply rigorous design are needed. The extracted data from this review are currently being used by FIND as the foundation of a dynamic database in which biomarker data and developmental status will be presented.

Biomarkers for tuberculosis: the case for lipoarabinomannan

Tuberculosis (TB) is considered the most onerous of infectious diseases according to recent reports from the World Health Organization. Available tests for TB diagnosis present severe limitations, and a reliable point-of-care (POC) diagnostic test does not exist. Neither is there a test to discern between the different stages of TB, and in particular to predict which patients with Mycobacterium tuberculosis infection and no clinical signs are more at risk of advancing to overt disease. We here review the usefulness of mycobacterial lipoarabinomannan (LAM) as a diagnostic marker for active and latent TB and, also, aspects of the immune response to LAM relevant to such tests. There is a high potential for urinary LAM-based POC tests for the diagnosis of active TB. Some technical challenges to optimised sensitivity of the test will be detailed. A method to quantify LAM in urine or serum should be further explored as a test of treatment effect. Recent data on the immune response to LAM suggest that markers for host response to LAM should be investigated for a prognostic test to recognise individuals at the greatest risk of disease activation.

There is a high potential for a urinary LAM-based point-of-care test to diagnose TB. Markers for host response to LAM should be explored to identify those at highest risk of developing active TB.http://ow.ly/FyCs30n4uFE

Current approaches toward identifying a correlate of immune protection from tuberculosis

INTRODUCTION

Mycobacterium tuberculosis kills more people than any other pathogen. Vaccination is the most cost-effective control measure for any infectious disease. Development of an effective vaccine against tuberculosis is hindered by the uncertain predictive value of preclinical animal models, incomplete understanding of protective immunity and lack of validated immune correlates of protection (COP).

AREAS COVERED

Here we review what is known about protective immunity against M.tb, the preclinical and clinical cohorts that can be utilized to identify COP, and COP that have been identified to date.

EXPERT COMMENTARY

The identification of COP would allow the rational design and development of vaccine candidates which can then be optimized and prioritized based on the induction of these immune responses. Once validated in field efficacy trials, such COP could potentially facilitate the development and licensure of vaccines, in combination with human efficacy data. The identification and validation of COP would represent a very significant advance in TB vaccine development. Every opportunity to collect samples and cohorts on which to cross-validate pre-existing COP and identify novel COP should be exploited. Furthermore, global cooperation and collaboration on such samples will ensure that the utility of such precious samples is fully exploited.