Utility of immunoglobulin isotypes against LID-1 and NDO-LID for, particularly IgG1, confirming the diagnosis of multibacillary leprosy

A recombinant chimeric antigen constructed with B-cell epitopes from Mycobacterium leprae hypothetical proteins is effective for the diagnosis of leprosy

The diagnosis if leprosy is difficult, as it requires clinical expertise and sensitive laboratory tests. In this study, we develop a serological test for leprosy by using bioinformatics tools to identify specific B-cell epitopes from Mycobacterium leprae hypothetical proteins, which were used to construct a recombinant chimeric protein, M1. The synthetic peptides were obtained and showed good reactivity to detect leprosy patients, although the M1 chimera have showed sensitivity (Se) and specificity (Sp) values higher than 90.0% to diagnose both paucibacillary (PB) and multibacillary (MB) leprosy patients, but not those developing tegumentary or visceral leishmaniasis, tuberculosis, Chagas disease, malaria, histoplasmosis and aspergillosis, in ELISA experiments. Using sera from household contacts, values for Se and Sp were 100% and 65.3%, respectively. In conclusion, our proof-of-concept study has generated data that suggest that a new recombinant protein could be developed into a diagnostic antigen for leprosy.

Algorithm design for a cytokine release assay of antigen-specific in vitro stimuli of circulating leukocytes to classify leprosy patients and household contacts

Background

Immunological biomarkers have often been used as a complementary approach to support clinical diagnosis in several infectious diseases. The lack of commercially available laboratory tests for conclusive early diagnosis of leprosy has motivated the search for novel methods for accurate diagnosis. In the present study, we describe an integrated analysis of a cytokine release assay using a machine learning approach to create a decision tree algorithm. This algorithm was used to classify leprosy clinical forms and monitor household contacts.

Methods

A model of Mycobacterium leprae antigen-specific in vitro assay with subsequent cytokine measurements by enzyme-linked immunosorbent assay was employed to measure the levels of tumor necrosis factor (TNF), interferon-γ, interleukin 4, and interleukin 10 (IL-10) in culture supernatants of peripheral blood mononuclear cells from patients with leprosy, healthy controls, and household contacts. Receiver operating characteristic curve analysis was carried out to define each cytokine’s global accuracy and performance indices to identify clinical subgroups.

Results

Data demonstrated that TNF (control culture [CC]: AUC = 0.72; antigen-stimulated culture [Ml]: AUC = 0.80) and IL-10 (CC: AUC = 0.77; Ml: AUC = 0.71) were the most accurate biomarkers to classify subgroups of household contacts and patients with leprosy, respectively. Decision tree classifier algorithms for TNF analysis categorized subgroups of household contacts according to the operational classification with moderate accuracy (CC: 79% [48/61]; Ml: 84% [51/61]). Additionally, IL-10 analysis categorized leprosy patients’ subgroups with moderate accuracy (CC: 73% [22/30] and Ml: 70% [21/30]).

Conclusions

Together, our findings demonstrated that a cytokine release assay is a promising method to complement clinical diagnosis, ultimately contributing to effective control of the disease.

Serum IgA Antibodies Specific to M. leprae Antigens as Biomarkers for Leprosy Detection and Household Contact Tracking

Leprosy remains endemic in several developing countries, such as India and Brazil, in part due to delayed diagnosis that facilitates ongoing transmission. Although immunoglobulins against several Mycobacterium leprae antigens have been indicated for the early diagnosis, and IgA participates in the early stages of leprosy and in subclinical infection, relatively little research has examined anti-M. leprae IgA responses. Here, we investigated serum IgA reactivity against NDO-HSA, LID-1 and NDO-LID, in paucibacillary (PB) and multibacillary (MB) patients and their household contacts, using enzyme-linked immunosorbent assay (ELISA). Diagnostic accuracy of each ELISA was evaluated by receiver operating characteristic (ROC) curve analysis. Our data reveal elevated IgA serum levels against the three M. leprae specific antigens in MB patients, whereas IgA reactivity in PB patients was increased only to NDO-HSA. Further, MB and PB household contacts displayed higher IgA reactivity to NDO-HSA than non-endemic controls. Our data suggest measurement of serum IgA against NDO-HSA as an additional tool in the diagnosis and classification of the disease, with potential utility for household contact follow-up.

Evaluation of antibody detection against the NDO-BSA, LID-1 and NDO-LID antigens as confirmatory tests to support the diagnosis of leprosy in Yunnan province, southwest China

Although multidrug therapy (MDT) has been widely used for the treatment of leprosy for nearly 40 y, the disease remains a public health concern in some areas. The early detection of leprosy cases is vital to interrupt Mycobacterium leprae transmission, but currently diagnosis is typically achieved during the recognition of clinical symptoms by professional staff performing physical examinations in conjunction with microbiological assessment of slit skin smears (SSSs) and histopathology. In the last 10 y, serum antibody detection tests have emerged to aid leprosy diagnosis. Here we evaluated the ability of antigens NDO-BSA and LID-1 (ML0405 and ML2331) and the conjugate of these, NDO-LID, to detect antibodies in the sera of 113 leprosy patients and 166 control individuals in Yunnan province in southwest China. We found that each antigen was readily detected by sera from multibacillary (MB) patients, with sensitivities of 97.3%, 97.3% and 98.6% for NDO-BSA, LID-1 and NDO-LID, respectively. Even among paucibacillary (PB) patients the antigens detected antibodies in 74.4%, 56.4% and 69.2% of serum samples, respectively. Receiver operating characteristics (ROC) curve analysis indicated that, irrespective of the leprosy case classification as MB or PB, the detection efficiency obtained with NDO-LID was better than that obtained with the other two antigens (with LID-1 being a slightly better than NDO-BSA). Our results indicate the utility of NDO-LID in assisting in the diagnosis of PB and MB leprosy patients and that these antibody detection assays represent powerful diagnostic tools. We suggest that could be implemented into the procedures of local health centres in leprosy-endemic regions to assist in earlier diagnosis.

Insights into Mycobacterium leprae Proteomics and Biomarkers-An Overview

Although leprosy is curable, the identification of biomarkers for the early diagnosis of leprosy would play a pivotal role in reducing transmission and the overall prevalence of the disease. Leprosy-specific biomarkers for diagnosis, particularly for the paucibacillary disease, are not well defined. Therefore, the identification of new biomarkers for leprosy is one of the prime themes of leprosy research. Studying Mycobacterium leprae, the causative agent of leprosy, at the proteomic level may facilitate the identification, quantification, and characterization of proteins that could be potential diagnostics or targets for drugs and can help in better understanding the pathogenesis. This review aims to shed light on the knowledge gained to understand leprosy or its pathogen employing proteomics and its role in diagnosis.

Functional biomarker signatures of circulating T-cells and its association with distinct clinical status of leprosy patients and their respective household contacts

BACKGROUND

Leprosy is a chronic infectious disease classified into two subgroups for therapeutic purposes: paucibacillary (PB) and multibacillary (MB), closely related to the host immune responses. In this context it is noteworthy looking for immunological biomarkers applicable as complementary diagnostic tools as well as a laboratorial strategy to follow-up leprosy household contacts.

METHODS

The cross-sectional study enrolled 49 participants, including 19 patients and 30 healthy controls. Peripheral blood mononuclear cells (PBMC) were isolated and incubated in the presence of Mycobacterium leprae bacilli. The cells were prepared for surface (CD4+ and CD8+) and intracytoplasmic cytokine staining (IFN-γ, IL-4 and IL-10). Multiple comparisons amongst groups were carried out by ANOVA, Kruskal-Wallis, Student T or Mann-Whitney test. Comparative analysis of categorical variables was performed by Chi-square. Functional biomarker signature analysis was conducted using the global median values for each biomarker index as the cut-off edge to identify the proportion of subjects with high biomarker levels.

RESULTS

The cytokine signature analysis demonstrated that leprosy patients presented a polyfunctional profile of T-cells subsets, with increased frequency of IFN-γ+ T-cell subsets along with IL-10+ and IL-4+ from CD4+ T-cells, as compared to health Controls (Venn diagram report). Moreover, statistical analysis was carried out using parametric or non-parametric variance analysis followed by pairwise multiple comparisons, according to the data normality distribution. L(PB) displayed a polyfunctional profile characterized by enhanced percentage of IFN-γ+, IL-10+ and IL-4+ produced by most T-cell subsets, as compared to L(MB) that presented a more restricted cytokine functional profile mediated by IL-10+ and IL-4+ T-cells with minor contribution of IFN-γ produced by CD4+ T-cells. Noteworthy was that HHC(MB) exhibited enhanced frequency of IFN-γ+ T-cells, contrasting with HHC(PB) that presented a cytokine profile limited to IL-10 and IL-4.

CONCLUSIONS

Our data demonstrated that L(PB) displayed enhanced percentage of IFN-γ+, IL-10+ and IL-4+ as compared to L(MB) that presented functional profile mediated by IL-10+ and IL-4+ T-cells and HHC(MB) exhibited enhanced frequency of IFN-γ+ T-cells, contrasting with HHC(PB). Together, our findings provide additional immunological features associated with leprosy and household contacts. These data provide evidence that biomarkers of immune response can be useful complementary diagnostic/prognostic tools as well as insights that household contacts should be monitored to access putative subclinical infection.

Prospects for new leprosy diagnostic tools, a narrative review considering ELISA and PCR assays

Slit skin smear and histopathological examinations are currently the main laboratory tools used to aid the diagnosis of leprosy. However, their sensitivity is low, and many cases are not detected. New methodologies have been studied to develop more accurate tests. This narrative review aims to raise attention to the results of molecular (polymerase chain reaction) and serological (Enzyme-Linked Immunosorbent Assay) tests applied to the diagnosis of leprosy, and to summarize the available information about the former. Original scientific articles published in indexed international journals, whose study involved aspects of the diagnosis and classification of leprosy cases or home contacts, were selected. The data were extracted independently using a standardized method that dictated the inclusion of the following information: diagnosis in Paucibacillary and Multibacillary cases and in household contacts; sample number; sample type; study design; studied variables; statistical analysis employed; main results; and limitations identified. In clinical practice, the results from molecular and serological tests are assessed separately, with moderate sensitivity and specificity. However, an integrated study of these methodologies has been suggested for greater accuracy in diagnosis.

Leprosy surveillance study in a highly endemic Brazilian area using leprosy specific serologic tests and IFNγ whole blood assay

This surveillance study evaluated leprosy-serologic tests and the IFNγ whole-blood-assay/WBA as adjunct diagnostic tools. Previously diagnosed leprosy index cases, intradomiciliary, peridomiciliary contacts from a Brazilian endemic area were enrolled during domiciliary visits. Physical evaluation was performed by trained nurses and leprosy diagnosis confirmed by expert dermatologist. ELISA detected IgM anti-PGL-I, IgG anti-LID-1, and IgM/IgG anti-ND-O-LID antibodies. Heparinized WBA plasma stimulated with LID-1, 46f + LID-1, ML0276 + LID-1 (24 h, 37 °C, 5% CO₂₎ was tested for human IFNγ (QuantiFERON®-TB Gold/QFT-G; Qiagen). The survey included 1731 participants: 44 leprosy index cases, 64 intradomiciliary, 1623 peridomiciliary contacts. Women represented 57.7%, median age was 32 years, 72.2% had BCG scar. Leprosy prevalence was higher in intradomiciliary (8.57%) versus peridomiciliary contacts (0.67%), p < 0.001. Among 23 suspects, five leprosy cases were confirmed: 4 multibacillary/MB and 1 paucibacillary/PB. Leprosy incidence was 0.30%: 1.56% in intradomiciliary versus 0.25% in peridomiciliary (p = 0.028). Seropositivity rates were 1.9% to PGL-I, 4.9% to LID-1, and 1.0% to ND-O-LID. LID-1 positivity was higher in all groups; incident cases were LID-1 seropositive. ND-O-LID positivity was higher in intra- versus peridomiciliary contacts (p = 0.022). IFNγ WBA (40 index cases, 19 suspects, 35 intradomiciliary, 74 peridomiciliary contacts) showed higher LID-1/WBA positivity in peridomiciliary contacts (p > 0.05); significant differences among groups were seen with 46f + LID-1 but 0276 + LID-1 induced higher IFNγ levels. Incident cases were LID-1 seropositive, while IFNγ-WBA had marginal diagnostic application. As seropositivity indicates exposed individuals at higher risk of disease development, the utility of serologic screening for surveillance and prophylactic measures remains to be demonstrated.

Association between NDO-LID and PGL-1 for leprosy and class I and II human leukocyte antigen alleles in an indigenous community in Southwest Amazon

The frequencies of the Human leukocyte antigen (HLA) alleles in the Puyanawa indigenous reserve population and their association with the NDO-LID and ELISA PGL-1 rapid serological test was assessed. This was a cross-sectional study with an epidemiological clinical design conducted in two indigenous communities in the state of Acre, Brazil. Blood was collected in a tube with EDTA to identify HLA alleles and perform serological tests. DNA was obtained using the salting out procedure. The LabType™ technique (One-Lambda-USA) was used for HLA class I (loci A*, B* and C*) and II (loci DRB1*, DQA1* and DQB1*) typing. Allele frequency was obtained by direct count, and the chi-square test was used to assess the association with the NDO-LID and PGL-1 tests. The most frequent alleles in the two communities were: HLA-A*02:01, HLA-B*40:02, HLA-DRB1*16:02, HLA-DQA1*05:05 and HLA-DQB1*03:01. The allele HLA-C*04:01 was the most common in the Barão community, and the allele HLA-C*07:01 in Ipiranga. Among individuals who presented seropositivity to the NDO-LID test, the association with alleles HLA-A*02 (43.18% vs 24.8%, p = 0.03, OR = 2.35) and HLA-B*53 (6.83% vs 0.0%, p = 0.03, OR = 8.95) was observed in the Barão community. HLA-B*15 was associated with non-seroconversion to the NDO-LID test in Ipiranga. In both communities, HLA-B*40 and HLA-C*03 were associated with positive serological response to ELISA PGL-1. The HLA class I and II alleles most frequently found in this study have already been described among Terena indigenous groups, and HLA class I contributes to seroconversion to NDO-LID and PGL-1 tests in inhabitants of the Barão and Ipiranga communities.

Diagnostic accuracy of tests using recombinant protein antigens of Mycobacterium leprae for leprosy: A systematic review

The aim of this systematic review was to investigate the studies that evaluated the sensitivity and specificity of serologic tests using recombinant protein antigens from Mycobacterium leprae for leprosy diagnosis. We included 13 studies that were available in PubMed, Brazilian Virtual Library of Health, Web of Science, ScienceDirect and Scopus. From these studies, we found that the recombinant serine-rich 45-kDa protein of M. leprae (ML0411) demonstrated high performance for multibacillary (MB) also to paucibacillary (PB) patients, although this study was tested only for Indian population. Despite that, studies using the ND-O-LID antigen have been able to more accurately identify new cases of leprosy among people living in endemic or non-endemic areas and household contacts in Brazil, Colombia, and the Philippines, especially when combined with other biomarkers. Finally, low sensitivity values for PB patients' antibodies response remain challenging for tests intended to diagnose clinical forms that comprise this classification in leprosy.

Utility and limitations of serodiagnostic tests in monitoring the response to treatment of leprosy patients

Simple measures that can facilitate early recognition of leprosy complications are still lacking. We therefore evaluated a lateral flow-based rapid diagnostic test and fast enzyme-linked immunosorbent assay measuring anti-LID-NDO antibody responses among leprosy cases in Cebu, Philippines. Responses were measured at diagnosis, then during and after the provision of standard multidrug therapy. Our data indicate that both platforms are highly sensitive tools for the primary diagnosis of, in particular, multibacillary leprosy. A gradual, quantifiable decline in both magnitude of response and percent positive responders was observed during and after treatment. As a group, patients that developed erythema nodosum leprosum (ENL) had a significantly higher response at diagnosis than patients that either developed reversal reactions or did not develop reactions. Although higher initial anti-NDO-LID responses were a risk factor for ENL, neither platform, however, could reliably predict the time of emergence of reactional episodes.

A novel integrated molecular and serological analysis method to predict new cases of leprosy amongst household contacts

Background

Early detection of Mycobacterium leprae is a key strategy for disrupting the transmission chain of leprosy and preventing the potential onset of physical disabilities. Clinical diagnosis is essential, but some of the presented symptoms may go unnoticed, even by specialists. In areas of greater endemicity, serological and molecular tests have been performed and analyzed separately for the follow-up of household contacts, who are at high risk of developing the disease. The accuracy of these tests is still debated, and it is necessary to make them more reliable, especially for the identification of cases of leprosy between contacts. We proposed an integrated analysis of molecular and serological methods using artificial intelligence by the random forest (RF) algorithm to better diagnose and predict new cases of leprosy.

Methods

The study was developed in Governador Valadares, Brazil, a hyperendemic region for leprosy. A longitudinal study was performed, including new cases diagnosed in 2011 and their respective household contacts, who were followed in 2011, 2012, and 2016. All contacts were diligently evaluated by clinicians from Reference Center for Endemic Diseases (CREDEN-PES) before being classified as asymptomatic. Samples of slit skin smears (SSS) from the earlobe of the patients and household contacts were collected for quantitative polymerase chain reaction (qPCR) of 16S rRNA, and peripheral blood samples were collected for ELISA assays to detect LID-1 and ND-O-LID.

Results

The statistical analysis of the tests revealed sensitivity for anti-LID-1 (63.2%), anti-ND-O-LID (57.9%), qPCR SSS (36.8%), and smear microscopy (30.2%). However, the use of RF allowed for an expressive increase in sensitivity in the diagnosis of multibacillary leprosy (90.5%) and especially paucibacillary leprosy (70.6%). It is important to report that the specificity was 92.5%.

Conclusion

The proposed model using RF allows for the diagnosis of leprosy with high sensitivity and specificity and the early identification of new cases among household contacts.

Leprosy is a chronic infectious disease caused by Mycobacterium leprae (M. leprae) that can infect cells in the skin and nerves. Despite efforts to eliminate leprosy, the number of M. leprae infected individuals who develop leprosy is still substantial in the world. The diagnosis relies mainly on clinical parameters. Histopathological and bacteriological analysis help to classify clinical forms of patients. Serology and polymerase chain reaction (PCR) assays are claimed by health professionals as auxiliary tools, but until now these tests have been used almost exclusively in research, with minor use in leprosy reference centers throughout Brazil. Here, we tested quantitative PCR (qPCR) designed to amplify specific M. leprae targets and ELISA assays to detect antibody response to recombinant antigens (LID-1, ND-O-LID). All results were analyzed by multivariate analysis based in artificial intelligence. We chose random forest as a classification algorithm to aid in the diagnosis and the monitoring of contacts. The results allowed us to diagnose cases of leprosy with high sensitivity and specificity and the early identification of new cases among household contacts.