Use of anti-PGL-1 antibodies to monitor therapy regimes in leprosy patients

Field-friendly anti-PGL-I serosurvey in children to monitor Mycobacterium leprae transmission in Bihar, India

Background

It has been amply described that levels of IgM antibodies against Mycobacterium leprae (M. leprae) phenolic glycolipid I (PGL-I) correlate strongly with the bacterial load in an infected individual. These findings have generated the concept of using seropositivity for antibodies against M. leprae PGL-I as an indicator of the proportion of the population that has been infected. Although anti-PGL-I IgM levels provide information on whether an individual has ever been infected, their presence cannot discriminate between recent and past infections. Since infection in (young) children by definition indicates recent transmission, we piloted the feasibility of assessment of anti-PGL-I IgM seroprevalence among children in a leprosy endemic area in India as a proxy for recent M. leprae transmission.

Material and methods

A serosurvey for anti-PGL-I IgM antibodies among children in highly leprosy endemic villages in Bihar, India, was performed, applying the quantitative anti-PGL-I UCP-LFA cassette combined with low-invasive, small-volume fingerstick blood (FSB).

Results

Local staff obtained FSB of 1,857 children (age 3-11 years) living in 12 leprosy endemic villages in Bihar; of these, 215 children (11.58%) were seropositive for anti-PGL-I IgM.

Conclusion

The anti-PGL-I seroprevalence level of 11.58% among children corresponds with the seroprevalence levels described in studies in other leprosy endemic areas over the past decades where no prophylactic interventions have taken place. The anti-PGL-I UCP-LFA was found to be a low-complexity tool that could be practically combined with serosurveys and was well-accepted by both healthcare staff and the population. On route to leprosy elimination, quantitative anti-PGL-I serology in young children holds promise as a strategy to monitor recent M. leprae transmission in an area.

Detection and Monitoring of Mycobacterium leprae Infection in Nine Banded Armadillos (Dasypus novemcinctus) Using a Quantitative Rapid Test

Leprosy is an infectious disease caused by Mycobacterium leprae with tropism for skin and peripheral nerves. Incessant transmission in endemic areas is still impeding elimination of leprosy. Although detection of M. leprae infection remains a challenge in asymptomatic individuals, the presence of antibodies specific for phenolglycolipid-I (PGL-I) correlate with bacterial load. Therefore, serosurveillance utilizing field-friendly tests detecting anti-PGL-I antibodies, can be applied to identify those who may transmit bacteria and to study (reduction of) M. leprae transmission. However, serology based on antibody detection cannot discriminate between past and present M. leprae infection in humans, nor can it detect individuals carrying low bacillary loads. In humans, anti-PGL-I IgM levels are long-lasting and usually detected in more individuals than anti-PGL-I IgG levels. Inherent to the characteristically long incubation time of leprosy, IgM/IgG relations (antibody kinetics) in leprosy patients and infected individuals are not completely clear. To investigate the antibody response directly after infection, we have measured antibody levels by ELISA, in longitudinal samples of experimentally M. leprae infected, susceptible nine-banded armadillos (Dasypus novemcinctus). In addition, we assessed the user- and field-friendly, low-cost lateral flow assay (LFA) utilizing upconverting reporter particles (UCP), developed for quantitative detection of human anti-PGL-I IgM (UCP-LFA), to detect treatment- or vaccination-induced changes in viable bacterial load. Our results show that serum levels of anti-PGL-I IgM, and to a lesser extent IgG, significantly increase soon after experimental M. leprae infection in armadillos. In view of leprosy phenotypes in armadillos, this animal model can provide useful insight into antibody kinetics in early infection in the various spectral forms of human leprosy. The UCP-LFA for quantitative detection of anti-PGL-I IgM allows monitoring the efficacy of vaccination and rifampin-treatment in the armadillo leprosy model, thereby providing a convenient tool to evaluate the effects of drugs and vaccines and new diagnostics.

Detection of anti-M. leprae antibodies in children in leprosy-endemic areas: A systematic review

BACKGROUND

Leprosy elimination primarily targets transmission of Mycobacterium leprae which is not restricted to patients' households. As interruption of transmission is imminent in many countries, a test to detect infected asymptomatic individuals who can perpetuate transmission is required. Antibodies directed against M. leprae antigens are indicative of M. leprae infection but cannot discriminate between active and past infection. Seroprevalence in young children, however, reflects recent M. leprae infection and may thus be used to monitor transmission in an area. Therefore, this literature review aimed to evaluate what has been reported on serological tests measuring anti-M. leprae antibodies in children without leprosy below the age of 15 in leprosy-endemic areas.

METHODS AND FINDINGS

A literature search was performed in the databases Pubmed, Infolep, Web of Science and The Virtual Health Library. From the 724 articles identified through the search criteria, 28 full-text articles fulfilled all inclusion criteria. Two additional papers were identified through snowballing, resulting in a total of 30 articles reporting data from ten countries. All serological tests measured antibodies against phenolic glycolipid-I or synthetic derivatives thereof, either quantitatively (ELISA or UCP-LFA) or qualitatively (ML-flow or NDO-LID rapid test). The median seroprevalence in children in endemic areas was 14.9% and was stable over time if disease incidence remained unchanged. Importantly, seroprevalence decreased with age, indicating that children are a suitable group for sensitive assessment of recent M. leprae infection. However, direct comparison between areas, solely based on the data reported in these studies, was impeded by the use of different tests and variable cut-off levels.

CONCLUSIONS

Quantitative anti-PGL-I serology in young children holds promise as a screening test to assess M. leprae infection and may be applied as a proxy for transmission and thereby as a means to monitor the effect of (prophylactic) interventions on the route to leprosy elimination.

Serological evidence of Toxoplasma gondii infection as potential risk for the development of lepromatous leprosy in an endemic area for both neglected tropical diseases in Brazil

Background

Mycobacterium leprae and Toxoplasma gondii infections are both neglected tropical diseases highly prevalent in Brazil. Infection with certain parasite species can significantly alter susceptibility to other important pathogens, and/or influence the development of pathology. Here we investigated the possible influence of M. leprae/T. gondii co-parasitism on the manifestation of leprosy and its clinical forms.

Methods

Participants (n = 291) were recruited in Campos dos Goytacazes city, Rio de Janeiro state, southeast Brazil, from August 2015 to December 2019 and clinically diagnosed for leprosy. Participants were selected based on the presence (patients) or absence (healthy controls) of the leprosy disease. Contacts of patients were also recruited for this study. Serum samples from patients (n = 199) with leprosy, contacts (n = 40) and healthy controls (n = 52) were investigated for levels of IgM and IgG anti-phenolic glycolipid-1 (PGL-1) by ELISA. Additionally, IgG antibody against soluble Toxoplasma antigen (STAg) was measured in sera samples from leprosy patients, contacts and healthy controls for Toxoplasma gondii serology by ELISA. Anti-PGL-1 IgG and IgM levels were compared using one-way ANOVA Kruskal-Wallis or Mann-Whitney, while Spearman test was used to correlate levels of IgG anti-STAg and IgM/IgG anti-PGL-1 from seropositive and seronegative individuals for T. gondii infection. The risk of T. gondii infection for leprosy disease was assessed using Fisher’s test.

Results

Levels of IgM anti-PGL-1 antibodies were significantly higher in multibacillary (MB) patients compared to paucibacillary (PB) patients (P = 0.0068). Higher IgM and IgG levels anti-PGL-1 were detected in patients with the lepromatous forms. The serologic prevalence for T. gondii infection was 74.9%. We detected increased anti-STAg antibody levels in leprosy patients (79.4%), reaching 88.8% within those with lepromatous form of this disease. The leprosy risk increase in T. gondii seropositive individuals was two-fold (odds ratio [OR] = 2.055; 95% confidence intervals [95% CI]: 1.18–3.51) higher than those seronegative, and considering the lepromatous leprosy risk this increase was even dramatic (OR = 4.33; 95% CI: 1.76–9.69) in T. gondii seropositive individuals. Moreover the leprosy risk in T. gondii seropositive individuals was weakly correlated to the levels of IgG anti-STAg and IgM/IgG anti-PGL-1.

Conclusions

Altogether, our results suggest that T. gondii infection may exert immunomodulatory properties that influence to the susceptibility of leprosy, mainly on its more severe clinical form. A better understanding of parasite immunomodulation can ultimately contribute to the development of medical applications.

Recent Laboratory Advances in Diagnostics and Monitoring Response to Treatment in Leprosy

The present review briefly summarizes the highlights of the recent advances in Mycobacterium leprae-specific tests for early diagnosis of leprosy. In addition to establishing the diagnosis of clinical cases of leprosy, these tests have also been used to detect subclinical infections in endemic population. Several attempts have been made from 1980 onward for standardization of specific diagnostic assays for early detection of leprosy. Brief account about the development and use of these assays has been described in this review article.

Serum anti-phenolic glycolipid-1 IgA correlates to IgM isotype in leprosy patients: a possible candidate for seroepidemiological surveys?

OBJECTIVE

The aim of this study was to compare serum anti-phenolic glycolipid-1 IgA, IgG, and IgM levels in leprosy patients and controls.

METHOD

Analysis of anti-PGL-1 IgA, IgG, or IgM in serum samples from multibacillary (MB, n=32) and paucibacillary (PB, n=22) leprosy patients, and in non-endemic controls (n=17), using an indirect enzyme-linked immunosorbent assay.

RESULTS

A strong correlation between serum IgM and IgA isotypes was found (r=.745, P<.0001) in MB patients. A moderate correlation was found in all analyses in PB patients. A moderate agreement was found between anti-PGL1 IgA and IgM tests. Based on the ROC curves, the cut-off values were selected and the parameters of validation were calculated. Considering the clinical forms altogether, the diagnostic sensitivities were 50.0% for IgA, 22.2% for IgG, and 74.1% for IgM. The positive (VPP) and negative (VPN) predictive values were estimated for each isotype. For IgA, the VPP and VPN were, respectively, 100.0% (87.0%-100.0%; 95% confidence interval) and 38.7% (24.4%-54.5%); for IgG, 100% (87.0%-100.0%) and 28.8% (17.8%-42.1%), respectively; and for IgM, 95.2% (83.8%-99.4%) and 51.7% (32.5%-70.6%), respectively.

CONCLUSION

Despite the limiting factors, anti-PGL1 IgA correlates to IgM levels and it could be considered as a possible laboratorial tool to be also used, for instance, in serological follow-up studies.

Anti-PGL1 salivary IgA/IgM, serum IgG/IgM, and nasal Mycobacterium leprae DNA in individuals with household contact with leprosy

OBJECTIVES

Leprosy household contacts represent a group at high risk of developing the disease. The aim of this study was to detect Mycobacterium leprae subclinical infection in this group through serological and molecular parameters.

METHODS

Serum anti-PGL1 IgG/IgM and salivary anti-PGL1 IgA/IgM was investigated using an ELISA, and nasal carriage of M. leprae DNA was detected by PCR, in leprosy household contacts of paucibacillary (PB) and multibacillary (MB) household leprosy patients (n=135), their index cases (n=30), and in persons living in a low endemic city (n=17).

RESULTS

Salivary anti-PGL1 IgA and IgM and serum anti-PGL1 IgG showed good correlation comparing contacts and index cases (p<0.01, p<0.005, and p<0.0001, respectively). This was not observed for serum anti-PGL1 IgM (p>0.05). A high frequency of anti-PGL1 IgM positivity was found in IgG-negative samples (p<0.0001). For IgG-positive samples, IgM antibodies were also positive in most of the samples. None of the 17 volunteers living in a low endemic city presented seropositivity for IgG; however, two of them showed positivity for anti-PGL1 IgM. M. leprae DNA was found in the nasal swabs of nine out of the 85 MB household leprosy contacts (10.6%) and in three out of the 50 PB household leprosy contacts (6.0%).

CONCLUSION

We strongly suggest that serum IgG/IgM and salivary anti-PGL1 IgA/IgM measurements are used to follow leprosy household contacts.

Primary neural leprosy: systematic review

The authors proposed a systematic review on the current concepts of primary neural leprosy by consulting the following online databases: MEDLINE, Lilacs/SciELO, and Embase. Selected studies were classified based on the degree of recommendation and levels of scientific evidence according to the “Oxford Centre for Evidence-based Medicine”. The following aspects were reviewed: cutaneous clinical and laboratorial investigations, i.e. skin clinical exam, smears, and biopsy, and Mitsuda's reaction; neurological investigation (anamnesis, electromyography and nerve biopsy); serological investigation and molecular testing, i.e. serological testing for the detection of the phenolic glycolipid 1 (PGL-I) and the polymerase chain reaction (PCR); and treatment (classification criteria for the definition of specific treatment, steroid treatment, and cure criteria).

Clinical and immunological evaluation after BCG-id vaccine in leprosy patients in a 5-year follow-up study

INTRODUCTION

The use of bacillus Calmette-Guérin (BCG) has long been considered a stimulus for immune reactivity in leprosy household contacts. Probably, the combination of multidrug therapy with BCG could facilitate the clearance of leprosy bacilli in the host, reduce relapse rates, and shorten the duration of skin-smear positivity.

METHODS

To investigate the mechanism of action of BCG, a study involving 19 leprosy patients, eleven multibacillary (MB) and eight paucibacillary, was performed to assess the in vitro production of interleukin (IL)-10, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, IL-6, and IL-17 in the supernatant of peripheral blood mononuclear cells, before and 30 days after inoculation with BCG intradermally (BCG-id). Peripheral blood mononuclear cells isolated by Ficoll-Hypaque gradient were cultivated with Concanavalin-A (Con-A), lipopolysccharides (LPS), or BCG. The supernatant was collected for ELISA quantification of cytokines. The immunohistochemistry of IFN-γ, IL-1, IL-10, IL-12, transforming growth factor (TGF)-β, and TNF-α was carried out in biopsies of skin lesions of leprosy patients before and 30 days after inoculation of BCG-id. These patients were followed up for 5 years to assess the therapeutic response to multidrug therapy, the occurrence of leprosy reactions, and the results of bacterial index and anti-PGL-1 serology after the end of treatment.

RESULTS

The results showed increased production of cytokines after BCG-id administration in MB and paucibacillary leprosy patients. There was statistically higher levels of TNF-α (P = 0.017) in MB patients and of IL-17 (P = 0.008) and IFN-γ (P = 0.037) in paucibacillary patients. Immunohistochemical staining, especially for TNF-α, was more intense in biopsies of MB leprosy patients taken after BCG-id administration, probably for induction of innate human immunity. The clinical evaluation suggests that BCG-id is able to induce a more effective therapeutic response, with reduction of the number and the intensity of leprosy reactions.

CONCLUSION

These results suggest that BCG-id induces activation of the initial phase of immunocellular activity: innate human immunity (increase in TNF-α, IL-12 and macrophage activation). Therefore, we conclude that the use of BCG-id could be indicated as an adjuvant to multidrug therapy in treatment of leprosy patients.

Early detection of leprosy by examination of household contacts, determination of serum anti-PGL-1 antibodies and consanguinity

A cross-sectional clinical trial in which the serum anti-phenolic glycolipid (anti-PGL-1) antibodies were analysed in household contacts (HHC) of patients with leprosy as an adjunct early leprosy diagnostic marker was conducted. The families of 83 patients underwent clinical examination and serum anti-PGL1 measurement using enzyme-linked immunosorbent assay. Of 320 HHC, 98 were contacts of lepromatous leprosy (LL), 80 were contacts of borderline lepromatous (BL), 28 were contacts of borderline (BB) leprosy, 54 were contacts of borderline tuberculoid (BT), 40 were contacts of tuberculoid (TT) and 20 were contacts of indeterminate (I) leprosy. Consanguinity with the patients was determined for 232 (72.5%) HHC. Of those 232 contacts, 183 had linear consanguinity. Forty-nine HHC had collateral consanguinity. Fifty-eight contacts (18.1%) tested positive for anti-PGL1 antibodies. The number of seropositive contacts based on the clinical forms of the index case was 17 (29.3%) for LL, 15 (25.9%) for BL, one (1.7%) for BB, 14 (24.1%) for BT, three (5.2%) for TT and eight (13.7%) for I. At the one year follow-up, two (3.4%) of these seropositive contacts had developed BT leprosy. The results of the present study indicate that the serum anti-PGL-1 IgM antibody may be useful for evaluating antigen exposure and as a tool for an early leprosy diagnosis in HHC.

Mycobacterium leprae-host-cell interactions and genetic determinants in leprosy: an overview

Leprosy, also known as Hansen's disease, is a chronic infectious disease caused by Mycobacterium leprae in which susceptibility to the mycobacteria and its clinical manifestations are attributed to the host immune response. Even though leprosy prevalence has decreased dramatically, the high number of new cases indicates active transmission. Owing to its singular features, M. leprae infection is an attractive model for investigating the regulation of human immune responses to pathogen-induced disease. Leprosy is one of the most common causes of nontraumatic peripheral neuropathy worldwide. The proportion of patients with disabilities is affected by the type of leprosy and delay in diagnosis. This article briefly reviews the clinical features as well as the immunopathological mechanisms related to the establishment of the different polar forms of leprosy, the mechanisms related to M. leprae-host cell interactions and prophylaxis and diagnosis of this complex disease. Host genetic factors are summarized and the impact of the development of interventions that prevent, reverse or limit leprosy-related nerve impairments are discussed.

Recent advances in leprosy and Buruli ulcer (Mycobacterium ulcerans infection)

PURPOSE OF REVIEW

After tuberculosis, leprosy (Mycobacterium leprae) and Buruli ulcer (M. ulcerans infection) are the second and third most common mycobacterial infections in humankind, respectively. Recent advances in both diseases are summarized.

RECENT FINDINGS

Leprosy remains a public health problem in some countries, and new case detections indicate active transmission. Newly identified M. lepromatosis, closely related to M. leprae, may cause disseminated leprosy in some regions. In genome-wide screening in China, leprosy susceptibility associates with polymorphisms in seven genes, many involved with innate immunity. World Health Organization multiple drug therapy administered for 1 or 2 years effectively arrests disseminated leprosy but disability remains a public health concern. Relapse is infrequent, often associated with higher pretreatment M. leprae burdens. M. ulcerans, a re-emerging environmental organism, arose from M. marinum and acquired a virulence plasmid coding for mycolactone, a necrotizing, immunosuppressive toxin. Geographically, there are multiple strains of M. ulcerans, with variable pathogenicity and immunogenicity. Molecular epidemiology is describing M. ulcerans evolution and genotypic variants. First-line therapy for Buruli ulcer is rifampin + streptomycin, sometimes with surgery, but improved regimens are needed.

SUMMARY

Leprosy and Buruli ulcer are important infections with significant public health implications. Modern research is providing new insights into molecular epidemiology and pathogenesis, boding well for improved control strategies.