Critical observation of WHO recommended multidrug therapy on the disease leprosy through mathematical study

Leprosy is a skin disease and it is characterized by a disorder of the peripheral nervous system which occurs due to the infection of Schwann cells. In this research article, we have formulated a four-dimensional ODE-based mathematical model which consists of the densities of healthy Schwann cells, infected Schwann cells, M. leprae bacteria, and the concentration of multidrug therapy (MDT). This work primarily aims on exploring the dynamical changes and interrelations of the system cell populations during the disease progression. Also, evaluating a critical value of the drug efficacy rate of MDT remains our key focus in this article so that a safe drug dose regimen for leprosy can be framed more effectively and realistically. We have examined the stability scenario of different equilibria and the occurrence of Hopf-bifurcation for the densities of our system cell populations with respect to the drug efficacy rate of MDT to gain insight on the precise impact of the efficiency rate on both the infected Schwann cell and the bacterial populations. Also, a necessary transversality condition for the occurrence of the bifurcation has been established. Our analytical and numerical investigations in this research work precisely explores that the process of demyelination, nerve regeneration, and infection of the healthy Schwann cells are the three most crucial factors in the leprosy pathogenesis and to control the M. leprae-induced infection of Schwann cells successfully, a more flexible version of MDT regime with efficacy rate varying in the range η∈(0.025,0.059) for 100-120 days in PB cases and 300 days in MB cases obtained in this research article should be applied. All of our analytical outcomes have been verified through numerical simulations and compared with some existing clinical findings.

Treatment and Evaluation Advances in Leprosy Neuropathy

Neuropathy and related disabilities are the major medical consequences of leprosy, which remains a global medical concern. Despite major advances in understanding the mechanisms of M. leprae entry into peripheral nerves, most aspects of the pathogenesis of leprosy neuropathy remain poorly understood. Sensory loss is characteristic of leprosy, but neuropathic pain is sometimes observed. Effective anti-microbial therapy is available, but neuropathy remains a problem especially if diagnosis and treatment are delayed. Currently there is intense interest in post-exposure prophylaxis with single-dose rifampin in endemic areas, as well as with enhanced prophylactic regimens in some situations. Some degree of nerve involvement is seen in all cases and neuritis may occur in the absence of leprosy reactions, but acute neuritis commonly accompanies both Type 1 and Type 2 leprosy reactions and may be difficult to manage. A variety of established as well as new methods for the early diagnosis and assessment of leprosy neuropathy are reviewed. Corticosteroids offer the primary treatment for neuritis and for subclinical neuropathy in leprosy, but success is limited if nerve function impairment is present at the time of diagnosis. A candidate vaccine has shown apparent benefit in preventing nerve injury in the armadillo model. The development of new therapeutics for leprosy neuropathy is greatly needed.

Mycobacterium leprae-Specific Antibodies in Multibacillary Leprosy Patients Decrease During and After Treatment With Either the Regular 12 Doses Multidrug Therapy (MDT) or the Uniform 6 Doses MDT

Leprosy serology reflects the bacillary load of patients and multidrug therapy (MDT) reduces Mycobacterium leprae-specific antibody titers of multibacillary (MB) patients. The Clinical Trial for Uniform Multidrug Therapy Regimen for Leprosy Patients in Brazil (U-MDT/CT-BR) compared outcomes of regular 12 doses MDT/R-MDT and the uniform 6 doses MDT/U-MDT for MB leprosy, both of regimens including rifampicin, clofazimine, and dapsone. This study investigated the impact of R-MDT and U-MDT and the kinetic of antibody responses to M. leprae-specific antigens in MB patients from the U-MDT/CT-BR. We tested 3,400 serum samples from 263 MB patients (R-MDT:121; U-MDT:142) recruited at two Brazilian reference centers (Dona Libânia, Fortaleza, Ceará; Alfredo da Matta Foundation, Manaus, Amazonas). Enzyme-linked immunosorbent assays with three M. leprae antigens [NT-P-BSA: trisaccharide-phenyl of phenollic glycolipid-I antigen (PGL-I); LID-1: Leprosy Infectious Disease Research Institute Diagnostic 1 di-fusion recombinant protein; and ND-O-LID: fusion complex of disaccharide-octyl of PGL-I and LID-1] were performed using around 13 samples per patient. Samples were collected at baseline/M0, during MDT (R-MDT:M1–M12 months, U-MDT:M1–M6 months) and after MDT discontinuation (first, second year). Statistical significance was assessed by the Mann–Whitney U test for comparison between groups (p values < 0.05). Mixed effect multilevel regression analyses were used to investigate intraindividual serological changes overtime. In R-MDT and U-MDT groups, males predominated, median age was 41 and 40.5 years, most patients were borderline lepromatous and lepromatous leprosy (R-MDT:88%, U-MDT: 90%). The bacilloscopic index at diagnosis was similar (medians: 3.6 in the R-MDT and 3.8 in the U-MDT group). In R-MDT and U-MDT groups, a significant decline in anti-PGL-I positivity was observed from M0 to M5 (p = 0.035, p = 0.04, respectively), from M6 to M12 and at the first and second year posttreatment (p < 0.05). Anti-LID-1 antibodies declined from M0 to M6 (p = 0.024), M7 to M12 in the R-MDT; from M0 to M4 (p = 0.003), M5 to M12 in the U-MDT and posttreatment in both groups (p > 0.0001). Anti-ND-O-LID antibodies decreased during and after treatment in both groups, similarly to anti-PGL-I antibodies. Intraindividual serology results in R-MDT and U-MDT patients showed that the difference in serology decay to all three antigens was dependent upon time only. Our serology findings in MB leprosy show that regardless of the duration of the U-MDT and R-MDT, both of them reduce M. leprae-specific antibodies during and after treatment. In leprosy, antibody levels are considered a surrogate marker of the bacillary load; therefore, our serological results suggest that shorter U-MDT is also effective in reducing the patients’ bacillary burden similarly to R-MDT.

Leprosy: current situation, clinical and laboratory aspects, treatment history and perspective of the uniform multidrug therapy for all patients

In this review, the most relevant and current epidemiological data, the main clinical, laboratory and therapeutical aspects of leprosy are presented. Detailed discussion of the main drugs used for leprosy treatment, their most relevant adverse effects, evolution of the therapeutic regimen, from dapsone as a monotherapy to the proposed polychemotherapy by World Health Organization (WHO) can be found in this CME. We specifically highlight the drug acceptability, reduction in treatment duration and the most recent proposal of a single therapeutic regimen, with a fixed six months duration, for all clinical presentations, regardless of their classification.

Uniform multidrug therapy for leprosy patients in Brazil (U-MDT/CT-BR): Results of an open label, randomized and controlled clinical trial, among multibacillary patients

Background

Leprosy control is based on early diagnosis and multidrug therapy. For treatment purposes, leprosy patients can be classified as paucibacillary (PB) or multibacillary (MB), according to the number of skin lesions. Studies regarding a uniform treatment regimen (U-MDT) for all leprosy patients have been encouraged by the WHO, rendering disease classification unnecessary.

Methodology and findings

An independent, randomized, controlled clinical trial conducted from 2007 to 2015 in Brazil, compared main outcomes (frequency of reactions, bacilloscopic index trend, disability progression and relapse rates) among MB patients treated with a uniform regimen/U-MDT (dapsone+rifampicin+clofazimine for six months) versus WHO regular-MDT/R-MDT (dapsone+rifampicin+clofazimine for 12 months). A total of 613 newly diagnosed, untreated MB patients with high bacterial load were included. There was no statistically significant difference in Kaplan-Meyer survival function regarding reaction or disability progression among patients in the U-MDT and R-MDT groups, with more than 25% disability progression in both groups. The full mixed effects model adjusted for the bacilloscopic index average trend in time showed no statistically significant difference for the regression coefficient in both groups and for interaction variables that included treatment group.

During active follow up, four patients in U-MDT group relapsed representing a relapse rate of 2.6 per 1000 patients per year of active follow up (95% CI [0·81, 6·2] per 1000). During passive follow up three patients relapsed in U-MDT and one in R-MTD. As this period corresponds to passive follow up, sensitivity analysis estimated the relapse rate for the entire follow up period between 2·9- and 4·5 per 1000 people per year.

Conclusion

Our results on the first randomized and controlled study on U-MDT together with the results from three previous studies performed in China, India and Bangladesh, support the hypothesis that UMDT is an acceptable option to be adopted in endemic countries to treat leprosy patients in the field worldwide.

Trial registration

ClinicalTrials.gov: NCT00669643

Since the introduction of multidrug therapy for leprosy in the 80’s, different classification criteria for leprosy patients have been proposed and treatment has been progressively shortened. Currently, leprosy patients are classified into paucibacillary/PB and multibacillary/MB based on the number of skins lesions. MB patients (over 5 skin lesions) receive three drugs (rifampicin, dapsone, clofazimine) for 12 months, while PB patients (up to 5 skin lesions) receive two drugs (rifampicin, dapsone) for 6 months. We conducted a randomized clinical trial to evaluate the efficacy of a uniform treatment (U-MDT) for both PB and MB leprosy patients, regardless any classification criteria. The current study includes results from: laboratory tests (bacilloscopic index/BI, serology and histopathology), clinical evaluation during a long follow-up, and uses adequate epidemiological analysis that gives robust evidence on main parameters used to evaluate the efficacy of U-MDT.

This study reports data among MB leprosy patients treated with regular/R-MDT and uniform/U-MDT regarding: (i) The frequency of leprosy reactions; (ii) BI decrease, (iii) Disability progression and (iv) Relapse. Overall, our results showed that there was no statistically significant difference in these outcomes for both treatment groups. In this sense, U-MDT can be considered as part of leprosy policy by control programs in endemic countries.

Whole genome sequencing distinguishes between relapse and reinfection in recurrent leprosy cases

BACKGROUND

Since leprosy is both treated and controlled by multidrug therapy (MDT) it is important to monitor recurrent cases for drug resistance and to distinguish between relapse and reinfection as a means of assessing therapeutic efficacy. All three objectives can be reached with single nucleotide resolution using next generation sequencing and bioinformatics analysis of Mycobacterium leprae DNA present in human skin.

METHODOLOGY

DNA was isolated by means of optimized extraction and enrichment methods from samples from three recurrent cases in leprosy patients participating in an open-label, randomized, controlled clinical trial of uniform MDT in Brazil (U-MDT/CT-BR). Genome-wide sequencing of M. leprae was performed and the resultant sequence assemblies analyzed in silico.

PRINCIPAL FINDINGS

In all three cases, no mutations responsible for resistance to rifampicin, dapsone and ofloxacin were found, thus eliminating drug resistance as a possible cause of disease recurrence. However, sequence differences were detected between the strains from the first and second disease episodes in all three patients. In one case, clear evidence was obtained for reinfection with an unrelated strain whereas in the other two cases, relapse appeared more probable.

CONCLUSIONS/SIGNIFICANCE

This is the first report of using M. leprae whole genome sequencing to reveal that treated and cured leprosy patients who remain in endemic areas can be reinfected by another strain. Next generation sequencing can be applied reliably to M. leprae DNA extracted from biopsies to discriminate between cases of relapse and reinfection, thereby providing a powerful tool for evaluating different outcomes of therapeutic regimens and for following disease transmission.

Leprosy reactions: The predictive value of Mycobacterium leprae-specific serology evaluated in a Brazilian cohort of leprosy patients (U-MDT/CT-BR)

Background

Leprosy reactions, reversal reactions/RR and erythema nodosum leprosum/ENL, can cause irreversible nerve damage, handicaps and deformities. The study of Mycobacterium leprae-specific serologic responses at diagnosis in the cohort of patients enrolled at the Clinical Trial for Uniform Multidrug Therapy Regimen for Leprosy Patients in Brazil/U-MDT/CT-BR is suitable to evaluate its prognostic value for the development of reactions.

Methodology

IgM and IgG antibody responses to PGL-I, LID-1, ND-O-LID were evaluated by ELISA in 452 reaction-free leprosy patients at diagnosis, enrolled and monitored for the development of leprosy reactions during a total person-time of 780,930 person-days, i.e. 2139.5 person-years, with a maximum of 6.66 years follow-up time.

Principal findings

Among these patients, 36% (160/452) developed reactions during follow-up: 26% (119/452) RR and 10% (41/452) had ENL. At baseline higher anti-PGL-I, anti-LID-1 and anti-ND-O-LID seropositivity rates were seen in patients who developed ENL and RR compared to reaction-free patients (p<0.0001). Seroreactivity in reactional and reaction-free patients was stratified by bacilloscopic index/BI categories. Among BI negative patients, higher anti-PGL-I levels were seen in RR compared to reaction-free patients (p = 0.014). In patients with 0<BI<3, (36 RR, 36 reaction-free), higher antibody levels to PGL-I (p = 0.014) and to LID-1 (p = 0.035) were seen in RR while difference in anti-ND-O-LID positivity was borderline (p = 0.052). Patients with BI≥3 that developed ENL had higher levels of anti-LID-1 antibodies (p = 0.028) compared to reaction-free patients. Anti-PGL-I serology had a limited predictive value for RR according to receiver operating curve/ROC analyses (area-under-the-curve/AUC = 0.7). Anti LID-1 serology at baseline showed the best performance to predict ENL (AUC 0.85).

Conclusions

Overall, detection of anti-PGL-I, anti-LID-1 and anti-ND-O-LID antibodies at diagnosis, showed low sensitivity and specificity for RR prediction, indicating low applicability of serological tests for RR prognosis. On the other hand, anti-LID-1 serology at diagnosis has shown prognostic value for ENL development in BI positive patients.

Trial Registration

ClinicalTrials.gov NCT00669643

Leprosy is a debilitating dermato-neurologic disease caused by Mycobacterium leprae. One of the main difficulties in the clinical management of leprosy patients is the development of leprosy reactions which are immune inflammatory episodes that can cause irreversible handicaps, incapacities and deformities. There are two major types of leprosy reactions: reversal reaction (RR) and erythema nodosum leprosum (ENL). Currently, there is no laboratory test able to predict the emergence of leprosy reactions among recently diagnosed patients. In order to investigate laboratory markers for the occurrence of leprosy reactions, we investigated the prognostic value of serologic responses to M. leprae antigens (PGL-I, LID-1, ND-O-LID) in 452 leprosy patients enrolled at the Clinical Trial for Uniform Multidrug Therapy Regimen for Leprosy Patients in Brazil/U-MDT/CT-BR. At diagnosis higher anti-PGL-I, anti-LID-1 and anti-ND-O-LID seropositivity rates were seen in patients who developed ENL and RR compared to reaction-free patients. The anti-PGL-I serology at diagnosis show low sensitivity to predict RR and anti-LID-1 serology at diagnosis has shown prognostic value for ENL development.

Can baseline ML Flow test results predict leprosy reactions? An investigation in a cohort of patients enrolled in the uniform multidrug therapy clinical trial for leprosy patients in Brazil

BACKGROUND

The predictive value of the serology to detection of IgM against the Mycobacterium leprae-derived phenolic glycolipid-I/PGL-I to identify leprosy patients who are at higher risk of developing reactions remains controversial. Whether baseline results of the ML Flow test can predict leprosy reactions was investigated among a cohort of patients enrolled in The Clinical Trial for Uniform Multidrug Therapy for Leprosy Patients in Brazil (U-MDT/CT-BR).

METHODS

This was a descriptive study focusing on the main clinical manifestations of leprosy patients enrolled in the U-MDT/CT-BR from March 2007 to February 2012 at two Brazilian leprosy reference centers. For research purposes, 753 leprosy patients were categorized according to a modified Ridley-Jopling (R&J) classification and according to the development of leprosy reactions (reversal reaction/RR and erythema nodosum leprosum/ENL), and whether they had a positive or negative bacillary index/BI.

RESULTS

More than half of the patients (55.5 %) reported leprosy reaction: 18.3 % (138/753) had a RR and 5.4 % (41/753) had ENL. Leprosy reactions were more frequent in the first year following diagnosis, as seen in 27 % (205/753) of patients, while 19 % (142/753) developed reactions during subsequent follow-up. Similar frequencies of leprosy reactions and other clinical manifestations were observed in paucibacillary (PB) and multibacillary (MB) leprosy patients treated with U-MDT and regular MDT (R-MDT) (P = 0.43 and P = 0.61, respectively). Compared with PB patients, leprosy reactions were significantly more frequent in MB patients with a high BI, and more patients developed RR than ENL. However, RR and neuritis were also reported in patients with a negative BI. At baseline, the highest rate of ML Flow positivity was observed in patients with a positive BI, especially those who developed ENL, followed by patients who had neuritis and RR. Among reaction-free patients, 81.9 % were ML Flow positive, however, the differences were not statistically significant compared to reactional patients (P = 0.45).

CONCLUSIONS

MB and PB patients treated with R-MDT and U-MDT showed similar frequencies of RR and other clinical manifestations. Positive ML Flow tests were associated with MB leprosy and BI positivity. However, ML Flow test results at baseline showed limited sensitivity and specificity for predicting the development of leprosy reactions.

Description of leprosy classification at baseline among patients enrolled at the uniform multidrug therapy clinical trial for leprosy patients in Brazil

The uniform multidrug therapy clinical trial, Brazil (U-MDT/CT-BR), database was used to describe and report the performance of available tools to classify 830 leprosy patients as paucibacillary (PB) and multibacillary (MB) at baseline. In a modified Ridley and Jopling (R&J) classification, considering clinical features, histopathological results of skin biopsies and the slit-skin smear bacterial load results were used as the gold standard method for classification. Anti-phenolic glycolipid-I (PGL-I) serology by ML Flow test, the slit skin smear bacterial load, and the number of skin lesions were evaluated. Considering the R&J classification system as gold standard, ML Flow tests correctly allocated 70% patients in the PB group and 87% in the MB group. The classification based on counting the number of skin lesions correctly allocated 46% PB patients and 99% MB leprosy cases. Slit skin smears properly classified 91% and 97% of PB and MB patients, respectively. Based on U-MDT/CT-BR results, classification of leprosy patients for treatment purposes is unnecessary because it does not impact clinical and laboratories outcomes. In this context, the identification of new biomarkers to detect patients at a higher risk to develop leprosy reactions or relapse remains an important research challenge.