The role of IgM antiphenolic glycolipid-1 antibodies in assessing household contacts of leprosy patients in a low endemic area

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.

Leprosy serology using PGL-I: a systematic review

Serology using a species-specific antigen for Mycobacterium leprae, PGL-I, could be a marker for the bacterial load of patients with leprosy. Various studies have identified the potential use of serology in the classification of patients for treatment purposes, case monitoring, identification of the risk of relapse and selection of household contacts with a higher risk of contracting the disease. A systematic review of the literature was conducted and 26 articles were included in this comparative analysis. The results of the use of PGL-I serology in different situations, its limitations and possible applications were evaluated. Studies show the efficacy of PGL-I serology in the classification of patients, treatment monitoring and as a predictive test for leprosy reactions. To improve early diagnosis and follow-up of the population at greatest risk of developing leprosy, the methodologies used in the past have yet to show a favorable cost-benefit ratio, although studies indicate that the use of the test might positively influence leprosy control programs. With simple and robust techniques, the use of PGL-I serology is viable.

Association between leprosy reactions after treatment and bacterial load evaluated using anti PGL-I serology and bacilloscopy

Leprosy (Hansen's disease, HD) reactions are immune-inflammatory phenomena that occur during the evolution of the disease. Given the current criteria for treatment of the disease, this event is often observed after the patient has been released from treatment (RFT) from multi-drug therapy (MDT). A case-control study was conducted comparing laboratory results of cases of leprosy reactions after RFT from multibacillary MDT (MDT/MB) with a control group to analyze the possible association between posttreatment reactions and bacterial load using the ML Flow serological test for detection of antibodies to Mycobacterium leprae and the results of bacilloscopic skin smears. The study was conducted in two reference centers in Recife, Pernambuco State, Brazil, involving 208 patients. The results obtained indicate that posttreatment reaction is statistically associated with bacterial load through positive serology post-RFT. In conclusion, common risk factors exist between relapses and post-RFT reactions.