Salivary anti-PGL-1 IgM may indicate active transmission of Mycobacterium leprae among young people under 16 years of age

Detection of Mycobacterium leprae DNA in clinical and environmental samples using serological analysis and PCR

BACKGROUND

Leprosy is a chronic infectious disease caused by Mycobacterium leprae and persists as a serious public health problem in Brazil. This microorganism is inculturable, making it difficult to diagnose and elucidate details of its transmission chain. Thus, this study aimed to analyze the dynamics of environmental transmission of M. leprae in a case-control study in the city of Mossoró, Brazil.

METHODS AND RESULTS

Data of clinical, epidemiological, bacilloscopic, and serological evaluation of 22 newly diagnosed patients were compared, with molecular results of detection of specific genome regions RLEP and 16S rRNA of M. leprae in samples of the nasal swab, saliva, and house dust of these individuals and their controls (44 household contacts and 44 peridomiciliar contacts). The rapid serological tests evaluated, ML flow (IgM ND-O-BSA) and OrangeLife® (IgM and IgG anti NDO-LID 1) showed similar results, with greater positivity among paucibacillaries by OrangeLife® (54.5%). Positivity for nasal swab and saliva in multibacillary patients with RLEP primer was 16.7% and 33.3%, respectively. There was no detection of bacterial DNA in house dust or among paucibacillaries. The OrangeLife® test indicated that the lower the amount of windows, the more transmission in the house (3.79 more chances). Having a history of leprosy cases in the family increased the risk by 2.89 times, and being over 60 years of age gave 3.6 times more chances of acquiring the disease. PCR positivity was higher among all clinical samples using the M. leprae RLEP region than 16S rRNA.

CONCLUSIONS

In this study, the serological and PCR analysis were capable of detecting M. leprae DNA in clinical samples but not in the environmental samples. Close monitoring of patients and household contacts appears an effective measure to reduce the transmission of leprosy in endemic areas.

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.

In search of biomarkers for leprosy by unraveling the host immune response to Mycobacterium leprae

Mycobacterium leprae, the causative agent of leprosy, is still actively transmitted in endemic areas reflected by the fairly stable number of new cases detected each year. Recognizing the signs and symptoms of leprosy is challenging, especially at an early stage. Improved diagnostic tools, based on sensitive and specific biomarkers, that facilitate diagnosis of leprosy are therefore urgently needed. In this review, we address the challenges that leprosy biomarker research is facing by reviewing cell types reported to be involved in host immunity to M leprae. These cell types can be associated with different possible fates of M leprae infection being either protective immunity, or pathogenic immune responses inducing nerve damage. Unraveling these responses will facilitate the search for biomarkers. Implications for further studies to disentangle the complex interplay between host responses that lead to leprosy disease are discussed, providing leads for the identification of new biomarkers to improve leprosy diagnostics.

Serum Anti-PGL-1 IgG, IgM, and IgA in a 3-Year Follow-up Study of 4-15-Year-old Leprosy Contacts

BACKGROUND

In 2015, the detection rate of leprosy in Santana do Ipanema municipality, Alagoas state, Brazil, was 39.3 cases per 100,000 inhabitants, and among young people below 15 years of age, it was 32.8 cases per 100,000 inhabitants.

MATERIAL AND METHODS

A prospective study was carried out from 2015 to 2017, in Santana do Ipanema city, with 69 leprosy contacts in the age group of 4-15 years. Measurement of serum IgM, IgG, and IgA against phenolic glycolipid antigen-1 (PGL-1) was done by an indirect enzyme-linked immunosorbent assay.

RESULTS

A high frequency of positive anti-PGL-1 IgM was found in both paucibacillary and multibacillary contacts. Twenty-three participants presented suspected lesions and 45 did not. In both groups a high frequency of positive IgM was found. In regard to anti-PGL-1 IgG, it was found a strong association between its positivity and the presence of lesions (relative risk of 3.25). Eight new cases of leprosy were diagnosed, five of which were seropositive for anti-PGL-1. Again, a striking association was found between positive IgG and leprosy (relative risk of 8.5). No significant association was found between IgM isotype and disease, nor between IgA and disease.

CONCLUSIONS

The present study reinforces the importance of measuring the three anti-PGL-1 isotypes in follow-up studies of leprosy contacts. Moreover, positive anti-PGL-1 IgG is associated with a high associated risk of disease.

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.