Mycobacterium leprae DNA in peripheral blood may indicate a bacilli migration route and high-risk for leprosy onset

Abstract

Leprosy epidemiological studies have been restricted to Mycobacterium leprae DNA detection in nasal and oral mucosa samples with scarce literature on peripheral blood. We present the largest study applying quantitative real‐time PCR (qPCR) for the detection of M. leprae DNA in peripheral blood samples of 200 untreated leprosy patients and 826 household contacts, with results associated with clinical and laboratory parameters. To detect M. leprae DNA a TaqMan qPCR assay targeting the M. leprae ML0024 genomic region was performed. The ML0024 qPCR in blood samples detected the presence of bacillus DNA in 22.0% (44/200) of the leprosy patients: 23.2% (16/69) in paucibacillary (PB), and 21.4% (28/131) in multibacillary (MB) patients. Overall positivity among contacts was 1.2% (10/826), with similar percentages regardless of whether the index case was PB or MB. After a follow‐up period of 7 years, 26 contacts have developed leprosy. Comparing the results of healthy contacts with those that become ill, ML0024 qPCR positivity at the time of diagnosis of their index case represented an impressive 14.78‐fold greater risk for leprosy onset (95% CI 3.6–60.8; p <0.0001). In brief, contacts with positive PCR in blood at diagnosis of index cases are at higher risk of later leprosy onset and this marker might be combined with other prognostic markers for management of contacts, which requires further studies.

Risk-benefit assessment of Bacillus Calmette-Guérin vaccination, anti-phenolic glycolipid I serology, and Mitsuda test response: 10-year follow-up of household contacts of leprosy patients

“…Paucibacillary (PB) patients usually display positive reactions (13) . For the HHCs of leprosy patients, a strong positive response to the Mitsuda test is associated with increased protection against the disease (14) (15) .…”

Asymptomatic Leprosy Infection among Blood Donors May Predict Disease Development and Suggests a Potential Mode of Transmission

“…The success of a leprosy control program must be supported by prevention, early diagnosis, treatment, and interruption of transmission. Hence, we underscore our previous recommendation for the adoption of chemoprophylaxis as a disease prevention strategy and to promote clearance of bacilli in close contacts of leprosy patients and in those with asymptomatic infection, consequently disrupting transmission of the disease (3,5,7).…”

“…It has recently been suggested that whole-blood nested-PCR amplification could be used for early diagnosis of leprosy (6) and that the presence of M. leprae DNA in peripheral blood may be associated with bacillary migration and a high risk for disease onset (7).…”

Presence of Mycobacterium leprae DNA and PGL-1 antigen in household contacts of leprosy patients from a hyperendemic area in Brazil

“…Additionally, contacts of leprosy patients that are positive for anti-PGL-1 have a 6-fold higher risk of illness compared to healthy individuals (Goulart et al, 2007). This reinforces that contacts carrying DNA sequences of M. leprae in high endemic areas may be involved in the disease transmission chain Job et al, 2008;Martinez et al, 2011;Reis et al, 2014).…”

“…Few studies have demonstrated association between DNA positivity and leprosy risk (Reis et al, 2014). However, it is necessary to monitor positive contacts for a minimum of 5 years over the incubation time of M. leprae in the host.…”