Pathogen-Specific Epitopes as Epidemiological Tools for Defining the Magnitude of <em>Mycobacterium leprae</em> Transmission in Areas Endemic for Leprosy

<div><p>During recent years, comparative genomic analysis has allowed the identification of <em>Mycobacterium leprae</em>-specific genes with potential application for the diagnosis of leprosy. In a previous study, 58 synthetic peptides derived from these sequences were tested for their ability to induce production of IFN-γ in PBMC from endemic controls (EC) with unknown exposure to <em>M. leprae</em>, household contacts of leprosy patients and patients, indicating the potential of these synthetic peptides for the diagnosis of sub- or preclinical forms of leprosy. In the present study, the patterns of IFN-γ release of the individuals exposed or non-exposed to <em>M. leprae</em> were compared using an Artificial Neural Network algorithm, and the most promising <em>M. leprae</em> peptides for the identification of exposed people were selected. This subset of <em>M. leprae</em>-specific peptides allowed the differentiation of groups of individuals from sites hyperendemic for leprosy versus those from areas with lower level detection rates. A progressive reduction in the IFN-γ levels in response to the peptides was seen when contacts of multibacillary (MB) patients were compared to other less exposed groups, suggesting a down modulation of IFN-γ production with an increase in bacillary load or exposure to <em>M. leprae</em>. The data generated indicate that an IFN-γ assay based on these peptides applied individually or as a pool can be used as a new tool for predicting the magnitude of <em>M. leprae</em> transmission in a given population.</p>