Identifying promising peptide targets for leprosy serological tests: From prediction to ELISA

Leprosy remains a significant health concern, particularly in India, Brazil, and Indonesia. Early diagnosis is essential to prevent complications, highlighting the need for improved diagnostic tools. This study aimed to identify novel Mycobacterium leprae antigens and assess their effectiveness against human sera through immunotools for antibody response evaluation. Using bioinformatics, we predicted B-cell epitopes in M. leprae, which were chemically synthesized and tested via dot blotting with sera from leprosy patients, tuberculosis patients, and healthy controls. Promising peptides underwent further analysis through ELISA using 465 serum samples from leprosy patients, household contacts, and healthy controls across Brazil. The samples were also tested against known antigens HSA-NDO, LID-1, and NDO-LID. A total of 102 epitope sequences were generated, of which eight (PEP1 to PEP8) demonstrated the ability to differentiate between individuals with and without exposure to M. leprae. The results of the ELISA test exhibited statistically significant differences in absorbance responses between the experimental groups for the novel synthetic peptides (p < 0.05). PEP3, PEP4, and PEP5 demonstrated the most favorable outcomes, with values of the area under the receiver operating characteristic curve (AUC) of 0.9759, 0.9796 and 0.9551 respectively in the comparison of healthy controls with household contacts, and 0.8257, 0.7945, and 0.7961 comparing the same controls with patients. Furthermore, the synthetic peptides demonstrated superior sensitivity, specificity, and AUC compared to HSA-NDO, LID-1, and NDO-LID. The identified peptides showed significant responses in samples from patients and household contacts (HHC), indicating their potential for tracing exposure to M. leprae bacilli. These novel synthetic peptides could enhance the sensitivity of rapid diagnostic tests for leprosy, facilitating early detection of the infection. This could help prevent disease progression and interrupt transmission.