Despite efforts for its elimination as a public health problem, leprosy remains highly prevalence in some countries, including Brazil, specially in the state of Pará, which accounts for approximately 10% of the 400,000 new cases in Brazil during the last 10 years. To date, there is no diagnostic test to detect leprosy in its early stages, thus contributing to the maintenance of high rates of disease incidence. In this sense, the Discovery of new specific antigens of M. leprae to enable the development of new diagnostic methods may facilitate early detection of disease prior to the onset of disfigurement and nerve damage and contribute to achieving the goals of leprosy control. In this study, dermatological clinical evaluation of the participants was performed to detect new cases and blood samples were collected for antibody screening at two different timpoints, T1 (2011) and T2 (2013), two years apart. IgM anti-ND-O-BSA and IgG anti-LID-1 titers were detected by ELISA, and anti-IgM and anti-IgG were combined for detection of both in plasma samples by ELISA or also the whole blood by OrangeLife® (OL) rapid test in 79 leprosy patients, 131 household contacts and 331 students from the municipality of Breves, Pará State. Samples collected at T1 showed a high number of new cases detected, with 18.6% of household contacts and 6.1% of students diagnosed, while two years later at T2, there were 19.8% of household contacts and 9.4% of students diagnosed. At T2, 44.3% of contacts were positive for anti-ND-O-BSA, 7.8% for anti-LID-1 and 37.4% for anti-NDO-LID. Mong the students 49.5% were positive for anti-ND-O-BSA, 5.1% for anti-LID-1 and 37% for anti-NDO-LID. The association between antigens showed a strong correlation to ND-O-BSA and NDO-LID. Positivity of the OL rapide test was 44.3% for newly diagnosed MB cases (BT majority), in students was 47.4% and 36.3% in household contacts, with poor agreement with ELISA anti-NDO-LID. At follow-up (T2), the percentage of new cases was 35% and the largest number was identified among individuals positive for anti-ND-O-BSA. The data show a high incidence in contacts and students through active search and serologic follow-up, and we concluded that the antigen ND-O-BSA was more sensitive in the ELISA assay for identifying new cases in populations endemic.
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