Uso de testes sorológicos e dosagem de quimiocinas: contribuições para a vigilância de contatos de casos de hanseníase

Abstract

The effective control of the leprosy transmission chain is dependent on actions such as the early identification of individuals infected with Mycobacterium leprae (M. leprae). The development and use of laboratory tests that may help in the identification of people exposed to M. leprae and at higher risk of illness can be useful in the surveillance of leprosy contacts. The aim of this study was to analyze the results of the synthetic anti-PGL-1 (NDO-HSA), anti-LID-1 and anti-NDO-LID tests, the serum levels of chemokines CCL2 and CXCL10, in cases of leprosy and their household and social contacts, and their contributions to contacts surveillance. This was an analytical cross-sectional study. Laboratory tests were performed using the immunoenzymatic method (ELISA). Serum samples from 21 leprosy cases, 35 household contacts (HC) and 145 social contacts (SC) residing in the city of Juiz de Fora - MG were analyzed. Data collection included the application of a questionnaire, venous blood sample collection and dermatoneurological evaluation, the latter being applied only to the contacts. The data were organized in the Open Data Kit Collect (ODK Collect) and analyzed using the Statistical Package for the Social Sciences (SPSS) 24 software for Windows, the R 3.4.2 software and the GraphPad Prism version 6. The results showed that, among the HC, the test with the highest number of positive results was the anti-NDO-HSA. Regarding the leprosy cases and SC, the greatest number of positive results was for anti-LID-1. In the bivariate analysis between the HC groups, the number of residents and number of rooms per resident was able to explain the difference in positivity for NDO-HSA and for NDO-LID, with the number of residents per room remaining significant for NDO-HSA after the logistic regression analysis. In the SC groups, the income and distance from the housing of the leprosy case explained the difference in positivity for NDO-HSA. It is noticed that in a region of low endemicity, the characteristics of housing and proximity to the index case significantly interfere in the exposure of individuals to M. leprae. When comparing the serum concentrations of chemokines, higher levels of CCL2 were observed in the contacts, compared to the cases; in addition, CCL2 presented a higher median related to the group of multibacillary (MB) cases, and contacts of MB cases, whereas CXCL10 had a higher median in the paucibacillary (PB) group. When assessing the relationship between chemokines and clinical characteristics, the highest rates of CCL2 in individuals not vaccinated with BCG stand out compared to those vaccinated. There was a positive correlation between the two chemokines, and between the three antigens. The combined evaluation of the results of the antigens, as well as the chemokines combined, can enhance the identification of contacts susceptible to illness. However, the simultaneous use of all tests can be a limitation for implementation in the routine of health services. In this way, the use of NDO-HSA and CCL2 is suggested in a region of low endemicity to identify individuals infected with M. leprae.