Efeito da revacinação com BCG na detecção de anticorpos ANTI-PGL1 e do Mycobacterium leprae em contatos menores de 15 anos de pacientes com hanseníase

Abstract

The BCG vaccine given at birth is also used in leprosy contacts, without signs and / or symptoms of the disease, and with one or no vaccine scar. In Brazil, the protection conferred by BCG against leprosy varies from 20 to 80%. Brazil has 96% of the new leprosy cases in the Americas in individuals up to 15 years old, making this age group the subject of studies for early diagnosis. Serological investigation of anti-PGL1 antibody (Mycobacterium leprae wall phenolic glycolipid-1) and the real time qPCR for the detection of mycobacteria are used to diagnose leprosy, where its positivity demonstrates the risk of illness among contacts. The aim of this study was to evaluate whether BCG revaccination in contacts less than 15 years of leprosy patients modulates the production of anti-PGL1 IgG and IgM antibodies and the detection of Mycobacterium leprae by real time qPCR. Samples of peripheral blood and nasal swab of 40 contacts were collected before and 60 days after the 2nd dose of vaccine, distributed according to the operational classification of the index case (paucibacilar -BP and multibacillary-MB), gender, in two age groups (Up to 7 years and up to 7 years), and presence or absence of vaccine scar of the 1st dose of BCG. Serum anti-PGL1 IgG and IgM antibodies were measured by ELISA, in which the reactivity threshold was 1.3 (index obtained by the ratio of the O.D. average of the triplicate sample to the mean of the negative control serum pool). For the detection of Mycobacterium leprae by real time qPCR, DNA was obtained from whole blood and nasal swab. Before BCG, 52.5% of contacts were positive for anti-PGL1 IgM, which was not altered with revaccination (pre-BCG IgM vs. post-BCG, Spearman r = 0.9202). Only when the contacts were separated by age groups did it appear that subjects older than 7 years showed a higher positivity for pre-BCG IgM, whose difference between groups disappears after revaccination. IgG anti-PGL1 positivity was very low (2.5%), unrelated to the other variables. Only the group of contacts up to 7 years showed a significant increase in anti-PGL1 IgG levels after BCG (Wilcoxon, p = 0.028). Mycobacterium leprae was detected in only 5 samples of nasal swab before revaccination, whose subjects became negative after BCG. Four subjects were contacts from the same index case (one sibling and three cousins), indicating a genetic tendency to the presence of infection, which was controlled with the revaccination. This in turn did not modulate anti-PGL1 antibody levels, so it is debatable to use serology to assess Mycobacterium leprae infection in contacts up to 15 years of leprosy patients.