BACKGROUND There is a lack of straightforward tests for field application and known biomarkers for predicting leprosy
progression in infected individuals.
OBJECTIVE The aim was to analyse the response to infection by
Mycobacterium leprae
based on the reactivity of specific
antigens: natural disaccharide linked to human serum albumin via an octyl (NDOHSA), a semisynthetic phenolic glycolipid-I
(PGL-I); Leprosy Infectious Disease Research Institute Diagnostic-1 (LID-1) and natural disaccharide octyl - Leprosy Infectious
Disease Research Institute Diagnostic-1 (NDOLID).
METHODS The study population consisted of 130 leprosy cases diagnosed between 2010 and 2015 and 277 household contacts.
An enzyme-linked immunosorbent assay (ELISA) was used to analyse the reactivity of antibodies against NDOHSA, LID-1
and NDOLID. The samples and controls were tested in duplicate, and the antibody titer was expressed as an ELISA index. Data
collection was made by home visits with application of questionnaire and dermatological evaluation of all household contacts to
identify signs and symptoms of leprosy.
FINDINGS Significant differences in the median ELISA results were observed among leprosy cases in treatment, leprosy cases that
had completed treatment and household contacts. Higher proportions of seropositivity were observed in leprosy cases in treatment.
Seropositivity was also higher in multibacillary in relation to paucibacillary, with the difference reaching statistical significance.
Lower titers were observed among cases with a longer treatment time or discharge. For household contacts, the differences according
to the clinical characteristics of the leprosy index case were less pronounced than expected. Other factors, such as the endemicity
of leprosy, exposure outside the residence and genetic characteristics, appeared to have a greater influence on the seropositivity.
MAIN CONCLUSIONS Serologic tests could be used as auxiliary tools for determining the operational classification, in addition
to identifying infected individuals and as a strategy for surveillance of household contacts.
