Resumo:
Introduction: Cutaneous leishmaniasis (CL), caused by Leishmania braziliensis, is
characterized by an intense inflammatory response and the development of skin ulcers.
In endemic areas, exposed individuals may develop subclinical infection (SC),
effectively controlling the parasite without presenting clinical symptoms. Understanding
the immunological mechanisms involved in this response is crucial for improving
diagnostic and preventive strategies against CL. Objectives: To evaluate, after 13 years,
the clinical and immunological responses of household contacts of CL patients who
were previously identified as subclinically infected, comparing them to individuals with
active CL, endemic normals (EN), and healthy controls (HC). This study aimed to
identify immunological markers associated with protection in these
individuals.Materials and Methods: This was a prospective cohort study conducted in
Corte de Pedra, Bahia, Brazil, involving 308 household contacts followed since 2010.
Levels of IFN-γ, TNF, IL-1β, IL-6, and Granzyme B were measured in whole blood
cultures stimulated with soluble Leishmania antigen from 18 SC individuals. Cytokine quantification and antibody detection were performed using enzyme linked immunosorbent assay (ELISA). Statistical analyses included the Kruskal-Wallis
test, Mann-Whitney U test, and Spearman’s correlation. Results: During the follow-up
period, 57 individuals developed CL. The 18 SC individuals maintained IFN-γ
production after 13 years, although at lower levels compared to active CL patients.
TNF, IL-1β, IL-6, and Granzyme B production was also lower in SC individuals
compared to CL but higher than in EN and HC. No direct correlation was observed
between delayed-type hypersensitivity (DTH) and IFN-γ levels; however, 77.8% of
DTH-positive individuals exhibited detectable IFN-γ. Conclusion: SC individuals
exhibited a lower inflammatory response, which may contribute to the absence of
disease manifestation. Although a linear correlation between DTH positivity and IFN-γ
production was not observed, frequency analysis revealed a significant association
between these variables. This indicates that IFN-γ is frequently produced in DTH positive individuals but can also be produced independently of DTH responses in some
cases.
