Cutaneous leishmaniasis (CL), caused by Leishmania braziliensis, is closely associated with a severe form of the disease, indicated by a positive Leishmania skin test (LST) that assesses and reflects the presence of immune T cells specific to Leishmania antigens. In this study, we compare the clinical, immunologic, and histopathologic features between Leishmania skin test-positive (LST+) and Leishmania skin test-negative (LST-) in CL. Compared to LST+ patients, LST- patients had larger lesions and had been sicker for longer, presented with more instances of therapeutic failure with meglumine antimonate, (MA) and the healing times were higher than LST+. While granulomas were less frequent and the parasite load was higher in LST-, there were more CD8+ T cells and an enhanced production of Granzyme B in the supernatants of biopsies from LST- subjects. This study shows that in LST-, an impairment in Th1 immune response is associated with a high parasite burden, and the pathology is mediated by CD8+ T cells and the enhanced production of Granzyme B. The abnormalities in the immunologic response in LST- patients lead to a more severe disease with a high rate of failure to therapy.
