Epidemiologic and immunologic findings for the subclinical form of Leishmania braziliensis infection.

The epidemiologic and immunologic findings for 104 subjects with subclinical Leishmania braziliensis infection were compared with those for 29 patients with cutaneous leishmaniasis (CL) from the same area of endemicity. Subjects had a positive leishmania skin test result and remained asymptomatic during the next 4 years of follow-up were considered to have subclinical infection. Patients with CL were younger, had larger-diameter indurations after skin testing, and were more likely to have positive serologic markers than were those with subclinical infection (P<.05). In subjects with subclinical infection, levels of interferon-gamma and tumor necrosis factor-alpha in lymphocyte supernatants were lower than they were in patients with CL (P<.05); however, mean interleukin-5 levels were slightly higher in patients with subclinical infection than in patients with CL. These data indicate that, unlike patients with CL, individuals who do not develop disease when infected with L. braziliensis may have the ability to modulate their immune response.