Introduction: Among HIV-1-infected patients, CD4 + T cell counts are well-established markers of cell-mediated immunity. Delayed-type hypersensitivity (DTH) skin tests can be used to evaluate in vivo cell-mediated immunity to common antigens. Methods: DTH responses to tuberculin purified protein derivative (PPD), sporotrichin, trichophytin, candidin and streptokinase/streptodornase antigens were assessed. Thirty-six HIV-1-infected children/adolescents and 56 age-and sex-matched HIV-1/ HIV-2-seronegative participants were tested. All participants had a BCG scar. Fisher's exact test was used to evaluate significant differences between groups (p<0.05). Results: The main characteristics of the HIV-1 patients were as follows: median age 8.1 years; 20/36 were males; 35 were vertical transmission cases; 34 were AIDS cases under antiretroviral therapy; median viral load = 3.04 log10 copies/ml; median CD4 + T cell count = 701 cells/µl. A total of 25% (9/36) and 87.5% (49/56) of HIV-1-infected and healthy participants, respectively, displayed DTH reactivity to at least one antigen (p<0.001). Among HIV-1-infected participants, reactivity to candidin predominated (8/36, 22.2%), while PPD positivity prevailed among healthy participants (40/56, 71.4%). PPD reactivity in the HIV-1-positive group was 8.3% (p<0.01). The median PPD induration was 2.5mm (range: 2-5mm) in the HIV-1 group and 6.0 mm among healthy participants (range: 3-15mm). There was no correlation between PPD positivity and age. No correlation between CD4 + T cell counts and DTH reactivity was observed among HIV-1-infected patients. Conclusions: DTH skin test responses, including PPD reactivity, were significantly lower among HIV-1-infected participants compared to healthy controls, which likely reflects advanced disease and T cell depletion.

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