[Preparation and study of a Paracoccidioides antigen needed for skin tests]

A cellular antigen from Paracoccidioides brasiliensis, obtained from the supernate of the disrupted yeast phase, was studied. It was prepared by a method similar to that for obtaining the spherulin from Coccidioides immitis. This antigen is composed of 55 mug/mg of polysaccharides, determined by the phenol method, and 7-8 mug/mg of protein, determined by Folin-Ciocalteu's technique. In vitro tests of antigenicity were done by immunodiffusion and complement fixation. The optimum dilution of the antigen was 0-5 mg/ml determined by microtiter complement fixation. The in vivo standardization of the cellular paracoccidioidin was performed on three groups of patients. The first was composed of 56 patients with mycologically proved paracoccidioidomycosis. The disease was active in 32 and clinically healed in 24 of this group. The second was composed of 15 cases of histoplasmosis with strong histoplasmin skin tests. The third group were 70 patients with no mycotic pulmonary diseases who had come from different zones in Argentina. Each individual was injected with 0-1 ml cellular paracoccidioidin (3 mg/ml), 0-1 ml of Fava Netto's antigen diluted 1/10, and 0-1 ml histoplasmin L48, diluted 1/100. The cellular paracoccidioidin skin test was positive in 44/56 (78.5%) patients with paracoccidioidomycosis. The Fava Netto's antigen gave 42 (75%) positive results and the histoplasmin skin tests gave 28 (50%) in the same group. Twenty-eight (50%) presented positive histoplasmin skin tests. The paracoccidioidin skin test was positive in 2 of the histoplasmosis group (13-3%) and the Fava Netto's antigen gave 3 positive results in the same group (20%). The histoplasmin skin test was positive in 32% of the individuals with no mycotic disease. Ten per cent of these exhibited positive reaction with both P. brasiliensis antigens. Of those paracoccidioidomycosis cases (Group 1) who had negative skin tests with 3 mg/ml of the cellular paracoccidioidin 7/10 gave positive skin tests when tested at a concentration of 8 mg/ml. Characteristic changes of cell medicated hypersensitivity were observed in the histopathological studies of the cellular paracoccidioidin skin test.