Serologic characterization of Paracoccidioides brasiliensis E2 antigen.

1. The behavior of the specific E2 antigen of Paracoccidioides brasiliensis was studied by agarose gel counterimmunoelectrophoresis. When the gel was read immediately after the electrophoretic run no precipitation band was visible. Visualization of the complex was possible only after incubation of the gel at room temperature overnight. 2. At alkaline pH, the E2 antigen migrates in the direction of the cathode, as do the immunoglobulins. The higher sensitivity of counterimmunoelectrophoresis when compared to double immunodiffusion for the diagnosis of paracoccidioidomycosis is due to the presence of antibodies directed against antigens which migrate to the anode. 3. The use of specific antiserum to E2 antigen as reference permits the double immunodiffusion method to be a very sensitive test for the specific serodiagnosis of paracoccidioidomycosis.