Increased Immunoglobulin G Anti-Paracoccidioides brasiliensis Serum Antibody Avidity as a Predictor of Favorable Posttherapeutic Evolution in Paracoccidioidomycosis

Paracoccidioidomycosis is endemic in Latin America, and ca. 80% of all cases occur in Brazil. Little is known about antibody avidity or the evolution of such avidity in the posttherapeutic period for the different clinical presentations of the disease. In the present study, we evaluated 53 patients with paracoccidioidomycosis and calculated the avidity index. Medium- and high-avidity antibodies were found in 79.5% of patients with chronic presentation (n = 39). Among patients with the acute form (n = 14), 57.1% of the antibodies presented low avidity. In the posttherapeutic period, there was a significant increase in antibody avidity in patients presenting with the chronic multifocal form. In our preliminary study, which needs to be confirmed using a larger number of samples, the optimized method for studying antibody avidity detected differences among the clinical presentations of the mycosis and indicated the value of the avidity index as a marker of posttherapeutic evolution of patients with a multifocal chronic form of the disease.Paracoccidioidomycosis is an important public health problem and one of the leading causes of occupational disease in Brazil (2). The disease can be classified according to the International Colloquium on Paracoccidioidomycosis (5) as an infection, acute form, chronic multifocal form, chronic unifocal form, and sequelae. The study of antibody avidity has been widely used in the diagnosis of infectious diseases, especially to differentiate between acute and chronic infections (6). In paracoccidioidomycosis, little is known about antibody avidity or the evolution of such avidity in the different clinical forms of the disease. The objective of the present study was to evaluate a method for the study of the avidity of immunoglobulin G (IgG) anti-Paracoccidioides brasiliensis antibodies in serum and to determine the value of the avidity evolution in the posttherapeutic period. To the best of our knowledge, this is the first time that such avidity has been investigated in the different clinical presentations of paracoccidioidomycosis.