EVALUATION OF RISK AND DIAGNOSTIC-VALUE OF QUANTITATIVE ASSAYS FOR ANTITOXOPLASMA GONDII IMMUNOGLOBULIN-A (IGA), IGE, AND IGM AND ANALYTICAL STUDY OF SPECIFIC IGG IN IMMUNODEFICIENT PATIENTS

To determine their prognostic and diagnostic values for toxoplasmosis in immunodepressed subjects, we assayed immunoglobulin A (IgA) and IgE antibodies bw means of immunocapture (IC) tests, with revelation done by using a suspension of T. gondii (ICT). We also carried out a simul taneous analytical study of IgG antibodies on cellulose acetate membra nes by using the comparative immunological profile method and an enzym e-linked immunofiltration assay (ELIFA). A total of 1,238 samples (ser um, cerebrospinal fluid, and aqueous humor from 318 patients) were tes ted. IgA and IgE antibodies were detected in all heart, kidney, and li ver transplant recipients with clinical manifestations of toxoplasmosi s; IgG was detected in the aqueous humor of a patient with chorioretin itis. In patients with AIDS-related toxoplasmosis, including the cereb ral form, IgA and IgE antibodies or a significant modification of ELIF A IgG values were observed in 38, 19, and 25% of patients, respectivel y. IgM was detected by ICT only in 12% of patients and aided the diagn osis in 1 of 71 patients. IC tests for specific IgA and IgE alone and combined with ELIFA were positive in 39 and 46% of patients who develo ped clinical toxoplasmosis, respectively. In a serial study of 16 pati ents in whom at least one of these three tests was positive, a signifi cant immunological signal sometimes preceded clinical onset by 1, 6, a nd even 17 months. Similarly, in a group of human immunodeficiency vir us-infected patients with evidence of previous exposure to T. gondii b ut no clinical manifestations, IgA, IgE, and IgA and/or IgE antibodies were detected in only 11, 4, and 12% of patients, respectively. These two situations point to peripheral T. gondii reactivation. IgA and Ig E emerged as interesting markers of the risk of toxoplasmosis in immun odepressed patients. They may also provide valuable assistance in the diagnosis of toxoplasmosis, especially because tests for specific IgM are disappointing. However, at least one in two patients with toxoplas mosis shelved no detectable immunological reaction, suggesting that th is polyisotypic approach should be combined with other noninvasive met hods such as gene amplification.