DIFFERENCES BETWEEN INTRAOCULAR AND SERUM ANTIBODY-RESPONSES IN PATIENTS WITH OCULAR TOXOPLASMOSIS

PURPOSE: To investigate the antigen specificity of the intraocular ant i-Toxoplasma gondii antibody response in patients with ocular toxoplas mosis. METHODS: Paired ocular fluid and serum samples were collected f rom 13 patients with active ocular toxoplasmosis. Serum IgM anti-T. go ndii antibodies were tested to distinguish recently-acquired from chro nic infection, Anti-T, gondii IgG specificity was analyzed by immunobl otting using a crude T, gondii extract.RESULTS: Two of the 13 patients tested were IgM positive and considered to have acquired ocular toxop lasmosis, The antibody specificity in ocular fluid and serum of these two patients was similar, whereas in the patients with presumed chroni c disease, marked differences could be observed. Most ocular fluid sam ples contained antibodies that stained a 28-kD antigen more intensely than did antibodies from paired serum samples. Using absorption and el ution experiments, we demonstrated that this 28-kD protein was identic al to the GRA-2 antigen, which is expressed in both the tachyzoite and the bradyzoite stages of the parasite, CONCLUSIONS: Our results show that the intraocular T, gondii antibody response of patients with recu rrent ocular toxoplasmosis differs from the systemic response. This fi nding may have implications for our understanding of the immunopathoge nesis of ocular toxoplasmosis and could be employed to improve diagnos is of the disease. (Am J Ophthalmol 1998;126:698-706, (C) 1998 by Else vier Science Inc. All rights reserved.).