Aqueous Humor and Serum Immunoblotting for Immunoglobulin Types G, A, M, and E in Cases of Human Ocular Toxoplasmosis

Abstract

The purpose of this study was to compare the local and systemic Toxoplasma-specific humoral immune responses in individuals with ocular toxoplasmosis (OT). To this end, paired aqueous humor and serum samples from 46 individuals with active OT and from 30 individuals without inflammatory eye disease (controls) were analyzed by immunoblotting for anti-Toxoplasma immunoglobulin G (IgG), IgA, IgM, and IgE directed against 20-to 120-kDa antigens. The presence in the aqueous humor of a unique band, or of at least three bands that were at least three times more intense in aqueous humor than in serum, was taken as evidence of local antibody production. IgG bands were detected in 98% of the aqueous humor samples, while IgA bands were detected in 76%, IgM bands were detected in 8%, and IgE bands were not detected in any. Evidence of local production of specific antibodies was found in 32 cases (70%) (IgG in 23 [50%]; IgA in 16 [35%]). In 10 instances (22%), routine laboratory tests were not indicative of OT. In 14 cases (30%), no local antibody production was detected by immunoblotting; 3 of these cases yielded evidence of local antibody production according to the Goldmann-Witmer coefficient. Local antibody production was revealed for 7 of the 30 controls (23%). Hence, the sensitivity of immunoblotting for IgG and IgA is 70%, and the specificity is 77%. We conclude that immunoblotting for local specific IgG and IgA supports the clinical diagnosis of OT in 70% of cases. In 22% of these, the diagnosis is not confirmed by other laboratory tests. Hence, immunoblotting increases the sensitivity of routine laboratory tests and should be considered for samples that register negative by such tests.

Comparison of Immunoblotting, Calculation of the Goldmann-Witmer Coefficient, and Real-Time PCR Using Aqueous Humor Samples for Diagnosis of Ocular Toxoplasmosis

“…PCR was positive on 75% of samples with positive results by one or another of the methods used to detect local Ab production. PCR positivity often is associated with a negative WB or GWC result (8,9,23) and is the only test that confirms the diagnosis (16). PCR is classically positive for immunocompromised patients, but this was the case for only 4 of the 13 PCR-positive patients in our study.…”

PCR-Based Detection of Toxoplasma gondii DNA in Blood and Ocular Samples for Diagnosis of Ocular Toxoplasmosis

“…In cases where the fundus is hidden by vitreous inflammation or clinical findings are atypical, physicians are obliged to draw ocular fluid samples to confirm the toxoplasmic origin of the lesions and discard other causes. In these cases, 3 biological methods can contribute to establishing a correct diagnosis: PCR, the calculation of the Goldmann-Witmer coefficient (GWC), and Western blot analysis (WB) (5). The last two methods are used to compare the specific antibody profiles in the ocular compartment and in the serum.…”

Anti-Toxoplasma gondii secretory IgA in tears of patients with ocular toxoplasmosis: immunodiagnostic validation by ELISA

“…Thus, using immunoblotting, the sensitivity for IgG detection was 50% with a specificity of 93%; for IgA detection, however, 35% of the patients tested positive and 20% of normal controls had IgA that was reactive to T. gondii (Garweg et al 2004). The combination of ELISA and immunoblotting tests for IgG detection in the aqueous humour resulted in diagnosis of 83% of patients with toxoplasmosis (Villard et al 2003).…”