Utilidade da pesquisa de anticorpos IgA anti-toxoplasma gondii para o diagnostico sorologico da toxoplasmose aguda adquirida

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

Toxoplasmosis, an infection caused by the intracellular parasite Toxoplasma gondii, is generally asymptomatic or is associated with mild, nonspecific clinical manifestations in immunocompetent subjects. The detection of Toxoplasma-specific antibodies has been considered the most valuable tool for diagnosing toxoplasmosis. Serological diagnosis of acute toxoplasmosis has traditonally been performed by detecting specific IgM antibodies and/or by demonstrating a significant increase in specific IgG antibody levels. However, the presence of high anti-Toxoplasma IgG antibody titers in a significant number of normal subjects and the persistence, in some persons, of specific IgM antibodies for several months or even years following the acute infection have complicated the interpretation of serological test results when toxoplasmosis is suspected. The present study was designed to evaluate the usefulness of detecting Toxoplasma - specific IgA antibodies for the diagnosis of acute acquired toxoplasmosis. The sensitivities and specificities of the direct ELISA (dELISA), immunocapture ELISA (cELISA) and immunocapture-agglutination assay (IC-A) for detecting Toxoplasma-specific IgA antibodies were determined by analysing the following groups of sera: 54 serum samples from patients with acute acquired toxoplasmosis, 50 serum samples from patients with heterologous infections and 27 serum samples from healthy controls. The performances of the three techniques were excellent and very similar: 98% sensitivity and 97% specificity for the dELISA, 100% sensitivity and 99% specificity for the cELISA and 100% sensitivity and specificity for the IC-A In a comparative study, the persistence of Toxoplasma- specific IgA antibodies, detected by dELISA cELISA and IC-A, and of Toxoplasma-specific IgM antibodies, detected by indirect immunofluorescence (IFI), cELISA and an enzyme-mediated chemiluminescent assay (QmL), were assessed using sequential serum samples obtained from ten patients at various intervals after the beginning of the clinical manifestations of toxoplasmosis Our results from screening for Toxoplasma - specific IgM antibodies confirmed the observations of others regarding the sustained persistence of such antibodies after infection with the parasite. A longer persistence of IgM was observed using the cELISA and QmL in a significant number of cases. The dELISA and IC-A techniques also detected specific IgA antibodies for a long period after the infection with T.gondii. The best results for IgA were obtained with the cELISA for which values>40 AU/ml represented significant antibody levels. We conclude that the screening for IgA antibodies by cELISA coupled with the screening for IgM antibodies by IFI or a technique with a higher sensitivity could significantly improve the serological diagnosis of acute acquired toxoplasmosis

ASSUNTO(S)

imunoglobulina a toxoplasmose

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