Utilidade da determinação da avidez dos anticorpos IgG anti-citomegalovirus humano (HCMV) para o imunodiagnostico da citomegalovirose

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The infection caused by human cytomegalovirus (HCMV) is generally asymptomatic or is associated with mild non-specific clinical symptoms in immunocompetent subjects. The virus can, however, cause serious illness in congenitally infected infants and in immunocompromised patients. The serological diagnosis of a recently acquired HCMV infection is usually based on the detection of specific IgM antibodies, seroconversion, and/or a four-fold or greater rise in the titre of HCMV-specific IgG antibodies. Since seroconversion and a rise in IgG titres are seldom demonstrable, the detection of HCMV-specific IgM antibodies has been the most frequently used serological marker for diagnosing acute infection. However, the use of tests with a low specificity and the persistence, in some patients, of specific IgM antibodies for a long time have led to the misdiagnosis of acute HCMV infection and unnecessary concern, especially with respect to pregnant women and immunocompromised patients. Based on the observation that antibody avidity gradually increases after exposure to an immunogen, several reports have shown that the avidity of IgG antibodies can be used as a marker for identifying recent primary and long-term infections, including HCMV infections. In Brazil, commercial assays for evaluating the avidity of HCMV-specific IgG are expensive and are not readily available. The aim of this study was to standardize an economical and simple in-house HCMV-enzyme-linked immunosorbent assay avidity test (ELISA HCMV) for distinguishing recent primary from long-term infection. The test was standardized with the commercial kit ETI-CYTOK G Plus (Sorin Biomedica, Italy) using 8 M urea in phosphate-buffered saline to dissociate low-avidity antibodies. To validate the ELISA HCMV test, its performance was compared with that of the commercial automated VIDAS CMV IgG avidity assay (bioMérieux, France), using well-characterized sera from patients with recent primary and long-term HCMV infections. Forty-nine sera, 24 from patients with a recent primary HCMV infection and 25 from patients with a long-term HCMV infection with a sustained persistence of specific IgM antibodies, were tested. Similar results were obtained with the two avidity methods. All sera from the 24 patients with recently acquired infection had avidity indices compatible with acute HCMV infection by the VIDAS test, whereas with the in-house test, one serum sample had an equivocal result. In the 25 sera from patients with long-term infection, identical results were obtained with the two methods, with only one serum sample having an incompatible value. These findings suggest that our in-house avidity test could be a potentially useful tool for the immunodiagnosis of HCMV infection

ASSUNTO(S)

tecnicas imunoenzimaticas sorologia virologia - tecnica

ACESSO AO ARTIGO

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