Avaliação do desempenho da pesquisa de anticorpos anti-Toxoplasma por citometria de fluxo no diagnóstico da toxoplasmose aguda humana

• Ano de defesa: 2010
• Autor(a) principal: Santos, Priscila Pinto e Silva dos
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Espírito Santo; BR; Mestrado em Doenças Infecciosas; Centro de Ciências da Saúde; UFES; Programa de Pós-Graduação em Doenças Infecciosas
• Palavras-chave em Português: Human acute toxoplasmosis; Serological diagnosis; Flow cytometry; Toxoplasmose aguda humana; Diagnóstico sorológico; Citometria de fluxo; Doenças Infecciosas e Parasitárias; 61
• Link de acesso: http://repositorio.ufes.br/handle/10/5918

The diagnosis of toxoplasmosis is based mainly on the detection of specific antibodies in sera of patients by serological tests. The major limitations of these tests are the high prevalence of IgG and IgM antibodies, which persist for long periods of time, hampering the diagnosis of acute infection. Therefore, the objective of this study was to evaluate the performance of an indirect immunofluorescence assay based on flow cytometry for the detection of the reactivity of anti-fixed tachyzoites antibodies (AFTA) of T. gondii and IgG avidity in the serodiagnosis of human acute toxoplasmosis. Serum samples from patients with acute toxoplasmosis (AC), chronic toxoplasmosis (CHR), non-infected individuals (NI), and patients with other diseases were analyzed. The analysis of AFTA IgM allowed to segregate groups AC and CHR using a serum dilution of 1:32,000 and a percentage of positive fluorescent parasites (PPFP) of 40% as cut off, resulting in 100% and 90% of sensitivity and specificity, respectively. However, the analysis of AFTA IgG using a PPFP of 10% as cut off and a serum dilution of 1:32,000 allowed to segregate only the group AC and NI, with 93,3% of sensitivity and 100% of specificity. The serum dilutions applied on the study of AFTA IgG subclasses in the diagnosis of acute toxoplasmosis using NI as control group were: 1:32,000 for IgG1, 1:400 for IgG2, 1:2,000 and 1:8,000 for IgG3, and 1:400 and 1:1,600 for IgG4. It was used a PPFP of 10% as a cut off for all subclasses. Moreover, only AFTA IgG2 and AFTA IgG4 showed 100% of sensitivity and specificity. The analysis of IgG avidity when to groups AC and CHR, showed 100% of sensitivity and specificity. Using the AFTA IgM as the initial test and IgG avidity as a confirmatory test, it was possible to establish the diagnosis of human acute toxoplasmosis. The evaluation of IgM cross-reactivity demonstrated false-positive results only for patients with malaria and infectious mononucleosis. The detection of IgM anti-T. gondii antibodies and IgG avidity by flow cytometry showed a better performance in comparison to the VIDAS® TOXO (ELFA - Enzyme Linked Fluorescent Assay) in the diagnosis of acute toxoplasmosis. These results demonstrate the applicability of the detection of anti-T. gondii antibodies by flow cytometry and its importance in the diagnosis of human acute toxoplasmosis.