Detection of antibodies to the 97 kDa component of Toxoplasma gondii in samples of human serum

Abstract

This study was carried out to investigate the immune response against 97 kDa (p97) molecular marker of Toxoplasma gondii that has been characterized as a cytosolic protein and a component of the excreted-secreted antigens from this parasite. A total of 60 serum samples from patients were analyzed by enzime-linked immunosorbent assay and Western blot for toxoplasmosis. These samples were organized in three groups, based on clinical symptoms and results of serological tests. Group I: 20 samples reactive to IgG and IgM (acute phase); group II: 20 non-reactive samples (control group); and group III: 20 samples reactive only to IgG (chronic phase). Western blot was performed with total antigenic extracts or with excreted and secreted antigen from T. gondii to identify the fraction correspondent to p97. It was observed that this cytosolic component from T. gondii stimulates the immunologic system to produce both IgM and IgG antibodies in the beginning of the acute infection and IgG throughout the chronic stage of the asymptomatic toxoplasmosis.

Sequential recognition of antigenic markers of Toxoplasma gondii tachyzoite by pooled sera of mice with experimental toxoplasmosis

“…Blocking a determined epitope of this component through monoclonal antibody inhibits T. gondii replication in vitro (Mineo et al 1994). However, when testing for IgG avidity, in a study carried out by Ribeiro et al (2002) analyzing human sera from acute and chronic phases of toxoplasmosis by immunoblot, the 97-kDa band was detected by high frequency by IgG antibodies in almost all samples, thus, could not be considered a good marker to distinguish acute from chronic infections in humans. This was found to be similarly occurring in mice infected with toxoplasmosis in the present study.…”

Novas abordagens antigênicas no sorodiagnóstico da toxoplasmose humana, com ênfase nas infecções primária e congênita

“…A sensibilidade e a especificidade dos ensaios sorológicos comumente utilizados no sorodiagnóstico da toxoplasmose humana são altamente dependentes do tipo de antígeno e da modalidade de teste utilizada. Assim, diferentes preparações antigênicas têm sido desenvolvidas: (1) antígenos solúveis e totais de taquizoítas contendo uma mistura de antígenos de superfície e antígenos intracelulares obtidos por criólise, sonicação ou solubilização em detergentes, como o STAg (antígeno solúvel de taquizoítas de T. gondii) RIBEIRO;MINEO, 2002); (2) taquizoítas fixados com formalina (contendo principalmente antígenos de superfície) (SILVA-DOS-SANTOS et al, 2012); (3) antígenos excretados e/ou secretados pelo parasita, como o ESA (excreted/secreted antigens) (YAMAMOTO et al, 1998); ( 4) proteínas nativas purificadas por meio de cromatografia de afinidade utilizando anticorpos monoclonais ; (5) proteínas recombinantes de antígenos imunodominantes do parasita SANTANA et al, 2012). Desta forma, quanto maior o grau de purificação dos antígenos, maior é a especificidade do teste (ELISA utilizando proteínas nativas ou recombinantes) e, por outro lado, quanto menos purificada a preparação antigênica (ELISA utilizando antígeno total), maior é a probabilidade de ocorrência de reatividade cruzada e inespecífica .…”