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BEPA. Boletim Epidemiológico Paulista (Online)

On-line version ISSN 1806-4272

BEPA, Bol. epidemiol. paul. (Online) vol.6 no.68 São Paulo Aug. 2009




Analysis of the antigenic potential of proteins excreted by taquizoits of Toxoplasma gondii



Thaís Alves da Costa Silva; Vera Lucia Pereira-Chioccol

Laboratório de Parasitologia. Instituto Adolfo Lutz. São Paulo, SP, 2008 [Dissertação de Mestrado – Área de concentração: Pesquisas Laboratoriais em Saúde Pública – Programa de Pós-graduação em Ciências. Coordenadoria de Controle de Doenças. Secretaria de Estado da Saúde de São Paulo]




This study evaluates aspects of the immune protective answer ensued by proteins excreted/secreted (ESAs) from Toxoplasma gondii. The antigen choice was based on the evolutionary form of the protozoa, since taquizotes are responsible for the stimulation of the immune cellular and humoral response in intermediate hosts. ESAs were obtained from floating from cell culture VERO infected with taquizotes of the RH strain, 48 hours after infection. Female mice from the A/Sn lineage were grouped in five and immunized by intraperitoneal via, with four doses of 20 µg ESAs and 5 µg of aluminum hydroxide, as an adjuvant, every fifteen days. Control groups received in the same dates only the adjuvant dissolved in 200 µl  PBS. A pool of chronically infested animal sera was employed as positive control. Blood collections were performed 15 days after each immunization and the analysis of antibodies was performed by Elisa, RIFI and Imunobloting. Antibody anti-ESA interaction ability to other mechanisms of immune response was evaluated by lise mediated by complement, agglutination test and  Antibody-mediated celular toxicity. Fifteen days after the last immunization, both animal groups were challenged with 103 taquizotes of the RH strain. Parasitemy, as determined bu PCR and survival rates were daily monitored. Results show that anti-ESA antibody titers grew at each immunization. They recognized a gross taquizote lise and linked themselves around the whole taquizote membrane, specifically in the apex region. They were able to agglutinate taquizotes, interact to proteins in the complement system and with spleen cells to lise in vitro taquizotes. Even challenging the mice with a lethal dose of an extremely virulent strain, results from the PCR suggested that immunized animals presented lower parasitemy when compared to those in the control group. As a consequence, the same happened to survival rates, in which immunized animals survival for 48 hours more than control animals. These data suggest the ability of ESAs to stimulate immune protective response in isogenic mice.



Correspondence to:
Thaís Alves da Costa Silva
Av. Dr. Arnaldo, 351
CEP: 01246-000 – São Paulo/SP – Brasil
Tel: 55 11 3068-1991



Financial Support: Disease Control Coordination of the State Secretary of Health of São Paulo CCD-SES/SP and Fundação de Amparo à Pesquisa do Estado de São Paulo (Fapesp)