Immunoregulatory properties of soluble extracts from Ascaris suum worms or eggs.

Author(s)

Valdênia Maria Oliveira de Souza

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 1999-10-20

Examining board members

Mahasti Sahihi de Macedo; Eva Burger; Hiro Goto

• Advisor: Mahasti Sahihi de Macedo

Abstract

The extract of Ascaris suum (whole Asc), prepared from male and female worms (with stored eggs) suppress the specific immune response to ovalbumin (OA). This extract was fractionated by gel filtration and high and low molecular weight (MW) proteins were obtained in the first (PI) and third peak (PIII), respectively. PI suppressed the OA-specific cellular and humoral responses and PIII stimulated more anti-Asc IgE antibodies. The whole Asc stimulated a Th2 response predominantly, with high levels of IL-4 and IL-10. These cytokines had an important role in the down-regulation of the Th1 response to OA. In some helminthic infections the Th2 response is stimulated by specific stages of the life cycle. Thus, in this work we investigated which components of whole Asc were responsible for immunosuppression. The worm extracts presented similar chromatographic profiles. The profile of Asc O was distinct, with the second peak being more evident and showing a fourth peak with much lower MW components. By polyacrylamide gel electrophoresis we observed a high concentration of proteins between 107 and 52 kDa. In addition, some bands between 27,2 and 19 kDa were only present in this extract. The extracts from worms and eggs suppressed the cell-mediated immune response to OA, measured by delayed-type hypersensitivity, proliferative response of draining lymph node cells and cytokine secretion. The anti-OA IgG1 and IgG2a antibody production were as drastically reduced by these extracts. The cytokines IL-4 and IL-10 were mainly secreted in response to worm extracts, whereas the egg extract stimulated more IFN-g. Regarding the different fraction of Asc O, PI and PIII components diminished the anti-OA IgE antibody production, whereas PII components stimulated higher anti-Asc O IgE synthesis. PIV components did not display any effect. Our results indicate that the immunosuppressive effect of whole Asc is due to male and female body components. However, extracts prepared from eggs do also display this effect, that seems to be mediated by different mechanisms. (AU)