Mapping IgE-binding epitopes of Ric c 1 and Ric c 3, allergens from Ricinus communis, by mast cell degranulation assay

Ric c 1 and Ric c 3 are the major castor bean allergens. In order to identify continuous IgE-epitopes in Ric c 1 and Ric c 3, pools of sera from rats immunized with a pool of 2S albumin from these seeds, Ric c 1 and Ric c 3 overlapping synthetic peptides, were used to screen for IgE-binding epitopes. The allergenic properties were monitored by mast cell degranulation assays, histamine quantification and human-IgE binding. Large and small chains isolated from these proteins present allergenic properties. Four continuous epitopes were identified in Ric c 3 and two in Ric c 1. This knowledge may allow the induction of protective antibody responses to antagonize the IgE recognition.

Hydroxyurea inhibits intracellular Toxoplasma gondii multiplication

Tachyzoites of Toxoplasma gondii multiply within the parasitophorous vacuole (PV) until the lysis of the host cell. This study was undertaken to evaluate the effect of hydroxyurea (a specific drug that arrests cell division at G1/S phase) on the multiplication of T. gondii tachyzoites in infected Vero cells. Infected host cells were treated with hydroxyurea for periods varying from 5 to 48 h, and the survival and morphology of the parasite were determined. Hydroxyurea arrested intracellular T. gondii multiplication in all periods tested. After 48 h of incubation with hydroxyurea, intracellular parasites were not easily observed in Vero cells. Ultrastructural observations showed that infected host cells treated with hydroxyurea for 24 h or more presented disrupted intracellular parasites within the PV. However, the host cells exhibited a normal morphology. Our observations suggest that hydroxyurea was able to interfere with the cycle of the intracellular parasite, leading to the complete destruction of the T. gondii without affecting the host cells.