RESUMO
A novel approach to chemicallu attenuate cercariae fo S. mansoni is presented. The method utilizes the biologically active surface proteins/glycoproteins which are essential for the survival of the organism as a target for inactivation. The inactivation was achieved by reaction with 0.01 M dimethil adipimidate, dimethyl pimelimidate or dimethyl suberimidate at pH 8.5. The cercariae lost their viability, but retained the ability to exclude trypan blue for up to 2 years when stored at 4-C in a manner similar to live cecariae and in contrast to dead cercariae witch took up the dye immediately. In addition, the attenuated cercariae reacted with monoclonal and policlonal antischistosome antibodies in an indirect immunofluorescence assay indacting the retention and preservation of surface antigens after attenuation. The immunochemical reactivity of the attenuated cercariae was preserved after storage for 2 years at 4-C as shown by reaction with antisera from infected mice and rats in IIF assay. Attenuated cercariae revealed the presence of antischistosome antibodies as early as one week after infection in mice and rats. The presence of receptors for the Fc portion of human IgG on the attenuated cercariae interfered in their use as an immunodiagnostic reagent for human schistosomiasis. The attenuated cercariae were also used to screen cultures for monoclonal antischistosome antibodies. preliminary results indicated that immunozation with attenuated cercariae was capable of imparting protective immunity in mice
