Antibody response of Echinococcus granulosus infected mice: Recognition of glucidic and peptidic epitopes and lack of avidity maturation

The antibody response was followed weekly during 68 weeks in 17 Balb/c mice intraperitoneally (i.p.) infected with 2000 Echinococcus granulosus protoscoleces (PSC) and in three mice i.P. immunized with 2000 dead PSC. Antibodies against hydatid cyst fluid (HCFA) and its peptidic (periodate-resistant) and carbohydrate (periodate-sensitive) epitopes were titrated by ELISA. Avidity and the antigen recognition pattern of antibodies were also analysed during infection and immunization by ELIZA and immunoblot, respectively. The antibody response of infected mice showed quantitative and qualitative variation during infection, since both titre as well as recognition of peptide and carbohydrate titre as well as recognition of peptide and carbohydrate epitopes in HCFA depended on time post infection. No avidity maturation was evident during the course of infection. Seral form infected mice recognized the 38 kDA subunit of Ag5 but dit not react with the 8 kDa subunit of AgB. On the contrary, the antibody response of immunized mice showed only one peak of antibodies that recognised both peptidic and carbohydrate epitopes of HCFA. In addition, sera from these mice recognized mainly 60 and 110 kDa bands. Our results suggest that: a) avidity and antigen recognition patterns of antibodies in mice treated with live PSC are different from those treated with dead PSC; b) antibodies against HCFA glucidic or peptidic epitopes appear at different times post infection.