Characterisation of a panel of recombinant antigens from Echinococcus granulosus and their role in the immunological follow up, after treatment, of cystic hydatid patients from Turkana, Kenya

Cystic echinococcosis is a serious zoonotic disease caused by the metacestode of Echinoccoccus granulosus inflicting significant morbidity and mortality in many parts of the world. Treatment of human hydatid cases involves chemotherapy with the drug Albendazole which has beneficial effects in some cases but not others. Disease progression can be monitored by ultrasound using the WHO classification system, but this only indicates large scale changes in cyst morphology. Antibody responses to cyst fluid antigens have previously been used to provide further information on follow up after treatment and the current project explores the usefulness of a panel of novel recombinant antigens in mapping antibody responses to cyst morphological changes. Positive clones pET19b-EgFABP1-C10, pET19b-EgHSP70-C10, pET19b- EgTPx-2Cb, pET19b-EgEF1-p/6-C9 and pET19b-EgAgB-C7 were selected and used to synthesise recombinant fatty acid binding protein 1 (EgFABPI), heat shock protein 70 (EgHSP70), thioredoxin peroxidase (EgfTPx) elongation factor 1-beta/delta (EgEF1-(3/6) and antigen B (EgAgB) fusion proteins respectively carrying N-terminal His-tagged sequences. A panel of defined sequential sera of Turkana origin (Kenya), untreated (n =9) and treated (n =22) was probed in ELISA with the recombinant parasite antigens. Results show that different antigens react differently towards total IgG and lgG1 and lgG4 isotype subclass antibodies. Some antigens are associated with fluctuation in antibody levels at or during the time of transition from one cyst morphology to that of another type, whilst other antigens show little or no difference in reactivity. In some cases, fluctuating levels of antibody are correlated to pre and post treatment with albendazole. Antibodies are rarely static and fluctuate up and down during and after treatment, indicating a more varied release of extraneous antigenic material supplementary to those antigens normally associated with hydatid cyst fluid. In a number of cases particular antibody profiles could be linked to important changes in cyst structure and could have potential as markers of cyst development. Throughout the current research, fluctuation in antibody responses in CE sequential sera towards recombinant AgB has shown consistency in line with other authors. A high level of total serum IgG and specific IgG subclass antibodies in response to REgTPx antigen and REgFABP1 has shown some association with active type cysts (CE1, CE2 and CE3). Furthermore, peaking levels in activity of serum IgG and specific lgG1 antibodies in response towards REgEF1-p/8 antigen seem strongly correlated to CE3 cysts just prior to, during, or upon transition to inactive type cysts (CE4 and CE5). These serum antibody responses are also seen with REgHSP70 antigen when other active type cysts (CE1 and CE2) show signs of deterioration. The results therefore conclude that serological responses to each antigen may differ in individual patients and that particular antibody reactivity may be useful in predicting disease progression or regression. Recombinant EgFABPI and EgTPx antigens may be functional as indicators of early cyst fertility and viability respectively; REgEF1-p/6 antigen might be valuable as a marker of disease regression and REgHSP70 antigen could be practical as an indicator of parasite instability